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.

2,349 results found
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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 encase the axons in the tracts compared to the grey matter, which contains predominantly...
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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 tracts tracts connecting the cortex with other area in the CNS, e.g. deep nuclei, brainstem, cerebellum or spine may be efferent (motor) or afferent tracts (sensory) white ma...
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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 and was based on the histological characteristics of the tumor. Although the most recent version of the 'blue book' is the 4th edition from 2007, an update has been released in 2016 3, which should...
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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...
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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 extraocu...
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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. Clinical presentation Clinical presentat...
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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...
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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...
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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. photon energy: 81 KeV physical half-life: 5.27 days biological half-life: 30 seconds normal distribution: lungs <15% of inhaled gas is absorb...
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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 ...
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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...
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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...
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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". 
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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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Zebra sign (cerebellum)

The zebra sign has been termed to describe the finding of layering of blood in amongst the folia of the cerebellum, particularly in the setting of remote cerebellar hemorrhage.1 This type of hemorrhage is characterized by a streaky pattern, like a zebra's stripes, due to blood spreading in the ...
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Zellweger syndrome

Zellweger syndrome (ZS), also known as the cerebrohepatorenal syndrome, is a multisystem metabolic abnormality. As the name implies it primarily affects the central nervous system (CNS), liver and kidneys.  Epidemiology The condition typically presents in neonates with poor feeding and/or seiz...
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Zimmerman-Laband syndrome

Zimmerman-Laband syndrome is a rare congenital syndrome, characterized primarily by gingival hypertrophy and skeletal abnormalities.  Pathology The molecular basis of the syndrome is currently unknown. An autosomal dominant mutation with high mutation rate and rare instances of germinal mosaic...
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Zinc toxicity

Zinc toxicity (also rarely known as zincalism) is rare as the body is remarkably efficient at excreting excess zinc. Typically oral zinc poisoning manifests primarily as: acute GI symptoms: vomiting, diarrhea, abdominal pain secondary copper deficiency zinc competes with copper for absorption...
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Zurich pituitary score

The Zurich pituitary score (ZPS) is a quantitative classification of pituitary adenomas based on coronal T1W magnetic resonance imaging with contrast, although the score can also be obtained with computed tomography. The ZPS is based on the ratio (R) between horizontal tumor diameter over inter...

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