[Quantitative changes in cerebral blood flow of Shy-Drager syndrome induced by upright position: assessment by 99mTc-HMPAO].

We assessed orthostatic changes of cerebral blood flow (CBF) in 4 patients with Shy-Drager syndrome. Brain perfusion index (BPI) was measured by 99mTc-hexamethylpropylene amine oxime (99mTc-HMPAO). Cerebral angiography using aortic time-activity curve as an input function BPI values in supine and upright positions in Shy-Drager syndrome were compared with those in 2 cerebrovascular disease patients without orthostatic hypotension. BPI values in the upright position were significantly decreased in patients with Shy-Drager syndrome as compared with these in the supine position. No significant decrease in BPI was noted in the patients without orthostatic hypotension. These results suggest that the BPI measurement by 99mTc-HMPAO cerebral angiography is useful for the noninvasive evaluation of the orthostatic changes of the CBF.