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Stapedius muscle

The stapedius muscle is the tiny muscle in the middle ear that attaches to the posterior aspect of the neck of the stapes, which when contracted dampens vibrations passed to the cochlea via the oval window. The muscle is anchored within the petrous temporal bone and emerges anteriorly into the m...

Stafne bone cavity

A Stafne bone cavity is a cortical defect near the angle of the mandible below the mandibular canal. It is usually an incidental finding and represents a depression in the medial aspect of the mandible filled by part of the submandibular gland or adjacent fat. Terminology A Stafne bone cavity...

Solitary bone cyst of the mandible

Solitary bone cysts of the mandible (also known as traumatic bone cyst of the jaw, hemorrhagic cyst of the mandible, extravasation cyst, progressive bone cavity or unicameral bone cyst) are an uncommon nonepithelial lined lucent mandibular lesion. It is one of a myriad of potential mandibular le...

Sialolithiasis

Sialolithiasis refers to the formation of calculi (sialoliths) inside the ducts or parenchyma of salivary glands and most commonly occurs in the submandibular glands and their ducts. Epidemiology Sialolithiasis is the most common disease of salivary glands, accounting for approximately 50% of ...

Sigmoid plate

The sigmoid plate is variously described as the plate of bone between the jugular bulb and the middle ear cavity (as shown in first image) or more generally as the thin bone separating the sigmoid sinus from adjacent structures (especially mastoid air cells). In the case of the former, the struc...

Internal auditory canal nerves (mnemonic)

A mnemonic to remember the relative position of nerves inside the internal auditory canal (IAC) is: Seven up, Coke down A variation may include the addition of: V8 on the back shelf Anatomy Four nerves pass through the IAC: facial nerve (CN VII) three components of the vestibulocochlear n...

Tuberculous cervical lymphadenitis

Tuberculous cervical lymphadenitis, also known as scrofula and king's evil, continues to be seen in endemic areas and in the industrialised world particularly among the immunocompromised. Epidemiology Tuberculous cervical lymphadenitis is the most common manifestation of extrapulmonary tubercu...

Sarcoidosis

Sarcoidosis is a non-caseating granulomatous multisystem disease with a wide range of clinical and radiographic manifestations. Individual systemic manifestations are discussed in respective articles: pulmonary and mediastinal manifestations cardiac manifestations musculoskeletal...

Salivary gland tumors

Salivary gland tumors are variable in location, origin, and malignant potential. Pathology In general, the ratio of benign to malignant tumors is proportional to the gland size; i.e. the parotid gland tends to have benign neoplasms, the submandibular gland 50:50, and the sublingual glands and...

Oral cavity carcinoma (staging)

Oral cavity carcinoma staging refers to TNM staging of carcinomas involving the oral cavity. The vast majority of applicable cases are squamous cell carcinomas, but other epithelial and minor salivary gland cancers are also included. The following article reflects the 8th edition published by th...

Retinoblastoma

Retinoblastomas are the most common intraocular neoplasm found in childhood and with modern treatment modalities, are, in most cases, curable. On imaging, they are generally characterized by a heterogeneous retinal mass with calcifications, necrotic components and increased vascularization on D...

Retinal detachment

Retinal detachment is a detachment of the neurosensory retina from the underlying pigmented choroid. Apposition of the retinal pigmented epithelium to the overlying retina is essential for normal retinal function. Terminology There are numerous subtypes of retinal detachment 5: rhegmatogenous...

Residual cyst

Residual cysts are inflammatory odontogenic cysts that develop following dental extraction. It is most frequently due to growth from a remnant of a radicular/periapical cyst 1. They occur more often in the maxilla 2.

Ranula

Ranulas are rare, benign, acquired, cystic lesions that occur at the floor of the mouth as sublingual or minor salivary gland retention cysts. Epidemiology For reasons that are unclear, they appear to be more common in the Maori of New Zealand and Pacific Island Polynesians 7. Clinical prese...

