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...
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.
The cranial vault consist...
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.
There are a number of underlying causes, and thus no specific demographic is affected.
Patients typically present ...
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) is an increasingly used test in the patient with multiple injuries sustained after significant trauma.
There is some evidence that trauma patients who undergo whole body CT (WBCT) / panscan have better survival than patients who undergo selectiv...
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...
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. They are very common and can lead to serious morbidity.
Focal enamel and dentin deminerlisation result in cavity formation. There are multiple theories in their pathogenesis but contributing factors include a combination of diet, anatomy, oral ca...
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...
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...
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 focussed, first described from early dissection-based anatomical studies which predated cross-sectional anatomical description based on imaging (see deep spaces of...
Disc herniation refers to the displacement of intervertebral disc material beyond the normal confines of the disc but involving less than 25% of the circumference (to distinguish it from a disc bulge. A herniation may contain nucleus pulposus, vertebral endplate cartilage, apophyseal bone/osteop...
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 characterise 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, the two structures parallel each other; the so-called "double disc" sign.
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...
Dysphagia refers to subjective awareness of difficulty or obstruction during swallowing. It is a relatively common and increasingly prevalent clinical problem.
Fluoroscopy is the mainstay of imaging assessment but manometry can help evaluate the esophageal motor pattern and lower esophageal sp...
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...
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 fibres.
systemic and syndromic disorders
typically upwards and out
most common spontaneous cause 2
homocystinuria - ty...
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 caecum at the posterior aspect of the tongue to its permanent location. This nor...
Endolymph is a one of two type of cochlear fluids, the other being perilymph. It is located in the scala media of the cochlea.
It is secreted by the stria vascularis (colloquially called 'battery of the cochlea') on the outer wall of the scala media.
It has a high level of potassium (K+) and g...
Endolymphatic sac tumours (ELST) are very rare, locally invasive tumours of endolymphatic sac. Early detection of these tumours is critical, because early surgical intervention may prevent further hearing loss. Endolymphatic sac tumours do not metastasize but are highly locally aggressive.