Regional cerebral blood flow is not decreased in young adults with Down syndrome

An index of regional cerebral blood flow (rCBF) of cortical gray matter, initial slope (IS), was measured with the noninvasive xenon-133 inhalation method on 2 consecutive days in 11 healthy, noninstitutionalized subjects with trisomy 21 Down syndrome (DS) (mean age 28.0 years) and in 22 sex-matched, healthy volunteers (mean age 27.3 years). IS did not differ between groups for any lobar region. The ratio of rIS to hemispheric IS, and right/left and frontal/nonfrontal ratios also failed to show significant regional differences between groups. These results show that healthy young DS adults do not show abnormalities in rCBF, as measured with xenon-133 clearance, prior to the age (35 years) when neuropathological changes of Alzheimer's disease are reported to occur.