The angiographic diagnosis of occlusions of the posterior cerebral artery.

The angiographic appearance of twenty-seven unilateral or bilateral occlusions of the posterior cerebral artery (PCA) are described. They are classified into proximal, interpeduncular, ambient or distal occlusions according to their prefered location. Ambient occlusions were by far the most common and have therefore probably not developed from a stenosing arteriosclerosis since this forms preferentially in the proximal and interpeduncular segment. Leptomeningeal anastomoses were common between all respective branches of the middle cerebral artery and the PCA but the anterior cerebral artery and the interarterial anastomoses rarely contributed to the collateral blood supply. A retrograde progression of the occlusion was observed on reangiography occasionally in cases in which there was no major artery originating just proximal to the occlusion. Anterograde progression and disintegration of obstructing material was also observed. PCA occlusions had a good prognosis in terms of survival but the associated visual field defects rarely improved.