Hyperintensity

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MRI scans showing hyperintensities

Hyperintensities refer to areas of high intensity on particular types of magnetic resonance imaging (MRI) scans of the human brain. These small regions of high intensity are observed on T2 weighted MRI images (typically created using 3D FLAIR) within cerebral white matter (white matter hyperintensities or WMH) or subcortical gray matter (gray matter hyperintensities or GMH). They are usually seen in normal aging but also in a number of neurological disorders and psychiatric illnesses. For example deep white matter hyperintensites are 2.5 to 3 times more likely to occur in bipolar disorder and major depressive disorder than control subjects.[1][2] WMH volume, calculated as a potential diagnostic measure, has been shown to correlate to certain cognitive factors.[3] Hyperintensities appear as "bright signals" (bright areas) on an MRI image and the term "bright signal" is occasionally used as a synonym for a hyperintensity.

Hyperintensities are commonly divided into 3 types depending on the region of the brain where they are found. Deep white matter hyperintensites occur deep within white matter, periventricular white matter hyperintensities occur adjacent to the lateral ventricles and subcortical hyperintensities occur in the basal ganglia.[citation needed]

Postmortem studies combined with MRI suggest that hyperintensities are dilated perivascular spaces, or demyelination caused by reduced local blood flow.[4]

Cognitive Effects[edit]

In most elderly people, presence of severe WMH and medial temporal lobe atrophy MTA was linked with an increase in frequency of mild cognitive deficits. Studies suggest that a combination of MTA and severe WMH showed more than a fourfold increase in the frequency of mild cognitive deficits.[5] It's also been consistently shown that severe WMH is known to be associated with gait disorders, impaired balance and cognitive disturbances. Certain features of gait pattern associated with WMH are: slight widening of the base, slowing and shortening of stride length and turning en bloc. Speed of cognitive processes and frontal skills may also be impaired in people with WMH.[6] It is also thought that WMH patients have a negative impact on cognition in Alzheimer's disease population. Pathological signs of oligodendritic apoptosis and damage to axonal projections have been evident. Sufficient damage to the axons that course through WMH can cause adequate interference with normal neuronal functions.[7]

See also[edit]

References[edit]

  1. ^ Kempton, Matthew J.; Geddes, JR; Ettinger, U; Williams, SC; Grasby, PM (2008). "Meta-analysis, Database, and Meta-regression of 98 Structural Imaging Studies in Bipolar Disorder". Archives of General Psychiatry 65 (9): 1017–32. doi:10.1001/archpsyc.65.9.1017. PMID 18762588. 
  2. ^ Videbech, P. (1997). "MRI findings in patients with affective disorder: A meta-analysis". Acta Psychiatrica Scandinavica 96 (3): 157–68. doi:10.1111/j.1600-0447.1997.tb10146.x. PMID 9296545. 
  3. ^ Brickman, Adam M.; Meier, Irene B.; Korgaonkar, Mayuresh S.; Provenzano, Frank A.; Grieve, Stuart M.; Siedlecki, Karen L.; Wasserman, Ben T.; Williams, Leanne M. et al. (2012). "Testing the white matter retrogenesis hypothesis of cognitive aging". Neurobiology of Aging 33 (8): 1699–715. doi:10.1016/j.neurobiolaging.2011.06.001. PMC 3222729. PMID 21783280. 
  4. ^ Thomas, Alan J.; Perry, Robert; Barber, Robert; Kalaria, RAJ N.; O'Brien, John T. (2002). "Pathologies and Pathological Mechanisms for White Matter Hyperintensities in Depression". Annals of the New York Academy of Sciences 977: 333–9. doi:10.1111/j.1749-6632.2002.tb04835.x. PMID 12480770. 
  5. ^ Van Der Flier, W M; Van Straaten, EC; Barkhof, F; Ferro, JM; Pantoni, L; Basile, AM; Inzitari, D; Erkinjuntti, T et al. (2005). "Medial temporal lobe atrophy and white matter hyperintensities are associated with mild cognitive deficits in non-disabled elderly people: The LADIS study". Journal of Neurology, Neurosurgery & Psychiatry 76 (11): 1497–500. doi:10.1136/jnnp.2005.064998. PMC 1739423. PMID 16227537. 
  6. ^ Gouw, A.A.; Flier, W.M.; Straaten, E.C.W.; Barkhof, F.; Ferro, J.M.; Baezner, H.; Pantoni, L.; Inzitari, D. et al. (2006). "Simple versus complex assessment of white matter hyperintensities in relation to physical performance and cognition: The LADIS study". Journal of Neurology 253 (9): 1189–96. doi:10.1007/s00415-006-0193-5. PMID 16998647. 
  7. ^ Bocti, C.; Swartz, R. H.; Gao, F.-Q.; Sahlas, D. J.; Behl, P.; Black, S. E. (2005). "A New Visual Rating Scale to Assess Strategic White Matter Hyperintensities Within Cholinergic Pathways in Dementia". Stroke 36 (10): 2126–31. doi:10.1161/01.STR.0000183615.07936.b6. PMID 16179569. 

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