X-rays can be used to identify abnormalities in the patient's sinus. [ 7 ]  MRI technology is typically a more efficient method to identify a tumor located in soft tissue and fluid, while CT scans serve to detect damage to bone tissue, especially in the  cribriform plate . [ 3 ]


A  biopsy  can be used to examine an excised sample of tissue with the help of a microscope. Biopsy results often determine the final diagnosis of paranasal sinus and nasal cavity cancer. [ 7 ]


When used for diagnosing paranasal sinus and nasal cancer, the main goal of a  bone scan  is to investigate whether the cancer cells have spread into the bone.


A nasoscopy is a type of  endoscopy  that can be used as a diagnosis method for paranasal sinus and nasal cavity cancer. [ 1 ]  A nasoscopy is performed by the insertion of a nasoscope into the patient’s nose to search for abnormal areas in the nasal cavity. The tissue may be extracted with tools attached to the nasoscope and later examined with a microscope for signs of cancer. [ 1 ]


A  PET scan  can also be implemented to detect cancer cells inside the body. [ 7 ]


Various treatments can be implemented to treat paranasal sinus and nasal cavity cancer. Generally, treatment uses methods such as surgery, radiation therapy, chemotherapy and proton therapy.


Surgery is often implemented in all stages of paranasal sinus and nasal cavity cancer. [ 1 ]  The main goal of surgery is to remove cancerous tissue. [ 1 ]  Surgery is typically followed by chemotherapy and radiation therapy, to kill off any remaining cancer cells. [ 1 ]


The type of surgery performed depends on the extent to which cancerous tissue has spread. If the cancer has significantly spread into neighboring structures, large portions of tissue may have to be removed. If necessary, a maxillectomy could be used to remove all or part of the  maxilla , which includes the  hard palate .  [ 7 ]  More extensive craniofacial surgery can be also used in the treatment of paranasal sinus and nasal cavity cancer, with more extensive tissue removal. The vacancy created by the removal of tissue can be filled by  prostheses  or soft tissue. [ 7 ]


If the cancer may have spread to the neck, a  neck dissection  might be performed in order to remove the lymph nodes in the neck area, in order to remove any cancerous cells there. [ 7 ]


Radiation therapy  aims to destroy cancer cells by using high energy radiation. [ 7 ]  Radiation therapy is an effective method for paranasal sinus and nasal cavity cancer after implementation of surgery. [ 8 ]  Radiation therapy can also be used as an alternative method for a patient who is unable to undergo surgery. [ 7 ]  For paranasal sinus and nasal cavity cancer, Volumetric Modulated Arc Therapy (VMAT) more consistently and accurately irradiated the target area than Intensity Modulated Radiation Therapy (IMRT). [ 9 ]  Tooth decay may be caused by radiation therapy. [ 7 ]  Tooth decay from radiation therapy may can be prevented by receiving dental treatment before radiation therapy. [ 7 ]  Radiation therapy may cause skin redness and irritation. [ 7 ]


Chemotherapy  is usually used before or after surgery or radiation therapy. [ 7 ]  Chemotherapy can be used in the treatment of paranasal sinus and nasal cavity cancer. [ 10 ]  Infections and hair loss might occur after the implementation of chemotherapy.


Paranasal sinuses  are a group of four paired  air-filled spaces  that surround the  nasal cavity . [ 1 ]  The  maxillary sinuses  are located under the  eyes ; the  frontal sinuses  are above the eyes; the  ethmoidal sinuses  are between the eyes and the  sphenoidal sinuses  are behind the eyes. The  sinuses  are named for the  facial bones and sphenoid bone  in which they are located. Their role is disputed.


Humans possess four pairs of paranasal sinuses, divided into subgroups that are named according to the  bones  within which the sinuses lie. They are all innervated by branches of the  trigeminal nerve  (CN V).


The paranasal sinuses are lined with  respiratory epithelium  (ciliated pseudostratified columnar epithelium).


One known function of the paranasal sinuses is the production of  nitric oxide , which also functions as a facilitator of oxygen uptake. [ 3 ]


Paranasal sinuses form developmentally through excavation of bone by air-filled sacs ( pneumatic diverticula ) from the  nasal cavity . This process begins prenatally (intrauterine life), and it continues through the course of an organism's lifetime.


The results of experimental studies suggest that the natural ventilation rate of a sinus with a single  sinus ostium  (opening) is extremely slow. Such limited ventilation may be protective for the sinus, as it would help prevent drying of its mucosal surface and maintain a near-sterile environment with high  carbon dioxide  concentrations and minimal  pathogen  access. Thus composition of gas content in the maxillary sinus is similar to  venous blood , with high carbon dioxide and lower  oxygen  levels compared to breathing air. [ 4 ]


At birth, only the  maxillary sinus  and the  ethmoid sinus  are developed but not yet pneumatized; only by the age of seven are they fully aerated. The  sphenoid sinus  appears at the age of three, and the  frontal sinuses  first appear at the age of six, and fully develop during adulthood. [ 5 ]


The, paranasal sinuses are joined to the  nasal cavity  via small orifices called  ostia . These become blocked easily by allergic inflammation, or by swelling in the nasal lining that occurs with a  cold . If this happens, normal drainage of  mucus  within the sinuses is disrupted, and  sinusitis  may occur. Because the maxillary posterior teeth are close to the maxillary sinus, this can also cause clinical problems if any disease processes are present, such as an infection in any of these teeth. These clinical problems can include secondary sinusitis, the inflammation of the sinuses from another source such as an infection of the adjacent teeth. [ 6 ]


These conditions may be treated with drugs such as  decongestants , which cause  vasoconstriction  in the sinuses; reducing inflammation; by traditional techniques of  nasal irrigation ; or by  corticosteroid . [ medical citation needed ]


Malignancies of the paranasal sinuses comprise approximately 0.2% of all malignancies. About 80% of these malignancies arise in the maxillary sinus. Men are much more often affected than women. They most often occur in the age group between 40 and 70 years.  Carcinomas  are more frequent than  sarcomas . Metastases are rare.  Tumours  of the sphenoid and frontal sinuses are extremely rare.


Sinus  is a  Latin  word meaning a fold, curve, or bay. Compare  sine .


Paranasal sinuses occur in many other animals, including most  mammals ,  birds , non-avian  dinosaurs , and  crocodilians . The bones occupied by sinuses are quite variable in these other species.


A  parapharyngeal abscess  is a deep  neck space   abscess  of the  parapharyngeal space  (or pharyngomaxillary space), which is lateral to the  superior pharyngeal constrictor muscle  and medial to the  masseter muscle .  [ 1 ]  This space is divided by the  styloid process  into anterior and posterior compartments. The posterior compartment contains the  carotid artery ,  internal jugular vein , and many nerves. [ 2 ]


Symptoms include fever, sore throat,  painful swallowing , and swelling in the neck. [ 2 ]
An anterior space abscess can cause  lockjaw  (spasm of jaw muscle), and hard mass formation along the angle of the  mandible , with medial bulging of the tonsil and lateral pharyngeal wall. A posterior space abscess causes swelling in the posterior pharyngeal wall, and lockjaw is minimal. Other structures within the carotid sheath may be involved, causing rigors, high fever, bacteremia, neurologic deficit, or a massive haemorrhage caused by carotid artery rupture. [ 2 ]


Infection can occur from:


Parapharyngeal abscess is more common in male than the female gender. [ 4 ] [ 5 ]   Any age group can develop a parapharyngeal abscess but it is most commonly seen in children and adolescents. [ 6 ]  Adults who are  immunocompromised  are also at high risk. [ 7 ]


The  parotid gland  is a major  salivary gland  in many animals. In humans, the two parotid glands are present on either side of the  mouth  and in front of both  ears . They are the largest of the salivary glands. Each parotid is wrapped around the  mandibular ramus , and secretes serous  saliva  through the  parotid duct  into the mouth, to facilitate  mastication  and  swallowing  and to begin the digestion of  starches . There are also two other types of  salivary  glands; they are  submandibular  and  sublingual  glands. [ 1 ]  Sometimes  accessory parotid glands  are found close to the main parotid glands. [ 2 ]


The word  parotid  literally means " beside the ear ". From Greek παρωτίς (stem παρωτιδ-) : (gland) behind the ear < παρά - pará : in front, and οὖς - ous (stem ὠτ-, ōt-) : ear.


The parotid glands are a pair of mainly  serous  salivary glands located below and in front of each  ear canal , draining their secretions into the vestibule of the mouth through the  parotid duct . [ 3 ]  Each gland lies behind the mandibular ramus and in front of the  mastoid process  of the  temporal bone . The gland can be  felt  on either side, by feeling in front of each ear, along the cheek, and below the  angle of the mandible . [ 4 ]


The parotid duct, a long excretory duct, emerges from the front of each gland, superficial to the  masseter muscle . The duct pierces the  buccinator muscle , then opens into the mouth on the inner surface of the cheek, usually opposite the  maxillary second molar . The parotid papilla is a small elevation of tissue that marks the opening of the parotid duct on the inner surface of the cheek. [ 4 ]


The gland has four surfaces – superficial or lateral, superior, anteromedial, and posteromedial. The gland has three borders – anterior, medial, and posterior. The parotid gland has two ends – a superior end in the form of a small superior surface and an inferior end (apex).


A number of different structures pass through the gland. From  lateral to medial , these are:


Sometimes accessory parotid glands are found as an  anatomic variation . These are close to the main glands and consist of  ectopic  salivary gland tissue. [ 2 ]


Capsule of parotid gland


A capsule of the parotid gland is formed from the investing layer of the deep cervical fascia. It is supplied by the great auricular nerve. The fascia splits to enclose the gland. This splitting occurs between the angle of the mandible and the mastoid process. The  superficial lamina (parotidomassetric fascia)  is thick and is attached to the zygomatic arch. The deep lamina is thin and is attached to the styloid process, tympanic plate, and the ramus of the mandible. The part of the deep lamina extending between the styloid process and the mandible is thickened to form a  stylomastoid ligament.  The stylomandibular ligament separates the parotid gland from the superficial lobe of the submandibular gland.  [ citation needed ]


The  facial nerve (CN VII)  splits into its branches within the parotid gland, thus forming its  parotid plexus . Nerves of this plexus then pass through the parotid gland without innervating the gland itself. [ 5 ]


Arterial supply


The external carotid artery and its terminal branches within the gland, namely, the superficial temporal and the maxillary artery, also the posterior auricular artery supply the parotid gland. [ citation needed ]


Venous drainage


Venous return is to the retromandibular veins. [ citation needed ]


Lymphatic drainage


The gland is mainly drained into the preauricular or parotid lymph nodes which ultimately drain to the deep cervical chain. [ citation needed ]


The parotid gland receives both sensory and autonomic innervation.


