Extra-Intracranial Bypass Surgery in Patients with Hemodynamic Cerebral Ischemia
Following the publication of the result of the International Cooperative Study on Extra-Intracranial Bypass Surgery, which had failed to show any beneficial effect of this operation in reducing the risk of stroke, the indication for this procedure has been almost entirely abandoned (Bogouslavsky and Regli 1986; EC-IC Bypass Study Group 1985). It has been argued, however, that the indications previously used for bypass surgery, which were mainly based on clinical and angiographic criteria, did not take into consideration the rather complicated pathophysiology of stroke. Using positron emission tomography (PET) which allows the simultaneous measurement of cerebral blood flow (CBF), cerebral blood volume (CBV), and various parameters of brain oxygen metabolism, it is now possible to identify a particular subgroup of patients with cerebrovascular insufficiency, namely those with hemodynamic cerebral ischemia (Gibbs et al. 1984; Powers and Raichle 1985; Powers et al. 1987). According to these studies, hemodynamic cerebral ischemia may occur in patients with cerebrovascular occlusive disease with poor collaterization and is characterized by a low CBF to CBV ratio, reflecting a decreased cerebral perfusion pressure.
KeywordsCerebral Blood Flow Cerebral Perfusion Pressure Carotid Artery Occlusion Internal Carotid Artery Occlusion Cerebrovascular Insufficiency
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