Articles

Articles are a collaborative effort to provide a single canonical page on all topics relevant to the practice of radiology. As such, articles are written and edited by countless contributing members over a period of time. A global group of dedicated editors oversee accuracy, consulting with expert advisers, and constantly reviewing additions.

2,703 results found
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VASARI MRI feature set

The VASARI (Visually AcceSAble Rembrandt Images) MRI feature set is a system designed to enable consistent description of gliomas using a set of defined visual features and controlled vocabulary. It is the result of work by The Cancer Imaging Archive (TCIA) who publish relevant guides to use, an...
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Vascular dementia

Vascular dementia, also known as vascular cognitive impairment, is the second most common cause of dementia after the far more common Alzheimer disease. It is primarily seen in patients with atherosclerosis and chronic hypertension and results from the accumulation of multiple white matter lesio...
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Vasculopathies caused by varicella zoster virus

Vasculopathies caused by varicella zoster virus (VZV) represent a group of illnesses involving both small and large CNS arteries caused by a inflammatory process involving the media and the vascular endothelium. Usually it occurs in immunocompromised individuals due the viral reactivation and sp...
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Vasogenic cerebral edema

Vasogenic cerebral edema refers to a type of cerebral edema in which the blood brain barrier (BBB) is disrupted (cf. cytotoxic cerebral edema, where the blood-brain barrier remains intact). It is an extracellular edema which mainly affects the white matter via leakage of fluid from capillaries. ...
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Vein of Galen aneurysmal malformation

Vein of Galen aneurysmal malformations (VGAMs), probably better termed as median prosencephalic arteriovenous fistulas, are uncommon intracranial anomalies that tend to present dramatically during early childhood with features of a left-to-right shunt and high-output cardiac failure. Epidemiolo...
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Veins of the brainstem

The veins of the brainstem drain the medulla, the pons and the mesencephalon, including the cerebral peduncles, tegmentum and quadrigeminal plate. They are characterized by several variations and feature multiple connections draining into the inferior, medial superior petrosal sinuses or form a ...
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Velum interpositum

The velum interpositum is a small membrane containing a potential space just above and anterior to the pineal gland which can become enlarged to form a cavum velum interpositum.  Gross anatomy The velum interpositum is formed by an invagination of pia mater forming a triangular membrane the ap...
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Venous circle of Trolard

The anastomotic venous circle of the base of the brain 1, also referred to as the venous circle of Trolard 2,3,5, is an inconsistently found venous homologue of the better-known arterial circle of Willis. It should not be confused with other venous structures also described by Trolard such as t...
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Venous distension sign

The venous distension sign is a finding that may be identified on sagittal imaging of the dural venous sinuses which is said to have a diagnostic sensitivity and specificity of 94% for intracranial hypotension. The sign is positive when there is a convex inferior margin of the midportion of the...
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Venous vascular malformation of the facial nerve

Venous vascular malformations of the facial nerve, previously known as facial nerve hemangiomas, are rare benign vascular malformations of the facial nerve usually presenting as a facial nerve palsy, which can be rapid in onset mimicking a Bell palsy.  Terminology As they do not appear to have...
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Ventral cord herniation

Ventral cord herniation, also known by a variety of other terms such as spontaneous thoracic cord herniation or idiopathic spinal cord herniation, is a rare cause of focal myelopathy due to herniation of the thoracic cord through a dural defect.  Post-surgical cord herniation can occur at any l...
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Ventral cord syndrome

Ventral cord syndrome (also known as anterior cord syndrome) is one of the incomplete cord syndromes and affects the anterior parts of the cord resulting in a pattern of neurological dysfunction dominated by motor paralysis and loss of pain, temperature and autonomic function. Anterior spinal ar...
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Ventral horn

The ventral horn of the spinal cord is one of the grey longitudinal columns found within the spinal cord. It contains the cell bodies of the lower motor neurons which have axons leaving via the ventral spinal roots on their way to innervate muscle fibers. Gross anatomy On transverse section of...
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Ventricular system

