POSITRON EMISSION TOMOGRAPHIC STUDY OF CONTRALATERAL HEMISPHERIC HYPOMETABOLISM IN MIDDLE CEREBRAL-ARTERY INFARCTION

The aim of the study was to investigate the conditions under which con tralateral hemispheric hypometabolism (CHH) occurs among patients with chronic, stable middle cerebral artery (MCA) infarcts. Twenty-eight p atients with chronic MCA infarction and 22 healthy volunteers were stu died using positron emission tomography and the oxygen-15 (O-15) stead y-state technique. In 43% of our patients decreased regional cerebral metabolic rate of O-2 (rCMRO2) in the contralateral mirror region and in the total contralateral MCA territory was observed. In patients wit h severe bilateral carotid disease regional cerebral blood flow and rC MRO(2) were more diminished than in those without, suggesting unsuspec ted ischaemic changes in the contralateral cerebral hemisphere. Howeve r the existence of transhemispheric diaschisis (THD) was still suggest ed as the rCMRO(2) values were also significantly lower in the contral ateral hemisphere of patients with isolated unilateral vascular lesion s in comparison to healthy volunteers. The presence of CHH and THD was related to more severe ischaemic changes in the homolateral cerebral hemisphere with predominant infarction in the cortical end zones of th e MCA.