The Coca-Cola bottle sign refers to the appearance of the muscles of the orbit in thyroid eye disease. The belly of the muscle enlarges with sparing of the tendinous insertion, giving the appearance of the traditional Coca-Cola bottle.
The enlargement of the muscles follows the I'M SLOW format...
Coccidioidomycosis refers to an infection caused by the dimorphic fungus Coccidioides spp, usually localised to the lungs. This disease is not to be confused with the similarly named paracoccidioidomycosis.
The most common forms of Coccidioides spp are Coccidioides immitis and Coc...
The cochlea is part of the inner ear osseous labyrinth found in the petrous temporal bone.
The cochlea is a shell-shaped spiral that turns between two-and-a-half and two-and-three-quarters times around the modiolus (a central column of porous bone).
The spiral of the cochlea is...
Cochlear anomalies are a variety of congenital anomalies which, depending on the exact time at which an insult occurs during embryogenesis, may have different manifestations. Terminology is often used imprecisely leading to confusion not only among clinicians, but also in the literature.
Cochlear aplasia, or complete absence of the cochlea is a rare anomaly which accounts for only 3% of cochlear malformations.1
complete absence of the cochlea. Dense otic bone is seen at the anatomical site of the cochlea 2
cochlear nerve canal and cochlear nerve are abse...
The cochlear duct (also known as the scala media) is housed centrally in the cochlea which is part of the inner ear along with the vestibular apparatus 1,4. The cochlea is located in the bony labyrinth, which is found in the temporal bone 2.
The cochlear duct is a cavity filled w...
Cochlear hypoplasia is defined by small underdeveloped cochlea <2 turns.
a small cochlear bud of variable length (usually 1–3 mm). It has only one turn or a partial turn is seen
cochlear nerve often hypoplastic or absent
cochlear nerve canal: absent, narrow or normal
Thin osseous septum separating the semicanal for tensor tympani and the bony Eustachian tube.
Cochlear implants (CI) are a surgically implanted electronic device that provides a sense of sound to a person who is profoundly deaf or severely hard of hearing. Unlike conventional hearing aids, the cochlear implant does not amplify sound, but works by directly stimulating any functioning audi...
Cochlear incomplete partition is a group of cochlear malformations associated with variable degree of inner ear architecture defects.
It is classified in three groups:
cochlear incomplete partition type I (IP-I)
a severe form of IP-I is known as cystic cochleovestibular malformation
Cochlear incomplete partition type I (IP-I) is a type of cochlear anomaly associated with sensorineural hearing loss.
The main findings on CT are:
absent interscalar septum
wide (most common) or normal cochlear nerve canal
Absence of these structu...
Cochlear incomplete partition type II (IP-II) is a type of cochlear anomaly associated with sensorineural hearing loss.
It should not be confused with Mondini anomaly, which his an historic term for a combination of IP-II and large vestibular aqueduct.
On CT, the co...
Cochlear incomplete partition type III (IP-III), also termed X-linked deafness, is a rare type of genetic cochlear anomaly associated with mixed conductive and sensorineural hearing loss.
It is caused a mutation in the POU3F4 gene located on the X chromosome.
The cochlear promontory is the name given to the bone that overlies the basal turn of the cochlea protruding into the middle ear cavity.
glomus tympanicum paragangliomas typically arise in the region of the cochlear promonotory
Cogan syndrome is a rare vasculitis of children and young adults which primarily characterised by 1,4,6:
inflammatory eye disease (ocular keratitis, uveitis, scleritis, optic neuritis) 6
audiovestibular symptoms (similar to Meniere disease) 6
However, it can potentially affect a multitude of ...
COL4A1-related disorders are a group of autosomal dominant disorders caused by a mutation in the COL4A1 gene.
The exact prevalence is unknown, but the group of disorders is considered to be under-recognised, especially asymptomatic variants 1.
The clinical ...
Collet-Sicard syndrome is a constellation of cranial nerve palsies due to a lesion at the jugular foramen such as a glomus jugulare tumour or schwannoma. It consists of :
Vernet syndrome, consisting of motor paralysis of
glossopharyngeal nerve (CN IX)
vagus nerve (CN X)
accessory nerve (CN X...
The colliscalene triangle is an important anatomical region of the neck, situated medial to the scalenus anterior muscle.
medial: lateral border of longus colli
lateral: medial border of scalenus anterior
inferior: first part of the subclavian artery
apex: carotid ...
Colloid nodules are non-neoplastic benign nodules occurring within the thyroid gland. They form the vast majority of nodular thyroid disease.
Colloid nodules are composed of irregularly enlarged follicles containing abundant colloid. Some colloid nodules can be cystic (cystic colloid...
Coloboma is collective term encompassing any focal discontinuity in the structure of the eye, and should not be confused with staphylomas, which are due to choroidal thinning.
