CHANGES IN CEREBRAL BLOOD-FLOW AND OXYGEN-METABOLISM RELATED TO MAGNETIC-RESONANCE-IMAGING WHITE-MATTER HYPERINTENSITIES IN ALZHEIMERS-DISEASE

We studied changes in cerebral perfusion and oxygen metabolism to eluc idate the pathophysiological nature and clinical significance of white matter hyperintensities in Alzheimer's disease (AD). Methods: Sixteen AD patients (age 71.6 +/- 3.1 yr) whose T2-weighted MR images showed white matter hyperintensities, and 16 age-matched AD patients (age 71. 0 +/- 4.3 yr) without white matter hyperintensities were compared. Reg ional cerebral brood Row (CBF), oxygen metabolism (CMRO2) and oxygen e xtraction fraction (OEF) were measured by using O-15 steady-state meth od and PET, Results: There was no significant difference in cognitive impairment between the two groups. Compared to the patients without wh ite matter hyperintensities, those with them had significantly low CBF values and significantly high OEF values in all cortical and white ma tter regions. However, there were no significant differences in CMRO2 values between the two groups, Severity of white matter hyperintensiti es correlated with the mean cortical and mean white matter OEF. Conclu sion: In AD patients, white matter hyperintensities on T-2-weighted MR images represent ischemic changes in which oxygen metabolism and func tion are fairly compensated. These changes are not disease-specific bu t are age-associated coincidences, as in normal aging with or without vascular risk factors.