The ventricular system in the brain is composed of cerebrospinal fluid (CSF)-filled ventricles and their connecting foramina. CSF is produced by ependymal cells which line the ventricles. They are continuous with the central canal. Ventricles contain around 20% of the total average adult CSF vol...
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Ventriculitis

Ventriculitis (plural: ventriculitides) refers to inflammation, usually due to infection, of the ependymal lining of the cerebral ventricles. It is most often due to meningitis. Terminology The entity or closely related variants have also been variously referred to as ependymitis, ventricular ...
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Ventriculoatrial shunt

Ventriculoatrial shunting is an alternative option for the diversion of CSF and relief of hydrocephalus. In this technique, the distal catheter is placed in the right atrium or even in the superior vena cava 1,2.  It is not the only alternative for the traditional ventriculoperitoneal shunt, an...
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Ventriculogallbladder shunt

Ventriculogallbladder shunts, also known as ventriculocholecystic shunts 5, are a rarely employed form of cerebrospinal fluid diversion, used when a ventriculoperitoneal shunt is not possible (e.g. intra-abdominal adhesions, peritonitis). Differential diagnosis a ventriculoperitoneal shunt in ...
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Ventriculomegaly

Ventriculomegaly is defined as enlargement of the ventricles. Simply, there are two causes: hydrocephalus communicating non-communicating parenchymal atrophy Refer to the article on hydrocephalus vs atrophy for more details on how to differentiate both entities. 
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Ventriculoperitoneal shunt

Ventriculoperitoneal (VP) shunts are a device used to shunt cerebrospinal fluid in the treatment of hydrocephalus. As the name suggests, a catheter is placed with its tip in the ventricle. The external portion of the catheter is connected to a valve that regulates the flow of CSF based on a pre...
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Ventriculopleural shunt

Ventriculopleural shunting is an alternative option for the diversion of CSF and relief of hydrocephalus. In this technique, the distal catheter is placed in the pleural space. It is an alternative to a ventriculoperitoneal shunt (often considered a next most used alternative). Complications s...
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Ventriculus terminalis

The ventriculus terminalis (or persistent terminal ventricle, or terminal ventricle of Krause, or 5th ventricle) is an ependymal-lined fusiform dilatation of the terminal central canal of the spinal cord, positioned at the transition from the tip of the conus medullaris to the origin of the filu...
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Venus necklace

A Venus necklace is a term almost never used, but for the sake of completeness is included here. It has been used by some authors 1 to describe a series of T2 hyperintense lesions on the inferior surface of the corpus callosum in the midline (callososeptal interface), most frequently seen in mul...
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Vermian lobulation

Evaluation of vermian lobulation is essential in assessment of the vermian maturity. MRI is a useful tool in assessment of the fetal posterior fossa. Radiographic features Normal vermian lobulation by weeks 1: by 21 weeks: the prepyramidal fissure can be seen between the tuber and pyramis 21...
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Vermian maturity assessment (approach)

Radiological evaluation of the posterior fossa is an essential part of the routine fetal assessment, including vermian maturity assessment. Radiographic features Ultrasonography is a readily available diagnostic tool in the assessment of the fetal posterior fossa but is sometimes limited due t...
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Vermis

The vermis (pl: vermes) of the cerebellum is an unpaired medial structure that separates the cerebellar hemispheres. It's anatomy broadly follows that of the cerebellar hemispheres.  Gross anatomy The vermis is separated into a small anterior lobe and a much larger posterior lobe by the primar...
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Vernet syndrome

Vernet syndrome, also known as jugular foramen syndrome, is a constellation of cranial nerve palsies due to compression from a jugular foramen lesion, such as a glomus jugulare tumor, schwannoma, or metastasis 2. Clinical presentation It consists of motor paralysis of: glossopharyngeal nerve ...
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Verocay bodies

Verocay bodies are a histological feature of schwannomas and represent a particular growth pattern of Antoni type A pattern in which tumor cells form alternating parallel rows of nuclear palisades separated by regions of acellularity 1. 
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Vertebral artery dissection

Vertebral artery dissection, like arterial dissection elsewhere, is a result of blood entering the media through a tear in the intima of the vertebral artery. It is potentially lethal and can be difficult to diagnose clinically and radiologically. Epidemiology Vertebral artery dissections have...
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Vertebral artery thrombosis

Vertebral artery thrombosis results in complete or partial occlusion of the vertebral artery and alteration of blood flow to the posterior cerebral circulation. Ischemia or infarction to structures supplied by these arteries may result in a range of symptoms. brainstem cerebellum occipital lo...
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Vertebral scalloping

Vertebral scalloping is a concavity to the posterior (or less commonly anterior) aspect of the vertebral body when viewed in a lateral projection. A small amount of concavity is normal, as is concavity of the anterior vertebral body (see vertebral body squaring). Posterior scalloping Causes of...
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Vestibular neuritis

Vestibular neuritis refers to the situation where there inflammation of the vestibular nerve/vestibulocochlear nerve. It can be associated with labyrinthitis. The vestibular nerve is a large division of cranial nerve eight (CN VIII) that transfers the equilibrium information from the inner ear ...
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Vestibular nuclei

The vestibular nuclei are a group of four small special sensory nuclei in the lower pons and upper medulla for the vestibular nerve component of the vestibulocochlear nerve. They are part of the extensive cranial nerve nuclei within the brainstem. Gross Anatomy There four nuclei are located ad...
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Vestibular paroxysmia

Vestibular paroxysmia describes a clinical syndrome of sudden and stereotyped episodes of vertigo-type symptoms which usually last for less than one minute, often attributed to being a nerve compression syndrome affecting the vestibular nerve. Epidemiology Vestibular paroxysmia most commonly m...
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Vestibular schwannoma

Vestibular schwannomas, also known as acoustic neuromas, are relatively common tumors that arise from the vestibulocochlear nerve (CN VIII) and represent ~80% of cerebellopontine angle (CPA) masses. Bilateral vestibular schwannomas are strongly suggestive of neurofibromatosis type 2 (NF2). On i...
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Vestibulocochlear nerve

The vestibulocochlear nerve (CN VIII) is the eighth cranial nerve and has two roles: innervation to the cochlea for hearing innervation to the vestibule for acceleration and balance senses Gross anatomy Nuclei There are two special sensory cochlear nuclei and four special sensory vestibular...
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Vidian nerve

Vidian nerve, also known as the nerve of the pterygoid canal or nerve of the Vidian canal, is so named because of the canal in which it travels: the Vidian canal. It is formed by the confluence of two nerves: greater superfical petrosal nerve (from the geniculate ganglion of the facial nerve) ...
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Viking helmet appearance

The Viking helmet appearance refers to the morphology of the lateral ventricles in the coronal plane in patients with dysgenesis of the corpus callosum. The cingulate gyrus is everted into narrowed and elongated frontal horns. An alternative name is moose head appearance. Other names include st...
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Viral encephalitides

Viral encephalitides are the result of brain parenchymal infection by a number of different viruses, many of which have similar presentations and imaging features. Specific diagnosis often requires PCR.  For viral infection of the meninges, please refer to the general article on viral meningiti...
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Viral meningitis

Viral meningitides correspond to a relatively common and self-limited type of CNS infection clinically diagnosed based on the cerebrospinal fluid analysis and proportionally more frequent in young children than adults. Enteroviruses represent nowadays the most common cause of viral meningitis fo...
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Visual agnosia

Visual agnosia is a special type of agnosia where patients are unable to recognize objects despite having knowledge about them and being able to visually perceive them. It typically occurs when there is damage to the ventral occipitotemporal pathway, such as in posterior cerebral atrophy (Benso...
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Visual hallucinations

