Cerebral blood flow and intelligence rating in persons over 90 years old

Cerebral blood flow (CBF) and intellectual rating scale (IRS) measurements were carried out in 54 subjects over the age of 90. Two successive measurements of CBF by the xenon-133 inhalation method, 20 min apart, were made in 38 of these persons under the same conditions in order to measure the precision (repeatability) of the CBF technique on this subject category. A statistically significant lower mean cerebral blood flow was found for this over-90-year-old group compared to young adults. The subjects were divided into subgroups according to their IRS score from normal to severely demented. Resting CBF in the various IRS groups did not differ significantly. However at low IRS values there was much less variability between successive CBF measurements in the same individual suggesting failing vasomotor tone with senile dementia.