Do cerebral arteriovenous malformations recur after angiographically confirmed total extirpation?

Cerebral arteriovenous malformations (AVMs) are thought to result from a failure of embryogenesis in the otherwise normal differentiation of primordial vascular channels into mature arteries, capillaries, and veins. Although these are essentially congenital vascular malformations, marked enlargement and/or recurrence of cerebral AVMs has been reported in the recent literature. Using MEDLINE (1966- 1998), we searched the recurrence of cerebral AVMs and analyzed all reported recurrent cases after total surgical extirpation and negative postoperative angiogram, and discussed the proposed mechanisms of the recurrence of cerebral AVMs. A thorough literature survey disclosed only 12 documented recurrent cases (9 were documented in English and 3 in Japanese), which shows the rarity of the recurrence of cerebral AVMs, although the actual rate of recurrence is not known because of the lack of routine long-term follow-up. The location of recurrent cerebral AVMs was the cerebral hemisphere, and initial presentation was hemorrhage in all cases. Recurrence occurred in patients under 20 years of age in 9 of 11 cases, which implies the propensity of recurrence of cerebral AVMs in immature brain vasculature. There are no definite proven mechanisms to explain why congenital anomalies such as cerebral AVMs recur after total extirpation, but recently two plausible mechanisms have been proposed. One is angiogenesis disregulated by vas-cular endothelial growth factor (VEGF) and the other is a new anatomical entity, 'hidden compart-ments'. Although VEGF is one of the main angiogenetic factors and its important role in fetal brain and pathological neovascularization has been reported, the synthesis of VEGF might be insufficient to explain the recurrence of cerebral AVMs because VEGF-positive staining is also found in nonrecurrent patients. Hidden compartments are angiographically unfilled compartments, in spite of an adequate examination, which may be located within, contiguous with, or relatively far from the angiographically demonstrated AVM. Although it might explain unsolved clinical phenomena such as regrowth, recurrence, and per- or postoperative unanticipated bleeding and brain swelling, the existence of hidden compartments should be proved by high-resolution radiological examinations or during operations. The presence of recurrent cerebral AVMs after complete extirpation by modern microsurgical techniques indicates that cerebral angiography in the early postoperative stage, the golden standard to assess the disappearance of cerebral AVMs, is not sufficient to eliminate the risk of hemorrhage, and careful long-term follow-up studies should be planned.