COL4A1 brain small-vessel disease is an autosomal dominant monogenic COL4A1-related disorder that primarily causes cerebral small vessel disease.
The exact prevalence is unknown, but the condition is likely under-diagnosed.
The clinical presentation is vari...
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-recognized, especially asymptomatic variants 1.
The clinical ...
COLD syndrome is the acronym for the concurrent diagnosis of Cowden syndrome and Lhermitte-Duclos disease. It has been suggested that COLD syndrome should be considered a phakomatosis 1.
The collateral sulcus, also known as the medial occipitotemporal sulcus, runs anteroposteriorly on the inferior surface of the temporal lobe and occipital lobe. Anteriorly it is sometimes continuous with the rhinal sulcus 1-3.
Anteriorly, it separates the fusiform gyrus laterally, from the par...
Collateral vessels are an important consideration during the acute imaging of ischemic stroke, as they can impact upon the evaluation of whether or not a patient will benefit from endovascular thrombectomy (ECR, endovascular clot retrieval) 1.
Studies have shown that in acute stroke, both CTA a...
Collet-Sicard syndrome, also known as condylar jugular syndrome, is a constellation of cranial nerve palsies due to neoplastic or non-neoplastic lesion at the jugular foramen 1,2.
Vernet syndrome, consisting of motor paralysis of
glossopharyngeal nerve (CN IX)
Colloid cysts of the third ventricle are benign epithelial lined cysts with characteristic imaging features. Although usually asymptomatic, they can rarely present with acute and profound hydrocephalus.
Classically these cysts are identified as a well-delineated hyperattenuated mass on unenhanc...
Coloboma is a 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.
Embryologically, colobomas are due to the failure of closure of the choroidal fissure. The most common si...
Colpocephaly is a descriptive term for a disproportionate prominence of the occipital horns of the lateral ventricles. It can result from a wide range of congenital insults.
Patients may present with motor abnormalities, cognitive deficit, visual abnormalities, and seizur...
Combined cerebral edema is a type of cerebral edema in which there is a mixed pattern of both cytotoxic and vasogenic cerebral edema.
It is usually associated with severe systemic damage, such as with:
severe sepsis / severe inflammatory condition
The combined conduit score (CCS) is a grading scheme for the assessment of the degree of transverse-sigmoid sinus stenosis in the setting of idiopathic intracranial hypertension. The score was initially developed for ATECO MR venography 1.
Assessment is performed using maximum inten...
Commissural fibers of the brain, also known as commissural tracts of the brain or commissures are a type of white matter tract that cross the midline, connecting the same cortical area in opposite hemispheres (right-left hemispheric connections 3).
Commissural fibers include:
corpus callosum (...
Communicating hydrocephalus is a type of hydrocephalus where CSF is able to leave the ventricular system.
Communicating hydrocephalus is commonly used as the opposite of obstructive hydrocephalus which leads to much unnecessary confusion, as most causes of communicating hydrocepha...
Complications of cranial radiation therapy are fairly common, particularly in long-term survivors, and especially in pediatric patients.
Cranial radiotherapy is used for a variety of brain tumors, either in isolation or in combination with concurrent chemotherapy. Complications from irradiation...
Compressive myelopathy refers to neurological deficits that result from abnormal compression of the spinal cord. It most commonly occurs in the cervical spinal cord.
Any cause of spinal canal stenosis including disc herniation, osteophytes, extradural mass, and/or paravertebral liga...
Computer vision syndrome is a condition that affects primarily workers who use computers (including tablets and other devices with computer screens) many hours a day with symptoms that can include blurred vision, eye strain, and headache.
Computer vision syndrome is a growing phen...
The concentric target sign is a typical sign for cerebral toxoplasmosis. It is seen on T2 weighted MR imaging as a deep parenchymal lesion showing a series of concentric rings with hyperintense and hypointense/isointense signal alternatingly. Strong perifocal edema is usually visible on T2/FLAIR...
Concurrent suprasellar and pineal region lesions have a relatively short differential to be considered, including:
other germ cell tumors
embryonal cell carcinoma
yolk sac tumor (endodermal sinus tumor)
primary CNS lymphoma
The condylar canal, or canalis condylaris, is a skull base canal in the posterior cranial fossa, located in the condylar fossa. It is the largest of the emissary foramina of the skull 1.
location: in the condylar fossa of the posterior cranial fossa, posterior to the occipital condyles...
