Pearls & oy-sters: a distinctive watershed area in the vertebrobasilar territory.

CASE REPORT A 78-year-old man experienced 2 short-lasting episodes of vertigo with unstable gait during the 5 days before admission. One week previously, he had carried large fiberboard panels, involving sustained rotation of the neck in both directions. His past medical history included arterial hypertension and dyslipidemia. The initial general and neurologic examination was normal except for high blood pressure (194/109 mm Hg). Over the next few days, the patient developed rapidly worsening bilateral dysmetria and dysdiadochokinesia, more marked on the left, cerebellar dysarthria, and unstable stance and gait. Cerebral CT showed leukoaraiosis and lacunar sequelae of both corona radiata and of the left thalamus and caudate nucleus. CT arteriography showed narrowing and irregularities of the V2 segment of the left vertebral artery and occlusion of its V3 segment. Ultrasonography and Doppler examination confirmed the stenosis of the left V2 segment and occlusion of the left V4 segment. There was also an 80% stenosis in the V2 segment of the right vertebral artery. Cerebral MRI showed symmetric acute ischemia of both middle cerebellar peduncles (MCPs) and of the deep right cerebellar hemisphere (figure, A). Fat saturation sequences showed a wall hematoma of the V2 segment of both vertebral arteries (figure, B), extending to V3 and V4 on the left side, suggesting bilateral vertebral artery dissection. Oral aspirin and cautious anticoagulation with IV heparin were introduced. Severe hypertension required IV labetalol and sodium nitroprusside. Cerebral arteriography was performed. Following aortic contrast injection, brain perfusion was delayed in the posterior fossa. Carotid artery catheterization disclosed a fetal origin of the left posterior cerebral artery and a very small right posterior communicating artery. Thus, the carotid circulation provided little blood supply to the posterior fossa. Both vertebral arteries showed diffuse stenosis, suggesting atherosclerosis. The very narrow left vertebral artery received small anastomoses from the left occipital and ascending cervical arteries. However, the basilar artery showed very little opacification following injection of the left subclavian artery (figure, C). Thus the right vertebral artery was the only significant vessel contributing blood flow to the basilar artery despite severe stenosis of the V2 segment (figure, D). Angioplasty of this stenosis was deemed too risky because of the absence of alternative blood supply to the posterior fossa during balloon inflation. Oral anticoagulation was started. Over the next 3 weeks, the patient’s condition stabilized and then slowly improved. After 3 months, he was able to walk with a walker and was independent for almost all activities of daily living. Five months later, he died of a massive hemorrhage in the right cerebral hemisphere that did not appear to involve the vertebrobasilar circulation.