Psammoma bodies

Psammoma bodies are round microscopic calcific collections. It is a form of dystrophic calcification. Necrotic cells form the focus for surrounding calcific deposition. They have a lamellated concentric calcified structure, sometimes large enough to be seen on CT. Psammoma bodies are found in ...

Pneumatized dorsum sella

Pneumatization of the dorsum sella is not uncommon, but needs to be remembered as an unusual site of sinus disease, which otherwise may be mistaken for intracranial of pituitary disease.

Pleomorphic adenoma of the salivary glands

Pleomorphic adenomas of the salivary glands, also known as benign mixed tumors (see below), are the most common salivary gland tumors. The salivary glands are the most common site of pleomorphic adenomas. On imaging, they commonly present as well-circumscribed rounded masses, most commonly loca...

Platybasia

Platybasia is characterized by abnormal flattening of the skull base as defined as a base of skull angle over 143º. Clinical presentation Platybasia alone does not usually cause symptoms unless it is associated with basilar invagination 6. Pathology Etiology congenital achondroplasia Dow...

Pituitary gland

The pituitary gland (a.k.a. hypophysis cerebri), together with its connections to the hypothalamus, acts as the main endocrine interface between the central nervous system and the rest of the body. Gross anatomy The pituitary gland sits atop the base of the skull in a concavity within the sph...

Phthisis bulbi

Phthisis bulbi, also known as end-stage eye, is an atrophic scarred and disorganized non-functioning globe that may result from a variety of severe ocular insults. Epidemiology In general, phthisis bulbi involves elderly patients, usually 65-85 years of age 7. Children and adolescents are onl...

Persistent ossiculum terminale

The ossiculum terminale appears as a secondary ossification center of the dens between 3-6 years and normally fuses by 12 years. Failure of fusion results in a persistent ossiculum terminale (also called Bergmann's ossicle or ossiculum terminale of Bergmann) and is considered a normal anatomical...

Petrous apicitis

Petrous apicitis, also known as apical petrositis, is infection with involvement of bone at the very apex (petrous apex) of the petrous temporal bone. Epidemiology Petrous apicitis is less common than it once was, on account of the widespread and early use of antibiotics for acute otomastoidit...

Periapical cyst

Periapical cysts, also known as radicular cysts, are the most frequent cystic lesion related to teeth (see mandibular lesions) and result from infection of the tooth. On imaging, they generally appear as a round- or pear-shaped, unilocular, lucent lesion in the periapical region, usually measuri...

Patulous tube syndrome

Patulous tube syndrome, or patulous dysfunction of the Eustachian tube, is a form of Eustachian tube dysfunction in which the tube remains abnormally open, allowing transmission of nasopharyngeal pressure to the middle ear. During strong inspiration (i.e 'sniff') transmits negative pressure to ...

Paraganglioma

Paragangliomas, sometimes called glomus tumors, are rare neuroendocrine tumors arising from paraganglia. Terminology Paraganglia are clusters of neuroendocrine cells dispersed throughout the body and closely related to the autonomic nervous system, with either parasympathetic or sympathetic f...

Papillary thyroid cancer

Papillary thyroid carcinoma (PTC) is the most common malignancy of the thyroid gland and frequently has nodal metastases at presentation. Terminology When the tumor measures <1 cm, the term micropapillary carcinoma (mPTC) is used 14. Epidemiology Papillary thyroid cancer (as is the case wit...

Pancoast syndrome

Pancoast syndrome (historically known as Ciuffini-Pancoast-Tobías syndrome, Hare syndrome or variation thereof) results from involvement of the brachial plexus and sympathetic chain by a Pancoast tumor or, less commonly, from other tumors - or even non-malignant disease - involving the lung apex...

