Catheter Angiogram-Negative Subarachnoid Hemorrhage: Delayed Cerebral Ischemia, Shunt Dependency, and Diagnostic Yield of Serial Angiography.

BACKGROUND AND OBJECTIVES:Initial cerebral angiogram-negative subarachnoid hemorrhage (SAH) represents approximately 10% of spontaneous SAH cases. There is variation in the extent to which these patients are investigated, and much of the literature describes the condition as benign. The objectives of this study were to determine the diagnostic yield of repeat angiography (beyond the index angiogram) and the rates of delayed cerebral ischemia (DCI) and hydrocephalus in this population. METHODS:A retrospective cohort study of patients with an initial negative angiogram after presenting with SAH between January 2020 and December 2024 was performed using data derived from a prospectively maintained database of patients with SAH (computed tomography- or lumbar puncture-proven) at a single institution. RESULTS:Two hundred and two patients had an initial angiogram-negative SAH during the study period. Cluster analysis identified 3 clusters: noncisternal SAH; perimesencephalic SAH, and diffuse SAH. Overall, 3 patients (1.5%) developed DCI, and all were in either the perimesencephalic (1/81; 1%) or diffuse group (2/66; 3%). Twenty-two patients (10.9%) developed hydrocephalus requiring temporary cerebrospinal fluid diversion, and 5 (2.5%) required a shunt. Eighty-one patients (40%) underwent a single additional angiogram, and 23 (11%) underwent 2 additional angiograms. The overall diagnostic yield of repeat cerebral angiography was 3.9%. All patients with a positive finding on repeat angiography were in the diffuse SAH subgroup apart from one with a focal cortical area of SAH. Seven patients had a complication from repeat angiography, including 2 patients suffering a permanent neurological deficit from a periprocedural stroke. All patients also underwent an MRI/magnetic resonance angiography of brain, which did not yield any positive findings. CONCLUSION:Hydrocephalus and DCI do occur in SAH patients with an initial negative angiogram, and the rates increase with more extensive SAH. Repeat angiography was only useful in patients with diffuse or focal blood distribution patterns. MRI/magnetic resonance angiography of brain did not yield a missed vascular lesion in any patient.