The value of repeat pan-angiography in cases of unexplained subarachnoid hemorrhage.

Four-vessel angiography was repeated in 56 patients with confirmed subarachnoid hemorrhage in whom the initial investigation was negative. Only one aneurysm was demonstrated. The results suggested that, with good technique, careful observation, and a complete four-vessel cerebral angiography, a false negative rate of less than 2% can be achieved. It is suggested that to repeat pan-angiography is seldom justified unless further bleeding episodes occur.