PHACE syndrome

PHACE syndrome, also known as cutaneous hemangioma–vascular complex syndrome or Pascual-Castroviejo type II syndrome, is a phakomatosis that comprises of: P: posterior fossa malformations (e.g. Dandy-Walker malformation) H: hemangiomas A: arterial anomalies C: coarctation of the aorta and ca...

Ostmann fat pad

The Ostmann fat pads (also known as Ostmann fatty bodies) are located inferolateral to the cartilaginous Eustachian tubes and are thought to be important in normal closure of eustachian tube, preventing transmission of nasopharyngeal pressure to the middle ear 5. Failure to visualize this thin t...

Middle ear ossicles

There are three tiny articulating bones in the middle ear known as ossicles (from lateral to medial): malleus incus stapes Their role is to mechanically amplify the vibrations of the tympanic membrane and transmit them to the cochlea where they can be interpreted as sound. They are located i...

Idiopathic orbital inflammation

Idiopathic orbital inflammation, also known as orbital pseudotumor and non-specific orbital inflammation, is an idiopathic inflammatory condition that most commonly involves the extraocular muscles. Less commonly there is inflammatory change involving the uvea, sclera, lacrimal gland, and retrob...

Optic nerve

The optic nerve is the second (CN II) cranial nerve (TA: nervus opticus or nervus cranialis II). It is a purely sensory nerve that conveys visual information from the eye to the brain. The nerve arises from the back of the globe exiting the orbit via the optic canal. It joins the contralateral...

Orbit

The orbits are two bony sockets at the front of the face that primarily house and protect the eyes and associated structures. Terminology Ocular or optic refers specifically to the globe (eyeball). Orbital refers to all the contents of the bony orbit, encompassing both the intra and extraocul...

Sphenoethmoidal air cell

Sphenoethmoidal air cell, also commonly known as the Onodi air cell, is an anatomical variant of the paranasal sinuses, important due to its close proximity to the optic nerve and internal carotid artery. Terminology The sphenoethmoidal air cell is generally defined as the posteriormost ethmoi...

Odontogenic myxoma

Odontogenic myxomas are rare tumors that involve the mandible or maxilla and account for 3-6% of odontogenic tumors 2. Epidemiology Typically seen in the 2nd to 3rd decades of life (slightly earlier than ameloblastomas). They are usually not painful. Pathology Arises from mesenchymal odontog...

Odontoma

Odontomas are one of the most common mandibular lesions encountered and the most common odontogenic tumors of the mandible. They account for up to two-thirds of all such tumors; the next most common are ameloblastomas, making up the majority of the remaining one-third. Epidemiology They can oc...

Odontogenic keratocyst

Odontogenic keratocysts (OKC), previously known as keratocystic odontogenic tumors (KCOT or KOT), are rare benign cystic lesions involving the mandible or maxilla and are believed to arise from dental lamina. Whether these lesions are developmental or neoplastic is controversial, with the 4th ed...

Oculomotor nerve

The oculomotor nerve is the third (CN III) cranial nerve (TA: nervus oculomotorius or nervus cranialis III). It is a mixed nerve containing motor, parasympathetic and sympathetic fibers. It arises from the midbrain and passes through the cavernous sinus to the orbit where it is responsible for t...

Oculomotor nerve palsy

Oculomotor nerve palsies, or third nerve palsies, result in weakness of the muscles supplied by the oculomotor nerve, namely the superior rectus, inferior rectus, medial rectus, inferior oblique, and levator palpebrae superioris muscles. Terminology If the pupil is normal-sized and reactive to...

Nerve to stapedius

The nerve to stapedius arises from the facial nerve to supply the stapedius muscle. The branch is given off in the facial nerve's mastoid segment, as it passes posterior to the pyramidal process. Damage to this branch with resulting paralysis of stapedius leads to hypersensitivity to loud noise...

Midline nasal region lesions

A variety of congenital midface anomalies occur in children. Although rare, these disorders are clinically important because of their potential for connection to the central nervous system. Lesions presenting as a midline nasal mass include: nasal glioma nasal encephalocele nasal dermoid cyst...