Most commonly colobomas are due to failure of closure of the choroidal fissure posteriorly. Typically colob...
The columella is the most anteroinferior portion of the nasal septum. It is a single midline structure composed of cartilage and overlying skin, extending posteriorly from the tip of the nose. The lateral aspects form the medial wall of each nostril.
History and etymology
From the Latin word f...
The common carotid artery is a paired structure that supplies blood to the head and neck.
left: branch of the aortic arch
right: branch of the brachiocephalic trunk
course: posterior to sternoclavicular joint, lateral to thyroid and trachea
supply: head and neck
Common cavity malformation is defined by the absence of the normal differentiation between the cochlea and vestibule, replaced instead by a cystic structure (i.e. the 'common cavity'). It accounts for about 25% of cochlear malformations 1.
confluence of the cochlea, vest...
The common facial vein is formed by the joining of the facial vein and anterior branch of the retromandibular vein. It is part of the venous drainage system of the face.
origin and termination: the facial vein (along with the facial artery) pierces the deep investing fascia of the neck...
Common variable immunodeficiency (CVID) is a condition that is associated with an impaired immune system. It is considered the most common symptomatic primary immunodeficiency, and is characterised by recurrent respiratory tract infections.
The commonest presentation is t...
Complex midfacial fractures consist of multiple facial fractures that cannot be classified as any of the defined complex facial fracture (e.g. Le Fort fracture, zygomaticomaxillary complex fracture, naso-orbital-ethmoid fracture).
A handy mnemonic to recall the complications of transverse and longitudinal petrous temporal bone fractures is:
listen carefully to something funny
listen carefully = longitudinal / conductive hearing loss
to something funny = transverse / sensorineural hearing loss and facial nerve...
Concha bullosa (plural: conchae bullosae) (also known as middle turbinate pneumatisation) is a common finding and although associated with deviation of the nasal septum, it is usually of little clinical importance.
Concha bullosa is a normal variant and is one of the most common v...
Conductive hearing loss is caused by a range of developmental, congenital or acquired pathology to the external, middle or inner ear.
Essentially any process that obstructs or disrupts the passage of sound waves through the outer or middle ear can cause conductive hearing loss and th...
The condylar canal, or canalis condylaris, is a skull base canal in the posterior cranial fossa, located in the condylar fossa.
location: in the condylar fossa of the posterior cranial fossa, posterior to the occipital condyles
emissary veins, connecting the sigmoid sinus to...
Condylar process fractures are fractures of the condylar process of the mandible. The condylar process of the mandible is involved in around 30% of all mandibular fractures.
Condylar fractures are classified according to the location of the fracture and the direction displacement of the condyle...
Congenital absence of the internal carotid artery (ICA) is a rare anomaly that occurs in less than 0.01% of the population. It encompasses agenesis, aplasia, and hypoplasia 1.
The most common type of collateral flow is through the circle of Willis, through the anterior communicating artery (ACO...
Congenital calvarial defects are a group of disorders characterised by congenital calvarial bone defects that vary in severity.
CT with 3D shaded surface reformats is the best imaging tool as it demonstrates calvarial defects and bone margins:
Congenital cataracts are a major cause of blindness with early detection the most important factor in reducing impact on future vision.
Incidence is ~3 per 100,000 in the United Kingdom 1. Will be higher in areas with increased rates of congenital infection 5.
Congenital cervical teratoma refers to a teratoma arising in the cervical region. They are thought to account for ~3% of teratomas in childhood/infancy 3.
The estimated occurrence in neonates is ~1:20,000-40,000 live births 8.
Most tumours are diagnosed at ...
Congenital cholesteatomas are identical to epidermoid cysts, differing only in name and location.
They are intraosseous inclusions of ectoderm, and are therefore comprised of keratin debris and cholesterol. Characteristically, they are located at the petrous apex. In contrast middle...
A congenital granular cell myoblastoma (also known as congenital epulis) is a very rare benign tumour which classically presents in the fetal-neonatal population.
It occurs almost exclusively in females when it presents in the fetal-neonatal population although no such predilectio...
Congenital hypothyroidism (CHT), previously known as cretinism, can be of thyroidal or central (hypothalamic/pituitary) origin and can have a widely diverse molecular aetiology.
Most children are asymptomatic at birth and are diagnosed after screening. In untreated CHT pa...
The features of an infant with congenital hypothyroidism can be recalled with the following mnemonic:
5 Ps of congenital hypothyroidism
P: pot belly
P: puffy face
P: protruding umbilicus
P: poked out tongue
Congenital anomalies of the ossicles are most frequently associated with external ear abnormalities also, although they can occur in isolation.
They cause conductive hearing loss (CHL).
When bilateral they are most frequently genetic, with autosomal dominant inheritance, whereas unilateral a...
