The extracranial-intracranial bypass study: how will the outcome affect us?

Extracranial-intracranial bypass is now a commonly performed procedure in centres with a high level of neurosurgical and vascular expertise. Bypass of surgically inaccessible stenoses or occlusions appears to be a logical technique to prevent future stroke but there is much uncertainty about the clinical indications for surgery and even the natural history of the lesions being bypassed. To answer these questions, the International EC/IC Bypass Study was set up in 1977 with relatively broad entry criteria. The data will be analysed in June 1985 and if the results support the use of bypass as a means of preventing subsequent stroke, the procedure should become firmly established. However, if the results are negative, or inconclusive, rather than discard the procedure, subsets of higher risk patients should be sought, in particular using newer methods of assessing cerebral perfusion and metabolism.