REDUCED CONTRALATERAL HEMISPHERIC FLOW MEASURED BY SPECT IN CEREBELLAR LESIONS - CROSSED CEREBRAL DIASCHISIS

Four patients with clinical signs of cerebellar stroke were studied tw ice by SPECT using Tc-99m-HMPAO as a tracer for cerebral blood flow (C BF). When first scanned 6 to 22 days after onset, all had a region of very low CBF in the symptomatic cerebellar hemisphere, and a mild to m oderate CBF reduction (average 10 %) in contralateral hemispheric cort ex. In all four cases clinical signs of unilateral cerebellar dysfunct ion were still present when rescanned 1 to 4 months later and the rela tive CBF decrease in the contralateral cortex of the forebrain also re mained. The basal ganglia contralateral to the cerebellar lesion CBF s howed variable alterations. A relative CBF decrease was seen in upper part of basal ganglia in all four cases, but it was not a constant phe nomenon. A relative CBF increase in both early and late SPECT scans wa s seen at low levels of neostriatum in two cases. The remote CBF chang es in cerebellar stroke seen in the forebrain are probably caused by r educed or abolished cerebellar output. The term ''Crossed Cerebral Dia schisis'' may be used to describe these CBF changes that would appear to reflect both decreased and increased neuronal activity.