Estimate of the incidence and importance of circulatory breakthrough in the surgery of cerebral arteriovenous malformations.

Severe hemorrhagic brain swelling has been described occasionally in patients with cerebral AVMs after surgical interruption for feeding arteries, surgical excision, and embolization. The proposed mechanism is an abrupt increase in perfusion pressure in the vasculature of the normal adjacent brain which has lost its capacity to autoregulate. The term circulatory breakthrough has been adopted to describe this. The authors found its incidence to be 3 in 66 patients in a surgical series, but lesser degrees of circulatory breakthrough in smaller lesions may have accounted for most of mortality and morbidity that was encountered. Its importance in embolization is less certain because of the possibility of infarction. It is proposed that better control of this problem by presurgical embolization, surgical staging, and graduated degrees of induced hypotension postsurgery may be necessary if the larger cerebral AVMs are to be excised with mortality and morbidity less than the natural history.