Sympathetic


The cell bodies of the preganglionic sympathetic fibres that supply the gland usually lie in the lateral horns of upper thoracic spinal segments (T1-T3).  [ citation needed ]  Postganglionic sympathetic fibers from  superior cervical ganglion  reach the gland by passing along the  external carotid artery  and  middle meningeal artery . They act to cause vasoconstriction. [ 6 ] : 359–360


Parasympathetic


Preganglionic parasympathetic fibers for the parotid gland arise in the brainstem in the  inferior salivatory nucleus , and leave the brain in the  glossopharyngeal nerve (CN IX) , then pass in the  tympanic nerve  to the  tympanic plexus , then from the tympanic plexus in the  lesser petrosal nerve  to the  otic ganglion  where they synapse. Postganglionic (post-synaptic) fibers from the ganglion then "hitch-hike" along the  auriculotemporal nerve  to reach the parotid gland. [ 7 ] [ 8 ] : 255


Sensory


General sensory innervation to the parotid gland and its  capsule  is provided by the  auriculotemporal nerve . [ 9 ]


The gland has a capsule of its own of dense connective tissue but is also provided with a false capsule by the investing layer of the deep cervical fascia. The fascia at the imaginary line between the angle of the mandible and the mastoid process splits into a superficial and a deep lamina to enclose the gland. The  risorius  is a small muscle embedded with this capsule substance.


The gland has short, striated ducts and long, intercalated ducts. [ 10 ]  The intercalated ducts are also numerous and lined with cuboidal epithelial cells and have lumina larger than those of the acini. The striated ducts are also numerous and consist of simple columnar epithelium, having striations that represent the infolded basal cell membranes and mitochondria. [ 8 ] : 273


Though the parotid gland is the largest, it provides only 25% of the total salivary volume. The serous cell predominates in the parotid, making the gland secrete a mainly serous secretory product. [ 10 ]


The parotid gland also secretes salivary alpha-amylase ( sAA ), which is the first step in the decomposition of starches during mastication. It is the main exocrine gland to secrete this. It breaks down amylose (straight chain starch) and amylopectin (branched starch) by hydrolyzing alpha 1,4 bonds. Additionally, the alpha amylase has been suggested to prevent bacterial attachment to oral surfaces and to enable bacterial clearance from the mouth. [ 11 ]


The parotid salivary glands appear early in the sixth week of the prenatal development and are the first major salivary glands formed. The epithelial buds of these glands are located on the inner part of the cheek, near the labial commissures of the primitive mouth (from ectodermal lining near angles of the  stomodeum  in the 1st/2nd pharyngeal arches; the stomodeum itself is created from the rupturing of the oropharyngeal membrane at about 26 days. [ 12 ] ) These buds grow up posteriorly toward the otic placodes of the ears and branch to form solid cords with rounded terminal ends near the developing facial nerve. Later, at around 10 weeks of prenatal development, these cords are canalized and form ducts, with the largest becoming the parotid duct for the parotid gland. The rounded terminal ends of the cords form the acini of the glands. Secretion by the parotid glands via the parotid duct begins at about 18 weeks of gestation. Again, the supporting connective tissue of the gland develops from the surrounding  mesenchyme . [ 10 ]


Inflammation of one or both parotid glands is known as  parotitis . The most common cause of parotitis is  mumps . Widespread vaccination against mumps has markedly reduced the incidence of mumps parotitis. The pain of mumps is due to the swelling of the gland within its fibrous capsule. [ 3 ]


Apart from viral infection, other infections, such as bacterial, can cause parotitis (acute suppurative parotitis or chronic parotitis). These infections may cause blockage of the duct by  salivary duct calculi  or external compression. Parotid gland swellings can also be due to benign lymphoepithelial lesions [ clarification needed ]  caused by  Mikulicz disease  and  Sjögren syndrome . Swelling of the parotid gland may also indicate the eating disorder  bulimia nervosa , creating the look of a heavy jaw line. With the inflammation of mumps or obstruction of the ducts, increased levels of the salivary alpha amylase secreted by the parotid gland can be detected in the blood stream.


Mumps  is seen to be a common cause of parotid gland swelling – 85% of cases occur in children younger than 15 years. The disease is highly contagious and spreads by airborne droplets from salivary, nasal, and urinary secretions. [ 13 ]  Symptoms include oedema in the area,  trismus  as well as otalgia. The lesion tends to begin on one side of the face and eventually becomes bilateral. [ 13 ]  The transmission of the  paramyxovirus  is by contact with the infected persons saliva. [ 13 ]  Initial symptoms tend to be a headache and fever. Mumps is not fatal, however further complications can include swelling of the ovaries or the testes. [ 13 ]  Diagnosis of mumps is confirmed through viral serology, management of the condition includes hydration and good oral hygiene of the patient [ 13 ]  requiring excellent motivation. However, since the development of the mumps vaccine, given at the age of between 4–6 years, the incidence of this viral infection has greatly reduced. This vaccine has reduced the incidence by 99%. [ 13 ]


Tuberculosis  and  syphilis  can cause  granuloma  formation in the parotid glands.


Salivary stones  mainly occur within the main confluence of the ducts and within the main parotid duct. The patient usually complains of intense  pain  when salivating and tends to avoid foods which produce this symptom. In addition, the parotid gland may become enlarged upon trying to eat. The pain can be reproduced in clinic by squirting lemon juice into the mouth. Surgery depends upon the site of the stone: if within the anterior aspect of the duct, a simple incision into the buccal mucosa with sphinterotomy [ clarification needed ]  may allow removal; however, if situated more posteriorly [ clarification needed ]  within the main duct, complete gland excision may be necessary.


The parotid salivary gland can also be pierced and the facial nerve temporarily traumatized when an inferior alveolar local anesthesia nerve block is incorrectly administered, causing transient facial paralysis. [ 4 ]


About 80% of tumors of the parotid gland are benign. [ 14 ]  The most common of these include  pleomorphic adenoma  (70% of tumors, [ 14 ]  of which 60% occur in females [ 14 ] ) and  Warthin tumor  (i.e.  adenolymphoma , which is more common in males than in females). Their importance is in relation to their anatomical position and tendency to grow over time. The tumorous growth can also change the consistency of the gland and cause facial pain on the involved side. [ 4 ]


Around 20% of parotid tumors are malignant, with the most common tumors being  mucoepidermoid carcinoma  and  adenoid cystic carcinoma . Other malignant tumors of the parotid gland include acinic cell carcinoma, carcinoma expleomorphic adenoma, adenocarcinoma (arising from ductal epithelium of parotid gland), squamous cell carcinoma (arising from parenchyma of parotid gland), and undifferentiated carcinoma. Metastasis from other sites like  phyllodes tumour  of breast presenting as parotid swelling have also been described. [ 15 ]  Critically, the relationship of the tumor to the branches of the  facial nerve  ( CN  VII) must be defined because resection may damage the nerves, resulting in paralysis of the muscles of facial expression.


Neoplastic  lesions of the parotid salivary gland can either be benign or malignant. Within the parotid gland, nearly 80% of tumours are  benign . [ 17 ]  Benign lesions tend to be painless,  asymptomatic  and slow-growing. The most common salivary gland neoplasms in children are  hemangiomas , lymphatic malformations, and  pleomorphic adenomas . [ 13 ]  Diagnosis of benign lesions require a fine-needle-like  aspiration biopsy . [ 13 ]  With various benign lesions, most commonly the pleomorphic adenoma, there is a risk of developing  malignancy  over time. [ 13 ]  As a result, these lesions are typically resected.


Pleomorphic adenoma is seen to be a common benign neoplasm of the salivary gland and has an overall incidence of 54–68%. [ 13 ]  The Warthin tumour has a lower incidence of 6–10%; this tumour is associated with smoking and is more common in older men. [ 13 ]  Benign lesions of the parotid gland have a significantly higher incidence than malignant lesions.


Malignant  salivary gland lesions are rare. However, when a tumour extends to the  submandibular ,  sublingual  and the minor salivary glands, they tend to be malignant. [ 13 ]  Distinguishing a malignant lesion from a benign one may be difficult as they both present as painless lesions. [ 13 ]  A  biopsy  is crucial in aiding diagnosis. There are common signs that can highlight the presence of a malignant lesion. These include facial nerve weakness, rapid increase of the size of the lump as well as ulceration of the mucosa of the skin. [ 13 ]


Mucoepidermoid carcinoma  is a common malignant tumour of the salivary glands and has a low incidence of 4–13%. [ 13 ]   Adenoid cystic carcinoma  is also a common malignant salivary gland lesion and has an incidence of 4–8%. This carcinoma tends to invade nerves and can re-occur post-treatment. [ 13 ]


A developmental polycystic disease of the salivary gland is seen to be extremely rare and is seen to be independent of recurrent  parotitis . [ 18 ]  The cause is thought to be a defect in the interactions between  activin ,  follistatin  and  TGF-β , leading to a developmental disorder of glandular tissue. [ 18 ]


Surgical treatment of parotid gland tumors is sometimes difficult because of the anatomical relations of the facial nerve parotid lodge, as well as the increased potential for postoperative relapse. Thus, detection of early stages of a parotid tumor is extremely important in terms of postoperative prognosis. [ 14 ]  Operative technique is laborious, because of relapses and incomplete previous treatment made in other border specialties. [ 14 ]  Surgical techniques in parotid surgery have evolved in the last years with the use of neuromonitoring of the facial nerve and have become safer and less invasive. [ 19 ]


After surgical removal of the parotid gland ( parotidectomy ), the  auriculotemporal  nerve is liable to damage and upon recovery it fuses with sweat glands. This can cause sweating on the cheek on the side of the face of the affected gland. This condition is known as  Frey's syndrome . [ 20 ]


Commonly caused by a retrograde bacterial infection as a result of illness,  sepsis , trauma, surgery, reduced salivary flow due to medications,  diabetes , malnutrition and dehydration. Classically symptoms of painful swelling in the parotid region when eating seen. Management is based upon antibacterials, rehydration combined with gentle massage to encourage salivary flow. [ 21 ]


A latent infection despite clinical resolution of the disease resulting in impaired function. Histologically glandular duct dilation, abscess formation and atrophy may be seen. Parotid secretions are viscous. Disease course shows pain and swelling, waxing and waning. Radiographic screening should be undertaken to rule out  sialolith . Management with  palliative care  with parotidectomy as a last resort. [ 21 ]


Acute non-suppurative disease that often occurs in epidemics. Prevented by  MMR vaccine . Caused by  paramyxovirus  that is transmitted by infected saliva and urine. A prodromal period of 24–28 hours is experienced, followed by rapid and painful swelling of the parotid gland. Treatment is supportive (bedrest, hydration) as spontaneous resolution occurs within 5–10 days. [ 21 ]


Diffuse gland enlargement is seen, and may affect patients throughout all stages of the infection. Lymphoepithelial cysts [ 22 ]  seen via imaging help aid diagnosis. Pathogenic process occurs due to circulating  CD8  lymphocytes within the salivary gland. Medical management via use of  antiretrovirals , excellent oral hygiene measures and sialogogues. [ 21 ]


Most commonly seen in fourth and fifth decades in women, and can affect any salivary gland. Presentation is a slowly enlarging gland, with diagnosis made by identification of the underlying systemic disorder and measurements of salivary chemical levels. Sodium and chloride ion levels will be elevated two or three times normal levels. Treatment is by addressing the underlying systemic condition. [ 21 ]


Sarcoidosis is a chronic systemic disease characterised by the production of non-caseating granulomas of unknown aetiology. It can affect any organ of the body, depressing cellular immunity and enhancing humoral immunity.


