CNS manifestations of Behçet disease, also known as neuro-Behçet disease, corresponds to the neurological involvement of the systemic vasculitis Behçet disease and has a variety of manifestations.
For a discussion of the disease in general please refer to Behçet disease article.
Bell palsy, also known as idiopathic peripheral facial paralysis, is characterized by rapid onset facial nerve paralysis, often with resolution in 6-8 weeks. As there are numerous causes of facial nerve palsy, many acute in onset, it is currently a diagnosis of exclusion supported by a typical p...
Benedikt syndrome, or paramedian midbrain syndrome, is a midbrain stroke syndrome that involves the fascicles of the oculomotor nerve and the red nucleus.
ipsilateral CN III palsy 1-4
crossed hemiataxia 1-4
crossed choreoathetosis 1-4
It is usually caused by...
Benign enhancing foramen magnum lesions have been anecdotally seen by radiologists for years but only recently described as an incidental finding in a typical location in the foramen magnum just behind the vertebral artery. Although the precise nature of this finding has not been entirely elucid...
Benign enlargement of the subarachnoid spaces in infancy (BESS or BESSI) also known as benign external hydrocephalus (BEH) is, as per the name, a benign enlargement of the subarachnoid spaces in infants. It usually involves the frontal lobe subarachnoid spaces, and it is characterized clinically...
Benign metastasising meningiomas are a rare occurrence, encountered as a complication of a tiny fraction of all meningiomas diagnosed. It refers to spread of the tumor via metastases to distant sites, analogous to benign metastasising leiomyoma from uterine fibroids.
There are a number of benign metastasising tumors:
benign metastasising meningioma 1,2
benign metastasising leiomyoma 3
primary adenoma of thyroid 4
giant cell tumor of bone 5
Benign notochordal cell tumors are vertebral lesions that are usually asymptomatic and discovered incidentally on imaging of the head or spine. As this is a poorly-recognised entity, it can often be confused with aggressive vertebral lesions, such as a chordoma, when it is seen on imaging.
Benign paroxysmal positional vertigo (BPPV) is one of the most common causes of vertigo. It occurs secondary to change in posture and typically is associated with nystagmus. The etiology is thought to be due to changes of position of the otoliths in the inner ear, most commonly into the posterio...
Benign regressive post-infectious neurological disorders (BRPINDs) refer to a group of neurological disorders and must be differentiated from the more malignant and progressive post-infectious neurological disorders such as SSPE (subacute sclerosing panencephalomyelitis) or rubella panencephalit...
Beta-propeller protein-associated neurodegeneration (BPAN) is a rare subtype of neurodegeneration with brain iron accumulation disease (NBIA).
It was previously known as static encephalopathy with neurodegeneration in childhood (SENDA), but it was renamed after the underlying genetic abnormalit...
Betz cells are pyramidal cell neurons located within the fifth layer of the primary motor cortex. They are some of the largest in the central nervous system, sometimes reaching 100 µm in diameter and send their axons down the corticospinal tracts to the anterior horn cells of the spinal cord.
The bicaudate index is the ratio of width of two lateral ventricles at the level of the head of the caudate nucleus to distance between outer tables of skull at the same level. It can be a useful marker of ventricular volume and in the diagnosis of hydrocephalus.
Bickers Adams Edwards syndrome is a rare x-linked disorder with profound mental retardation, adducted thumb and large head which is comprising of a constellation of congenital CNS anomalies including :
congenital aqueductal stenosis
corpus callosum agenesis
absence of the medullary pyramids
Bickerstaff encephalitis is a rare immune-mediated condition believed to be one of a number of conditions sharing a similar immunological mechanism, and collectively termed anti-GQ1b IgG antibody syndrome.
Bickerstaff encephalitis is often seen following varicella zoste...
The Biffl scale or grade illustrates the spectrum of blunt cerebrovascular injury (BCVI) seen on angiography (both CTA and DSA). Some authors refer to the grading scale as the Denver scale, which is not to be confused with the Denver criteria, a series of clinical indications and risk factors fo...
The bifid postcentral gyrus sign, also known as the pars deflection sign, is a landmark useful for identifying the central sulcus on cross-sectional imaging.
The medial aspect of the postcentral gyrus splits in two before meeting the interhemispheric fissure. The two legs straddle the pars marg...
Bilateral frontoparietal polymicrogyria (BFPP) is a rare genetic condition consisting of extensive bilateral perisylvian polymicrogyria. So far (as of 2015) only a single gene association has been identified; GPR56 gene located on chromosome 16q12.2–21 1. It is inherited as an autosomal recessiv...
