Moyamoya disease. Posterior cerebral artery occlusion and pattern-reversal visual-evoked potential

Although vascular abnormality in moyamoya disease predominates in the anterior and middle cerebral arteries, the posterior cerebral artery (PCA) has been found to be involved in the course of the disease. To explore PCA occlusion by noninvasive means, we studied visual-evoked potentials in the patients with PCA occlusion (occlusive group), as well as in those without PCA occlusion (nonocclusive group). The results were compared with those of other examinations that also detected an occipital lobe pathologic condition. Abnormalities of those examinations were highly specific to PCA occlusion. Positron emission tomography and pattern-reversal visual-evoked potentials yielded high incidence of abnormality in the occlusive group (86% and 75%, respectively), and expressed the side of PCA occlusion if the occlusion was unilateral. Since pattern-reversal visual-evoked potentials is popular and a low-cost examination compared with positron emission tomography, we conclude that pattern-reversal visual-evoked potentials is the most practical mean to explore PCA occlusion in the course of moyamoya disease.