The corrugator supercilii muscles are two small, triangular muscles of facial expression, which contribute to movement of the eyebrows, including frowning. They are located deep to the frontal part of occipitofrontalis and orbicularis oculi muscles, with which they blend 2.
The costocervical trunk is one of the branches of the second part of the subclavian artery. It arises from the posterior wall of the subclavian artery, posterior or medial to the anterior scalene muscle and courses posterosuperiorly across the suprapleural membrane where it divides into 2 branc...
Cracking thyroid is a term given to a very rare complication of thyroid fine needle aspiration (FNA) biopsy where there is acute pain and transient thyroid swelling characterized by hypoechoic avascular septations on ultrasound 1.
The cranial vault, also known as the skull vault, skullcap or calvaria, is the cranial space that encases and protects the brain together with the base of the skull (chondrocranium). The cranial vault and the base of skull together form the neurocranium.
The cranial vault consist...
Craniofacial fibrous dysplasia is one of four types of fibrous dysplasia and is characterized, as the name suggests, by involvement of the skull and facial bones.
For a general discussion of the underlying pathology, refer to the parent article fibrous dysplasia.
Although the term...
A craniotomy is a surgical procedure where a piece of calvarial bone is removed to allow intracranial exposure. The bone flap is replaced at the end of the procedure, usually secured with microplates and screws. If the bone flap is not replaced it is either a craniectomy (bone removed) or cranio...
The cribriform plate is a sieve-like structure between the anterior cranial fossa and the nasal cavity. It is a part of ethmoid bone and supports the olfactory bulb, which lies in the olfactory fossa. It is perforated by foramina for the passage of the olfactory nerves and the anterior ethmoidal...
The cricoid cartilage is a ring-shaped structure that sits just below the thyroid cartilage, at the level of the C6 vertebra. It is the only complete cartilaginous ring of the whole airway.
The anterior portion is called the arch and the posterior quadrangular shaped portion is t...
Cricopharyngeal muscle spasm is also known as cricopharyngeal achalasia, although some authors distinguish between these entities, and may present as a cause of dysphagia.
There is confusing use of the terms cricopharyngeal muscle spasm, cricopharyngeal achalasia and cricopharyngea...
The crista galli is a thick, midline, smooth triangular process arising from the superior surface of the ethmoid bone, projecting into the anterior cranial fossa. It separates the olfactory bulbs, which lie either side of it in the olfactory fossae of the cribriform plate. It serves as an anteri...
A crus (plural: crura) is an anatomical term used for a structure which resembles a leg.
crus (internal capsule)
crus (semicircular duct)
The crystalline lens (or simply, the lens, plural: lenses) is in the ocular globe between the posterior chamber and the vitreous body. It is transparent and biconvex in morphology, and aids the focusing of light onto the retina.
The lens lies in the globe at the poster...
CSF otorrhea is defined as leakage of cerebrospinal fluid (CSF) from the subarachnoid space into the middle ear cavity or mastoid air cells (cf. CSF rhinorrhea)
There are a number of underlying causes, and thus no specific demographic is affected.
CT polytrauma/multitrauma, also called trauma CT, whole body CT (WBCT) or panscan, is an increasingly used investigation in patients with multiple injuries sustained after significant trauma.
Clinical assessment and mechanism of injury may underestimate injury severity by 30% 8. There is some e...
The cuneiform cartilage is a small, paired cartilage which resides in the aryepiglottic fold. It takes the form of a club-like nodule, visible as an elevation beneath the mucosa (the cuneiform tubercle) anterosuperior to the corniculate cartilages.
History and etymology
The word cuneiform deri...
Cutaneous carcinoma of the head and neck staging refers to TNM staging of nonmelanoma skin cancer involving the scalp, external ear, neck, or face including external lips. The system applies to cutaneous squamous cell carcinoma and numerous other skin carcinomas, notably excluding eyelid carcino...
Cutis verticis gyrata is a rare progressive dermatological condition characterized by excessive skin folds in the scalp, resembling the surface of the cerebral cortex.
It occurs more commonly in males, with a male-to-female ratio of approximately 5:1 1.
The head and neck manifestations of cystic fibrosis are common compared to the well-known respiratory manifestations.
For general discussion of cystic fibrosis, and a discussion of its other manifestations, please refer to:
cystic fibrosis (parent article)
pulmonary manifestations of cystic ...
