Arteriovenous malformations (AVMs) are vascular lesions characterized by direct connections between feeding arteries and draining veins without an intervening capillary network. Two hypotheses, normal perfusion pressure breakthrough (NPPB) and occlusive hyperemia, prevail in the literature regarding the occasional development of hemorrhage and edema following AVM resection. The NPPB hypothesis was introduced in 1978. Since the occlusive hyperemia hypothesis was first postulated in 1993, however, a debate has persisted within the cerebrovascular community concerning which hypothesis better explains the complications of edema and hemorrhage seen after AVM resection. Recent advances in cerebrovascular imaging and hemodynamic analysis have allowed a better evaluation of intracerebral changes following AVM resection. It is likely that these 2 hypotheses are not mutually exclusive and perhaps exist in a spectrum of hemodynamic alteration following AVM resection.