Background and Purpose Patients suspected of having aneurysmal subarachnoid hemorrhage (SAH) are initially evaluated with noncontrast head computed tomography (CT). If the CT is negative, but clinical concern for SAH is high, a lumbar puncture (LP) with cerebrospinal fluid (CSF) analysis is typically performed. The purpose of this study was to evaluate the accuracy of CSF xanthochromia and erythrocytosis for aneurysmal SAH. Methods Medical records of all patients who underwent catheter angiography at Barnes Jewish Hospital between July 2002 and April 2012 for clinical suspicion of a ruptured brain aneurysm after a negative CT scan and an LP suspicious for SAH were reviewed. The CSF analysis results, angiographic findings and outcomes of each case were recorded. Results Fifty nine patients were identified. Two angiographic lesions were identified in patients with xanthochromia was 8.3% (2/24), both of which were confirmed to have ruptured. The diagnostic yield in patients with non-clearing erythrocytosis and no xanthrochromia was 6.3% (1/16), though this lesion was not considered the source of SAH. Conclusion Catheter angiography should be performed in patients with CT negative but suspicious LP, particularly in the presence of xanthrochromia. The benefit of angiography in patients with erythrocytosis only is unclear and deserves future study.

Our anatomic definition of PSAH correlated with a low risk of brain aneurysm and was applied with excellent inter-observer agreement.