Salivary gland involvement primarily involves both parotid glands, causing enlargement and swelling. Salivary gland biopsy with histopathologic examination is needed to make the distinction between whether Sjoren's syndrome or sarcoidosis is the cause of this. [ 21 ]


Salivary gland enlargement occurs in up to 30% of patients with Sjogren's syndrome, with the parotid gland being most often enlarged, and bilateral parotid gland enlargement seen in 25–60% of patients. However, the parotid glands have a longer-lasting secretory capacity in Sjogren's syndrome patient and therefore are the last glands to manifest hyposalivation in the disease. Histopathology shows clustering of lymphocytic infiltrates and epimyoepithelial islands. [ 21 ]


The most common head and neck manifestation of tuberculosis mycobacterial disease is infection of cervical lymph nodes. The infection is thought to originate in the tonsils or gingiva, ascending to the parotid gland. Two clinical forms; acute and chronic lesions. Acute lesions have diffuse glandular edema, easily confused with acute sialdentitis or abscess. The chronic lesions occur as slow growing masses mimicking tumors. [ 21 ]


A patient with parotid swelling may complain of swelling, pain,  xerostomia , bad taste and sometimes  sialorrhoea . [ 23 ]


The most common presenting symptom of  neoplasms  (both benign and malignant) is an asymptomatic swelling. Pain is more common in patients with parotid cancer (10–29% feel pain) than those with benign neoplasms (only 2.5–4%), [ 23 ]  but pain itself it not diagnostic of malignancy.


Episodic swelling of major salivary glands accompanied by pain and related to salivary stimuli suggests duct obstruction.


Also need to assess the facial nerve. The facial nerve passes through the parotid so may be affected if there is a change in the parotid gland. Facial nerve paralysis in a previously untreated patient usually indicates that a tumour is malignant. [ 23 ]


The superficial location of the salivary glands allows palpation and visual inspection. The inspection must be systematic, both intraorally and extraorally, so no area is missed.


For extraoral examination the patients head should be inclined forwards in order to maximally expose the parotid and submandibular glands. A normal parotid gland is barely palpable and a normal sublingual gland is not palpable. [ 23 ]


Intra-oral examination should include observations for asymmetry, discolouration, pulsation and obstructions in the duct orifices. Swelling of the deep lobe of the parotid gland may be seen intra-orally, and may also displace the tonsil. The minor salivary glands should be examined. The labial, buccal and posterior palatal mucosa should be dried with an air blower or tissue and pressed to assess the flow of saliva. [ 23 ]


Salivary stimulation


Sialography


Sialochemistry


Radioisotope scintigraphy


The  parotid plexus  or  plexus parotideus  is the branch point of the  facial nerve  (extratemporal) after it leaves the  stylomastoid foramen . This division takes place within the  parotid gland .


Commonly, it divides into the following branches (several variations):


Patient registration  is used to correlate the reference position of a  virtual   3D   dataset  gathered by computer  medical imaging  with the reference position of the patient. This procedure is crucial in  computer assisted surgery , in order to insure the reproducitibility of the preoperative registration and the clinical situation during surgery.
The use of the term "patient registration" out of this context can lead to a confusion with the procedure of registering a patient into the files of a medical institution.


In  computer assisted surgery , the first step is to gather a 3D dataset that reproduces with great accuracy the geometry of the normal and pathological tissues in the region that has to be operated on. This is mainly obtained by using  CT  or  MRI  scans of that region. The role of patient registration is to obtain a close-to-ideal reference reproducibility of the dataset – in order to correlate the position (offset) of the gathered dataset with the patient's position during the surgical intervention. Patient registration (1) eliminates the necessity of maintaining the same strict position of the patient during both preoperative scanning and surgery, and (2) provides the surgical robot the necessary reference information to act accurately on the patient, even if he has (been) moved during the intervention.


Patient registration was used mostly in head surgery – oral and maxillofacial surgery, neurosurgery, otolaryngology. With the advent of marker- and markerless-registration, the concept has been extended for abdominal surgery.


The first attempts in 3D mapping of human tissues were made by  V. Horsley  and R. Clarke in 1906. [ 1 ]  They have built a rectangular  stereotactic  headframe that had to be fixed to the head. It was based on cartesian principles and allowed them to accurately and reproductibly guide needle-like electrodes for neurophysiological experiments. They have experimented animals and were able to contribute to the mapping of the cerebellum. Improved versions of the  Horsley–Clarke apparatus  are still in used today in experimental neurosurgery. [ citation needed ]


The first stereotactic device for humans was also developed in neurosurgery, by E. Spiegel and H. Wycis in 1947. [ 2 ]  It was used for surgical treatment of  Parkinson's disease  and, during time, its applicability was extended for the surgical treatment of tumors, vascular malformations, functional neurosurgery etc. The system was based both on headframes and X-ray images taken for all three planes of space.


Further development of stereotactic surgery was made by Brown, Roberts and Wells in 1980. [ 3 ]  They have developed a halo ring that was applied on the skull, during a  CT  scan and neurosurgical interventions. This method provided improved surgical guidance and was in fact the first development of computer guided surgery.


Patient registration for the head area has developed for nearly two decades on the same principle of combining CT scans with mechanical reference devices such as headframes or halo rings. But the clinical experience showed that headgear is very uncomfortable to wear and even impossible to apply on little children, because their lack of cooperation; furthermore, the headframes can create  artifacts  in preoperative data gathering, or during surgery. [ citation needed ]


In 1986, a different approach was developed by Roberts und Strohbehn. [ 4 ]  They have used as landmarks several markers on the patient's skin both preoperative CT registration, and intraoperatively. This was a new current of the time in patient registration. Still, the method is time-consuming, and the exact reproducitibility of the marker positions is questionable.


The bony structures can provide a much better stability and reproducibility of the landmarks for patient registration. Based on this concept, a further technique was used: to implant temporary markers into bone structures that are superficial to the skin, under local anestesia. [ 5 ]  This was also combined with surface markers and CT registration. [ 6 ]  The technique has the disadvantage of a further minimal surgical procedure of placing the bone implants, with some risk of infection for the patient.


Dental splints have been traditionally used for transferring and reproducing 3D reference landmarks for positioning cast models in  articulators  – in  dental prosthetics ,  orthodontics  and orthognathic surgery. By applying several infrared markers on the splints and using an infrared camera, a better registration was obtained. [ 7 ]


The first attempts, based on the identification of anatomical landmarks were made by Caversaccio and Zulliger. [ 8 ]  The method was based on identifying certain antropometrical points and other anatomical landmarks on the skull, in correlation with the CT registration. But the landmarks cannot be exactly pointed out and reproduced during patient dataset registration and surgery, therefore the method is not precise enough.


Since 1998, new procedures have been developed by Marmulla and co-workers, using a different approach to the problem. [ 9 ] [ 10 ]  Both during CT dataset gathering and surgical intervention, the patient registration was made by registering complete areas and surfaces, instead of distinctive surface markers. This was achieved by using laser scanners and a small guiding transmitter. The precision of the patient registration was significantly improved with this method.


Based on this concept, several registration and navigation systems were built by the same team. The  Surgical Segment Navigator (SSN and SSN++)  is such a system, developed for the first time for  oral and maxillofacial surgery . This system correlates three different coordinate sets: CT data set, surface laser scan data set and the dataset produced by a small guiding transmitter, placed on the patient's head. The Laboratory Unit for Computer-Assisted Surgery (LUCAS) is used for planning surgery in the laboratory. This technological and surgical advance has permitted the elimination of mechanical guidance systems and improved the accuracy of the determinations, and thus the surgical act.


A research group at  Ryerson University (now Toronto Metropolitan University)  developed a method to use optical topographical imaging (OTI) to create a 3D model of the surface of open surgical sites and perform surface registration to  CT  and  MRI  data sets for  neurosurgical   navigation . [ 11 ] [ 12 ]  The OTI technology is being licensed by  7D Surgical  for their navigation platform. [ 12 ]


A  perforated eardrum  ( tympanic membrane perforation ) is a prick in the  eardrum . It can be caused by  infection  ( otitis media ),  trauma ,  overpressure  (loud  noise ), inappropriate  ear clearing , and changes in middle ear pressure. An  otoscope  can be used to view the eardrum to diagnose a perforation. Perforations may heal naturally or require surgery.


A perforated eardrum leads to  conductive hearing loss , which is usually temporary. Other symptoms may include  tinnitus ,  ear pain ,  vertigo , or a discharge of  mucus . [ 1 ]   Nausea  and/or  vomiting  secondary to vertigo may occur. [ 2 ]


A perforated eardrum can have one of many causes, such as:


An  otoscope  can be used to look at the  ear canal . This gives a view of the  ear canal  and  eardrum , so that a perforated eardrum can be seen.  Tympanometry  may also be used. [ 6 ]


A perforated eardrum often heals naturally. [ 2 ] [ 7 ]  It may heal in a few weeks or may take up to a few months. [ 2 ]


Some perforations require surgical intervention. [ 3 ]  This may take the form of a paper patch to promote healing (a simple procedure by an  ear, nose and throat specialist ), or surgery ( tympanoplasty ). [ 2 ]  However, in some cases, the perforation can last several years and will be unable to heal naturally. For patients with persistent perforation, surgery is usually undertaken to close the perforation. The objective of the surgery is to provide a platform of sort to support the regrowth and healing of the tympanic membrane in the two weeks post-surgery period. There are two ways of doing the surgery:


The success of surgery is variable based on the cause of perforation and the technique being used. Predictors of success include traumatic perforation, dry ear, and central perforations. Predictors of failure includes young age and poor Eustachian tube function. [ 9 ]   The use of minimally invasive endoscopic technique does not reduce the chance of successful outcome. [ 10 ]  Hearing is usually recovered fully, but chronic infection over a long period may lead to permanent hearing loss. Those with more severe ruptures may need to wear an  ear plug  to prevent water contact with the ear drum.


Periodic fever, aphthous stomatitis, pharyngitis and adenitis  syndrome is a medical condition, typically occurring in young children, in which high  fever  occurs periodically at intervals of about 3–5 weeks, frequently accompanied by  aphthous-like ulcers ,  pharyngitis  and cervical adenitis ( cervical lymphadenopathy ). The syndrome was described in 1987 and named two years later. [ 1 ] [ 2 ] [ 3 ]


The key symptoms of PFAPA are those in its name: periodic high  fever  at intervals of about 3–5 weeks, as well as  aphthous ulcers ,  pharyngitis  and  adenitis . In between episodes, and even during the episodes, the children appear healthy. At least 6 months of episodes. Diagnosis requires recurrent negative throat cultures and that other causes (such as  EBV ,  CMV ,  FMF ) be excluded. [ 3 ]


The cause of PFAPA is unknown. [ 4 ]  It is frequently discussed together with other  periodic fever syndromes . [ 3 ]


Possible causes include primarily  genetic  factors or it may be due to an initial  infection .


