title: Cortical and subcortical cerebrovascular resistance index in mild cognitive impairment and Alzheimer's disease.
abstract: BACKGROUND
  Reduced regional cerebral blood flow (rCBF) is a well-established finding in Alzheimer's disease (AD), although fewer studies have examined the role of increased regional cerebrovascular resistance. By calculating the ratio of mean arterial pressure to rCBF, it is possible to estimate an index of regional cerebrovascular resistance (CVRi) that may be a sensitive measure of occult cerebrovascular disease.
  
  
  OBJECTIVE
  To compare probable AD patients to mild cognitive impairment (MCI) and normal control (NC) participants on CVRi, the ratio of mean arterial pressure to rCBF.
  
  
  METHODS
  Eighty-one participants (12 AD, 23 MCI, 46 NC) were compared on CVRi using voxel-wise analyses. Region-of-interest analyses examined correlations between subcortical CVRi and both cognition and white matter lesion (WML) volume.
  
  
  RESULTS
  Voxel-wise analyses revealed CVRi elevation in AD relative to NCs (subcortical, medial temporal, posterior cingulate, precuneus, inferior parietal, superior temporal) and MCI (subcortical, posterior cingulate). MCI participants exhibited intermediate CVRi values within cortical and medial temporal areas. Significant CVRi clusters were larger and more widespread than those of parallel CBF analyses. Among MCI and AD participants, subcortical CVRi elevation was associated with lower Dementia Rating Scale score (r = -0.52, p = 0.001, for both thalamus and caudate), and caudate CVRi correlated with WML volume (r = 0.45, p = 0.001).
  
  
  CONCLUSIONS
  Cortical and subcortical CVRi is elevated in AD, particularly within the caudate and thalamus, where it is associated with decreased cognitive performance and increased WMLs. Findings suggest CVRi may play a role in cognitive decline and cerebrovascular disease in MCI and AD.
authors.affiliation: Veterans Affairs San Diego Healthcare System, San Diego, CA 92161, USA.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Nation
authors.forename: Christina E
authors.initials: CE
authors.lastname: Wierenga
authors.forename: Lindsay R
authors.initials: LR
authors.lastname: Clark
authors.forename: Sheena I
authors.initials: SI
authors.lastname: Dev
authors.forename: Nikki H
authors.initials: NH
authors.lastname: Stricker
authors.forename: Amy J
authors.initials: AJ
authors.lastname: Jak
authors.forename: David P
authors.initials: DP
authors.lastname: Salmon
authors.forename: Lisa
authors.initials: L
authors.lastname: Delano-Wood
authors.forename: Katherine J
authors.initials: KJ
authors.lastname: Bangen
authors.forename: Robert A
authors.initials: RA
authors.lastname: Rissman
authors.forename: Thomas T
authors.initials: TT
authors.lastname: Liu
authors.forename: Mark W
authors.initials: MW
authors.lastname: Bondi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000175:diagnosis / Q000503:physiopathology*; D002540:Cerebral Cortex / Q000098:blood supply* / Q000503:physiopathology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D060825:Cognitive Dysfunction / Q000175:diagnosis / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male