Angiogram Negative Subarachnoid Hemorrhage: Outcomes and the Necessity of Repeated Angiogram

Objectives: This retrospective case-control study was conducted to ascertain the clinical course and outcomes of the patients with angiogram-negative SAH, and to evaluate the necessity of repeat DSA in subgroups of patients with SAH with negative initial DSA. Patients and Methods: Retrospective analysis of clinical records and imaging of all patients presenting to our institution with nontraumatic SAH. Results were analyzed for presenting grades, blood distribution, outcomes, repeat DSA and findings. Bleeding pattern was determined from computed tomography (CT) and was categorized as perimesencephalic (PMN), diffuse, cortical. The criteria for bleeding pattern categorization were adapted from previous studies. PMN group included those with hemorrhage limited in one or more basal cisterns. Diffuse group included those with hemorrhage extending to the sylvian fissure, peripheral sulci, or intraventricular space. Cortical hemorrhage is defined as isolated blood in the peripheral sulci without hemorrhage in the basal cisterns. Results: 37 patients with proven nontraumatic SAH of which 9 (24.3%) had no vascular cause identified on their initial angiogram were identified. The blood distribution was perimesencephalic in 2, diffuse in 6, and cortical in 1. 7 patients (16%) underwent repeat cranial DSA. 2 of the repeat angiograms showed an underlying etiology for the SAH. Overall, the false-negative rate of the initial DSA was 28.57% (2/7 patients). 2 patient with SAH underwent 3rd DSA and no aneurysms were found. Patients with angiogramnegative SAH have better admitting consciousness (p=0.040306), different blood distribution pattern (p=0.023), better outcomes (p=0.004402). We also performed a review of the literature and meta-analysis of the data therein. We compared outcome between PMN subgroup and the diffuse subgroup and false negative rates on repeated DSA in the PMN subgroup and the diffuse subgroup. The meta-analysis revealed better outcome in PMN subgroup and significant lower false negative rate of detection aneurysm after repeated DSA in the patients with PMN. Conclusion: In the line with the results of the current study, angiogram negative subarachnoid hemorrhage has generally more benign course than SAH of known cause. We should be highly suspicious of patients with initial angiogram negative SAH, especially those with a diffuse SAH pattern. Repeat DSA is necessary for angiogram negative SAH