Visual hallucinations are relatively uncommon, and can be due to a variety of 'organic' brain diseases, affecting a variety of regions of the brain.  The use of the term organic here is by convention, and should not be taken to imply absence of brain dysfunction in psychiatric illness. Clini...
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Visual pathway deficits

Visual pathway or visual field deficits are defects in visual space determined by the location of a lesion in the neurological visual pathway from eye to brain cortex. Understanding of the visual system is paramount 1: retina or optic nerve anopia or central scotoma (ipsilateral) optic chiasm...
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Visual system

The visual system or the optic pathway transmits visual information from the retina within the eyes to the primary visual cortex of the occipital lobe as well as the pretectal nuclei and superior colliculi of the midbrain. Gross anatomy Below the visual pathway is described from distal to prox...
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Vitamin B1

Vitamin B1 (thiamine) is a water-soluble vitamin, that is part of the vitamin B complex, and is an important coenzyme for two reactions in the citric acid cycle (Kreb cycle). It therefore is vital for cellular ATP production, particularly in the central nervous system. Terminology Thiamine is ...
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Vitamin B12 deficiency

Vitamin B12 deficiency, also known as hypovitaminosis B12 or hypocobalaminemia, is not uncommon, with potentially serious sequelae if not adequately treated. Clinical presentation Vitamin B12 deficiency results in a reduction of two metabolic pathways 3:  conversion of L-methylmalonyl coenzym...
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Vitamin B3

Vitamin B3 (niacin or nicotinic acid) is a water-soluble vitamin, part of the vitamin B complex, that is an important part of the coenzyme nicotinamide adenine dinucleotide (NAD+) which is involved in many reactions of cellular metabolism. Vitamin B3 is one of the hematinics. Related pathology ...
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Vitamin B5 deficiency

Vitamin B5 deficiency, also known as hypovitaminosis B5, is extremely rare. Pantothenic acid (vitamin B5) is needed for the formation of coenzyme A, itself essential for the synthesis of acetylcholine and melatonin. Pantothenic acid is also required for normal functioning of the tricarboxylic ac...
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Vitamin B6 deficiency

Vitamin B6 deficiency (also known as hypovitaminosis B6) is rare, as the B6 vitamers are present in many commonly-consumed foodstuffs. It is most commonly seen in the context of chronic ethanol excess, although many other risk factors are known. In children, deficiency may manifest as seizures. ...
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Vitamin B6 excess

Vitamin B6 excess (hypervitaminosis B6) is caused by excessive consumption of supplemental pyridoxine, which is used as a therapeutic agent for several conditions.  Epidemiology This hypervitaminosis is almost exclusively seen in those taking pyridoxine as prescription medication, it remains i...
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Vitamin B9

Vitamin B9 (folate or folic acid) is a water-soluble vitamin, part of the vitamin B complex, vital for the synthesis of several amino acids, the purines adenosine and guanine and the pyrimidine thymine (three of the four nucleotide bases and hence critical for the synthesis of nucleic acids). T...
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Volcano sign (meningioma)

Volcano sign refers to the appearance of classical meningioma that resembels the appearance of volcano (viewed in cross-section MRI, parallel to dural attachment) in which there is triangular hyperostosis at the base of the meningioma (mountain) with the tumor being the cloud around it. The intr...
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Voltage gated potassium channel (VGKC) antibody encephalitis

Voltage-gated potassium channel (VGKC) antibody encephalitis is autoimmune encephalitis with antibodies against the voltage-gated potassium channel. It is one of the most common forms of autoimmune limbic encephalitis in the absence of primary extra-CNS tumors. Autoimmune VGKC encephalitis can b...
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Von Hippel-Lindau disease

Von Hippel-Lindau (vHL) disease is characterized by the development of numerous benign and malignant tumors in different organs (at least 40 types 1) due to mutations in the VHL tumor suppressor gene on chromosome 3. Epidemiology The disease is rare with an estimated prevalence of 1:35,000-50,...
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V sign (disambiguation)

