Isotope cerebral perfusion studies before and after extracranial/intracranial bypass.

A quick, inexpensive, and reliable method of estimating cerebral perfusion is described that uses simple gamma camera and computer facilities readily available in almost all neuroradiology departments. Eighty-eight patients with unilateral cerebral ischemia were studied who satisfied the criteria for inclusion in the international cooperative study for extracranial/intracranial arterial anastomosis. The results of their isotope cerebral perfusion studies were compared with their computed tomographic scans and cerebral angiograms. The aims of the study were: (1) to ascertain whether the isotope study could predict the presence of a stenosis or occlusion; (2) to determine whether it could forecast the presence of a collateral blood flow and allow an assessment of the contribution of the collaterals to the overall cerebral perfusion; and (3) to assess the patency of the extracranial/intracranial bypass and monitor the effects of that procedure on hemisphere perfusion. The results show that this examination does predict the angiographic findings in nearly all patients and provides useful information about the natural collateral blood flow so that appropriate surgical treatment can be planned for the patient. The changes in cerebral perfusion after bypass were correlated with postoperative angiograms and offer a possible means of assessing and monitoring the effects of revascularization surgery and its contribution to the perfusion of that hemisphere.