Subarachnoid hemorrhage without evident cause on initial angiography studies: diagnostic yield of subsequent angiography and other neuroimaging tests

86 patients with subarachnoid hemorrhage (SAH) in whom initial transfemoral catheter angiography failed to reveal the cause, identified from a cohort of 806 patients admitted over a 6.5-year period. Subtypes included 41 with nonperimesencephalic SAH, 36 with perimesencephalic SAH, and 9 with CT-negative SAH.

Subsequent imaging tests including repeated catheter angiography, CT angiography, MR angiography, and MR imaging of the brain and spine.

Diagnostic yield of subsequent imaging tests to determine the cause of SAH.surrogate