The condylar emissary veins (anterior, lateral, posterior) are major posterior cranial fossa emissary veins:
anterior condylar vein connects the internal vertebral venous plexus to the internal jugular vein
lateral and posterior condylar veins connect the external vertebral venous system with ...
The confluence of sinuses, also known as the torcula or torcular herophili is the site of the confluence of:
superior sagittal sinus
The anatomy is highly variable and three types can be distinguished:
type 1: superior sagittal sinus drains...
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 anomalies of the posterior arch of the atlas (C1) are relatively common anomalies. They may range from partial defects presenting as clefts to complete absence of the posterior arch (aplasia).
These anomalies are classified according to Currarino (see below). It should not be confuse...
Congenital calvarial defects are a group of disorders characterized 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. Although the incidence tends to be higher in areas with increased rates of congenital infec...
Congenital cerebral toxoplasmosis is a manifestation of congenital toxoplasmosis and refers to development of cerebral toxoplasmosis in the fetus through maternal transmission.
Please refer on congenital toxoplasmosis to a broad discussion on epidemiology and pathology.
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...
Congenital cytomegalovirus infections result from intrauterine fetal infection by cytomegalovirus (CMV).
Cytomegalovirus is the most common cause of intrauterine infection and the most common cause of congenital infective and brain damage, occurring in 0.2-2.4% of live births.
Congenital facial nerve aplasia is a rare condition where the patient presents with signs of facial nerve paralysis.
Patients present with unilateral or bilateral facial weakness characterized by facial asymmetry, incomplete closure of eyelid, deviation of angle of mouth ...
A congenital facial palsy is an uncommon cause of neonatal asymmetric crying facies, which are more frequently due to absence or hypoplasia of the depressor anguli oris muscle, often associated with other congenital anomalies.
Congenital facial palsy is reported with an incidence...
Congenital muscular dystrophies are a heterogeneous group of autosomal recessive myopathies presenting at birth with hypotonia, delayed motor development, and early onset of progressive muscle weakness, confirmed with a dystrophic pattern on muscle biopsy.
There is a wid...
Congenital anomalies of the ossicles are most frequently associated with external ear abnormalities also, although they can occur in isolation.
These anomalies result in conductive hearing loss.
When bilateral, they are most frequently genetic with autosomal ...
Congenital spinal meningoceles are developmental anomalies of meningothelial elements displaced into the skin and subcutaneous tissues.
Please refer to the meningocele article for a broad overview of all types of this condition.
It is a defect of the neural tube, an embryonic struc...
Congenital ventriculomegaly can have a large number of syndromic associations.
fetal alcohol syndrome
A conjoined root is a type of developmental anomaly involving a nerve root. It is the most common nerve root developmental anomaly of the cauda equina being twice as common as two roots in the same foramen, the next most common anomaly.
The incidence in cadaveric studies is ~10 (r...
Connatal cysts, also known as coarctation of the lateral ventricles or frontal horn cysts, are cystic areas adjacent to the superolateral margins of the body and frontal horns of the lateral ventricles and are believed to represent a normal variant.
The incidence is 0.7% in low bi...
Contrast-induced neurotoxicity, also known as iodinated contrast-induced encephalopathy, is a rare complication of iodinated intravascular contrast resulting in a usually temporary neurological deficit. CT imaging findings can be dramatic, demonstrating contrast staining and edema, but spontaneo...
The conus medullaris is the terminal end of the spinal cord.
After the cord terminates, the nerve roots descend within the spinal canal as individual rootlets, collectively termed the cauda equina. The conus medullaris most commonly terminates at the L1/2 intervertebral disc leve...
Conus medullaris syndrome is caused by an injury or insult to the conus medullaris and lumbar nerve roots. It is a clinical subset of spinal cord injury syndromes. Injuries at the level of T12 to L2 vertebrae are most likely to result in conus medullaris syndrome.