The condition appears to be the result of a disturbance of innate immunity. [ 5 ]  The changes in the immune system are complex and include increased expression of complement related genes ( C1QB ,  C2 ,  SERPING1 ), interleukin-1-related genes ( interleukin-1β ,  interleukin 1 RN ,  CASP1 ,  interleukin 18 RAP ) and  interferon  induced ( AIM2 , IP-10/ CXCL10 ) genes.  T cell  associated  genes  ( CD3 ,  CD8B ) are down regulated. Flares are accompanied by increased serum levels of activated T lymphocyte chemokines (IP-10/CXCL10, MIG/ CXCL9 ),  G-CSF  and proinflammatory  cytokines  ( interleukin 6 ,  interleukin 18 ). Flares also manifest with a relative  lymphopenia . Activated  CD4 + / CD25 +  T-lymphocyte counts correlated negatively with serum concentrations of IP-10/CXCL10, whereas CD4 + / HLA-DR +  T lymphocyte counts correlated positively with serum concentrations of the counterregulatory IL-1 receptor antagonist. [ citation needed ]


PFAPA syndrome typically resolves spontaneously. Treatment options are used to lessen the severity of episodes. [ 6 ]  These treatments are either medical or surgical:


One treatment often used is a dose of a  corticosteroid  at the beginning of each fever episode. [ 4 ]  A single dose usually ends the fever within several hours. [ 4 ]  However, in some children, they can cause the fever episodes to occur more frequently. [ 4 ]   Interleukin-1  inhibition appears to be effective in treating this condition. [ 5 ]


There has been some evidence for the use of medications to reduce the frequency of flare-ups, including  colchicine  and  cimetidine . [ 7 ]


Surgical removal of the tonsils appears to be beneficial compared to no surgery in symptom resolution and number of future episodes. [ 6 ]  The evidence to support surgery is; however, of moderate quality. [ 6 ]


Children with PFAPA have an impaired quality of life, which may be treated via individual  counseling . [ 8 ]


According to present research, PFAPA does not lead to other diseases and spontaneously resolves as the child gets older, with no long term physical effects. [ 2 ]
 [ 9 ]
 [ 10 ]
However, PFAPA has been found in adults and may not spontaneously resolve. [ 11 ] [ non-primary source needed ]  Children with PFAPA experience lower physical, emotional, and psychosocial functioning. [ 8 ]  Their performance in school is also substantially impacted. [ 8 ]


A  peritonsillar abscess  ( PTA ), also known as a  quinsy , is an accumulation of  pus  due to an  infection  behind the  tonsil . [ 2 ]  Symptoms include  fever , throat pain,  trouble opening the mouth , and a change to the voice. [ 1 ]  Pain is usually worse on one side. [ 1 ]  Complications may include blockage of the airway or  aspiration pneumonitis . [ 1 ]


PTA is typically due to infection by a number of types of  bacteria . [ 1 ]  Often it follows  streptococcal pharyngitis . [ 1 ]  They do not typically occur in those who have had a  tonsillectomy . [ 1 ]  Diagnosis is usually based on the symptoms. [ 1 ]   Medical imaging  may be done to rule out complications. [ 1 ]


Treatment is by removing the pus,  antibiotics , sufficient fluids, and  pain medication . [ 1 ]   Steroids  may also be useful. [ 1 ]  Admission to hospital is generally not needed. [ 1 ]  In the United States about 3 per 10,000 people per year are affected. [ 1 ]  Young adults are most commonly affected. [ 1 ]


Physical signs of a peritonsillar abscess include  redness  and  swelling  in the tonsillar area of the affected side and swelling of the  jugulodigastric lymph nodes . The  uvula  may be displaced towards the unaffected side. [ 3 ]


Unlike  tonsillitis , which is more common in children, PTA has a more even age spread, from children to adults. Symptoms start appearing two to eight days before the formation of an  abscess . A progressively severe sore throat on one side and pain during swallowing ( odynophagia ) usually are the earliest symptoms. As the abscess develops, persistent pain in the peritonsillar area,  fever ,  a general sense of feeling unwell , headache, and a distortion of vowels informally known as "hot potato voice" may appear. Neck pain associated with  tender, swollen lymph nodes , referred ear pain and  foul breath  are also common. While these signs may be present in tonsillitis itself, a PTA should be specifically considered if there is limited ability to open the mouth ( trismus ). [ 3 ]


While most people recover uneventfully, there is a wide range of possible complications. [ 4 ]  These may include: [ 1 ]


Difficulty swallowing can lead to decreased oral intake and  dehydration .


PTA usually arises as a complication of an untreated or partially treated episode of acute tonsillitis. The infection, in these cases, spreads to the peritonsillar area (peritonsillitis).  This region comprises loose connective tissue and is hence susceptible to formation of an abscess.  PTA can also occur  de novo . Both aerobic and anaerobic bacteria can be causative. Commonly involved aerobic pathogens include  Streptococcus ,  Staphylococcus  and  Haemophilus . The most common anaerobic species include  Fusobacterium necrophorum ,    Peptostreptococcus ,  Prevotella species , and  Bacteroides . [ 5 ] [ 6 ] [ 7 ] [ 8 ] [ 9 ] [ 10 ]


Diagnosis is usually based on the symptoms. [ 1 ]   Medical imaging  may be done to rule out complications. [ 1 ]  Medical imaging may include  CT scan ,  MRI , or  ultrasound  is also useful in diagnosis. [ 1 ]


Medical treatment with antibiotics, volume repletion with fluids, and pain medication is usually adequate, although in cases where airway obstruction or systemic sepsis occurs, surgical drainage may be necessary. [ 1 ] [ 11 ]   Corticosteroids  may also be useful. [ 1 ]  Admission to hospital is generally not needed. [ 1 ]


The infection is frequently penicillin resistant. [ 1 ]  There are a number of antibiotics options including  amoxicillin/clavulanate ,  ampicillin/sulbactam ,  clindamycin , or  metronidazole  in combination with  benzylpenicillin  (penicillin G) or  penicillin V . [ 1 ] [ 12 ]   Piperacillin/tazobactam  may also be used. [ 1 ]


The pus can be removed by a number of methods including  needle aspiration ,  incision and drainage , and  tonsillectomy . [ 1 ]  Incision and drainage may be associated with a lower chance of recurrence than needle aspiration but the evidence is very uncertain. Needle aspiration may be less painful but again the evidence is very uncertain. [ 13 ]


Treatment can also be given while a patient is under anesthesia, but this is usually reserved for children or anxious patients.  Tonsillectomy  can be indicated if a patient has recurring peritonsillar abscesses or a history of tonsillitis. For patients with their first peritonsillar abscess most ENT-surgeons prefer to "wait and observe" before recommending tonsillectomy. [ 14 ]


It is a commonly encountered  otorhinolaryngological (ENT)  emergency. [ 14 ]


The number of new cases per year of peritonsillar abscess in the  United States  has been estimated approximately at 30 cases per 100,000 people. [ 15 ]  In a study in  Northern Ireland , the number of new cases was 10 cases per 100,000 people per year. [ 16 ]
In  Denmark , the number of new cases is higher and reaches 41 cases per 100,000 people per year. [ 17 ]  Younger children who develop a peritonsillar abscess are often immunocompromised and in them, the infection can cause airway obstruction. [ 18 ]


The condition is often referred to as "quincy", "quinsy", [ 19 ]  or "quinsey", anglicised versions of the French word  esquinancie  which was originally rendered as squinsey and subsequently quinsy. [ 20 ]


The ancient Roman goddess  Angerona  was claimed to cure quinsy (Latin  angina ) in humans and sheep. [ 26 ] [ 27 ]


The  petrous part  of the  temporal bone  is pyramid-shaped and is wedged in at the base of the  skull  between the  sphenoid  and  occipital bones . Directed medially, forward, and a little upward, it presents a base, an apex, three surfaces, and three angles, and houses in its interior the components of the  inner ear . The petrous portion is among the most basal elements of the skull and forms part of the  endocranium . Petrous comes from the Latin word  petrosus , meaning "stone-like, hard". It is one of the densest bones in the body. In other mammals, it is a separate bone, the  petrosal bone .


The petrous bone is important for studies of ancient DNA from skeletal remains, as it tends to contain extremely well-preserved DNA.


The base is fused with the internal surfaces of the  squamous ,  tympanic , and  mastoid parts . [ 1 ]


The apex, which is rough and uneven, is received into the angular interval between the posterior border of the  great wing  of the  sphenoid bone  and the  basilar part  of the  occipital bone ; it presents the anterior or internal opening of the  carotid canal , and forms the postero-lateral boundary of the  foramen lacerum .


The anterior surface forms the posterior part of the  middle cranial fossa  of the base of the skull, and is continuous with the inner surface of the squamous portion, to which it is united by the  petrosquamous suture , remains of which are distinct even at a late period of life. It is marked by depressions for the convolutions of the brain, and presents six notable points:


The  posterior surface  forms the anterior part of the  posterior cranial fossa  of the base of the skull, and is continuous with the inner surface of the mastoid portion.


Near the center is a large orifice, the  internal acoustic opening , the size of which varies considerably; its margins are smooth and rounded, and it leads into the  internal auditory meatus  a short canal, about 1 cm. in length, which runs lateralward. It transmits the facial and acoustic nerves and the internal auditory branch of the  basilar artery .


The lateral end of the canal is closed by a vertical plate, which is divided by a horizontal crest, the  falciform crest , into two unequal portions.


Each portion is further subdivided by a vertical ridge into an anterior and a posterior part.


Behind the internal acoustic meatus is a small slit almost hidden by a thin plate of bone, leading to a canal, the aquæductus vestibuli, which transmits the ductus endolymphaticus together with a small artery and vein.


Above and between these two openings is an irregular depression that lodges a process of the dura mater and transmits a small vein; in the infant, this depression is represented by a large fossa, the  subarcuate fossa , which extends backward as a blind tunnel under the  superior semicircular canal .


The  inferior surface  is rough and irregular, and forms part of the exterior of the base of the skull. It presents eleven points for examination:


The  superior angle , the longest, is grooved for the  superior petrosal sinus , and gives attachment to the  tentorium cerebelli ; at its medial extremity is a notch, in which the  trigeminal nerve  lies.


The  posterior angle  is intermediate in length between the superior and the anterior. Its medial half is marked by a sulcus, which forms, with a corresponding sulcus on the occipital bone, the channel for the inferior petrosal sinus. Its lateral half presents an excavation — the jugular fossa — which, with the jugular notch on the occipital, forms the jugular foramen; an eminence occasionally projects from the center of the fossa, and divides the foramen into two.


The  anterior angle  is divided into two parts—a lateral joined to the squamous part by a suture (petrosquamous), the remains of which are more or less distinct; a medial, free, which articulates with the spinous process of the sphenoid.


At the angle of junction of the petrous and the squamous parts are two canals, one above the other, and separated by a thin plate of bone, the septum canalis musculotubarii; both canals lead into the tympanic cavity.


In ancient DNA studies, scientists extract and sequence DNA from ancient skeletal remains of humans and other species. In many cases the DNA is highly degraded, and contaminated by DNA from soil microbes. In 2015 it was found that the petrous bone has remarkably well-preserved DNA. [ 2 ]  A 2017 study [ 3 ]  comparing DNA from different skeletal sites concluded that "The inner part of petrous bones and the cementum layer in teeth roots are currently recognized as the best substrates for (ancient DNA) research ... Both substrates display significantly higher endogenous DNA content (average of 16.4% and 40.0% for teeth and petrous bones, respectively) than parietal skull bone (average of 2.2%)."


