A 51-year-old woman presents with a generalized tonic-clonic seizure. After a brief postictal period, she recovers fully and does not report headache or other neurologic symptoms. She takes no medications and her medical history is unremarkable. Computed tomography of the head suggests a right occipital arteriovenous malformation, without evidence of hemorrhage. Computed tomographic angiography, magnetic resonance imaging, and magnetic resonance angiography of the brain show a right occipital arteriovenous malformation, 3.5 cm in diameter, as well as a feeding-artery aneurysm, 1.5 cm in diameter. How should her case be further evaluated and managed? The Cl inic a l Probl e m Arteriovenous malformations of the brain are focal abnormal conglomerations of dilated arteries and veins within brain parenchyma, in which a loss of normal vascular organization at the subarteriolar level and a lack of a capillary bed result in abnormal arteriovenous shunting (Fig. 1). Arteriovenous malformations can occur anywhere in the central nervous system; in this article, I focus on those in the brain. Small arteries involved in arteriovenous malformation are deficient in the smoothmuscle layer. 1 The tangle of abnormal arteries and veins in the malformation (often referred to as the arteriovenous malformation nidus) are connected by one fistula or, more commonly, several fistulas. The direct arteriovenous connection results in high-pressure vascular channels, particularly in veins with fibromuscular thickening and incompetent elastic lamina; these veins are at risk of rupture, often with catastrophic results. The most common presenting sign of an arteriovenous malformation is intracerebral hemorrhage (occurring in 42 to 72% of clinically apparent arteriovenous malformations). 2-7 A first hemorrhage most commonly occurs in patients between 20 and 40 years of age. 2-4 Data are conflicting regarding associations between age and the risk of hemorrhage, with studies reporting either a higher risk in older patients, in younger patients, or in both (bimodal peaks) or a constant risk over time. 4,5,8,9 Sex does not appear to affect the risk of rupture. 6,10,11 Hemorrhage of arteriovenous malformations accounts for approximately 2% of all strokes. 10,12 Other presenting signs of arteriovenous malformations include seizures, mass effect (from direct compression or swelling related to the malformation, putting pressure on surrounding structures), and ischemic steal (due to preferential low-resistance blood flow through the arteriovenous malformation, resulting in the hypoperfusion of adjacent structures). Even in the absence of bleeding, headaches (specifically migraines) have been associated with arteriovenous malformations. 13 The prevalence of arteriovenous malformation is estimated at approximately 0.01% of the general population, but reported rates range from 0.001% to 0.52%. 3,10,11,14,15 The lesions are thought to be congenital in origin. Although occa-This Journal feature begins with a case vignette highlighting a common clinical proble...