Convexal subarachnoid hemorrhages (cSAH) are non-traumatic intracranial hemorrhages that occur within the surface sulci of the brain (cf. basal cisternal distribution of aneurysmal SAH).
There are various causes of convexal subarachnoid hemorrhage, some of which include:
Convolutional markings are normal impressions of the gyri on the inner table of the skull. They appear during times when the brain is growing rapidly, typically between the ages of 3 and 7 years of age 4. They are seen predominantly posteriorly.
If they are pronounced and over the more anterio...
Copper (chemical symbol Cu) is one of the trace elements. It has an important biological role as a redox agent and as a cofactor in cuproproteins, facilitating many vital metabolic reactions.
Copper is a transition metal with the atomic number 29 and an atomic weight...
Copper beaten skull, also known as beaten silver skull or beaten brass skull, refers to the prominence of convolutional markings (gyral impressions on the inner table of the skull) seen throughout the skull vault.
The appearance of a copper beaten skull is associated with...
Copper deficiency (also known as hypocupremia) is unusual due to the ubiquity of copper in the normal diet.
Copper deficiency is thought to be rare, but exact numbers are difficult to ascertain.
The typical presentation of copper deficiency mimics the more ...
Copper deficiency myeloneuropathy is rare but increasingly recognized as a cause of neurological impairment, presenting similarly to subacute combined degeneration of the cord secondary to vitamin B12 deficiency.
Patients typically present with a proprioceptive loss, due...
The cord sign refers to cordlike hyperattenuation within a dural venous sinus on non-contrast enhanced CT of the brain due to dural venous sinus thrombosis. The sign is most commonly seen in the transverse sinus because along the origin of the tentorium it runs approximately in the axial plane s...
Corkscrew sign can refer to:
corkscrew sign (midgut volvulus)
corkscrew sign (tertiary esophageal contractions)
corkscrew sign (corkscrew cochlea)
The corona radiata refer to a pair of white matter tracts seen at the level of the lateral ventricles. Superiorly they are continuous with the centrum semiovale. Inferiorly these tracts converge as the internal capsule.
The corpora amylacea ("bodies of starch") are a histologic finding, encountered more frequently in the brain, prostate, lung, and uterus. The corpora amylacea are thought to be sulfated glycosaminoglycans 1. Some have described it as a localized amyloidosis 2.
In the prostate they appear to ar...
The corpora quadrigemina (Latin for "quadruplet bodies", singular: corpus quadrigeminum) are the four colliculi, two inferior and two superior, that sit on the quadrigeminal plate on the posterior surface of the midbrain.
The corpora quadrigemina are reflex centers involving vision and hearing:...
The corpus callosum (plural: corpora callosa) is the largest of the commissural fibers, linking the cerebral cortex of the left and right cerebral hemispheres. It is the largest white matter tract in the brain.
located inferior to the cerebral cortices, and superior to the thalamus
The development of the corpus callosum occurs between the 12th and 16-20th weeks of gestation. It begins with the genu and then continues posteriorly along the body to the splenium. The rostrum is the last part to be formed.
This can be remembered with the help of this mnemonic :
A useful mnemonic to remember the causes of corpus callosum hyperintensity is:
I MADE A PHD
I: infections (e.g. tuberculosis, varicella, rotavirus, HSV)
M: Marchiafava-Bignami syndrome
A: AIDS encephalopathy
D: diffuse axonal injury and diffuse vascular injury
Corpus callosum impingement syndrome (CCIS) is caused by impingement of the corpus callosal fibers against inferior free margin of the falx cerebri due to longstanding and severe hydrocephalus and stretching of the lateral ventricles. This results in ischemia and eventually atrophy of the neural...
A useful mnemonic to help remember the parts of the corpus callosum, from anterior to posterior, is:
Remember Genu Before Splenium
Remember G Before S (as G comes before S alphabetically)
B: body (trunk)
The corpus striatum is a collective name given to the caudate nucleus and lentiform nucleus within the basal ganglia.
History and etymology
The term originates from the Latin "striatus", meaning "striped", referring to the caudatolenticar bridges of grey matter crossing the internal capsule fr...
Cortical blindness is a condition resulting from lesions in the primary visual cortex (V1) characterized by visual impairment but with an intact anterior visual pathway (normal pupillary reflexes and fundal appearance).