Bilateral megalencephaly refers to megalencephaly affecting both cerebral hemispheres.
neurofibromatosis type 1 (NF1)
tuberous sclerosis (TS)
Involvement of both middle cerebellar peduncles is uncommon, but has a relatively long list of differential diagnoses, including 1:
multiple systemic atrophy (MSA)
Bilateral thalamic gliomas are rare but characteristic low-grade astrocytomas that occur in both children and young adults.
Presentation may vary with age. Young children with bilateral thalamic glioma often have signs of increased intracranial pressure and movement disor...
Bill bar is a bony anatomical landmark that divides the superior compartment of the internal acoustic meatus into an anterior and posterior compartment. Anterior to Bill bar, in the anterior superior quadrant, are the facial nerve (CN VII) and nervus intermedius, and posterior to it, in the post...
Bing-Neel syndrome is an extremely rare neurological complication of Waldenström macroglobulinemia where there is malignant lymphocyte infiltration into the central nervous system (CNS).
The exact incidence is unknown, however in one study of patients with Waldenström macroglobuli...
Biotinidase deficiency is a rare autosomal recessive condition in which the body is unable to break down the conjugated form of the vitamin B7 (biotin), resulting in low levels of available biotin.
Profound deficiency (<10% of normal level) is estimated at ~1:100,000 of newborns. ...
Biotin-thiamine-responsive basal ganglia disease (BTBGD) is a rare neurometabolic syndrome caused by defective thiamine transporter 2 (THTR2) activity due to mutations in the solute carrier family 19 member 3 gene (SLC19A3).
The presentation of BTBGD is variable and has been docu...
Birth trauma relates to those conditions caused by both physical/mechanical and hypoxic injuries.
Birth trauma occurs in ~5 per 1000 births 2.
Bilateral thalamic lesions are usually seen in combination with basal ganglia, white matter and sometimes cortical lesions. Symmetrical bilateral involvement of the thalami has a broad differential diagnosis:
deep cerebral vein thrombosis and dural venous sinus thrombosis:
Neuroanatomy of the bladder is complex, described here is a summary of the co-ordination of micturition.
The bladder acts as a reservoir normally storing 400-500 mL of urine under low pressure (<15 cmH2O) before voluntary voiding can occur at a socially-convenient time. Bladder filling and empt...
Blake's pouch cyst is a cystic appearing structure that represents posterior ballooning of the inferior medullary velum into the cisterna magna, below and posterior to the vermis that communicates with an open fourth ventricle. It is caused by a failure of regression of Blake's pouch secondary t...
The blend sign refers to a CT appearance of early intracranial hematoma growth. It is defined as blending of a hypoattenuating area and a hyperattenuating region with a well-defined margin.
The blood-brain barrier (BBB) forms a physical resistance to the passage of lipophobic substances from cerebral capillaries into the brain and is a key reason why there is no CSF enhancement following intravenous contrast media in CT and MR imaging.
The BBB is formed by a combina...
The blood supply of the meninges generally concerns the blood supply of the outer layer of dura mater rather than the inner layer of dura mater, arachnoid or pia mater which do not require a large blood supply. There are several arteries that supply the dura in the anterior, middle, and posterio...
Blumcke et al. proposed the most recent (2011) 2 and now widely adopted consensus classification system for focal cortical dysplasia, which shares many features with the previously described classifications system by Palmini (2004) and Barkovich (2005).
Unfortunately, as is the case with many ...
Blunt cerebrovascular injury (BCVI) is an uncommon but serious consequence of blunt trauma to the head and neck.
It is often part of multi-trauma with a significant series of blunt trauma CTA reporting an incidence of approximately 1% 3. A large systematic review and meta-analysis...
Bochdalek's flower basket is the eponymous name for the incidental finding of protrusion of the choroid plexus through the foramina of Luschka. This is a relatively common finding.
It is an important normal variant to recognize as the presence of protruding calcified choroid tissue in the fourt...
Blood oxygenation level dependent (BOLD) imaging is the standard technique used to generate images in functional MRI (fMRI) studies, and relies on regional differences in cerebral blood flow to delineate regional activity.
Blood flow in the brain is highly locally controlled in response to oxy...
