Indications for extra-intracranial bypass surgery. New orientation after the Toronto Bypass Study based on angiographic and non-invasive ultrasound flow measurements.

Abstract

Angiographic and flow measurement results in 18 cases, who underwent extra-intracranial bypass surgery, are presented. The method was the Mavis ultrasound technique. Patients with unilateral internal carotid artery (ICA) occlusion and additional contralateral ICA stenosis or occlusion had a permanent cerebral blood flow (CBF) increase as a consequence of the anastomosis. On the contrary, patients without contralateral flow impairment or with good spontaneous extra-intracranial anastomosis did not have a real CBF improvement but only a temporary flow increase on the anastomotic side with comparable flow decrease in the contralateral ICA. The so-called Toronto Bypass Study was designed to evaluate the effectiveness of extra-intracranial bypass surgery for stroke prevention but it did not prove its effectiveness in this regard. Intentionally it did not put or answer the question of possible haemodynamic benefit for special subgroups of patients with cerebrovascular occlusive disease. Our results suggest such a haemodynamic benefit, and in consequence an indication for bypass treatment may be given in cases with ICA occlusion and additional contralateral flow impairment and without sufficient spontaneous collateralization. The question of a stroke preventing effect in this special subgroup should be answered by another controlled study. But this will be almost impossible to realize because--as a consequence of the Toronto study--at least in our country almost no further patients are transferred to the neurosurgeon for possible bypass surgery.