Cystic hygroma, also known as cystic or nuchal lymphangioma, refers to the cystic variety of congenital lymphangioma which, most commonly, occur in the cervicofacial regions, particularly at the posterior cervical triangle.
They usually occur in the fetal/infantile and pediatric...
The differential diagnosis of a cystic mass adjacent to the angle of mandible includes:
2nd branchial cleft cyst
lymphatic malformation (lymphangioma)
from metastatic squamous cell carcinoma
from metastatic papillary thyroid cancer
Cystic or necrotic appearing lymph nodes can be caused by a number of infectious, inflammatory or malignant conditions:
squamous cell carcinoma metastases
plasmacytoid T-cell leukemia
acute myeloid leukemia
herpes simplex lymphadenit...
The differential for cystic parotid lesions includes:
bilateral cystic parotid lesions
benign lymphoepithelial lesions of HIV
unilateral cystic parotid lesion(s)
first branchial cleft cyst
Cytomegalovirus retinitis is a late complication of cytomegalovirus (CMV) infection, usually occurring in immunosuppressed patients. It is an acquired immune deficiency syndrome (AIDS) defining illness.
The reported incidence and prevalence of CMV retinitis varies with geographica...
Dacryoadenitis is infection of the lacrimal gland results in diffuse homogeneous enlargement, which can sometimes compress the globe. Most common organisms are Staphylococcus aureus, mumps, infectious mononucleosis, and influenza virus.
Dacryocystitis is the inflammation of the nasolacrimal sac related to impairment in the lacrimal drainage system and superimposed infection.
Dacryocystitis has a bimodal distribution: neonates due to congenital abnormalities and when acquired, usually affect individuals older tha...
Dacryocystoceles are caused by obstruction of both the proximal and distal ends of the nasolacrimal duct. An imperforate Hasner valve causes the distal blockage, but the cause of proximal obstruction is less clearly understood but the Rosenmuller valve has been implicated.
Dacryocystography (DCG) is a fluoroscopic contrast examination of the nasolacrimal apparatus. The nasolacrimal duct is cannulated enabling iodinated contrast to be instilled into the nasolacrimal system.
The most frequent indication is epiphora: excessive tearing or watering of the...
The danger space is a deep compartment of the head and neck located behind the true retropharyngeal space, extending from the skull base to the mediastinum.
The danger space has no specific contents apart from a small amount of loose fatty connective tissue and is thus usually indi...
Deafness (also known as hearing loss or impairment) is the partial or complete loss of the sense of hearing.
It may be subdivided etiologically into
conductive: impairment of the passage of sound waves from the auricle to the inner ear
sensorineural: impairment localizes to the inner ear, in...
The deep auricular artery is the first named branch of the maxillary artery and passes through the bony or cartilaginous wall of the external acoustic meatus to supply the skin of that canal and part of the tympanic membrane. It can sometimes contribute a small branch to the arterial supply of t...
Deep brain ultrasound (DBUS) therapy is a form of precision medicine using a technique based on the principle of high-intensity focused ultrasound (HIFU), also referred to as focused ultrasound surgery (FUS).
The method combines two main components 1:
MRI of the ...
The deep cervical fascia consists of three separate but related fascial layers that encircle structures in the neck and allow anatomic compartmentalisation into the deep spaces of the head and neck. Each layer contributes to the carotid sheath. See the separate articles for further details:
The deep layer of the deep cervical fascia is one of the three layers of the deep cervical fascia. It encases the paravertebral muscles and forms the perivertebral space. It consists of the perivertebral fascia (the anterior part of which is called the prevertebral fascia) and alar fascia 1-3.
The deep petrosal nerve transmits post-ganglionic sympathetic fibers from the internal carotid plexus to the Vidian nerve on its way to the pterygopalatine ganglion.
The nerve begins at the internal carotid plexus and runs alongside the lateral aspect of the internal carotid arte...
The deep spaces of the head and neck refer to compartments delimited by the deep cervical fascia. While these concepts overlap with traditional anatomical description, their existence highlights the importance of fascia in confining various pathologies.
A knowledge of these spaces not only allo...
The deep temporal arteries (anterior, middle and posterior) are branches from the second part of the maxillary artery. They ascend between the temporalis muscle and the pericranium supplying the overlying muscle.
The anterior branch communicates with the lacrimal artery by means of small branch...
The deep temporal nerves are a pair of motor branches of the anterior division of the mandibular division of the trigeminal nerve. It should not be confused with the temporal branch of the facial nerve.