The boomerang sign refers to a boomerang-shaped region of cytotoxic edema in the splenium of the corpus callosum typically seen in cytotoxic lesions of the corpus callosum (CLOCCs) 1-4.
boomerang sign in peroneus brevis split syndrome
boomerang sign in horizontal meniscal flap tear
The Borden classification of dural arteriovenous fistulas (DAVF) groups these lesions into three types based upon the site of venous drainage and the presence or absence of cortical venous drainage. It was first proposed in 1995 1. At the time of writing (July 2016), it is probably less popular ...
The Boston criteria were first proposed in 1995 in order to standardize the diagnosis of cerebral amyloid angiopathy (CAA) 1. They comprise of combined clinical, imaging and pathological parameters.
The criteria are divided into four tiers and are as 3-4:
full post-mortem examin...
Bouthillier et al. described (in 1996) 1 a seven segment internal carotid artery (ICA) classification system. It remains the most widely used system for describing ICA segments at the time of writing (mid-2016).
There are a few other classifications systems including those proposed by Fisher (1...
Brachial plexus injuries are a spectrum of upper limb neurological deficits secondary to partial or complete injury to the brachial plexus, which provides the nerve supply of upper limb muscles.
Trauma, usually by motor vehicle accidents, involves severe traction on the ...
Mnemonics for brachial plexus root subdivisions include:
Rad Techs Drink Cold Beer
Robbie T Drinks Cold Beer
Rugby Teams Drink Cold Beers
Reach To Drink Cold Beer
Read That Damn Cadaver Book
Really Tired, Don't Care Now (nerve instead of branch)
Red Tits Don't Come Back (red-headed tit = ...
The bracket sign of the pars marginalis, also known as the pars bracket sign, refers to the appearances of the superior most extent of the pars marginalis of the cingulate sulcus on axial imaging. It forms two roughly symmetric brackets, open anteriorly. The next sulcus anteriorly is the central...
The bracket sign refers to a radiographic appearance seen with the tubulonodular variety of pericallosal lipoma. It reflects calcification seen at the periphery of the midline lipoma. It is best seen on coronal imaging and historically was identified on frontal radiographs.
It should not be con...
The brain is the vital neurological organ composed of:
The brain is housed in the skull and bathed in cerebrospinal fluid. It is continuous with the cervical spinal cord at the cervicomedullary junction.
Brain abscess is a potentially life-threatening condition requiring rapid treatment, and prompt radiological identification. Fortunately, MRI is usually able to convincingly make the diagnosis, distinguishing abscesses from other ring-enhancing lesions.
Demographics reflect at-ri...
Brain death refers to the irreversible end of all brain activity and is usually assessed clinically. Radiographic testing may be used as additional support for a clinical diagnosis of brain death, such as when clinical tests are impossible to perform, e.g. ocular trauma, precluding brainstem fun...
Brain development occurs from the three vesicles of the embryo's neural tube.
By approximately 4.5 to 5 menstrual weeks, the primitive neural plate has developed. The neural plate then divides into the neural crest and...
MRI protocol for brain infection assessment is a group of MRI sequences put together to best approach CNS infections in general.
Note: This article is intended to outline some general principles of protocol design. The specifics will vary depending on MRI hardware and software, radiologist's an...
This is a basic article for medical students and other non-radiologists
Brain mass lesions are a broad collection of pathological processes that result in changes on brain imaging (usually CT or MRI). They are a very disparate group of conditions ranging from infection (abscess) to brain tumors...
Brain metastases are estimated to account for approximately 25-50% of intracranial tumors in hospitalised patients. Due to great variation in imaging appearances, these metastases present a common diagnostic challenge which can importantly affect the management approach for individual patients.
The brainstem is the most caudal part of the brain. It adjoins, is structurally continuous with the spinal cord and consists of the:
pons (part of the metencephalon)
medulla oblongata (myelencephalon)
The brainstem provides the main motor and sensory innervation to t...
Brainstem gliomas consist of a heterogeneous group which vary greatly in histology and prognosis.
It should be noted that if not otherwise specified the term brainstem glioma usually refers to the most common histology, the diffuse brainstem glioma, and in children is most likely a...
The brainstem nuclei are the nuclei in the brainstem. These include:
the cranial nerve nuclei
Brainstem stroke syndromes, also known as crossed brainstem syndromes, refer to a group of syndromes that occur secondary to lesions, most commonly infarcts, of the brainstem.
Although many different brainstem stroke syndromes have been classically described, the majority appear e...
The brain MRI stereotactic study, also known as frame-based stereotactic MRI study or conventional brain MRI stereotaxis, is a localisation MRI protocol that delineates an intracranial structure or lesion in relation to a three-dimension coordinate system allowing a precise surgical access to th...
