On apples, oranges, and ARUBA.

Abstract

Arteriovenous malformations (AVMs) are congenital vascular lesionsthatareassociatedwith long-term excessmortalityand morbidity essentially related to haemorrhagic stroke [10]. The prevalence of brain AVMS (BAVMs) is believed to be between 15 and 18 per 100,000 adults [1], and the incidence is estimated at 1 per 100,000 per year [19]. Roughly half of the patients with BAVMs present with intracerebral haemorrhage (ICH), resulting in a first-ever hemorrhage rate of 0.55 per 100,000 person-years [19]. The annual risk of haemorrhage is estimated at 1– 4%[ 12], but it may be as low as 0.9 % in patients with unruptured, superficially located brain AVMs with superficial drainageandmaybeas high as 34% inpatients with ruptured, deeply seated brain AVMs with deep venous drainage [20]. The known risk factors for bleeding include AVM size, deep venous drainage, deep location, and associated aneurysm [4, 9, 20, 21]. BAVMs are commonly classified according to the five-tier Spetzler-Martin scale, which is a composite score of nidus size, eloquence of adjacent brain and presence of deep venous drainage [17], although, recently, a simplified three-tier classification has been proposed [18]. The increasing use of non-invasive diagnostic imaging for various indications has increased the incidence of unruptured BAVMs and inevitably raises the question of their curative treatment [15]. The goals of BAVM treatment are to eliminate the risk of haemorrhage with the preservation of functional status [7], be it via microsurgery, endovascular embolisation or stereotactic radiosurgery (SRS). In order to obtain the former goal, the BAVM nidus must be obliterated, as subtotal treatment does not confer protection against future haemorrhage [7]. However, the argument for a conservative approach for patients with unruptured BAVM is based on three factors, namely that the annual risk of ICH for patients with unruptured BAVM may have overestimated older studies [10], that the morbidity associated with BAVM bleeding may be less than previously thought [22], and thirdly, that the risks of treatment of unruptured BAVM may be greater than previously described [14].