The degree of visual impairment is related to the ex...
Cortical laminar necrosis, also known as pseudolaminar necrosis, is necrosis of neurons in the cortex of the brain in situations when the supply of oxygen and glucose is inadequate to meet regional demands. This is often encountered in cardiac arrest, global hypoxia and hypoglycemia.
A handy mnemonic to recall cortically-based brain tumors is:
P: pleomorphic xanthoastrocytoma
D: dysembryoplastic neuroepithelial tumor (DNET); desmoplastic infantile astrocytoma and ganglioglioma
Cortical tubers or subcortical tubers (with involvement of the underlying white matter) are a common finding in tuberous sclerosis, present in 95-100% of cases 1.
These benign hamartomatous lesions can be epileptogenic foci, and are important to diagnose on imaging (typically MRI) as they can a...
The cortical vein sign refers to the presence of superficial cortical veins seen on MRI and CT (particularly with contrast injection) traversing an enlarged subarachnoid space, differentiating it from the similar radiological appearance of a subdural hygroma.
Although initially proposed as a me...
Cortical vein thrombosis, also known as superficial cerebral vein thrombosis, is a subset of cerebral venous thrombosis involving the superficial cerebral veins besides the dural sinus, often coexisting with deep cerebral vein thrombosis or dural venous sinus thrombosis. It has different clinica...
Corticobasal degeneration is an uncommon neurodegenerative disease and is one of the subset of tauopathies.
The vast majority of cases are sporadic, although a number of familial cases have been described 2. Patients are usually in the fifth to seventh decades of life 5, with the ...
The corticobulbar (or corticonuclear) tract originates primarily in Brodmann area 4 and exits at the brainstem to synapse on the lower motor neurons of the cranial nerves bilaterally. The exception to this is the facial nerve and hypoglossal nerve.
Innervation to the lower half of the face (via...
The corticorubral tract contains neurons that connect the primary motor and sensory areas to the red nucleus. The rubrospinal tract then descends through the spinal cord.
The tract is thought to excite flexor muscles and inhibit extensor muscles.
The corticospinal tract (or pyramidal tract) is a descending white matter tract primarily concerned with motor function extending from the motor cortex down to synapse with motor neurons of the spinal cord in the anterior horns.
Corticospinal fibers are axon...
The cotton wool appearance is a plain film sign of Paget disease and results from thickened, disorganized trabeculae which lead to areas of sclerosis in a previously lucent area of bone, typically the skull. These sclerotic patches are poorly defined and fluffy.
Other Paget disease re...
A coup-contrecoup injury is a term applied to head injuries and most often cerebral contusions and traumatic subarachnoid hemorrhage. It refers to the common pattern of injury whereby damage is located both at the site of impact (often less marked) and on the opposite side of the head to the poi...
Coup de poignard of Michon refers to spinal subarachnoid hemorrhage, usually as a result of a spinal AVM.
Presentation is with sudden excruciating back pain, akin to being stabbed with a dagger (poignard = french for dagger). It is the corollary of the thunderclap headache.
Cowdry bodies are eosinophilic or basophilic neuronal intranuclear inclusions composed of nucleic acid and protein, this cytopathic changes are considered a hallmark of viral infection.1.
Cowdry bodies are in fact fixation artifacts and not directly the result of the intracellular vi...
The cranial foramina are the holes that exist in the skull to allow the passage of structures into and out of the cranium. Some clefts/fissures, which are not entirely surrounded by bone, and canals, which are longer than their diameter, are often included in this category.
Most cranial foramin...
The cranial meninges (singular: meninx) surround the brain and are made up of three layers (from outermost to innermost):
The dura mater can also be known as the pachymeninx. The arachnoid mater and pia mater are collectively known as the leptomeninges 3....
Enhancement of cranial nerves has a lenghy differential including 1-2:
mycobacterial: tuberculosis, leprosy
spirochetes: Lyme disease, syphilis
viruses: e.g. herpes zoster virus, influenza virus, human herpesvirus 1 (HHV1) 3
The cranial nerve nuclei are a series of bilateral grey matter motor and sensory nuclei located in the midbrain, pons and medulla that are the collections of afferent and efferent cell bodies for many of the cranial nerves.
