“…Baseline characteristics varied substantially among the studies due to the different inclusion criteria. Variation was observed in the types of aneurysms (several types [14,16,19,22,23,25,26,[28][29][30]32,33,36] versus a single type of aneurysm [7,15,17,18,20,21,24,27,31,34,35,37]), location (anterior versus posterior), clinical presentation, and the timing of treatment. For example, of patients with known World Federation of Neurosurgical Societies (WFNS) or Hunt and Hess (HH) grades at presentation (n = 348), 96 patients (28%, range 0-71%) showed an unfavorable WFNS or HH grade of 4 or 5.…”