Consequently, petrous bones are now the most widely-used skeletal site for the study of ancient DNA.


This article incorporates text in the  public domain  from  page 142  of the 20th edition of   Gray's Anatomy   (1918)


The  pharyngeal arches , also known as  visceral arches ,  are transient structures seen in the  embryonic development  of  humans  and other  vertebrates , that are recognisable precursors for many structures. [ 1 ]  In  fish , the arches support the  gills  and are known as the  branchial arches , or gill arches.


In the  human embryo , the arches are first seen during the fourth week of  development . They appear as a series of outpouchings of  mesoderm  on both sides of the developing  pharynx . The  vasculature  of the pharyngeal arches are the  aortic arches  that arise from the  aortic sac .


In  humans  and other  vertebrates , the pharyngeal arches are derived from all three  germ layers  (the primary layers of cells that form during  embryonic development ). [ 2 ]   Neural crest cells  enter these arches where they contribute to features of the  skull  and  facial skeleton  such as bone and cartilage. [ 2 ]  However, the existence of pharyngeal structures before neural crest cells evolved is indicated by the existence of neural crest-independent mechanisms of pharyngeal arch development. [ 3 ]  The first, most anterior  pharyngeal arch  gives rise to the  mandible .  The second arch becomes the  hyoid  and jaw support. [ 2 ]   In fish, the other posterior arches contribute to the branchial skeleton, which support the gills; in tetrapods the anterior arches develop into components of the ear, tonsils, and thymus. [ 4 ]  The genetic and developmental basis of pharyngeal arch development is well characterized.  It has been shown that  Hox genes  and other developmental genes such as  DLX  are important for patterning the anterior/posterior and dorsal/ventral axes of the  branchial arches . [ 5 ]  Some fish species have a second set of jaws in their throat, known as  pharyngeal jaws , which develop using the same genetic pathways involved in oral jaw formation. [ 6 ]


During  embryonic development , a series of pharyngeal arch pairs form. These project forward from the back of the embryo toward the front of the face and neck. Each arch develops its own artery, nerve that controls a distinct muscle group, and skeletal tissue. The arches are numbered from 1 to 6, with 1 being the arch closest to the head of the embryo, and arch 5 existing only transiently. [ 7 ]


These grow and join in the ventral midline. The first arch, as the first to form, separates the mouth pit or  stomodeum  from the  pericardium .  By differential growth the neck elongates and new arches form, so the pharynx has six arches ultimately.


Each pharyngeal arch has a  cartilaginous  stick, a  muscle  component that differentiates from the cartilaginous tissue, an artery, and a  cranial nerve . Each of these is surrounded by  mesenchyme . Arches do not develop simultaneously but instead possess a "staggered" development.


Pharyngeal pouches  form on the  endodermal  side between the arches, and  pharyngeal grooves  (or clefts) form from the lateral  ectodermal  surface of the  neck  region to separate the arches. [ 8 ]  In fish, the pouches line up with the clefts, and these thin segments become  gills . In mammals the  endoderm  and  ectoderm  not only remain intact but also continue to be separated by a  mesoderm  layer.


The development of the pharyngeal arches provides a useful landmark with which to establish the precise stage of embryonic development.  Their formation and development corresponds to  Carnegie stages  10 to 16 in  mammals , and  Hamburger–Hamilton stages  14 to 28 in the  chicken . Although there are six pharyngeal arches, in humans the fifth arch exists only transiently during  embryogenesis . [ 9 ]


The  first pharyngeal arch , also  mandibular arch  (corresponding to the first branchial arch of fish), is the first of six pharyngeal arches that develops during the fourth week of  development . [ 10 ]   It is located between the  stomodeum  and the  first pharyngeal groove .


This arch divides into a  maxillary process  and a  mandibular process , giving rise to structures including the  bones  of the lower two-thirds of the face and the jaw.  The maxillary process becomes the  maxilla  (or  upper jaw , although there are large differences among animals [ 11 ] ), and  palate  while the mandibular process becomes the  mandible  or  lower jaw . This arch also gives rise to the  muscles of mastication .


Meckel's cartilage  forms in the  mesoderm  of the mandibular process and eventually regresses to form the  incus  and  malleus  of the  middle ear , the anterior ligament of the malleus and the  sphenomandibular ligament . The  mandible  or lower jaw forms by perichondral  ossification  using Meckel's cartilage as a 'template', but the maxillary does  not  arise from direct ossification of Meckel's cartilage.


The skeletal elements and muscles are derived from mesoderm of the pharyngeal arches.


Skeletal


Muscles


Other


Mucous membrane  and glands of the  anterior two thirds of the tongue  are derived from  ectoderm  and  endoderm  of the arch.


The mandibular and maxillary branches of the  trigeminal nerve  ( CN V ) innervate the structures derived from the corresponding processes of the first arch. In some lower animals, each arch is supplied by two cranial nerves. The nerve of the arch itself runs along the cranial side of the arch and is called post-trematic nerve of the arch. Each arch also receives a branch from the nerve of the succeeding arch called the pre-trematic nerve which runs along the caudal border of the arch. In human embryo, a double innervation is seen only in the first pharyngeal arch. The mandibular nerve is the post-trematic nerve of the first arch and  chorda tympani  (branch of facial nerve) is the pre-trematic nerve. This double innervation is reflected in the nerve supply of anterior two-thirds of  tongue  which is derived from the first arch. [ 12 ]


The artery of the first arch is the first  aortic arch , [ 13 ]  which partially persists as the  maxillary artery .


The  second pharyngeal arch  or  hyoid arch , is the second of fifth pharyngeal arches that develops in  fetal life  during the fourth week of development [ 10 ]  and assists in forming the side and front of the  neck .


Cartilage in the second pharyngeal arch is referred to as Reichert's cartilage and contributes to many structures in the fully developed adult. [ 14 ]  In contrast to the  Meckel's cartilage  of the  first pharyngeal arch  it does not constitute a continuous element, and instead is composed of two distinct cartilaginous segments joined by a faint layer of  mesenchyme . [ 15 ]   Dorsal ends of Reichert's cartilage  ossify  during development to form the  stapes  of the  middle ear  before being incorporated into the middle ear cavity, while the ventral portion ossifies to form the lesser cornu and upper part of the body of the  hyoid bone . Caudal to what will eventually become the  stapes , Reichert's cartilage also forms the  styloid process  of the  temporal bone . The cartilage between the  hyoid bone  and  styloid process  will not remain as development continues, but its  perichondrium  will eventually form the  stylohyoid ligament .


From the cartilage of the second arch arises


Facial nerve  (CN VII)


The artery of the second arch is the second  aortic arch , [ 13 ]  which gives origin to the  stapedial artery  in some mammals but atrophies in most humans.


Pharyngeal muscles or Branchial muscles  are  striated muscles  of the head and neck. Unlike  skeletal muscles  that developmentally come from  somites , pharyngeal muscles are developmentally formed from the pharyngeal arches.


Most of the skeletal musculature supplied by the cranial nerves ( special visceral efferent ) is pharyngeal. Exceptions include, but are not limited to, the  extraocular muscles  and some of the muscles of the tongue. These exceptions receive  general somatic efferent  innervation.


All of the  pharyngeal muscles  that come from the first pharyngeal arch are innervated by the mandibular divisions of the  trigeminal nerve . [ 16 ]   These muscles include all the  muscles of mastication , the anterior belly of the  digastric , the  mylohyoid ,  tensor tympani , and  tensor veli palatini .


All of the pharyngeal muscles of the second pharyngeal arch are innervated by the  facial nerve .  These muscles include the  muscles of facial expression , the posterior belly of the  digastric , the  stylohyoid  muscle, the auricular muscle [ 16 ]  and the  stapedius  muscle of the middle ear.


There is only one muscle of the third pharyngeal arch, the  stylopharyngeus . The stylopharyngeus and other structures from the third pharyngeal arch are all innervated by the  glossopharyngeal nerve .


All the pharyngeal muscles of the fourth and sixth arches are innervated by the superior laryngeal and the recurrent laryngeal branches of the  vagus nerve . [ 16 ]  These muscles include all the muscles of the palate (exception of the  tensor veli palatini  which is innervated by the  trigeminal nerve ), all the muscles of the pharynx (except  stylopharyngeus  which is innervated by the  glossopharyngeal nerve ), and all the muscles of the larynx.


It has been proposed that the five arches in amniotes numbered 1–4 and 6, be re-named as simply 1–5. [ 17 ]  The fifth arch is seen to be a transient structure and becomes the sixth arch, (the fifth being absent). More is known about the fate of the first arch than the remaining four. The first three contribute to structures above the larynx, whereas the last two contribute to the  larynx  and  trachea .


The  recurrent laryngeal nerves  are produced from the nerve of arch 5, and the laryngeal cartilages from arches 4 and 5. The superior laryngeal branch of the vagus nerve arises from arch 4. Its arteries, which project between the nerves of the fourth and fifth arches, become the left-side arch of the aorta and the right  subclavian artery . On the right side, the artery of arch 5 is obliterated while, on the left side, the artery persists as the  ductus arteriosus ; circulatory changes immediately following birth cause the vessel to close down, leaving a remnant, the  ligamentum arteriosum . During growth, these arteries descend into their ultimate positions in the chest, creating the elongated recurrent paths. [ 7 ]


Left 4th aortic arch:  aortic arch


Left 5th aortic arch:  pulmonary artery  and  ductus arteriosus


It has been proposed that the arches be re-named simply as 1–5. The argument is the existence of the fifth arch (and pouch), held to be a transient structure in the embryo. [ 17 ] [ 23 ]


Pharyngitis  is  inflammation  of the back of the  throat , known as the  pharynx . [ 2 ]  It typically results in a  sore throat  and  fever . [ 2 ]  Other symptoms may include a  runny nose ,  cough ,  headache , difficulty swallowing, swollen  lymph nodes , and a  hoarse voice . [ 1 ] [ 6 ]  Symptoms usually last 3–5 days, but can be longer depending on cause. [ 2 ] [ 3 ]  Complications can include  sinusitis  and  acute otitis media . [ 2 ]  Pharyngitis is a type of  upper respiratory tract infection . [ 7 ]


Most cases are caused by a  viral infection . [ 2 ]   Strep throat , a  bacterial infection , is the cause in about 25% of children and 10% of adults. [ 2 ]  Uncommon causes include other bacteria such as  gonococcus ,  fungi , irritants such as  smoke ,  allergies , and  gastroesophageal reflux disease . [ 2 ] [ 4 ]  Specific testing is not recommended in people who have clear symptoms of a viral infection, such as a  cold . [ 2 ]  Otherwise, a  rapid antigen detection test  or  throat swab  is recommended. [ 2 ]   PCR  testing has become common as it is as good as taking a throat swab but gives a faster result. [ 8 ]  Other conditions that can produce similar symptoms include  epiglottitis ,  thyroiditis ,  retropharyngeal abscess , and occasionally  heart disease . [ 2 ]