Some nuclei are small and contribute to a single cranial nerve, such as...
The cranial nerves are the 12 paired sets of nerves that arise from the cerebrum or brainstem and leave the central nervous system through cranial foramina rather than through the spine. The cranial nerves are numbered one to twelve, always using the Roman numerals, I to XII. Most have cranial n...
There are many cranial nerve mnemonics that can be memorable and rude/lewd. Either way, they can be helpful for remembering the names of the twelve cranial nerves, as well as remembering which nerves are sensory, motor, or both.
Remembering cranial nerve names in order of CN I to CN XII:
A craniectomy is a common neurosurgical procedure in which a portion of the skull is resected, but not put back (cf. craniotomy in which the bone flap is re-attached to the surgical defect) 1. The defect is usually covered over with a skin flap. If the defect is closed by a prosthetic covering t...
Craniopharyngiomas are relatively benign (WHO grade I) neoplasms that typically arise in the sellar/suprasellar region. They account for ~1-5% of primary brain tumors, and can occur anywhere along the infundibulum (from the floor of the third ventricle to the pituitary gland).
There are two his...
Cranioplasty is the surgical intervention to repair cranial defects, and is mostly performed after traumatic injuries. The procedure is performed using different materials and techniques, with no consensus about the best option. Methyl methacrylate is the prosthetic material most extensively use...
Craniorachischisis, also known as craniorachischisis totalis, is a rare birth defect and the most severe of the neural tube defects. It refers to the presence of both anencephaly and spina bifida.
In one study the prevalence of craniorachischisis was 0.51 per 10,000 live births in...
Craniosynostosis refers to the premature closure of the cranial sutures. The skull shape then undergoes characteristic changes depending on which suture(s) close early.
There is a 3:1 male predominance with an overall incidence of 1 in 2000-2500. 8% of cases are syndromic or famil...
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...
Creatine is one of the compounds examined in MR spectroscopy. It resonates at 3.0 ppm chemical shift and is found in metabolically active tissues (brain, muscle, heart) where it is important in storage and transfer of energy. It tends to be maintained at a relatively constant level, and is predo...
Creutzfeldt-Jakob disease (CJD) is a spongiform encephalopathy that results in a rapidly progressive dementia and death usually within a year from onset. The vast majority are sporadic, but familial and acquired forms are occasionally encountered.
On imaging, it classically manifests as hyperin...
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...
Crossed cerebellar diaschisis refers to a depression in function, metabolism, and perfusion affecting a cerebellar hemisphere occurring as a result of a contralateral focal supratentorial lesion, classically an infarct.
Other than neurological deficits and other clinica...
A crus (plural: crura) is an anatomical term used for a structure which resembles a leg.
crus (internal capsule)
crus (semicircular duct)
Cryptococcomas are a rare complication of infection by the Cryptococcus genus of invasive fungi, where a discrete, encapsulated lesion of immune infiltrates and pathogen forms. Cryptococcus gattii is most often isolated but Cryptococcus neoformans may also form cryptococcomas.
Cryptococcosis is a fungal infection caused by Cryptococcus neoformans, a globally distributed fungus that is commonly found in soil, especially that containing pigeon and avian droppings. Infection is acquired by inhaling spores of fungus.
Occurs worldwide without any defined en...
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...
The CSF cleft sign in neuroimaging can be used to distinguish an extra-axial lesion from an intra-axial lesion and is typically used in the description of a meningioma.
Classically, the cleft was regarded as representing a thin rim of CSF between a tumor and brain parenchyma. However, it often ...
CSF flow studies are performed using a variety of MRI techniques and are able to qualitatively assess and quantify pulsatile CSF flow. The most common technique used is time-resolved 2D phase contrast MRI with velocity encoding.
Note, when referring to CSF flow in the context of imaging we are...
CSF rhinorrhea refers to a symptom of cerebrospinal fluid (CSF) leakage extracranially into the paranasal sinuses, thence into the nasal cavity, and exiting via the anterior nares. It can occur whenever there is an osseous or dural defect of the skull base (cf. CSF otorrhea).