Occult arteriovenous malformation of the brainstem simulating multiple sclerosis.

A patient who proved to have an angiographically occult arteriovenous malformation of the brainstem and cerebellum was thought to have multiple sclerosis for 20 years, because of fluctuating brainstem symptoms and signs. Although the computed tomographic (CT) appearance of the lesion suggested a vascular malformation, because it bridged the subarachnoid space between the brainstem and cerebellum, an arteriogram was normal. This report stresses the importance of CT in making the diagnosos of occult arteriovenous malformations of the brainstem. On CT scan, these lesions generally have a high-density multiform appearance, which may enhance with contrast infusion. This lesion should be suspected clinically when there are fluctuating neurologic symptoms and signs attributable to the same neuroanatomic location within the brainstem. Surgical biopsy may confirm the diagnosis, but attempts to remove these lesions from the brainstem parenchyma are hazardous and probably are not indicated, considering the chronic and relatively benign course.