False-negative angiograms in subarachnoid haemorrhage due to intracranial aneurysms

Of 440 patients with spontaneous subarachnoid haemorrhage in whom an aneurysm was suspected, 60 had a negative angiogram. A second angiogram performed 1-4 weeks later revealed an aneurysm in 5 of 40 cases. Of these patients, 3 had a second haemorrhage. In all cases, diffuse bleeding, with involvement of the anteroinferior interhemispheric fissure, was present on CT. There were three aneurysms of the anterior communicating artery and two of the carotid siphon. The reasons for the false-negative angiograms and the usefulness of repeated angiography are discussed.