Brain stones, also known as cerebral calculi, refers to large intracranial calcifications that may be solitary or multiple.
If symptomatic, patients most commonly present with seizures.
Localisation of brain stones can help narrow the underlying etiology but...
MRI protocol for brain trauma is a group of MRI sequences put together to best approach traumatic brain injury, especially diffuse axonal injury.
Note: This article is intended to outline some general principles of protocol design. The specifics will vary depending on MRI hardware and software...
MRI protocol for brain tumor assessment is a group of MRI sequences put together to best approach CNS tumors in general.
Note: This article is intended to outline some general principles of protocol design. The specifics will vary depending on MRI hardware and software, radiologist's and referr...
Brain tumors arise from the normal constituents of the brain and its coverings (meninges). Spinal tumors are considered separately.
As a general rule, brain tumors increase in frequency with age, with individual exceptions (e.g. pilocytic astrocytoma, the vast majority of which a...
Common brain tumors in infancy (i.e. under one year of age) are quite different from those of brain tumors in adulthood. Most are located in the supratentorial region (~65%) and they carry a poor prognosis.
The frequency of these tumors varies according to studies, but the most common brain tum...
The bright rim sign, also known as the hyperintense ring sign, has been described in dysembryoplastic neuroepithelial tumors (DNET) and is seen, as the name so aptly describes, as a rim of high signal around the DNET on FLAIR sequences.
The pathologic correlate of this sign is glioneural elemen...
Brissaud-Sicard syndrome is a very rare pontine stroke syndrome that involves the anterolateral and inferior pons.
Classically, the syndrome presents as ipsilateral facial cramps and contralateral hemiparesis 1-3.
It has been postulated that the syndrome is ca...
Broca's area (Brodmann area 44) is an area of the lateral frontal lobe in the dominant hemisphere concerned with the production of speech.
Broca's area is located in the posterior inferior frontal gyrus (pars opercularis and pars triangularis) of the dominant hemisphere, anterior...
Brodmann areas are a system to divide the cerebral cortex according to cytoarchitectural organization, and are, despite controversy, still very widely used as a standardized nomenclature which is superimposed on the somewhat variable gyral and sulcal anatomy.
The classification relies on the f...
Brown-Séquard syndrome, also known as hemicord syndrome, is the result of damage to, or impairment of, the left or right side of the spinal cord. It is characterized by a characteristic pattern of motor and sensory deficits that are determined by the decussation pattern of various white matter t...
The Brown syndrome refers to an inability of a patient to perform an upward gaze while the eye is adducted due to an abnormality of the superior oblique tendon sheath complex.
History and etymology
It was first described by Allan Brown in 1950 1.
Brudzinski sign occurs in meningitis (of any etiology) where passive flexion of one leg causes flexion in the opposite leg. Passive flexion of the neck brings about flexion of the legs as well.
First described by Jósef Brudziñski (1874-1917), pediatrician from Warsaw, Poland...
Bruns sign occurs in patients with an obstructing fourth ventricle tumor. It consists of:
The symptoms are often exacerbated with sudden movements of the head
Buphthalmos is a descriptive term which simply means an enlarged eyeball or ocular globe due to increased intraocular pressure (glaucoma), without deformation or and intrinsic mass lesion.
It typically manifests in infants and young children.
It usually indicates the p...
A burnt out meningioma is a term used to denote a meningioma which has become completely calcified / ossified 1. The term refers to the usually indolent behavior, with these tumors rarely seen to grow.
Most burnt out meningiomas are likely to be psammomatous meningiomas, as these are far more ...
A burst lobe is an uncommonly used description of traumatic lobar intraparenchymal hemorrhage of the brain that ruptures into the subdural space and communicates with subdural hemorrhage 1.
As traumatic hemorrhages are more common in the frontal and temporal lobes, these lobes are the most affe...
Butterfly gliomas are a high grade astrocytoma, usually a glioblastoma (WHO grade IV), which crosses the midline via the corpus callosum. Other white matter commissures are also occasionally involved. The term butterfly refers to the symmetric wing-like extensions across the midline.
The butterfly sign refers to the normal appearance of the choroid plexuses on axial imaging of the fetal brain, commonly observed on the antenatal ultrasound. Its absence may suggest holoprosencephaly 1.
In the CNS, the term should not be confused with a butterfly glioma, which is a glioblastom...
