Artery-to-artery embolism causing stroke in the posterior circulation.

The features of strokes caused by embolism from the vertebral artery (VA) to the posterior cerebral artery (PCA) are reported in 12 patients ("local" or "artery-to-artery embolism"). Occipital infarction occurred with prominent, fluctuating brainstem ischemic symptoms in six; with minor, transient brainstem symptoms in five; and with basilar artery occlusion in one. Visual field abnormalities were found on initial examination in eight and several days after the onset of brainstem symptoms in four. Radiographic studies in 11 identified extracranial (5 patients) or intracranial (3 patients) VA disease, or occlusion of both segments (3 patients) as sources of emboli to the PCA. Mural thrombus in the VA or embolic occlusion of distal branches of the PCA was visualized in five.