title: Functional magnetic resonance imaging detection of vascular reactivity in cerebral amyloid angiopathy.
abstract: OBJECTIVE
  In addition to its role in hemorrhagic stroke, advanced cerebral amyloid angiopathy (CAA) is also associated with ischemic lesions and vascular cognitive impairment. We used functional magnetic resonance imaging (MRI) techniques to identify CAA-associated vascular dysfunction.
  
  
  METHODS
  Functional MRI was performed on 25 nondemented subjects with probable CAA (mean ± standard deviation age, 70.2 ± 7.8 years) and 12 healthy elderly controls (age, 75.3 ± 6.2 years). Parameters measured were reactivity to visual stimulation (quantified as blood oxygen level-dependent [BOLD] response amplitude, time to peak response, and time to return to baseline after stimulus cessation) and resting absolute cerebral blood flow in the visually activated region (measured by arterial spin labeling).
  
  
  RESULTS
  CAA subjects demonstrated reduced response amplitude (percentage change in BOLD signal, 0.65 ± 0.28 vs 0.89 ± 0.14; p < 0.01), prolonged time to peak (11.1 ± 5.1 vs 6.4 ± 1.8 seconds; p < 0.001), and prolonged time to baseline (16.5 ± 6.7 vs 11.6 ± 3.1 seconds; p < 0.001) relative to controls. These differences were independent of age, sex, and hypertension in multivariable analysis and were also present in secondary analyses excluding nonresponsive voxels or voxels containing chronic blood products. Within the CAA group, longer time to peak correlated with overall volume of white matter T2 hyperintensity (Pearson correlation, 0.53; p = 0.007). Absolute resting blood flow in visual cortex, in contrast, was essentially identical between the groups (44.0 ± 12.6 vs 45.0 ± 10.0 ml/100 g/min, p = 0.8).
  
  
  CONCLUSIONS
  Functional MRI identifies robust differences in both amplitude and timing of the response to visual stimulation in advanced CAA. These findings point to potentially powerful approaches for identifying the mechanistic links between vascular amyloid deposits, vascular dysfunction, and CAA-related brain injury.
authors: Hemorrhagic Stroke Research Center, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, USA.
authors: Andrew
authors: A
authors: Dumas
authors: Gregory A
authors: GA
authors: Dierksen
authors: M Edip
authors: ME
authors: Gurol
authors: Amy
authors: A
authors: Halpin
authors: Sergi
authors: S
authors: Martinez-Ramirez
authors: Kristin
authors: K
authors: Schwab
authors: Jonathan
authors: J
authors: Rosand
authors: Anand
authors: A
authors: Viswanathan
authors: David H
authors: DH
authors: Salat
authors: Jonathan R
authors: JR
authors: Polimeni
authors: Steven M
authors: SM
authors: Greenberg
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000098:blood supply / Q000503:physiopathology*; D016657:Cerebral Amyloid Angiopathy / Q000503:physiopathology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003072:Cognition Disorders / Q000503:physiopathology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged