Intentionally staged operation for large and high-flow cerebral arteriovenous malformation.

This paper describes two cases of large and high-flow cerebral arteriovenous malformations (AVMs) which were successfully treated by intentionally staged operations. During dissection of the nidus, uncontrollable bleeding from the nidus and surrounding brain tissue was encountered in both cases, and staged operations were attempted. The isolated remaining nidus and the main draining vein were thoroughly covered with a non-adhesive material (Gelfilm(R)) to prevent adhesion. We performed cerebral angiography before the second operation. In both cases, the extent of size-reduction of the remaining nidus on angiography was more than that of the actual preparation in the first operation due to thrombosis. Intentionally staged surgery for a large and high-flow AVM is beneficial because it prevents 'normal perfusion pressure breakthrough' or 'overload phenomenon', which is one of the factors affecting the patient's prognosis. For the subsequent operation, it is beneficial to use the non-adhesive material to prevent adhesion between remaining nidus and surrounding brain tissue. It is a safer procedure for the total removal of the remaining nidus. It is also important to perform the angiography before the second operation. Precise analysis of the the extent of remaining nidus before the second operation enables preparation of appropriate surgical strategies.