Abstract 1122‐000050: Arterial Steal in AVM: An Etiology of Ischemic Stroke

Abstract

Introduction : Arteriovenous malformations (AVM) are rare congenital malformations in the brain, often presenting with cerebral hemorrhage. Unruptured AVMs usually remain asymptomatic, or they can present with headache, seizure, or focal neurological deficits. “Arterial steal” is one of the mechanisms which can lead to focal neurological deficits. The idea of vascular steal through high flow shunting within brain AVMs is not a new concept. There is, however, debate about whether the vascular steal phenomenon indeed exists empirically. In a study focused on vascular reserve in patients with cerebral AVMs (utilizing acetazolamide augmentation and perfusion CT methods), decreased hemodynamic reserve was noted in 27% of parenchymal regions of interest close to the AVM and in 17% of parenchymal regions of interest far from the AVM. Other imaging modalities have shown abnormal blood regulation around AVM however there exists a level of discordance between various modalities which questions whether vascular steal exists in vivo. We present an ischemic stroke caused by “arterial steal” phenomenon. Methods : Case report Results : 63‐year‐old male with past medical history of seizure, hypertension presented with confusion and dysarthria for 3 weeks. On exam he was found to have right upper quadrantanopia. CT head without contrast and MRI of brain revealed an evolving infarct in the left posterior cerebral artery (PCA) territory. CT angiogram showed possible occlusion in the left PCA P2 segment which correlated to the previously described stroke and in addition showed evidence of left thalamic AVM. Evaluation for cardioembolic or atheroembolic sources was unrevealing. A diagnostic cerebral angiogram showed a 1.3 mm AVM fed through anterior choroidal branches as well as posterior choroidal branches through left posterior communicating artery. There was delayed filling in the left PCA territory likely due to steal phenomenon which might be the etiology of the stroke. Conclusions : In our case, as demonstrated on angiogram, vascular steal phenomenon through high flow shunting of AVM is the likely explanation for the ischemic stroke.