Surgical management of large AVMs.

The surgical management of large AVMs (those greater than 6 cm in maximal diameter) should be based on a thorough understanding of the chronic hemodynamic changes produced by lesions and the acute stress placed on the cerebral vasculature by their removal. In addition to haemorrhage, seizure, and headache, these larger lesions often present with symptoms of cerebral vascular insufficiency. Angiography frequently demonstrates a high-flow arteriovenous shunt with evidence of vascular steal from the surrounding brain. In many cases there is a virtual absence of normal hemispheric filling. When the steal is sufficient to produce an area of chronic ischaemia in the brain surrounding the AVM, there is an increased risk of swelling and haemorrhage associated with complete excision. We have developed a strategy for the surgical management of these large lesions that involves a stepwise reduction of flow through the AVM using pre- and intraoperative embolization, followed by complete excision. The details of this management strategy are described, and results in 24 patients with exceptionally large AVMs are presented.