Angiogram-negative subarachnoid hemorrhage: outcomes data and review of the literature.

Spontaneous subarachnoid hemorrhage (SAH) is most commonly caused by rupture of a saccular aneurysm or other structural pathologies. Occasionally, no structural cause for the hemorrhage can be identified by radiographic imaging. These hemorrhages, termed angiogram-negative SAH, are generally considered to have a better prognosis than aneurysmal SAH. Angiogram-negative SAH subgroups include benign perimesencephalic SAH (PMH) and aneurysmal-type SAH. Outcome data for these subgroups differ from those for the group as a whole. We report data for 31 patients who presented to our institution from 2006 to the present. We performed a retrospective chart review, and report outcome data that include rates of rehemorrhage, hydrocephalus, vasospasm, permanent ischemic deficits, headaches, and outcomes based on modified Rankin Scale scores. We also performed a review of the literature and meta-analysis of the data therein. We compared rates of complications in the PMH subgroup and the diffuse-type hemorrhage subgroup. The chart review revealed no poor outcomes and no rehemorrhages in the patients with PMH. In the diffuse hemorrhage subgroup, 1 patient had a rehemorrhage and 2 patients had a poor outcome. Our literature review found an OR of 6.23 for a good outcome for PMH versus diffuse-type hemorrhage, and an OR of 2.78 for rehemorrhage in PMH versus diffuse-type hemorrhage. Angiogram-negative SAH is not a benign entity. Complications are present but are significantly reduced, and outcomes are improved, compared with aneurysmal SAH.