NSAIDs , such as  ibuprofen , can be used to help with the pain. [ 2 ]  Numbing medication, such as topical  lidocaine , may also help. [ 4 ]  Strep throat is typically treated with  antibiotics , such as either  penicillin  or  amoxicillin . [ 2 ]  It is unclear whether  steroids  are useful in acute pharyngitis, other than possibly in severe cases, but a recent (2020) review found that when used in combination with antibiotics they moderately reduced pain and the likelihood of resolution. [ 9 ] [ 10 ]


About 7.5% of people have a sore throat in any 3-month period. [ 5 ]  Two or three episodes in a year are not uncommon. [ 1 ]  This resulted in 15 million physician visits in the United States in 2007. [ 4 ]  Pharyngitis is the most common cause of a sore throat. [ 11 ]  The word comes from the  Greek word   pharynx  meaning "throat" and the suffix  -itis  meaning "inflammation". [ 12 ] [ 13 ]


Pharyngitis is a type of inflammation caused by an  upper respiratory tract infection . It may be classified as acute or chronic. Acute pharyngitis may be  catarrhal ,  purulent , or  ulcerative , depending on the  causative agent  and the  immune capacity  of the affected individual. Chronic pharyngitis may be catarrhal,  hypertrophic , or  atrophic . [ citation needed ]


Tonsillitis  is a subtype of pharyngitis. [ 14 ]  If the inflammation includes both the  tonsils  and other parts of the throat, it may be called  pharyngotonsillitis  or  tonsillopharyngitis . [ 15 ]  Another subclassification is  nasopharyngitis  (the common cold). [ 16 ]


Clergyman's sore throat  or  clergyman's throat  is an archaic term formerly used for chronic pharyngitis associated with overuse of the voice as in public speaking. It was sometimes called  dysphonia clericorum  or chronic  folliculitis  sore throat. [ 17 ]


Most cases are due to an  infectious organism  acquired from close contact with an infected individual. [ citation needed ]


These comprise about 40–80% of all infectious cases and can be a feature of many different types of viral infections. [ 11 ] [ 18 ]


A number of different bacteria can infect the human throat. The most common is  group A streptococcus  ( Streptococcus pyogenes ), but others include  Streptococcus pneumoniae ,  Haemophilus influenzae ,  Bordetella pertussis ,  Bacillus anthracis ,  Corynebacterium diphtheriae ,  Neisseria gonorrhoeae ,  Chlamydophila pneumoniae ,  Mycoplasma pneumoniae ,  and  Fusobacterium necrophorum . [ 19 ]


Streptococcal pharyngitis or strep throat is caused by a  group A beta-hemolytic streptococcus  (GAS). [ 20 ]  It is the most common bacterial cause of cases of pharyngitis (15–30%). [ 19 ]  Common symptoms include  fever ,  sore throat , and large lymph nodes. It is a contagious infection, spread by close contact with an infected individual. A definitive diagnosis is made based on the results of a  throat culture .  Antibiotics  are useful to both prevent complications (such as  rheumatic fever ) and speed recovery. [ 21 ]


Fusobacterium necrophorum  is a normal inhabitant of the oropharyngeal  flora  and can occasionally create a  peritonsillar abscess . In one out of 400 untreated cases,  Lemierre's syndrome  occurs. [ 22 ]


Diphtheria  is a potentially life-threatening upper respiratory infection caused by  Corynebacterium diphtheriae , which has been largely eradicated in developed nations since the introduction of childhood  vaccination  programs, but is still reported in the  Third World  and increasingly in some areas in  Eastern Europe . Antibiotics are effective in the early stages, but recovery is generally slow. [ citation needed ]


A few other causes are rare, but possibly fatal, and include  parapharyngeal space  infections:  peritonsillar abscess  ("quinsy abscess"),  submandibular space infection  (Ludwig's angina), and  epiglottitis . [ 23 ] [ 24 ] [ 25 ]


Some cases of pharyngitis are caused by  fungal infection , such as  Candida albicans , causing  oral thrush . [ 26 ]


Pharyngitis may also be caused by mechanical, chemical, or thermal irritation, for example cold air or  acid reflux . Some medications may produce pharyngitis, such as  pramipexole  and  antipsychotics . [ 27 ] [ 28 ]


Differentiating a viral and a bacterial cause of a sore throat based on symptoms alone is difficult. [ 29 ]  Thus, a throat swab often is done to rule out a bacterial cause. [ 30 ]


The modified  Centor criteria  may be used to determine the management of people with pharyngitis. Based on five clinical criteria, it indicates the probability of a streptococcal infection. [ 21 ]


One point is given for each of the criteria: [ 21 ]


The  Infectious Disease Society of America  recommends against  empirical treatment  and considers antibiotics only appropriate following positive testing. [ 29 ]  Testing is not needed in children under three, as both group A strep and  rheumatic fever  are rare, except if they have a sibling with the disease. [ 29 ]


The majority of the time, treatment is symptomatic. Specific treatments are effective for bacterial, fungal, and  herpes simplex  infections.


Gargling  salt water  is often suggested, but there is no evidence to support or discourage this practice. [ 4 ]   Alternative medicines  are promoted and used for the treatment of sore throats. [ 37 ]  However, they are poorly supported by evidence. [ 37 ]


Acute pharyngitis is the most common cause of a  sore throat  and, together with cough, it is diagnosed in more than 1.9 million people a year in the United States. [ 11 ]


The  pharynx  ( pl. :  pharynges ) is the part of the  throat  behind the  mouth  and  nasal cavity , and above the  esophagus  and  trachea  (the tubes going down to the  stomach  and the  lungs  respectively). It is found in vertebrates and invertebrates, though its structure varies across species. The pharynx carries food to the esophagus and air to the  larynx . The flap of cartilage called the  epiglottis  stops food from entering the larynx.


In humans, the pharynx is part of the  digestive system  and the  conducting zone  of the  respiratory system . (The conducting zone—which also includes the  nostrils  of the  nose , the  larynx ,  trachea ,  bronchi , and  bronchioles —filters, warms and moistens air and conducts it into the  lungs ). [ 1 ]  The human pharynx is conventionally divided into three sections: the  nasopharynx ,  oropharynx , and  laryngopharynx .


In humans, two sets of  pharyngeal muscles  form the pharynx and determine the shape of its  lumen . They are arranged as an inner layer of longitudinal muscles and an outer circular layer.


The upper portion of the pharynx, the nasopharynx, extends from the base of the  skull  to the upper surface of the  soft palate . [ 2 ]  It includes the space between the  internal nares  and the soft palate and lies above the oral cavity. The  adenoids , also known as the pharyngeal tonsils, are  lymphoid tissue  structures located in the posterior wall of the nasopharynx.  Waldeyer's tonsillar ring  is an annular arrangement of lymphoid tissue in both the nasopharynx and oropharynx. The nasopharynx is lined by  respiratory epithelium  that is pseudostratified, columnar, and ciliated.


Polyps  or  mucus  can obstruct the nasopharynx, as can congestion due to an upper respiratory infection. The  auditory tube , which connects the middle ear to the pharynx, opens into the nasopharynx at the pharyngeal opening of the auditory tube. The opening and closing of the auditory tubes serves to equalize the barometric pressure in the middle ear with that of the ambient atmosphere.


The anterior aspect of the nasopharynx communicates through the  choanae  with the nasal cavities. On its lateral wall is the  pharyngeal opening of the auditory tube , somewhat triangular in shape and bounded behind by a firm prominence, the  torus tubarius  or cushion, caused by the medial end of the cartilage of the tube that elevates the  mucous membrane .
Two folds arise from the cartilaginous opening:


The oropharynx lies behind the oral cavity, extending from the  uvula  to the level of the  hyoid bone . It opens anteriorly, through the  isthmus faucium , into the mouth, while in its lateral wall, between the  palatoglossal arch  and the  palatopharyngeal arch , is the  palatine tonsil . [ 4 ]  The anterior wall consists of the base of the tongue and the  epiglottic vallecula ; the lateral wall is made up of the tonsil, tonsillar fossa, and tonsillar (faucial) pillars; the superior wall consists of the inferior surface of the soft palate and the uvula. Because both food and air pass through the pharynx, a flap of connective tissue called the  epiglottis  closes over the  glottis  when food is swallowed to prevent  aspiration . The oropharynx is lined by non-keratinized squamous stratified epithelium.


The  HACEK  organisms ( H aemophilus ,  A ctinobacillus actinomycetemcomitans ,  C ardiobacterium hominis ,  E ikenella corrodens ,  K ingella ) are part of the normal oropharyngeal flora, which grow slowly, prefer a carbon dioxide-enriched atmosphere, and share an enhanced capacity to produce  endocardial  infections, especially in young children. [ 5 ]   Fusobacterium  is a pathogen. [ 6 ]


The laryngopharynx, ( Latin :  pars laryngea pharyngis ), also known as  hypopharynx , is the  caudal  part of the pharynx; it is the part of the throat that connects to the esophagus. It lies inferior to the epiglottis and extends to the location where this common pathway diverges into the respiratory ( laryngeal ) and digestive ( esophageal ) pathways. At that point, the laryngopharynx is continuous with the esophagus posteriorly. The esophagus conducts food and fluids to the stomach; air enters the larynx anteriorly. During swallowing, food has the "right of way", and air passage temporarily stops. Corresponding roughly to the area located between the 4th and 6th  cervical vertebrae , the superior boundary of the laryngopharynx is at the level of the  hyoid bone . The laryngopharynx includes three major sites: the  pyriform sinus , postcricoid area, and the posterior pharyngeal wall. Like the oropharynx above it, the laryngopharynx serves as a passageway for food and air and is lined with a  stratified squamous epithelium . It is innervated by the  pharyngeal plexus  and by the  recurrent laryngeal nerve .


The vascular supply to the laryngopharynx includes the  superior thyroid artery , the  lingual artery  and the  ascending pharyngeal artery . The primary neural supply is from both the  vagus  and  glossopharyngeal  nerves. The vagus nerve provides an  auricular branch  also termed "Arnold's nerve" which also supplies the external auditory canal, thus laryngopharyngeal cancer can result in referred  ear pain . This nerve is also responsible for the  ear-cough reflex  in which stimulation of the ear canal results in a person coughing.


The pharynx moves food from the mouth to the esophagus. It also moves air from the  nasal  and  oral  cavities to the  larynx . It is also used in human speech, as  pharyngeal consonants  are articulated here, and it acts as a  resonating chamber  during phonation.


Inflammation of the pharynx, or  pharyngitis , is the painful inflammation of the throat.


Pharyngeal cancer  is a cancer that originates in the neck and/or throat.


Waldeyer's tonsillar ring  is an anatomical term collectively describing the annular arrangement of lymphoid tissue in the pharynx. Waldeyer's ring circumscribes the naso- and oropharynx, with some of its tonsillar tissue located above and some below the soft palate (and to the back of the oral cavity). It is believed that Waldeyer's ring prevents the invasion of microorganisms from going into the air and food passages and this helps in the defense mechanism of the respiratory and alimentary systems. [ 7 ]


The word  pharynx  ( / ˈ f ær ɪ ŋ k s / [ 8 ] [ 9 ] ) is derived from the  Greek  φάρυγξ  phárynx , meaning "throat". Its plural form is  pharynges   / f ə ˈ r ɪ n dʒ iː z /  or  pharynxes   / ˈ f ær ɪ ŋ k s ə z / , and its adjective form is  pharyngeal  ( / ˌ f æ r ɪ n ˈ dʒ iː əl /   or   / f ə ˈ r ɪ n dʒ i əl / ).


