Choroid plexus papillomas are an uncommon, benign (WHO grade I) neuroepithelial intraventricular tumour which can occur in both the paediatric (more common) and adult population.
On imaging, these tumours are usually identified in the fourth ventricle in adults and in the lateral ventricles in...
Choroid plexus tumours can be classified as primary or secondary neoplasms of the choroid plexus:
choroid plexus papilloma (CPP)
WHO Grade I, and WHO Grade II when atypical
choroid plexus carcinoma (CPC)
WHO Grade III
Choroid plexus xanthogranulomas are common, incidental and almost invariably asymptomatic lesions. It is unclear in much of the literature whether they represent a distinct entity from adult choroid plexus cysts, but they share imaging characteristics and are only likely to be distinguishable on...
There are many signs in radiology that are related to Christmas:
snowcap sign in avascular necrosis
in total anomalous pulmonary venous return
in pituitary macroadenomas
snowstorm appearance in complete hydatidiform and testicular microlithiasis
holly leaf sign in calcified pl...
There are several viral and prion infections which can result in a chronic encephalitis with slow progression into brain atrophy. These have very poor prognosis with no effective treatment. Some of these include:
progressive multifocal leukoencephalitis
subacute sclerosing panencephalitis
Chronic inflammatory demyelinating polyneuropathy (CIDP) is an acquired demyelinating disease involving peripheral nerves, and is generally considered the chronic counterpart to Guillain-Barré syndrome (GBS).
Patients typically present with a gradual and protracted (> 2 ...
Chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids (CLIPPERS) is an uncommon and only recently described disorder characterised by infiltration of the brain by inflammatory cells. It has a predilection for the pons, with fairly characteristic curvilinea...
Chronic otomastoiditis (COM) should be considered a separate entity from acute otomastoiditis, and is defined as persistent or recurrent inflammation of the middle ear and mastoid, lasting usually for a minimum of 12 weeks, and resulting in permanent perforation of the tympanic membrane.
Chronic traumatic encephalopathy (CTE) is a neurodegenerative tauopathy that is thought to result from mild repetitive head trauma.
The exact incidence and prevalence is unknown. It is most commonly seen in amateur and professional sports players where head contact is common (e.g...
The cingulate gyrus lies on the medial aspect of the cerebral hemisphere. It forms a major part of the limbic system which has functions in emotion and behaviour. The frontal portion is termed the anterior cingulate gyrus (or cortex) 1-2.
The cingulate gyrus extends from the sub...
The cingulate sulcus is situated directly superior to the cingulate gyrus, which is formed by the medial surface of the cerebral hemisphere that is directly above the corpus callosum.
The cingulate sulcus sign has been proposed as being useful as an MRI feature of idiopathic normal pressure hydrocephalus (NPH). It denotes the posterior part of the cingulate sulcus being narrower than the anterior part. The divider between the anterior and posterior parts of the sulcus being a...
The Circle of Willis is an arterial polygon formed as the internal carotid and vertebral systems anastomose around the optic chiasm and infundibulum of the pituitary stalk in the suprasellar cistern. This communicating pathway allows equalization of blood-flow between the two sides of the brain,...
Cerebral vascular malformations encompass a large variety vascular lesions which differ in haemodynamics, structure and prognosis. Some can be life threatening (e.g. vein of Galen aneurysmal malformations, arteriovenous malformations) whilst others are almost always incidental and asymptomatic (...
Spinal meningeal cysts can be classified according to a system published by Nabor et. al 2:
type I: extradural meningeal cyst without neural tissue
type Ia: extradural spinal arachnoid cyst
type Ib: sacral meningocele
type II: extradural meningeal cyst containing neural tissue, e.g. Tarlov c...
Classification system for malformations of cortical development organises a myriad of conditions according to one of three major underlying mechanisms:
abnormal cell proliferation
abnormal neuronal migration
abnormal cortical organisation
As is to be expected a number of conditions fall out...
Classification systems for malformations of the cerebellum are varied and are constantly being revised as greater understanding of the underlying genetics and embryology of the disorders is uncovered. A classification proposed by Barkovich et al in 2009 1 divides cerebellar malformations in two ...
Classification systems for midline abnormalities of the brain and skull are varied and constantly changing as the underlying embryology and genetics are uncovered. A relatively simple and robust classification system is based on the location of abnormalities, always remembering that midline abno...
Claude syndrome is one of the brainstem stroke syndromes in which there is infarction of the dorsomedial aspect of the midbrain secondary to occlusion of the small perforating branches of the posterior cerebral artery supplying this area 1-4. The infarction involves the medial aspect of red nucl...
The claustrum is a vertical curved sheet of subcortical grey matter oriented sagittally between the white matter tracts of the external capsule and extreme capsule. It is lateral to the putamen and medial to the insular cortex. It is not part of the basal ganglia.
There are lateral and medial t...
The claw sign is useful in determining whether a mass arises from a solid structure or is located adjacent to it and distorts the outline.
It refers to the sharp angles on either side of the mass, which the surrounding normal parenchyma forms when the mass has arisen from the parenchyma. As suc...
Clear cell ependymomas are a histological variant of ependymoma characterised by prominent perinuclear cytoplasmic clearing, reminiscent of oligodendrogliomas 1.
