Crossed cerebellar hypoperfusion indicates the degree of uncoupling between blood flow and metabolism in major cerebral arterial occlusion.

BACKGROUND AND PURPOSE In patients who have major cerebral arterial occlusive disease with low perfusion, a decrease in cerebral metabolism may be reflected by a reduction in contralateral cerebellar blood flow (crossed cerebellar hypoperfusion). This study was done to investigate whether comparison of the extent of cerebral blood flow asymmetry and crossed cerebellar hypoperfusion could be used to estimate the degree of uncoupling of cerebral blood flow and metabolism on the basis of a single blood flow study. METHODS We used positron emission tomography before and after reconstructive vascular surgery to evaluate regional blood flow and oxygen metabolism in the cerebral and cerebellar cortexes of 11 patients with major cerebral arterial occlusive disease. RESULTS Preoperatively these patients had cortical blood flow asymmetry in the middle cerebral artery territory. The degree of crossed cerebellar hypoperfusion had no relation to the extent of cerebral blood flow asymmetry but was significantly correlated with the extent of asymmetry in cerebral oxygen metabolism. The preoperative extent of asymmetry in the cerebral oxygen extraction fraction and the postoperative improvement of asymmetry in cerebral blood flow were correlated with the preoperative difference between the severity of cerebral blood flow asymmetry and crossed cerebellar hypoperfusion. CONCLUSIONS The difference between the extent of cerebral blood flow asymmetry and crossed cerebellar hypoperfusion can be used to estimate the degree of uncoupling between blood flow and metabolism, which can in turn predict the postoperative improvement of cerebral blood flow asymmetry. We suggest that this approach may be a simple means of estimating the relative uncoupling between blood flow and metabolism from a single blood flow study in patients who have major cerebral arterial occlusive disease with low perfusion.