Signs inspired by the letter V have been described in several different pathologies: inverted V sign (pneumoperitoneum) inverted V sign (spinal cord) Naclerio V sign (pneumomediastinum)
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Walker-Warburg syndrome

Walker-Warburg syndrome (WWS), sometimes known as HARDE syndrome, is an extremely rare lethal form of congenital muscular dystrophy. It is primarily characterized by: fetal hydrocephalus: almost always present neuronal migrational anomalies: agyria (cobblestone lissencephaly / lissencephaly ty...
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Wallerian degeneration

Wallerian degeneration is the process of antegrade degeneration of the axons and their accompanying myelin sheaths following proximal axonal or neuronal cell body lesions. It may result following neuronal loss due to cerebral infarction, trauma, necrosis, focal demyelination, or hemorrhage.  In...
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Walnut kernel microbleed pattern

The walnut kernel microbleed pattern along with the starfield pattern and corpus callosum diffusion restriction appears to be the most important imaging markers of cerebral fat embolism 1-3. In this pattern, there is a diffuse presence of round microbleeds (punctate focal hypointensities) of mo...
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Wasp-waist sign (spine)

The wasp-waist sign is a radiographic appearance seen in patients with Klippel Feil syndrome. It results from fusion of the vertebral bodies such that the anteroposterior diameter at the level of the affected discovertebral joint is smaller than the diameter at the superior and inferior limits o...
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Watershed cerebral infarction

Watershed cerebral infarctions, also known as border zone infarcts, occur at the border between cerebral vascular territories where the tissue is furthest from arterial supply and thus most vulnerable to reductions in perfusion.  Epidemiology Watershed cerebral infarction accounts for 5-10% of...
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Weber syndrome

Weber syndrome is a midbrain stroke syndrome that involves the cerebral peduncle and the ipsilateral fascicles of the oculomotor nerve 1-3,5. Occasionally the substantia nigra can also be involved 5.  Clinical presentation ipsilateral CN III palsy diplopia ptosis  afferent pupillary defect ...
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Wernekink commissure syndrome

The Wernekink commissure syndrome (sometimes spelled Wernekinck) is a rare brainstem syndrome caused by lesions (usually infarcts) involving the decussation of the superior cerebellar peduncles (Wernekink commissure) at the caudal midbrain. Clinical presentation The syndrome is characterized b...
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Wernicke aphasia

Wernicke aphasia, also known as receptive aphasia or fluent aphasia, is the inability to grasp the meaning of spoken or written words and sentences while producing connected speech is not greatly affected. Receptive aphasia is usually caused by injury to the dominant posterior temporal lobe (We...
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Wernicke encephalopathy

Wernicke encephalopathy, also referred as Wernicke-Korsakoff syndrome, is a form of thiamine (vitamin B1) deficiency, and is typically seen in alcoholics. On imaging, it is commonly seen on MRI as areas of symmetrical increased T2/FLAIR signal involving the mammillary bodies, dorsomedial thalam...
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Wernicke's area

Wernicke's area (Brodmann area 22) is an area of the posterior temporal lobe in the dominant hemisphere concerned with the receptive components of speech. Gross anatomy Wernicke's area is located in the superior temporal gyrus, posterior to the posterior commissure line. Relations It is boun...
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Wernicke's Korsakoff (mnemonic)

A mnemonic to recall some of the important features of Wernicke's Korsakoff syndrome is: COMBAT Mnemonic C: confusion, confabulatory amnesia O: ophthalmoplegia M: mamillary bodies B: B1(vitamin), bariatric surgery A: alcoholics T: thalami, tectal plate, third ventricle
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West Nile virus

West Nile virus (WNV) is an arbovirus and one of the Flavivirus genus known to cause neuroinvasive disease, including Flavivirus encephalitis. According to the CDC, the majority of mosquito-borne disease in the continental United States is attributed to West Nile virus infection 1.  Epidemiolog...
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WFNS grading system