Nasopharyngeal choristoma

A nasopharyngeal choristoma is a rare, non-neoplastic mass (type of choristoma) typically located in the lateral aspect of the nasopharynx without intracranial extension. These lesions are composed of fibrovascular tissue and fat. Resection is curative. Differential diagnosis nasopharyngeal ca...

Myoepithelioma

Myoepitheliomas and malignant myoepitheliomas were considered a variant of pleomorphic adenomas until 1991. However, these are also found in the breast and bronchus and have gained recognition as separate entities 1. Epidemiology They account for <1% of salivary gland tumors, and only rarely u...

Myokymia

Myokymia refers to a fine undulating fascicular tremor of facial musculature which should be distinguished from hemifacial spasm which involves entire muscles rather than individual fascicles. The two conditions may co-exist. Female gender and cold climate are the two of most predominant risk fa...

Muscles of mastication

The muscles of mastication can be divided into primary and secondary groups according to whether they connect the mandible directly to the skull or if they attach to other structures in the neck, e.g. hyoid, thyroid cartilage. Primary temporalis muscle masseter muscle medial pterygoid muscle...

Muscles of the tongue

The muscles of the tongue are divided into 2 groups each comprising 4 muscles. They are classified as intrinsic (to the tongue) and extrinsic muscles. They allow for the complex movements of the tongue and are all innervated by the hypoglossal nerve (CN XII) except one: intrinsic muscles of th...

Multiple endocrine neoplasia syndromes

Multiple endocrine neoplasia (MEN) syndromes are a collection of syndromes characterized by the presence of, as the name would suggest, multiple endocrine tumors. They are autosomal dominant in inheritance. MEN1 (Wermer syndrome) MEN2 (multiple endocrine adenomatosis) MEN2a (Sipple syndrome) ...

Middle ear granulation tissue

Development of granulation tissue in the middle ear cavity is a generalized response to injury/inflammation, chronic otomastoiditis. It can either be typical or go down the pathway of becoming a cholesterol granuloma. Radiographic features Typical granulation tissue is common, more so than cho...

Middle ear effusion

Middle ear effusions are frequent in children due to prominent adenoids and horizontal Eustachian tubes. These do not require imaging and can be treated expectantly / medically / surgically with tympanostomy tubes. Eustachian tube dysfunction is the accepted etiology, with resorption of air and ...

Middle ear tumors

There are a range of middle ear tumors, which are more likely to be benign than malignant. Pathology The three most common middle ear tumors are (not in any particular order as there are differences in the literature) 1-3: glomus tympanicum paraganglioma congenital cholesteatoma middle ea...

Mandibular lesions

Mandibular lesions are myriad and common. The presence of teeth results in lesions that are specific to the mandible (and maxilla) and a useful classification that defines them as odontogenic or non-odontogenic. While it may often not be possible to make a diagnosis on imaging alone, this classi...

Malleus

The malleus (plural: mallei) is the most lateral middle ear ossicle, located between the tympanic membrane and the incus. Gross anatomy The malleus has a head, neck, and three distinct processes (manubrium (handle), anterior and lateral processes). The head is oval in shape, and articulates p...

MacEwen triangle

The MacEwen triangle (also called the suprameatal triangle or mastoid fossa) is a surgical landmark on the surface of the temporal bone just superior to the external auditory canal used to locate the level of the mastoid antrum. Three lines form the triangle: superior: inferior temporal line/s...

Multiple endocrine neoplasia type IIb

Multiple endocrine neoplasia (MEN) type IIb, also known as MEN type 3 (MEN3) 3 or mucosal neuroma syndrome 2, accounts for only 5% cases of MEN2 and is characterized by: pheochromocytoma(s): in 50% of patients, often bilateral, and can be extra-adrenal medullary thyroid cancer: 100% of patient...