The two deep temporal nerves divide off the anterior division and course abov...
Dehiscence is a general term referring to 'splitting open' and is used in a variety of contexts in medicine generally and radiology more specifically.
The two most common usages are:
splitting open of a wound (e.g. sternal dehiscence)
loss of bone separating one structure from another (e.g. ...
Dehiscent jugular bulbs are present when the sigmoid plate between a high riding jugular bulb and the middle ear is absent, allowing the wall of the jugular bulb to bulge into the middle ear cavity.
The estimated incidence is ~5% (range 3.5-7%) of the symptomatic population (e.g. ...
The Delphian (prelaryngeal/precricoid) lymph node (often shortened to Delphian node) is one of the cervical lymph node groups that comprise level VI cervical lymph nodes and is not routinely excised in radical neck dissections.
It is located between the cricothyroid muscles, abov...
Dental (periapical) abscesses are an acute infection of the periapical tissue around the root of the tooth.
Patients may present with pain, edema, and purulent discharge localized to the site of pathology with or without fever and tender cervical lymphadenopathy 1.
Dental caries are cavities in teeth ('caries' is both the singular and plural form). They are very common and can lead to serious morbidity.
Tooth decay is asymptomatic in its early stages. Once the enamel has been breached and the dentin is exposed then people may exper...
Dental fractures are often clinically apparent but can be overlooked in the cases of associated facial fractures, especially as root fractures may be clinically occult.
When both a tooth and alveolar process are fractured, the term dentoalveolar fracture can be used 1.
Dental implants are a common procedure used to replace absent teeth. Radiology has a role in pre-implant planning as well as post-implant assessment including identification of complications.
Dental CT is the most common modality used in dental implant imaging.
Dental luxation is a common manifestation of dental trauma and may be associated with socket fractures.
Dental luxation is a general term encompassing 1:
concussion: tender tooth, no loosening/displacement
subluxation: tender tooth, loosening without displacement
Dental trauma is common, affecting up to one-third of the population. While often clinically apparent, they may be overlooked in the setting of severe trauma.
The maxillary incisors are the most commonly injured tooth. Dental trauma can be classified as 1,2:
luxation (loosening): m...
Dentigerous cysts, also called follicular cysts, are slow growing benign and non-inflammatory odontogenic cysts that are thought to be developmental in origin.
On imaging, they usually present as a well-defined and unilocular radiolucency surrounding the crown of an unerupted or impacted tooth ...
The Denver criteria are a set of screening criteria for blunt cerebrovascular injury (BCVI) in trauma used to reduce the need for CT angiography and its associated radiation exposure.
The screening protocol criteria 1,3 for blunt cerebrovascular injury are divided into sign...
Depressed skull fractures result in the bone of the skull vault being folded (depressed) inward into the cerebral parenchyma. It is usually the result of a high energy impact to the skull.
These mostly (~75%) occur in the frontoparietal region 3.
There are a number of ...
The depressor anguli oris muscle (also known as the triangularis muscle) is one of the muscles of facial expression.
origin: oblique line of the mandible
angle of the mouth
superficial fibers from both sides merge to form the transversus menti
innervation: facial nerve...
The depressor septi nasalis muscles (DSN) (also known as the depressor septi nasi muscles) are paired muscles of the nose, a subset of the muscles of facial expression, which depress the nose.
insertion: nasal septum, medial crura, membranous septum
De Quervain thyroiditis, or subacute granulomatous thyroiditis, is a form of self-limited subacute thyroiditis usually preceded by an upper respiratory tract viral infection such as mumps, measles, coxsackie virus, adenovirus, and influenza viruses.
It usually affects middle-age f...
The dermolipoma is one of the fat-containing epibulbar mass lesions of lateral canthal area beneath the temporal or superotemporal bulbar conjunctivae. This should be differentiated from subconjunctival fat prolapse as they have different radiological features and treatment stratagies 4.
Descending necrotizing mediastinitis is a severe form of mediastinitis and refers to an acute, polymicrobial infection of the mediastinum that usually spreads downwards from oropharyngeal, cervical, and odontogenic infection.
diabetes: more than one-third of patients...
Developmental orbital cysts correspond to a heterogeneous group of congenital orbital developmental anomalies with cystic component, ranging from closed sacs lined by an ectodermal epithelium, such as epidermoid and dermoid, to neoplasms as teratoma 1.
choristoma: it is formed by heterotopic...
