Early diagnosis of basilar artery occlusion using magnetic resonance imaging.

Three patients with a clinical diagnosis of pontine infarction probably due to basilar artery occlusion were studied with magnetic resonance imaging within 24 hours after onset or latest progression of symptoms. The earliest changes on magnetic resonance images were an absence of signal void in the basilar artery suggestive of severe reduction of blood flow or occlusion (flow-void phenomena). The presumed basilar artery thrombosis was best demonstrated as a linear structure isointense or hyperintense with the brainstem in the pontine cistern on T1-weighted parasagittal images and as either absence of flow-void phenomena or higher signal intensity at various levels corresponding to the course of the basilar artery on the axial T2-weighted images. Brainstem parenchymal changes characteristic of infarction were not obvious for at least 12 hours after onset or 90 minutes after latest progression of symptoms and were best shown by both axial and coronal T2-weighted images. Recognition of these magnetic resonance imaging findings may allow earlier diagnosis and treatment of acute ischemia in the vertebrobasilar system.