The Cognard classification of dural arteriovenous fistulas correlates venous drainage patterns with increasingly aggressive neurological clinical course. It was first described in 1995 1 and at the time of writing (July 2016) is probably the most widely used classification system for dural arter...
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-recognised, 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...
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 masses on nonenh...
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...
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 oedema is a type of cerebral oedema in which there is a mixed pattern of both cytotoxic and vasogenic cerebral oedema.
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...
There are a number of white matter tracts that cross the midline, connecting the two cerebral hemispheres. These are known as commissures and include:
hippocampal commissure (psalterium)
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 paediatric patients.
Cranial radiotherapy is used for a variety of brain tumours, either in isolation or in combination with concurrent chemotherapy. Complications from irradiati...
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 central canal stenosis including disc herniation, osteophytes, extradural mass, and/or paravertebral lig...
Concurrent suprasellar and pineal region lesions have a relatively short differential to be considered, including:
other germ cell tumours
embryonal cell carcinoma
yolk sac tumour (endodermal sinus tumour)
primary CNS lymphoma
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...
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 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 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 infection results from intra-uterine fetal infection by cytomegalovirus (CMV).
CMV is the most common cause of intra-uterine infection and most common cause of congenital infective and brain damage, occurring in 0.2-2.4% of live births.
Antibodies to ...
A congenital facial palsy (CFP) 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.
CFP are reported with an incidence of ~0.2% of ...
Congenital muscular dystrophies (CMD) 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.
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...
Congenital spinal meningoceles are developmental anomalies of meningothelial elements displaced into the skin and subcutaneous tissues.
Please refer on menigocele article for a broad overview of all types of this condition.
It is defect of the neural tube, an embryonic structure th...
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 about ...
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 oedema, but spontane...
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 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
Convolutional markings are normal impressions of the gyri on the inner table of the skull, seen predominantly posteriorly. If they are pronounced and over the more anterior parts of the skull, then this is referred to as a copper beaten skull and raises the possibility of raised intracranial pre...
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 copper beaten skull is associated with r...
Copper deficiency myeloneuropathy is rare but increasingly recognised as a cause of neurological impairment, presenting similarly to subacute combined degeneration of the cord secondary to B12 deficiency.
Patients typically present with a proprioceptive loss, due to dors...
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...
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 quadrigemina (Latin for "quadruplet bodies") 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 centres involving vision and hearing:
superior colliculi: involved i...
The corpus callosum is the largest of the commissural fibres, linking the cerebral cortex of the left and right cerebral hemisphere. It is the largest white matter tract in the brain.
located inferior to the cerebral cortices, and superior to the thalamus
connects left and right cereb...
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 ischaemia and eventually atrophy of the neura...
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) characterised 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 extent...
Cortical laminar necrosis, also known as pseudolaminar necrosis, is necrosis of neurons in the cortex of the brain in situations when supply of oxygen and glucose is inadequate to meet regional demands. This is often encountered in cardiac arrest, global hypoxia and hypoglycaemia.
A handy mnemonic to recall cortically-based brain tumours is:
P: pleomorphic xanthoastrocytoma
D: dysembryoplastic neuroepithelial tumour (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 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 is a descending white matter tract primarily concerned with motor function extending from the motor cortex down to synapse with motor neurones of the spinal cord in the anterior horns.
Corticospinal fibres are axons from upper motor n...
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 haemorrhage. 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 po...
Coup de poignard of Michon refers to spinal subarachnoid haemorrhage, 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 neuronal intranuclear inclusions seen in Herpes simplex virus infections 1.
Cowdry bodies are in fact fixation artifacts and not directly the result of the intracellular virus 2.
The cranial foramina are the holes that exist in the base of skull to allow the passage of structures into and out of the cranium:
anterior ethmoidal foramen
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 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 using the Roman numerals, I to XII.
The first and se...
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:
Craniopharyngiomas are relatively benign (WHO grade I) neoplasms that typically arise in the sellar/suprasellar region. They account for ~1-5% of primary brain tumours, and can occur anywhere along the infundibulum (from the floor of the third ventricle, to the pituitary gland).
There are two p...
