Spontaneous subarachnoid hemorrhage with negative angiography: CT findings

Computed tomography of 31 patients with spontaneous subarachnoid hemorrhage (SAH) but negative angiography was evaluated to find out whether the pattern of SAH as seen in CT offers indications for a possible reexamination with angiography. Based on the distribution and the amount of SAH, classification into three groups was possible: (a) 18 cases, normal CT (but blood in the CSF, gained by lumbar puncture) or SAH in the basal cisterns only; repeat angiography was negative in all these cases; (b) nine cases, SAH in the basal cisterns as well as in one or both Sylvian fissures; in addition, small amounts of blood in the interhemispheric fissure and/or in the sulci; repeat angiography revealed an aneurysm in one of these cases; (c) four cases, large quantities of blood in all subarachnoid spaces; in all but one of these cases a vascular lesion was visualized with repeat angiography or verified at autopsy. In conclusion, repeat angiography is mandatory in cases with SAH patterns that can be classified into group b or c, whereas it can be omitted in patients with small amounts of blood confined to the basal cisterns.