They are typically encountered in younger patients and usually in the supratentorial compartment 1.
They have a tendency to be qui...
Clear cell meningiomas are a histological variant of meningioma with poorer prognosis and a higher rate of recurrence. They are therefore considered WHO grade 2 tumours, regardless of mitotic index, cellular atypia/anaplasia, or presence of brain invasion.
Clear cell meningiomas ...
Clinically isolated syndrome (CIS) is the first episode suggestive of demyelination. It can either be monofocal (single lesion) or multifocal. Not all patients with CIS will go on to develop multiple sclerosis (MS) however if at presentation there are changes on MRI suggestive of MS, then the ch...
Clinically unclassifiable parkinsonism (CUP) is a term applied to patients who have some parkinsonism features, but who do not fulfil clinical criteria for a particular disorder such as:
progressive supranuclear palsy (PSP)
multiple system atrophy (MSA-P)
The differential of a mass involving or arising from the clivus is a relatively narrow one and can be divided into whether the lesion arises from the skull base itself, from the intracranial compartment or from below the base of skull.
When evaluating the clivus it is important to compare the...
CNS aspergillosis results from angioinvasive infection of the central nervous system by the fungus Aspergillus spp. Along with CNS cryptococcosis, it is one of the most common fungal opportunistic infections of the central nervous system.
The disease predominates in immunocompromi...
CNS capillary telangiectasiae(s) are small, asymptomatic low flow vascular lesions of the brain.
As these lesions are asymptomatic, diagnosis usually matches the age of first imaging with MRI, and as such are most frequently found in middle-aged and elderly adults. Their incidenc...
CNS cryptococcosis results from infection of the central nervous system with the yeast-like fungus Cryptococcus neoformans. It is the most common fungal infection and second most common opportunistic infection of the central nervous system.
For a general discussion of infection with this organi...
This article aims to be a collection of articles that represent the central nervous system infectious diseases. There will be some overlap between articles as they are listed and discussed in a mixture of anatomical and aetiological classification.
It is important to remember tha...
CNS lymphoma refers to the involvement of the central nervous system with lymphoma. It can be broadly divided into primary and secondary, with a number of special types of also recognised.
primary CNS lymphoma (PCNSL)
MALT lymphoma of the dura 5
secondary CNS lymphoma...
The acronym COACH describes a syndrome associated with:
C - cerebellar vermis defect (Joubert syndrome)
O - oligophrenia
A - ataxia
C - coloboma
H - hepatic fibrosis
There only as little as 11 cases having been reported in the English medical literature....
Coalescent mastoiditis is simply the term given to acute otomastoiditis when mucoperiosteal disease extends to involve the bone. The septae which normally separate one mastoid air cell from another are resorbed. This change is only easily appreciated on thin section bone-algorithm through the te...
CoA synthase protein associated neurodegeneration (CoPAN) is a type of neurodegeneration with brain iron accumulation (NBIA).
Patients typically present with a variety of symptoms including spastic-dystonic paraparesis, Parkinsonism, cognitive impairment, obsessive-compul...
Coccidioidal meningitis refers to central nervous system involvement of the dimorphic fungus Coccidioides spp, mainly Coccidioides immitis and Coccidioides posadasi.
Coccidioidomycosis is endemic to many parts of North, Central, and South America 1. It usually only manifests as co...
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...
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...
Cockayne syndrome is a rare autosomal recessive dysmyelinating disease. Cockayne syndrome is classified among the childhood leukodystrophies, and brain imaging findings are cardinal features suggesting the diagnosis of Cockayne syndrome. Previously published Cockayne syndrome imaging studies hav...
Coffin-Siris syndrome, first described in 1970, is a rare genetic abnormality.
It occurs more frequently in females (with a M:F of ~4:1).
It is thought most likely to relate to a gene on chromosome 7, however its exact location has yet to be determined.
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...
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 to a disproportionate prominence of the occipital horns of the lateral ventricles. It can result from a wide range of congenital insults.
Patient may present with motor abnormalities, cognitive deficit, visual abnormalities, and seizures...
The column of Burdach, also known as the cuneate fasciculus or fasciculus cuneate, 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 column of Goll, also known as the gracile fasciculus or fasciculus gracilis, represents the medial portion of the dorsal columns and carries input from below and including T7 1.
The gracile fasciculus is responsible for transmitting vibration, conscious proprioception, and fine (d...
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...
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 meningocoeles are developmental anomalies of meningothelial elements displaced into the skin and subcutaneous tissues.
Please refer on menigocoele article for a broad overview of all types of this condition.
It is defect of the neural tube, an embryonic structure ...
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 1.
The incidence in cadaveric studies is abo...
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.
The conus medullari...
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 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 raised intracranial pres...
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 (CC) is the largest of the commissural fibres, linking the cerebral cortex of the left and right cerebral hemisphere. It is the largest fibre pathway in the brain.
The corpus callosum is approximately 10 cm in length and is C-shaped, like most of the supratent...
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.
History and etymology
The term originates from the Latin "striatus", meaning "striped", referring to the caudatolenticar bridges of grey matter crossing the internal capsule from the putamen to the cau...
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...