Deviated nasal septums are a common, usually incidental, finding seen on brain and paranasal sinus CT studies. They are commonly seen with external nose deformities.
Symptomatic patients can present with unilateral nasal obstruction or less commonly epistaxis, obstructiv...
Diabetes insipidus (DI) is the deficiency or resistance to the hormone vasopressin (antidiuretic hormone), which results in polyuria and polydipsia.
DI occurs in 3 per 100,000 people 2.
DI may be described as 1-3:
central/neurogenic/hypothalamic: vasopressin deficie...
Differential diagnosis for calcified masses in the mandible includes:
calcifying odontogenic cyst (Gorlin cyst)
calcifying epithelial odontogenic tumor (Pindborg tumor)
Differentiated thyroid cancer staging refers to TNM staging of papillary thyroid cancer and follicular thyroid cancer. Anaplastic thyroid carcinoma and medullary thyroid carcinoma are staged separately. The following article reflects the 8th edition manual published by the American Joint Committ...
The digastric line, also known as the biventer line, has been described and used to evaluate basilar invagination on frontal skull plain film and coronal CT images.
The digastric line is drawn between right and left digastric grooves, which are located medial to the mastoid apices. These are co...
The digastric muscle is composed of two bellies, anterior and posterior, connected by an intermediate round tendon. The two bellies of the muscle have different embryonic origins and hence are supplied by different cranial nerves.
anterior belly: digastric fossa on the deep sur...
The digastric triangle is one of the paired triangles in the anterior triangle of the neck. The triangles of the neck are surgically focused, first described from early dissection-based anatomical studies which predated cross-sectional anatomical description based on imaging (see deep spaces of ...
Dilator naris muscle forms the alar component of nasalis muscle, and is one of the muscles of the nose, a subset of the muscles of facial expression.
insertion: nasal ala
innervation: facial nerve (VII)
action: flaring of the nostril
Dolan's lines are the collective name given to three lines described by Dolan and Jacoby 1 that aid in evaluating for maxillofacial fractures on an occipitomental skull radiograph. They are usually used as an adjunct to McGrigor-Campbell lines.
orbital line traces the inner margins of the later...
The term dolichoectasia means dilated and elongated. It is used to characterize arteries that have shown a significant deterioration of their tunica intima (and occasionally the tunica media), weakening the vessel walls and causing the artery to elongate and distend.
Dorello canal channels the abducens nerve (CN VI) from the pontine cistern to the cavernous sinus.
Dorello canal is found at the medial most end of the petrous ridge at the confluence of the inferior petrosal, basal, and cavernous sinuses.
The dorsal nasal artery, also known as the dorsonasal artery, is a terminal branch of the ophthalmic artery.
Arising as a terminal branch of the ophthalmic artery, the dorsal nasal artery exits the orbit after piercing the orbital septum above the medial canthal tendon (medial pa...
The dorsum sellae is the square shaped process of the sphenoid bone. It ascends superiorly from the posterior part of the sphenoid body to form the posterior wall of the sella turcica.
The dorsum sellae forms the posterior wall of the sella turcica, which houses the pi...
Thickening of the insertion of the lateral pterygoid muscle can mimic an anterior displaced temporomandibular disc. When both thickening of the inferior belly insertion and an anteriorly displaced disc are present, as in temporomandibular joint dysfunction, the two structures parallel each other...
The duct of Rivinus connects the sublingual gland to the floor of the mouth.
Despite its name, it is not a single duct, but numerous small ducts all of which open into the floor of the mouth and are collectively termed the duct of Rivinus.
The largest of these little ductules is the major duct...
The ducts of the salivary glands allow the passage of salivary juice from the glands to the oral cavity:
parotid duct (Stenson duct): connects the parotid gland to the buccal mucosa, adjacent to maxillary second molar
submandibular duct (Wharton duct): connects the submandibular gland to the f...
A useful mnemonic to remember differential diagnoses associated with a dural tail sign is:
My Scary Dog Likes To Stand Guard
D: dural metastases
Dysphagia refers to subjective awareness of difficulty or obstruction during swallowing. It is a relatively common and increasingly prevalent clinical problem. Odynophagia is the term for painful swallowing.
Fluoroscopy is the mainstay of imaging assessment but manometry can help evaluate the e...