Café au lait spots are a type of pigmented skin lesions which are classically described as being light brown in color.
Conditions associated with them include:
neurofibromatosis type 1 (NF1)
McCune-Albright syndrome: typically irregular which has been likened to t...
Caisson disease is an uncommon diving-related decompression illness that is an acute neurological emergency typically occurring in deep sea divers.
Diving-related decompression illness is classified into two main categories 3:
arterial gas embolism secondary to pulmonary decompression barotra...
The calcarine artery, named according to its course in the calcarine fissure, is a branch of the posterior cerebral artery, usually from the P3 segment. It may also arise from the parieto-occipital artery or posterior temporal branches. It courses deep in the fissure, giving branches both to th...
The calcarine fissure, or calcarine sulcus, is located on the medial surface of the occipital lobe and divides the visual cortex (a.k.a. calcarine cortex) into two.
The fissure is variable in course (figure 1), but is generally oriented horizontally, anteriorly joining the parieto-occipital fi...
Calcification of the globe has many causes, varying from the benign to malignant. When calcification is seen of the posterior half of the globe, it could relate to any of the layers (scleral, choroidal or retinal), as it is not possible to separate them out on CT.
drusen: 1% population...
Calcified cerebral embolus is an uncommon and often overlooked cause of embolic ischemic stroke.
Although emboli are a common cause of ischemic stroke, calcified cerebral emboli are considered rare. With only a paucity of literature regarding calcified cerebral emboli – only 48 r...
Calcified chronic subdural hematomas are rare variants of chronic subdural hematomas.
Calcified chronic subdural hematomas are uncommon, accounting for only 0.3-2.7% of chronic subdural hematomas 1-3. They are seen more commonly in children than in adults 1-3.
In order of frequency, a useful mnemonic to remember glial tumors which calcify is:
Old Elephants Age Gracefully
G: glioblastoma multiforme
Calcifying pseudoneoplasms of the neuraxis (CAPNON) are very rare heavily calcified discrete intraparenchymal or extra-axial lesions that can occur anywhere along the neuraxis.
Given the rarity of these lesions, detailed epidemiological data is not available.
Call-Fleming syndrome, also called Call syndrome, essentially synonymous with the more current term reversible cerebral vasoconstriction syndrome (RCVS), although it is felt to be a subset of the former by some, representing the idiopathic RCVS.
Call-Flemming syndrome is therefore characterize...
The callosal angle has been proposed as a useful marker of patients with idiopathic normal pressure hydrocephalus (iNPH), helpful in distinguishing these patients from those with ex-vacuo ventriculomegaly (see hydrocephalus versus atrophy).
Ideally the angle should be measured on a cor...
The callosal sulcus is a sulcus of the brain, located on the medial side of each cerebral hemisphere, deep within the medial longitudinal fissure.
The callosal sulcus runs posteriorly from the genu to the splenium of the corpus callosum. It separates the cingulate gyrus dorsally...
The callosomarginal artery, also known as median artery of corpus callosum, is the largest branch of the pericallosal artery. It courses within or posterior to the cingulate sulcus, in parallel orientation to the pericallosal artery. It divides to give two or more cortical branches to supply the...
The callososeptal interface is located on the inferior surface of the corpus callosum, where the septum pellucidum abuts it.
It came to radiological attention when T2 hyperintense lesions affecting this region were believed to be specific for multiple sclerosis. This has, as is usually the cas...
Calvarial thickening can occur from a number of causes. These include:
chronic ventricular shunting 1
anemias (largely associated with massive hematopoiesis)
The Canadian CT head rule (CCTHR) is a validated clinical decision rule to determine the need for CT head in adult emergency department patients with minor head injuries.
Patient has suffered minor head trauma with resultant:
loss of consciousness
Canavan disease, also known as spongiform degeneration of white matter (not to be confused with Creutzfeldt-Jakob Disease) or aspartoacylase deficiency, is a leukodystrophy clinically characterized by megalencephaly, severe mental and neurological deficits, and blindness.
Capillary hemangiomas of the orbit, also known as strawberry hemangiomas, on account of its coloring, or orbital infantile hemangiomas, are the most common orbital tumors of infancy, and unlike orbital cavernous hemangiomas, they are neoplasms rather than vascular malformations.
The caput medusae sign, refers to developmental venous anomalies of the brain, where a number of veins drain centrally towards a single drain vein. The appearance is reminiscent of Medusa, a gorgon of Greek mythology, who was encountered and defeated by Perseus.
The sign is seen on both CT and ...