Multiple endocrine neoplasia type II

Multiple endocrine neoplasia type II (MEN2) is also known as mucosal neuroma syndrome or multiple endocrine adenomatosis. It is a collection of syndromes characterized by the presence of multiple endocrine tumors. They are autosomal dominant in inheritance, and share medullary thyroid carcinom...

Multiple endocrine neoplasia type IIa

Multiple endocrine neoplasia (MEN) type IIa, also known as Sipple syndrome, accounts for most cases of MEN2 and is characterized by: pheochromocytomas: in 50% of patients, often bilateral, and can be extra-adrenal medullary thyroid cancer: 100% of patients, aggressive, and may secrete calciton...

Multiple endocrine neoplasia type 1

Multiple endocrine neoplasia type 1 (MEN1), also known as Wermer syndrome, is an autosomal dominant genetic disease that results in proliferative lesions in multiple endocrine organs, particularly the pituitary gland, pancreas, and parathyroid glands. There are other multiple endocrine neoplas...

Radiolucent lesions of the mandible (differential)

Lucent lesions of the mandible are not uncommon and may be the result of odontogenic or non-odontogenic processes. Lucency may be conferred by a cystic process (e.g. periapical cyst) or a lytic process (e.g. mandibular metastases). Pathology Etiology Odontogenic periapical (radicular) cyst (...

Lymph node levels of the neck

The lymph nodes in the neck have historically been divided into at least six anatomic neck lymph node levels for the purpose of head and neck cancer staging and therapy planning. Differing definitions exist across specialties 1-4. The following is a synthesis of radiologically useful boundaries ...

Linear scleroderma

Linear scleroderma, also known as scleroderma en coup de saber, is a very focal form of scleroderma classically characterized by a linear band of atrophy involving the frontal or frontoparietal scalp and subjacent thinned calvaria associated with ipsilateral focal brain abnormalities. Linear sc...

Lesser petrosal nerve

The lesser petrosal nerve carries preganglionic parasympathetic fibers to the parotid gland. It is considered a branch of the glossopharyngeal nerve although it receives contributions from two further sources 3: tympanic plexus: glossopharyngeal nerve via Jacobson's nerve (main contribution) n...

Lemierre syndrome

Lemierre syndrome (also known as postanginal septicemia) refers to thrombophlebitis of the internal jugular vein(s) with distant metastatic anaerobic septicemia in the setting of initial bacterial oropharyngeal infection such as pharyngitis/tonsillitis into lateral pharyngeal spaces of the neck ...

Laryngocele

A laryngocele is the dilatation of the saccule of the laryngeal ventricle and is unilateral in the vast majority of cases 8. On imaging, these lesions are generally characterized as well-defined, thin-walled, fluid or air-filled cystic lesions in the paraglottic space. The communication with th...

Laryngeal carcinoma (staging)

Laryngeal carcinoma staging refers to TNM staging of carcinomas involving the supraglottic, glottic, and subglottic larynx. The vast majority of applicable cases are squamous cell carcinomas, but other epithelial tumors are also included. The following article reflects the 8th edition published ...

Labyrinthitis

Labyrinthitis is inflammation of the membranous labyrinth. Pathology Labyrinthitis can be divided according to etiology. Tympanogenic Labyrinthitis is a potential complication of acute otomastoiditis with the spread of infection or of toxins from the middle ear to the inner ear via either th...

Kimura disease

Kimura disease, also known historically as eosinophilic hyperplastic lymphogranuloma, is a rare benign inflammatory disease that characteristically manifests as enlargement of cervical lymph nodes and salivary glands. Epidemiology Kimura disease typically affects males (80%) between 20-40 year...

Labyrinthine artery

The labyrinthine artery, also known as the auditory artery or internal auditory artery, is a long and slender artery that is the main arterial supply to the vestibular apparatus and cochlea. It also vascularizes the VII and VIII cranial nerves. It usually originates from the AICA (~85%), althou...

