SEMIQUANTITATIVE ANALYSIS OF CEREBRAL BLOOD-FLOW BY MEANS OF (99)TCM-HMPAO SPECT IN INDIVIDUALS BEFORE AND AFTER A HIGH-ALTITUDE HIMALAYAN EXPEDITION

Nine members of the 'Belgian Tibet Expedition 1991' underwent a Tc-99m-hexamethylpropyleneamine oxime (HMPAO) brain single photon emission computed tomographic study before and after their stay at high altitude. Cerebral and cerebellar activity were analysed in three circumference profiles, representing the lower, middle and upper transaxial sections of the brain. The count value of each volume element (VE) was normalized to the maximum cerebellar value. In order to compare individual regional cerebral blood flow (rCBF) before and after the expedition, the relative differences in rCBF were calculated for each VE as: relDELTA (%) = 100 x (value after expedition - value before expedition)/value before expedition. In 4/9 cases regional relDELTA values were negative in most cortical regions; in 3/9 individuals nonsignificant changes were found and 2/9 climbers showed a positive relDELTA value in most cortical regions. For the group as a whole there was (1) a mean decrease of 1.7% in global cortical CBF and (2) a significantly (P < 0.01) diminished rCBF was observed in both temporal and the left frontotemporal areas.