To demonstrate the effect of interhemispheric diaschisis in acute unilateral cerebral
infarction, the changes of regional cerebral blood flow (rCBF) following experimental
occlusion of one middle cerebral artery(MCA) for up to 16 hours were investigated in an
unanesthetized cat model using the technique of transorbital snare ligature implanted in the
intact cranium. rCBF of both MCA territories and both marginal zones were measured simultaneously
by the hydrogen clearance technique. 25 cats were divided into 2 groups according
to the size of infarct; Group A, infarct larger than 10% of ipsilateral coronal sectional surface of
hemisphere and Group B, smaller than 10%. DUring the initial stage of ischemia, significant
decrease in rCBF of the contralateral hemisphere was observed in both groups, however, in
Group A, rCBF gradually increased toward preocclusion level. In Group B, rCBF decreased
further and remained low till the 16th hour after occlusion. These results suggested that mild
ischemic Group B would take advantage of interhemispheric diaschisis during the late phase of
infarct development as well as the substantial collateral flow from the surrounding anterior and
posterior cerebral artery territories