All vertebrates have a pharynx, used in both feeding and respiration. The pharynx arises during development in all vertebrates through a series of six or more outpocketings on the lateral sides of the head. These outpocketings are  pharyngeal arches , and they give rise to a number of different structures in the skeletal, muscular, and circulatory systems. The structure of the pharynx varies across the vertebrates. It differs in dogs, horses, and ruminants. In dogs, a single duct connects the nasopharynx to the nasal cavity. The tonsils are a compact mass that points away from the lumen of the pharynx. In the horse, the auditory tube opens into the guttural pouch and the tonsils are diffuse and raised slightly. Horses are unable to breathe through the mouth as the free apex of the rostral epiglottis lies dorsal to the soft palate in a normal horse. In  ruminants , the tonsils are a compact mass that points towards the lumen of the pharynx.


Pharyngeal arches are characteristic features of vertebrates whose origin can be traced back through  chordates  to basal  deuterostomes  who also share endodermal outpocketings of the pharyngeal apparatus. Similar patterns of gene expression can be detected in the developing pharynx of  amphioxi  and  hemichordates . However, the vertebrate pharynx is unique in that it gives rise to  endoskeletal  support through the contribution of  neural crest  cells. [ 10 ]


Pharyngeal jaws  are a "second set" of  jaws  contained within the pharynx of many species of fish, distinct from the primary (oral) jaws. Pharyngeal jaws have been studied in  moray eels  where their specific action is noted. When the moray bites  prey , it first bites normally with its oral jaws, capturing the prey. Immediately thereafter, the pharyngeal jaws are brought forward and bite down on the prey to grip it; they then retract, pulling the prey down the eel's esophagus, allowing it to be swallowed. [ 11 ]


Invertebrates  also have a pharynx. Invertebrates with a pharynx include the  tardigrades , [ 12 ]   annelids  and  arthropods , [ 13 ]  and the  priapulids  (which have an eversible pharynx). [ 14 ]


The "pharynx" of the  nematode  worm is a muscular food pump in the head, triangular in cross-section, that grinds food and transports it directly to the intestines. A one-way valve connects the pharynx to the excretory canal.


General


The  posterior auricular muscle  is a  muscle  behind the  auricle  of the  outer ear . It arises from the mastoid part of the temporal bone, and inserts into the lower part of the cranial surface of the  auricle  of the  outer ear . It draws the auricle backwards, usually a very slight effect.


The posterior auricular muscle is found behind the  auricle  of the  outer ear . [ 1 ]  It consists of two or three fleshy  fasciculi . These arise from the  mastoid part  of the  temporal bone  by short aponeurotic fibers. [ 1 ]  They insert into the lower part of the cranial surface of the  auricle  of the  outer ear . [ 1 ]


The posterior auricular muscle is supplied by branches of the  posterior auricular artery , which continues deep to the muscle. [ 2 ]  It is drained by the  posterior auricular vein  that accompanies the artery. [ 2 ]


The posterior auricular muscle is supplied by the  posterior auricular nerve , a branch of the  facial nerve  (VII). [ 2 ] [ 3 ]


The posterior auricular nerve draws the auricle of the outer ear backwards. [ 2 ]  This effect is usually very slight, although some people can wiggle their ears due to a more significant muscle movement. [ 2 ]


The  postauricular reflex  is a  vestigial  myogenic [ 4 ]  muscle response in humans that acts to pull the ear upward and backward. [ 5 ]  Research suggests neural circuits for  auricle  orienting have survived in a vestigial state for over 25 million years. It is often assumed the reflex is a vestigial  Preyer reflex  (also known as the  pinna reflex ). [ 6 ] [ 7 ]


A study on auriculomotor activity found that in the presence of sudden, surprising sounds, the muscles around the ear closest to the direction of the sound would respond by moving involuntarily, causing the pinna to be pulled backwards and flatten. [ 8 ]


If the posterior auricular muscle inserts into an unusual part of the  auricle  of the  outer ear , this can cause  protruding ears . [ 1 ]  In one study, the muscle was found to be absent in 5% of people. [ 9 ]


The  posterior auricular nerve  is a  nerve  of the  head . It is a branch of the  facial nerve  (CN VII). It communicates with branches from the  vagus nerve , the  great auricular nerve , and the  lesser occipital nerve . Its auricular branch supplies the  posterior auricular muscle , the intrinsic muscles of the  auricle , and gives sensation to the auricle. Its occipital branch supplies the  occipitalis muscle .


The posterior auricular nerve arises from the  facial nerve  (CN VII). [ 1 ]  It is the first branch outside of the  skull . [ 2 ]  This origin is close to the  stylomastoid foramen . It runs upward in front of the  mastoid process . It is joined by a branch from the  auricular branch  of the  vagus nerve  (CN X). It communicates with the posterior branch of the  great auricular nerve , as well as with the  lesser occipital nerve .


As it ascends between the  external acoustic meatus  and mastoid process it divides into auricular and occipital branches.


The posterior auricular nerve supplies the  posterior auricular muscle , and the intrinsic muscles of the  auricle . [ 1 ]  It gives sensation to the auricle. [ 1 ]  It also supplies the  occipitalis muscle . [ 1 ]


The posterior auricular nerve can be tested by contraction of the  occipitalis muscle , and by sensation in the  auricle . [ 1 ]  This testing is rarely performed. [ 1 ]


The posterior auricular nerve can be biopsied. [ 3 ]  This can be used to test for  leprosy , which can be important in diagnosis. [ 3 ]


1:  Dorsum sellae  of the  sphenoid bone
2: Superior borders of the  petrous part of the temporal bone


The  posterior cranial fossa  is the part of the  cranial cavity  located between the  foramen magnum , and  tentorium cerebelli . It is formed by the   sphenoid bones ,  temporal bones , and  occipital bone . It lodges the  cerebellum , and parts of the  brainstem .


The posterior cranial fossa is formed by the  sphenoid bones ,  temporal bones , and  occipital bone . [ 1 ]  It is the most inferior of the  fossae . [ citation needed ]  It houses the  cerebellum ,  medulla oblongata , and  pons . [ 2 ]


Anteriorly, the posterior cranial fossa is bounded by the  dorsum sellae , posterior aspect of the  body of sphenoid bone , and the  basilar part of occipital bone / clivus . [ 2 ]


Laterally, it is bounded by the  petrous parts  and  mastoid parts  of the  temporal bones , and the  lateral parts of occipital bone . [ 2 ]


Posteriorly, it is bounded by the  squamous part of occipital bone . [ 2 ]


The foramen magnum is a large opening of the floor of the posterior cranial fossa, its most conspicuous feature. [ 2 ]


Lies in the anterior wall of the posterior cranial fossa. It transmits the facial (VII) and  vestibulocochlear  (VIII)  cranial nerves  into a canal in the  petrous temporal bone .


Lies between the inferior edge of the petrous temporal bone and the adjacent  occipital bone  and transmits the  internal jugular vein  (actually begins here), the  glossopharyngeal nerve (CN IX) ,  vagus nerve (CN X) , and  accessory nerve (CN XI) .


Lies at the anterolateral margins of the  foramen magnum  and transmits the  hypoglossal nerve (CN XII) .


Also visible in the posterior cranial fossa are depressions caused by the venous sinuses returning blood from the brain to the venous circulation:
Right and left transverse sinuses which meet at the confluence of sinuses (marked by the internal occipital protuberance).


The transverse sinuses pass horizontally from the most posterior point of the occiput.


Where the apex of the petrous temporal meets the squamous temporal, the transverse sinuses lead into sigmoid (S-shaped) sinuses (one on each side).


These pass along the articulation between the posterior edge of the petrous temporal bone and the anterior edge of the occipital bones to the  jugular foramen , where the  sigmoid sinus  becomes the  internal jugular vein .


Note that a superior petrosal sinus enters the junction of the transverse and sigmoid sinuses. Also an inferior petrosal sinus enters the sigmoid sinus near the jugular foramen.


The posterior cranial fossa is formed in the  endocranium , and holds the most basal parts of the  brain .


An underdeveloped posterior cranial fossa can cause  Arnold–Chiari malformation .  These can be either acquired or congenital disorders. [ citation needed ]


The  posterior ethmoidal artery  is an  artery  of the head which arises from the  ophthalmic artery  to supply the  posterior ethmoidal air cells , and the  meninges . [ 1 ]  It is smaller than the  anterior ethmoidal artery . [ 2 ]


The posterior ethmoidal artery is an orbital branch of the  ophthalmic artery . [ 1 ]


After branching from the  ophthalmic artery , the posterior ethmoidal artery passes between the upper border of the  medial rectus muscle  and  superior oblique muscle [ citation needed ]  to reach, enter and traverse the  posterior ethmoidal canal . [ 3 ]


Meningeal branch


It emits a meningeal branch to the  dura mater  after entering the cranium. [ 2 ] [ 3 ]


Nasal branches


It emits nasal branches that pass through the  cribriform plate  to reach the nasal cavity. The nasal branches form  anastomoses  with the  sphenopalatine artery . [ 4 ]


This artery supplies the posterior  ethmoidal air sinuses , the dura mater [ 2 ]  of the  anterior cranial fossa , and the upper part of the  nasal mucosa  of the  nasal septum . [ citation needed ]


This article incorporates text in the  public domain  from  page 570  of the 20th edition of   Gray's Anatomy   (1918)


The  pterion  is the region where the  frontal ,  parietal ,  temporal , and  sphenoid  bones join. [ 1 ]  It is located on the side of the  skull , just behind the  temple . It is also considered to be the weakest part of the skull, which makes it clinically significant, as if there is a  fracture  around the pterion it could be accompanied by an  epidural hematoma .


The pterion is located in the  temporal fossa , approximately 2.6 cm behind and 1.3 cm above the posterolateral margin of the  frontozygomatic suture . [ 2 ]


It is the junction between four bones:


These bones are typically joined by five  cranial sutures :


The pterion is known as the weakest part of the skull. [ 3 ]   The anterior division of the  middle meningeal artery  runs underneath the pterion. [ 4 ]  Consequently, a traumatic blow to the pterion may rupture the middle meningeal artery causing an  epidural haematoma . The pterion may also be fractured indirectly by blows to the top or back of the head that place sufficient force on the skull to fracture the pterion.


The pterion is a structural landmark for  neurosurgical  approach to middle cerebral artery  aneurysms . [ 5 ]


The pterion receives its name from the Greek root  pteron , meaning  wing . In  Greek mythology ,  Hermes , messenger of the gods, was enabled to fly by winged sandals, and wings on his head, which were attached at the pterion.


This article incorporates text in the  public domain  from  page 182  of the 20th edition of   Gray's Anatomy   (1918)


The  pterygoid canal  (also  vidian canal ) is a passage in the sphenoid bone of the  skull  leading from just  anterior  to the  foramen lacerum  in the  middle cranial fossa  to the  pterygopalatine fossa . [ 1 ]


It transmits the  nerve of pterygoid canal (Vidian nerve) , the  artery of the pterygoid canal (Vidian artery) , and the vein of the pterygoid canal (Vidian vein).


