Clinical outcome and prognostic factors of patients with angiogram-negative and non-perimesencephalic subarachnoid hemorrhage: benign prognosis like perimesencephalic SAH or same risk as aneurysmal SAH?

Subarachnoid hemorrhage (SAH) is usually caused by a ruptured intracranial aneurysm. However, in some patients, no source of hemorrhage might be detected despite repeated digital subtraction angiography (DSA). Our objective was to analyze factors influencing the clinical outcome in patients suffering from non-aneurysmal and non-perimesencephalic (NPM) SAH. Between 1999 and 2011, 68 of 1,188 patients with SAH (5.7%) suffered from non-aneurysmal and NPM-SAH. Outcome was assessed according to the modified Rankin Scale (mRS) at 6 months (mRS 0-2 favorable vs. 3-6 unfavorable). In patients with angiogram-negative and NPM-SAH, favorable outcome was achieved in 56 patients (82.4%). In the multivariate analysis, age <65 years and non-Fisher 3 bleeding pattern were significantly associated with favorable outcome. Angiogram-negative and NPM-SAH had good prognoses. Patients with non-Fisher-type 3 bleeding had excellent outcomes similar to patients with perimesencephalic SAH, but patients with Fisher-type 3 bleeding were at risk for poor outcome like aneurysmal SAH patients due to cerebral vasospasm and delayed cerebral ischemia. Age and bleeding type were detected as prognostic factors in the multivariate analysis.