The conjunctiva is a transparent membrane is attached at the margins of the cornea. It is loosely attached to the sclera and thence reflected over the inner surface of the eyelids. It is firmly attached to the tarsal plates and blends with the skin at the margins of the lids.
Convexal subarachnoid haemorrhages (cSAH) are nontraumatic intracranial haemorrhages that occur within the surface sulci of the brain (c.f. basal cisternal distribution of aneurysmal SAH). There are various causes of convexal SAH, some of which include:
dural venous sinus thromboses
A convoluted cerebriform pattern is a term used to denote the appearance of a sinonasal inverted papilloma on MRI. The appearance is seen on both T2 and post contrast T1 images and appears as alternating roughly parallel lines of high and low signal intensity.
This sign has been reported as pre...
The corniculate cartilages are paired, elastic and accessory cartilages of the larynx that lie superior to and articulate with the apices of the arytenoid cartilages. They are components of the laryngeal cartilages. The word 'corniculate' comes from the latin word 'cornu' meaning horn-like.
The coronal suture is the cranial suture formed between the two parietal bones and the frontal bone. At the junction of coronal, sagittal and frontal sutures is the anterior fontanelle which is open at birth and usually fuses at around 18-24 months after birth.
Fusion of the coronal suture occu...
The corrugator supercilii are two small, triangular muscles that allow facial expression through movement of the eyebrows, including frowning. They originate from the medial end of the supraorbital margins and insert deep to and can cause traction on the skin over the middle of the supraorbital ...
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...
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.
Although commonly seen in r...
Craniofacial fibrous dysplasia is one of four types of fibrous dysplasia and is characterised, 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...
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 or cranioplasty.
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. 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 the lamina. It articulates with th...
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...
CSF otorrhoea is defined as leakage of cerebrospinal fluid (CSF) from the subarachnoid space into the middle ear cavity or mastoid air cells (cf. CSF rhinorrhoea)
There are a number of underlying causes, and thus no specific demographic is affected.
The subdural (blood) window can be used when reviewing a CT brain as it makes intracranial haemorrhage more conspicuous, and may help in the detection of thin acute subdural haematomas that are against the calvarium. It is a wider setting than the standard non-contrast window, and there are a nu...
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...
Cutis verticis gyrata is a rare progressive dermatological condition characterised 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.
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 paediatri...
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: parotid lymphoepithelial cy...
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 th...
Dacryocystoceles are caused by obstruction of both the proximal and distal ends of the nasolacrimal duct. An imperforate Hasner membrane causes the distal blockage, but the cause of proximal obstruction is less clearly understood.
Dacryocystoceles, although rare, are the second mo...
Dacryocystography is a fluoroscopic contrast examination of the nasolacrimal apparatus. The 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 eyes.
The danger space is a potential space located behind the true retropharyngeal space, which connects the deep cervical spaces to the mediastinum.
anteriorly: alar fascia
posteriorly: prevertebral layer of the deep cervical fascia
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 3 separate but related fascial layers that encircle structures in the neck and allow anatomic compartmentalisation. These layers cannot be visualized directly by cross sectional imaging. All 3 layers meet to form the carotid sheath. From superficial to deep, ...
The deep petrosal nerve transmits post-ganglionic sympathetic fibres 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...
Head and neck anatomy is described in slightly different terms in the radiology literature reflecting the importance of fascia lined spaces in confining various pathologies. As such the neck has been divided into a number of 'deep spaces' which overlap with traditional anatomical description.
The deep temporal arteries (anterior 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 branches which...
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) 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, above the thyroid isthmus, lying directly ant...
Dental (periapical) abscess is an acute infection of the periapical tissue around the root of the tooth.
Patients may present with pain, oedema, and purulent discharge localised 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.
Focal enamel and dentin demineralisation result in cavity formation. There are multiple theories for their pathogenesis but contributing facto...
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 BCVI are divided into signs and symptoms of BCVI a...
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 number of as...
The depressor anguli oris (triangularis) muscle is one of the muscles of facial expression.
origin: oblique line of the mandible
angle of the mouth
superficial fibres from both sides merge to form the transversus menti
innervation: facial nerve
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.
Dermolipomas are congenital and more commonly seen in young patients with mean age of 30 years old. There is no gender predilect...
Descending necrotising 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...
A deviated nasal septum is a common incidental finding seen on brain and paranasal sinus CT studies.
It can be congenital or acquired. The most common acquired cause is trauma from motor vehicle collisions, sports-related injuries, and altercations.
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 tumour (Pindborg tumour)
The digastric (or biventer) line has been described and used to evaluate basilar invagination on frontal skull plain film and coronal recontructed CT image.
The digastric line is drawn between right and left digastric grooves. The tip of the odontoid process and atlanto-occipital joint normall...