The WFNS (World Federation of Neurosurgical Societies) grading system uses the Glasgow Coma Scale and presence of focal neurological deficits to grade the clinical severity of subarachnoid hemorrhage. This grading system was proposed in 1988, and this is one of the accepted systems (although not...
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Whipple disease (neurological manifestations)

Neurological manifestations of Whipple disease are rare. Whipple disease may appear as a primary neurological disorder in rare cases. It is rarely found as a cause of progressive neurological deterioration in patients. It has been suggested that neurological involvement will eventually occur in...
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White cerebellum sign

White cerebellum sign, also called reversal sign or dense cerebellum sign, is encountered when there is a diffuse decrease in density of the supratentorial brain parenchyma, with relatively increased attenuation of the thalami, brainstem and cerebellum. This sign indicates irreversible brain dam...
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White cord syndrome

White cord syndrome refers to the sudden onset of neurological deterioration following spinal decompressive surgery. The condition is believed to be a form of reperfusion injury of the spinal cord, not to be confused with central cord syndrome. Epidemiology White cord syndrome is rare with onl...
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White epidermoid cyst

White epidermoids are a rare type of epidermoid cyst that do not follow the usual near-CSF density and signal intensity on CT and MR respectively. To make matters worse the literature uses the term inconsistently, although generally the 'white' refers to the T1 weighted imaging appearance.  Rad...
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White grey sign

White grey sign is useful for identifying the central sulcus on MRI images. It reflects that fact that primary motor and sensory cortex has more myelin in it than other cortices. This results in a whitening of the cortex on T1-weighted imaging, especially noticeable at higher field strengths. On...
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White matter

The white matter is the substance of the brain and spinal cord that contains the fiber tracts of neuronal axons in the central nervous system. The term is due to the paler color of the lipid-rich myelin that encases the axons in the tracts compared to the grey matter, which contains predominantl...
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White matter buckling sign

The white matter buckling sign is helpful in distinguishing an extra-axial intracranial mass from an intra-axial one and represents the white matter projecting into gyri being compressed and displaced by the mass, even in the presence of edema (which would usually expand gyri, if the mass were i...
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White matter changes in HIV

White matter changes in HIV have overlapping appearances and varied in etiology. These can be divided into: primary effects of HIV opportunistic infection neoplasms vascular disease metabolic and nutritional disorders Primary effects of HIV HIV encephalitis Opportunistic infection cytom...
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White matter disorders

White matter diseases are a group of conditions that predominantly or significantly affect the white matter of the brain. They comprise a vast heterogeneous group and have a variety of appearances and presentations. They cause disease by altering the process of normal myelination.  Useful group...
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White matter tracts

White matter tracts in the brain, also known as white matter fibers, are classified into three categories: projection fibers association fibers commissural fibers The white matter can be observed well on T1W, T2W and FLAIR sequences. Some white matter tracts are quite well demonstrated espec...
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White matter tracts of the spinal cord

The spinal cord has numerous tracts of white matter that ascend and descend in the peripheral substance of the cord. They can be divided by their location and function: anterolateral columns anterior corticospinal tract medial longitudinal fasiculus spinothalamic tracts lateral spinothalami...
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WHO classification of CNS tumors

The WHO classification of CNS tumors is the most widely accepted system for classifying CNS tumors, now into its 5th edition, traditionally published in a blue cover (thus "blue book"). Although traditionally based on histological characteristics of the tumors, since the 2016 revised 4th editio...
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WHO grading of CNS tumors

WHO (World Health Organization) grading of CNS tumors is based on histological characteristics such as cellularity, mitotic activity, pleomorphism, necrosis, and endothelial proliferation (neoangiogenesis). It is used in the WHO classification of CNS tumors.  It should be noted that at the time...
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WHO grading system for diffuse astrocytomas