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 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 a Texas-Mexico border population 1.
Craniosynostosis refers to 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 familial....
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.
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 other non-specific neurological features and death usually within a year or less from onset.
On imaging, it classically manifests as T2/FLAIR hyperintensities within the basal gan...
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...
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) 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 posterior aspect of th...
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 tumour 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 rhinorrhoea 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 otorrhoea).
CSF-venous fistulas are rare and only recently recognised causes of spontaneous intracranial hypotension. They are a direct communication between the spinal subarachnoid space and epidural veins allowing for the loss of CSF directly into the circulation and can be either iatrogenic or spontaneou...
The CT angiographic (CTA) spot sign is defined as unifocal or multifocal contrast enhancement within an acute primary intracerebral haemorrhage (ICH) visible on CTA source images and discontinuous from adjacent normal or abnormal blood vessels 1. It should not be present on pre-contrast images. ...
CT angiography of the cerebral arteries is a noninvasive technique allows visualization of the internal and external carotid arteries and vertebral arteries and can include just the intracranial compartment or also extend down to the arch of the aorta.
By using multidetector CT (MDCT) after int...
CT cerebral venography is a contrast enhanced examination with an acquisition delay providing an accurate detailed depiction of the cerebral venous system.
Rapid diagnosis of cerebral venous thrombosis.
general CT contraindications such as pregnancy, etc.
Computed tomography (CT) cisternography is an imaging technique used to diagnose CSF rhinorrhoea or CSF otorrhoea (CSF leaks), as CT allows the assessment of the bones of the base of skull.
pre-contrast CT is performed with thin slices
3-10 mL of an iodinated non-ionic low-osmolar ...
The CT comma sign is a characteristic sign seen in head trauma. It is the presence of concurrent epidural and subdural haematomas, which gives the characteristic appearance of this sign as a "comma" shape.
CT head (sometimes termed CT brain), refers to a computed tomography examination of the of the brain and surrounding structures. It can be performed as a single non-contrast study or the combination of a non-contrast and post-contrast (delayed) study. This allows the identification of abnormal c...
The approach taken to interpreting a CT scan of the head is no doubt different depending on the circumstances and the reading clinician, however, most radiologists will go through the same steps. What follows is merely a suggested approach to interpreting a CT of the head.
An important aspect ...
A CT head standard report may not be applicable in all situations, but gives an idea of some of the areas to cover when reporting a CT head.
Standardised reports are controversial and should be used with caution.
Headache with photophobia.
CT head without ...
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 calvaria. It is a wider setting than the standard non-contrast window, and there are a num...
CT head technique describes how a CT head is performed.
The technique for performing a CT of the head depends on the scanner available and fall into two broad camps:
volumetric acquisition (most common)
Step-and-shoot scanning was the first describe...
CT perfusion in ischaemic stroke has become established in most centres with stroke services as an important adjunct, along with CT angiography (CTA), to conventional unenhanced CT brain imaging.
It enables differentiation of salvageable ischaemic brain tissue (the penumbra) from irrevocably d...
The cuneate fasciculus, also known as the fasciculus cuneate or column of Burdach, represents the lateral portion of the dorsal columns and carries input from between and including C1 and T6 1.
The cuneate fasciculus is responsible for transmitting vibration, conscious proprioception...
The cuneus is a wedge-shaped region on the medial surface of the occipital lobe.
Anterosuperiorly the parieto-occipital sulcus separates the cuneus from the precuneus of the parietal lobe.
Posteroinferiorly the cuneus abuts the calcarine sulcus which separates it from...
The Cushing response/reflux occurs in the setting of raised intracranial pressure and is the triad of:
Cyanide poisoning is a cause of an acute anoxic-ischaemic encephalopathy that also has eventual chronic sequelae.
Acute cyanide poisoning is rare and often occurs after suicidal oral ingestion of cyanide-containing compounds, however there are other sources such as after smoke in...
Cyclopia refers to a rare fetal malformation characterised by a single palpebral fissure and a single midline orbit. This orbit may contain either a single globe or two separate globe.
The condition is thought to affect approximately 1 in 40,000 to 95,000 births (inclusive of stil...