The pterygoid canal runs through the  medial pterygoid plate  of the  sphenoid bone  to the back wall of the  pterygopalatine fossa .


The  pterygoid processes of the sphenoid  (from Greek   pteryx ,  pterygos , "wing"), one on either side, descend perpendicularly from the regions where the  body  and the  greater wings  of the  sphenoid bone  unite.


Each process consists of a  medial pterygoid plate  and a  lateral pterygoid plate , the latter of which serve as the origins of the  medial  and  lateral pterygoid muscles . The medial pterygoid, along with the  masseter  allows the jaw to move in a vertical direction as it contracts and relaxes. The lateral pterygoid allows the jaw to move in a horizontal direction during mastication (chewing). Fracture of either plate are used in clinical medicine to distinguish the  Le Fort fracture classification  for high impact injuries to the  sphenoid  and  maxillary bones .


The superior portion of the pterygoid processes are fused anteriorly; a vertical groove, the  pterygopalatine fossa , descends on the front of the line of fusion. The plates are separated below by an angular cleft, the  pterygoid notch , the margins of which are rough for articulation with the pyramidal process of the  palatine bone .


The two plates diverge behind and enclose between them a V-shaped fossa, the  pterygoid fossa , which contains the  medial pterygoid muscle  and the  tensor veli palatini .


Above this fossa is a small, oval, shallow depression, the  scaphoid fossa , which gives origin to the tensor veli palatini.


The anterior surface of the pterygoid process is broad and triangular near its root, where it forms the posterior wall of the pterygopalatine fossa and presents the anterior orifice of the  pterygoid canal .


In many mammals it remains as a separate bone called the  pterygoid bone .


Its name is Greek for "resembling a fin or wing", from its shape.


The  medial pterygoid plate  (or  medial pterygoid lamina ) of the  sphenoid bone  is a horse-shoe shaped  process  that arises from its underside.


It is narrower and longer than the  lateral pterygoid plate  and curves lateralward at its lower extremity into a hook-like process, the  pterygoid hamulus , around which the tendon of the  tensor veli palatini  glides.


The lateral surface of this plate forms part of the  pterygoid fossa , the medial surface constitutes the lateral boundary of the  choana  or posterior aperture of the corresponding nasal cavity.


Superiorly the medial plate is prolonged on to the under surface of the body as a thin lamina, named the vaginal process, which articulates in front with the  sphenoidal process  of the palatine and behind this with the  ala  (wing) of the  vomer .


The angular prominence between the posterior margin of the vaginal process and the medial border of the  scaphoid fossa  is named the  pterygoid tubercle , and immediately above this is the posterior opening of the  pterygoid canal .


On the under surface of the vaginal process is a furrow, which is converted into a canal by the sphenoidal process of the  palatine bone , for the transmission of the pharyngeal branch of the  internal maxillary artery  and the pharyngeal nerve from the  sphenopalatine ganglion .


The  pharyngeal aponeurosis  is attached to the entire length of the posterior edge of the medial plate, and the  constrictor pharyngis superior  takes origin from its lower third.


Projecting backward from near the middle of the posterior edge of this plate is an angular process, the processus tubarius, which supports the pharyngeal end of the Eustachian tube.


The anterior margin of the plate articulates with the posterior border of the vertical part of the palatine bone.


In many animals it is a separate bone called the  pterygoid bone .


The  lateral  pterygoid  plate  of the  sphenoid  (or  lateral lamina of pterygoid process ) is broad, thin, and everted and forms the lateral part of a horseshoe like process that extends from the inferior aspect of the sphenoid bone, and serves as the origin of the lateral pterygoid muscle, which functions in allowing the mandible to move in a lateral and medial direction, or from side-to-side.


Its lateral surface forms part of the medial wall of the infratemporal fossa, and gives attachment to the  lateral pterygoid muscle ; its medial surface forms part of the pterygoid fossa, and gives attachment to the  medial pterygoid muscle . Posterior edge is sharp, and often has sharp projection -  pterygospinous process  (Civinini process).


This article incorporates text in the  public domain  from  page 151  of the 20th edition of   Gray's Anatomy   (1918)


The  pterygomandibular space  is a  fascial space of the head and neck  (sometimes also termed  fascial  spaces or tissue spaces). It is a  potential space  in the head and is paired on each side. It is located between the  medial pterygoid muscle  and the medial surface of the  ramus of the mandible . The pterygomandibular space is one of the four  compartments  of the  masticator space . [ 1 ]


The boundaries of each pterygomandibular space are: [ 1 ]


The communications of each pterygomandibular space are: [ 1 ]


The pterygomandibular space is the area where  local anesthetic  solution is deposited during an  inferior alveolar nerve block , a common procedure used to anesthetize the distribution of the inferior alveolar nerve. Rarely,  pathogenic  micro-organisms from the mouth may be seeded into the pterygomandibular space during this injection and cause a  needle tract infection  of the space. [ 1 ]  It is also occasionally reported that the needle breaks off and is retained in the pterygomandibular space during this injection. [ 3 ]  Minor oral surgery is then required to remove the fractured needle. [ 3 ]  Due to its high vascularity, injections into the pterygomandibular space carry a high risk of  intravascular injection  (injecting into a blood vessel). [ 4 ]  Another possible complication of an inferior alveolar nerve block occurs when the needle is placed too deep, passing through the pterygomandibular space and into the parotid gland behind. Branches of the  facial nerve  (which gives the motor supply to the  muscles of facial expression ) run through the substance of the parotid gland and so this is manifest as a transient  facial palsy . The pterygomandibular space is one of the possible spaces into which a tooth may be displaced into during  dental extraction , e.g. of a maxillary  wisdom tooth . [ 5 ]  A  mandibular fracture  in the angle region may also be the cause of a pterygomandibular space infection. [ 1 ]


The signs and symptoms of an isolated pterygomandiublar infection may include  trismus  (difficulty opening the mouth), however there is not usually any externally visible facial swelling. [ 1 ]  Intra-orally, there may be swelling and  erythema  (redness) of the anterior tonsillar pillar (the  Palatoglossal arch ) and deviation of the  uvula  to the unaffected side. [ 1 ]  The airway may be compressed. Treatment is by surgical  incision and drainage , and the incision may be placed inside the mouth or two incisions may be used, one inside the mouth and one outside. [ 1 ]


Odontogenic infections  may spread to involve the pterygomandibular space, and the most common teeth responsible for this are the mandibular second and third molar teeth. [ 6 ]


The  pterygopalatine ganglion  (aka  Meckel's ganglion ,  nasal ganglion , or  sphenopalatine ganglion ) is a  parasympathetic ganglion  in the  pterygopalatine fossa . It is one of four parasympathetic ganglia of the head and neck, (the others being the  submandibular ,  otic , and  ciliary ganglion ).


It is innervated by the  Vidian nerve  (formed by the  greater superficial petrosal nerve  branch of the  facial nerve  and  deep petrosal nerve ) and  maxillary division  of the  trigeminal nerve . Its postsynaptic axons project to the  lacrimal glands  and nasal mucosa. [ 1 ]


The flow of blood to the  nasal mucosa , in particular the venous plexus of the conchae, is regulated by the pterygopalatine ganglion and heats or cools the air in the  nose .


The pterygopalatine ganglion (of  Meckel ), the largest of the parasympathetic ganglia associated with the branches of the  maxillary nerve , is deeply placed in the  pterygopalatine fossa , close to the  sphenopalatine foramen . It is triangular or heart-shaped, of a reddish-gray color, and is situated just below the maxillary nerve as it crosses the fossa.


The pterygopalatine ganglion supplies the  lacrimal gland ,  paranasal sinuses , glands of the mucosa of the  nasal cavity  and  pharynx , the  gingiva , and the mucous membrane and  glands  of the  hard palate . It communicates anteriorly with the  nasopalatine nerve .


It receives a sensory, a parasympathetic, and a sympathetic root.


Its sensory root is derived from two  sphenopalatine  branches of the  maxillary nerve  of the  trigeminal nerve ; their fibers, for the most part, pass directly into the  palatine nerves ; a few, however, enter the ganglion, constituting its sensory root.


Its parasympathetic root is derived from the  nervus intermedius  (a part of the  facial nerve ) through the  greater petrosal nerve .


In the pterygopalatine ganglion, the preganglionic parasympathetic fibers from the greater petrosal branch of the facial nerve synapse with neurons whose postganglionic axons, vasodilator, and secretory fibers are distributed with the deep branches of the  trigeminal nerve  to the mucous membrane of the  nose ,  soft palate ,  tonsils ,  uvula , roof of the mouth, upper lip and gums, and upper part of the  pharynx .  It also sends postganglionic parasympathetic fibers to the  lacrimal nerve  (a branch of the  ophthalmic nerve , also part of the trigeminal nerve) via the  zygomatic nerve , a branch of the  maxillary nerve  (from the trigeminal nerve), which then arrives at the lacrimal gland.


The  nasal glands  are innervated with secretomotor fibers from the nasal branches. Likewise, the  palatine glands  are innervated by the  nasopalatine ,  greater palatine nerve  and  lesser palatine nerves . The  pharyngeal nerve  innervates pharyngeal glands. These are all branches of  maxillary nerve .


The ganglion also consists of sympathetic efferent (postganglionic) fibers from the  superior cervical ganglion .  These fibers, from the superior cervical ganglion, travel through the  carotid plexus , and then through the  deep petrosal nerve . The deep petrosal nerve (carrying postganglionic sympathetics) joins with the  greater petrosal nerve  (carrying preganglionic parasympathetics) to form the  nerve of the pterygoid canal , which passes through the pterygoid canal before entering the ganglion. The stellate ganglion is at the bottom of the cervical sympathetic chain.  Fibers from the stellate ganglion pass up the chain to the superior cervical sympathetic ganglion and into and through the sphenopalatine ganglion.


Blockade of the ganglion with local anesthetic, clinically referred to as a 'sphenopalatine ganglion block' may be performed transcutaneously with a small needle, or topically via the nose with local anesthetic soaked swabs. The topical sphenopalatine ganglion block is used for  treatment of persistent migraines and cluster headaches , demonstrating relief within 10–20 minutes. Sphenopalatine ganglion block has been used to treat  post-dural-puncture headache , [ 2 ]  though a 2020 trial comparing local anaesthetic sphenopalatine ganglion block to sham injection with saline failed to show difference in pain scores for those receiving local anaesthetic vs placebo, suggesting any efficacy is unrelated to local anaesthetic blockade. [ 3 ]


Self-administration of sphenopalatine ganglion blocks with cotton-tipped catheters and continual capillary feed is the most cost-effective method of treatment and has the benefit of allowing patients to avoid visits to physicians and emergency rooms.  After initial visit self-administered sphenopalatine ganglion blocks are less than $1.00 per application. Frequent repeated administration of sphenopalatine ganglion blocks seems to increase effectiveness initially, after which decreased frequency is required.  Self-administered sphenopalatine ganglion blocks can be used to treat acute pain symptoms, and prophylactically to reduce the onset of painful conditions and anxiety.