title: MRI-leukoaraiosis thresholds and the phenotypic expression of dementia.
abstract: OBJECTIVE
  To examine the concept of leukoaraiosis thresholds on working memory, visuoconstruction, memory, and language in dementia.
  
  
  METHODS
  A consecutive series of 83 individuals with insidious onset/progressive dementia clinically diagnosed with Alzheimer disease (AD) or small vessel vascular dementia (VaD) completed neuropsychological measures assessing working memory, visuoconstruction, episodic memory, and language. A clinical MRI scan was used to quantify leukoaraiosis, total white matter, hippocampus, lacune, and intracranial volume. We performed analyses to detect the lowest level of leukoaraiosis associated with impairment on the neuropsychological measures.
  
  
  RESULTS
  Leukoaraiosis ranged from 0.63% to 23.74% of participants' white matter. Leukoaraiosis explained a significant amount of variance in working memory performance when it involved 3% or more of the white matter with curve estimations showing the relationship to be nonlinear in nature. Greater leukoaraiosis (13%) was implicated for impairment in visuoconstruction. Relationships between leukoaraiosis, episodic memory, and language measures were linear or flat.
  
  
  CONCLUSIONS
  Leukoaraiosis involves specific threshold points for working memory and visuoconstructional tests in AD/VaD spectrum dementia. These data underscore the need to better understand the threshold at which leukoaraiosis affects and alters the phenotypic expression in insidious onset dementia syndromes.
authors: Department of Clinical and Health Psychology, University of Florida, Gainesville, USA. cep23@phhp.ufl.edu
authors: Catherine C
authors: CC
authors: Price
authors: Sandra M
authors: SM
authors: Mitchell
authors: Babette
authors: B
authors: Brumback
authors: Jared J
authors: JJ
authors: Tanner
authors: Ilona
authors: I
authors: Schmalfuss
authors: Melissa
authors: M
authors: Lamar
authors: Tania
authors: T
authors: Giovannetti
authors: Kenneth M
authors: KM
authors: Heilman
authors: David J
authors: DJ
authors: Libon
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003704:Dementia / Q000150:complications / Q000473:pathology* / Q000523:psychology*; D006624:Hippocampus / Q000473:pathology*; D006801:Humans; D007802:Language; D049292:Leukoaraiosis / Q000150:complications / Q000473:pathology* / Q000523:psychology*; D008279:Magnetic Resonance Imaging / Q000379:methods / Q000523:psychology; D061212:Memory, Episodic; D008570:Memory, Short-Term; D009413:Nerve Fibers, Myelinated / Q000473:pathology; D059906:Neuroimaging / Q000379:methods / Q000523:psychology*; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D009929:Organ Size; D010641:Phenotype; D011597:Psychomotor Performance; D012720:Severity of Illness Index