Juvenile nasopharyngeal angiofibroma

Juvenile nasopharyngeal angiofibromas are a rare benign, but locally aggressive, vascular tumors that occur almost exclusively in young men. On imaging, they present as a vividly enhancing soft-tissue masses centered on the sphenopalatine foramen. Given its vascularity, prominent flow voids ar...

Jugular spine

The jugular spine is a small sharp bony ledge which separates the two parts of the jugular foramen - pars nervosa anteromedially and pars vascularis posterlaterally. It is an important landmark, as masses of the jugular foramen (e.g. glomus jugulare) may erode the jugular spine, helping distingu...

Jacobson nerve

Jacobson nerve is the eponymous name of the tympanic branch of the glossopharyngeal nerve (CN IX) and arises from the inferior ganglion of the glossopharyngeal nerve. It also carries preganglionic parasympathetic fibers, from the inferior salivary nucleus, which eventually enter the otic ganglio...

Jaffe-Campanacci syndrome

Jaffe-Campanacci syndrome is characterized by: multiple non-ossifying fibromas of the long bones and jaw café au lait spots intellectual disability kyphoscoliosis hypogonadism or cryptorchidism ocular malformations cardiovascular malformations giant cell granuloma of the jaw axillary an...

Intracranial lipoma

Intracranial lipomas are not tumors as such, but rather a result of abnormal differentiation of embryologic meninx primitiva. They are frequently associated with abnormal development of adjacent structures. Terminology The term intracranial lipoma is used somewhat loosely. The broadest usage w...

Incus

The incus (plural: incudes) is the middle of the three ossicles articulating with the head of the malleus anteromedially, forming the incudomalleolar joint, and the stapes inferomedially, forming the incudostapedial joint. Four parts of the incus are named: body contiguous with the short and ...

Extraocular muscle involvement in thyroid associated orbitopathy (mnemonic)

A mnemonic to remember the order in which extraocular muscles are involved in thyroid-associated orbitopathy (TAO) is: I'M SLOw Mnemonic I: inferior rectus M: medial rectus S: superior rectus L: lateral rectus O: obliques muscles (superior oblique and inferior oblique) There is some deba...

Hypoglossal canal

The hypoglossal canal is located between the occipital condyle and jugular tubercle and runs obliquely forwards (posteromedial to anterolateral) allowing the hypoglossal nerve to exit the posterior cranial fossa. Its proximal portion is often divided by a fibrous (sometimes ossified) septum, w...

Hyperostosis of the skull (differential)

Hyperostosis of the skull has many causes, broadly divided into focal or diffuse. Diffuse Paget disease of bone metastatic disease, especially prostate carcinoma chronic, severe anemia hyperparathyroidism acromegaly osteopetrosis hyperostosis frontalis interna long-term phenytoin use g...

Hyperparathyroidism

Hyperparathyroidism is the effect of excess parathyroid hormone in the body. It can be primary, secondary, or tertiary. There are many characteristic imaging features, predominantly involving the skeletal system. It accounts for the 'H' in the popular mnemonic for lucent bone lesions FEGNOMASHI...

High riding jugular bulb

A high riding jugular bulb indicates the dome (roof) of the jugular bulb extends more superiorly in the petrous temporal bone than is typical. The transverse level above which a jugular bulb is considered high riding has been variably defined as the following 1,6,8: floor of the internal acoust...

Hemifacial spasm

Hemifacial spasm is characterized by episodic facial spasms due to irritation of the facial nerve (CN VII). Clinical presentation Often the condition begins insidiously with painless spasm of the orbicularis oculi gradually spreading in extent and severity to involve the majority of the face, ...