Eagle syndrome refers to symptomatic elongation of the styloid process or calcified stylohyoid ligament 1,2. It is often bilateral. In most cases, the cause is unknown; however, the condition is sometimes associated with disorders causing heterotopic calcification such as abnormal calcium/phosph...
The ear refers to the entire vestibulocochlear organ and is divided anatomically into:
Epstein-Barr virus-associated smooth muscle tumors (EBV-SMT) are rare and encountered in immunocompromised individuals.
These tumors are generally exceedingly rare, and only seen with any frequency in the setting of immunosuppression, particularly in HIV/AIDS patients, but also po...
Ectodermal dysplasia (ED) refers to a heterogeneous group of genetic disorders that cause abnormal ectoderm development. The effect is a non-progressive defect in the development of two or more tissues derived from embryonic ectoderm.
ED is rare with an estimated prevalence of 1:...
Ectopia lentis refers to subluxation or dislocation of the lens of the eye secondary to dysfunction or disruption of zonular fibers.
systemic and syndromic disorders
typically upwards and out
most common spontaneous cause 2
homocystinuria - typ...
An ectopic thyroid gland is one which is located in a location other than the normal position anterior to the laryngeal cartilages.
During embryological development, the thyroid gland migrates down from the foramen cecum at the posterior aspect of the tongue to its permanent lo...
Edentulism (or edentulousness) means absence of dentition and can have a significant impact on a patient's quality of life in addition to the negative cosmetic effects.
When edentulism is used as a standalone term it usually means that all the teeth are absent, i.e. complete edentu...
Emissary veins (also known as the vena emissaria) are small valveless, thin-walled veins that pass via the foramina of the skull, providing a venous communication between the dural venous sinuses and veins of the scalp or veins inferior to the skull base (cranial-cerebral anastomosis). Thus, the...
The empty nose syndrome refers to a paradoxical sensation of nasal obstruction despite objectively patent nasal airways following inferior and/or middle turbinate resection.
The condition is rare, occuring in a minority of patients who have undergone prior turbinate resection.
Endolymph is one of the two types of cochlear fluids, the other being perilymph. It is located in the scala media of the cochlea.
It is secreted by the stria vascularis (also colloquially called the 'battery of the cochlea') on the outer wall of the scala media. It has a high level of potassium...
The endolymphatic duct is a small epithelial-lined channel, part of the membranous labyrinth that passes through the vestibular aqueduct in the bony labyrinth of the petrous temporal bone. It arises from the utricle and saccule via the utriculosaccule duct and drains endolymph. The distal end is...
Endolymphatic sac tumors (ELSTs) 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.
Endophthalmitis is a potentially sight-threatening condition that involves intraocular inflammation of any cause. It is distinguished from panophthalmitis in that it does not extend beyond the sclera. It is either infectious or non-infectious in etiology, but in clinical practice, intraocular in...
There is a short list of causes for enlarged extraocular muscles:
thyroid associated orbitopathy
amyloidosis (very rare) 2
Enophthalmos refers to the posterior displacement of the globe in the orbit. It implies that the globe itself is normal and is caused by either one or a combination of 1:
structural alterations in the bony orbit
orbital fat atrophy
Specific causes include 2:
orbital blowout fract...
The epiglottis is a single midline leaf-shaped fibrocartilaginous structure that forms part of the supraglottic larynx and defines the division of the hypopharynx from the larynx.
The epiglottis projects posterosuperiorly from its stem-like base, which is attached to the thyroid...
Epiglottitis, also known as supraglottitis, is a life-threatening condition caused by inflammation of the epiglottis and aryepiglottic folds 1, which can lead to acute airway obstruction.
The traditional age of presentation is in children of 3 to 6 years, although this has been c...
Epignathus is a term given to a very rare form of teratoid tumor that arises from the oropharyngeal region.
There may be a slight female predilection ref. The estimated incidence is ~ 1 in 35,000 to 200,000 births.
The tumor classically presents in utero or...
Epiphora (plural: epiphoras) represents excessive tearing of the eye and is a common clinical presentation to ophthalmological practice. It is most frequently due to an obstruction of the nasolacrimal drainage apparatus. Less commonly, overproduction of tears may be responsible.
Epistaxis (plural: epistaxes) is the medical term for a nosebleed, and is very common in clinical practice with a broad differential diagnosis. Anterior epistaxes mainly bleed from Kiesselbach's plexus and posterior epistaxes (5% of all epistaxis) from Woodruff's plexus.