Partially thrombosed vertebral artery dissecting aneurysm presenting as delayed bulbar compression after lateral medullary infarction.

A 48-year-old man experienced lateral medullary infarction resulting from spontaneous vertebral artery (VA) dissection. Minimal fusiform dilatation was noted on basi-parallel anatomic scanning-magnetic resonance imaging; therefore, the patient was treated conservatively. Eight months later, he experienced deterioration of dysphagia and the onset of gait ataxia. Repeated imaging studies showed enlargement of the VA aneurysm with bulbar compression. Parent artery occlusion on the proximal side of the VA affected by the dissection relieved the patient's symptoms. Although the majority of dissected lesions stabilize within a few months, studies with longer observation periods and more frequent neuroimaging examinations are required.