Occipital lobe arteriovenous malformations. Clinical and radiologic features in 26 cases with comments on differentiation from migraine.

The differentiation of migraine headache, preceded by visual aura, from cerebral arteriovenous malformation (AVM) is often regarded as difficult. A study of 26 patients with occipital lobe AVM revealed two distinct syndromes in 18 patients--occipital epilepsy and occipital apoplexy. Occipital epilepsy is characterized either by elementary visual phenomena, such as brief flashes of light, or by dimming of a homonymous field. Occipital apoplexy results from hemorrhage and hematoma formation within the occipital lobe and is characterized by sudden headache and homonymous visual field loss. We conclude that patients harboring occipital AVMs may, indeed, have visual phenomena and headache that should not be confused with migraine because either a history of generalized seizure or bruits on examination will probably be present.