Heerfordt syndrome

Heerfordt syndrome, also known as Heerfordt-Waldenström syndrome or uveoparotid fever, is a variant of sarcoidosis, comprising of: fever parotid enlargement facial palsy ocular involvement (anterior uveitis) Epidemiology The exact prevalence is unknown, as only isolated case reports exist....

Haller cells

Haller cells, also known as infraorbital ethmoidal air cells, are ethmoid air cells located lateral to the maxillo-ethmoidal suture along the inferomedial orbital floor. Epidemiology They are present in ~20% (range 2-45%) of patients, depending on their exact definition 1-3. Clinical present...

Griesinger sign (mastoid)

The Griesinger sign refers to edema of the postauricular soft tissues overlying the mastoid process as a result of thrombosis of the mastoid emissary vein. It is a complication of acute otomastoiditis and may be associated with dural sinus occlusive disease (DSOD). It is said to be a pathognomon...

Gradenigo syndrome

Gradenigo syndrome consists of the triad of: suppurative otitis media with persistent otorrhea and ear pain abducens nerve palsy, secondary to involvement of the nerve as it passes through Dorello canal retro-orbital pain, or pain in the cutaneous distribution of the frontal and maxillary div...

Fossa of Rosenmüller

The fossa of Rosenmüller, also known as the posterolateral pharyngeal recess, is the most common site of origin for nasopharyngeal carcinoma 5. Gross anatomy It is located superior and posterior to the torus tubarius (the posterior projection of the cartilaginous portion of the Eustachian tube...

Fatty nodal metaplasia

Fatty nodal metaplasia in the neck occurs as a result of chronic inflammation or radiotherapy 3. The normal fatty nodal hilum enlarges, such that the lymph node appears cystic. However, its center is of fatty density. There is no surrounding stranding, and the node otherwise looks normal. Diffe...

Fallopian canal

The fallopian canal or facial nerve canal refers to a bony canal through which the facial nerve traverses the petrous temporal bone, from the internal acoustic meatus to the stylomastoid foramen. There are three segments of the canal, corresponding to the segments of the facial nerve they cont...

Facial nerve

The facial nerve is the seventh (CN VII) cranial nerve and comprises two roots, a motor root and a smaller mixed sensory, taste and parasympathetic root, known as nervus intermedius, which join together within the temporal bone (TA: nervus facialis or nervus cranialis VII). The facial nerve has...

Le Fort fracture classification

Le Fort fractures are fractures of the midface, which collectively involve separation of all or a portion of the midface from the skull base. In order to be separated from the skull base, the pterygoid plates of the sphenoid bone need to be involved as these connect the midface to the sphenoid b...

Extramural air cell

An extramural air cell is one that is not contained within its named parent bone. So, the infraorbital ethmoidal air cells that lie within the maxilla rather than the ethmoidal bone are an example of extramural air cells.

External auditory canal atresia

External auditory canal atresia, also known as congenital aural atresia, is characterized by complete or incomplete bony atresia of the external auditory canal (EAC), often in association with a dysplastic auricle and an abnormal middle ear cavity or ossicles. Epidemiology The incidence is 1 i...

External ear

The external ear (or outer ear) comprises the auricle (or pinna), the external auditory meatus, and the tympanic membrane ("eardrum"). The auricle concentrates and amplifies sound waves and funnels them through the outer acoustic pore into the external auditory meatus to the tympanic membrane. ...

Eustachian tube dysfunction

Eustachian tube dysfunction, also known as pharyngotympanic tube or auditory tube dysfunction, refers to the failure of the Eustachian tube to open or close properly. Therefore, it encompasses a spectrum from patulous to obstructive pathophysiology. Eustachian tube dysfunction predisposes to chr...

Endolymphatic sac tumor

Endolymphatic sac tumors are very rare, locally invasive tumors of endolymphatic sac. Early detection of these tumors is critical, because early surgical intervention may prevent further hearing loss. Endolymphatic sac tumors do not metastasize but are highly locally aggressive. Epidemiology ...

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