Normal and abnormal patterns of cerebrovascular reserve tested by 133 Xe inhalation.

Cerebrovascular functional reserve was tested by noninvasive measurement of regional cerebral blood flow (nrCBF) at rest in quiet darkness and when repeated during standard multiple psychophysiologic activation. The test was applied to normal volunteers and patients with different neurologic disorders. The test included counting, conversation, music, and observing movements, while rCBF was measured over both cerebral hemispheres, brain stem, and cerebellum. In normal persons at rest, mean gray matter flow (Fg) values were the same for each hemisphere. Highest Fg values were observed in brain stem and both frontal regions. During activation in normal persons, there was a significant increase in Fg values over both hemispheres and in brain stem. During activation, three types of abnormal rCBF responses were seen: Demented patients showed no change, patients with vascular occlusion showed little or no increase over the ischemic hemisphere, and some patients with epilepsy showed excessive increases.