 The WHO grading system is the most widely used system for grading diffuse astrocytomas (at the time of writing i.e. mid-2016) and is an adaptation of the now superseded St Anne-Mayo grading system (also known as the Daumas-Duport grading system).  Grade I is reserved for localized astrocytomas...
Article

Wildervanck syndrome

Wildervanck syndrome, also known as cervico-ocular-acoustic dysplasia, consists of the triad of: Klippel-Feil syndrome congenital ossicular anomalies: usually diffuse ossicular ankylosis and sensorineural deafness Duane syndrome: an ocular motility disturbance due to fibrosis of the extraocul...
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Wilson disease

Wilson disease, also known as hepatolenticular degeneration, is a rare autosomal recessive disorder of copper metabolism affecting multiple systems.  Epidemiology Wilson disease is commonly found in Japan. It affects 1 in 30,000-40,000 individuals 12. 1 in 90 individuals are a heterozygous car...
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Wilson disease (CNS manifestations)

Wilson disease, also known as hepatolenticular degeneration, is a multisystem disease due to abnormal accumulation of copper. It is characterized by early onset liver cirrhosis with CNS findings most frequently affecting the basal ganglia and midbrain. This article aims to discuss the central n...
Article

Wolfram syndrome (type one)

Wolfram syndrome type one, also known as DIDMOAD, is a disease caused by an autosomal recessive genetic trait, caused by mutations in the WFS1 gene, with incomplete penetrance. The syndrome presents with early onset of insulin-dependent diabetes mellitus, progressive optic atrophy, diabetes ins...
Article

Wyburn-Mason syndrome

Wyburn-Mason syndrome (also known as Bonnet-Dechaume-Blanc syndrome) is a rare, nonhereditary neurocutaneous disorder that typically presents with unilateral vascular malformations that primarily involve the brain, orbits and facial structures. It is currently classified as a craniofacial arteri...
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Xanthomatous meningioma

Xanthomatous meningiomas are rare histological variants of meningiomas grouped into the subtype of metaplastic meningiomas, being WHO grade I tumors. They are characterized by cells with a lipid-filled vacuolated cytoplasm. Although reported numbers are too small to confirm that this is definit...
Article

Xenon-133

Xenon-133 is a radiopharmaceutical principally used when a performing VQ scan. Inhalation of this gas can also be used to assess cerebral blood flow. Mode of decay: Beta decay photon energy: 81 KeV physical half-life: 5.27 days biological half-life: 30 seconds normal distribution: lungs <1...
Article

X-linked adrenoleukodystrophy

X-linked adrenoleukodystrophy is an inherited metabolic peroxisomal disorder and one of the more common leukodystrophies in both children and adults. It is characterized by a lack of oxidation of very long chain fatty acids (VLCFAs) that results in severe inflammatory demyelination typically of ...
Article

Yasargil classification of vein of Galen aneurysmal malformations

The Yasargil classification is one of the two common systems for classifying vein of Galen malformations that is currently in use at the time of writing (mid 2016).  Classification type I: small pure cisternal fistula between the vein of Galen (voG) and either the pericallosal arteries (anteri...
Article

Yin-yang sign (solitary fibrous tumor)

The yin-yang sign is a radiologic appearance described in solitary fibrous tumor of the dura on MR. On T2-weighted images, these tumors have two separate solid components, one that is hyperintense and one that is iso- to hypointense relative to brain parenchyma. Histologically, the former repre...
Article

Y sign (epidural lipomatosis)

The Y sign refers to a common appearance in lumbar epidural lipomatosis where excess fat in the extradural space compresses the dural sac into the shape of the letter "Y". NB: Y sign also refers to the appearance of incudomalleolar disarticulation on CT, more commonly known to radiologists as t...
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Zabramski classification of cerebral cavernous malformations

The Zabramski classification of cerebral cavernomas has been proposed as a way of classifying cerebral cavernous malformations, and although not used in clinical practice it is useful in scientific publications that seek to study cavernous malformations. The classification was proposed in 1994 ...

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