Clinical relevance of negative initial angiogram in spontaneous subarachnoid hemorrhage

Background: We aimed to compare the presentation, management, and clinical course in patients with perimesencephalic and nonperimesencephalic (aneurysmal) bleeding patterns on noncontrast CT, but negative initial 4-vessel digital subtraction angiography (DSA). Methods: We retrospectively reviewed clinical and imaging data for 280 patients presenting with spontaneous SAH admitted between 2005 and 2011. We identified 56 patients (20%) with SAH diagnosed on high resolution head CT performed within 48 hours of admission, and negative initial DSA, and divided them into perimesencephalic and non-perimesencephalic groups based on hemorrhage patterns. Patients with traumatic subarachnoid bleeding and those with initial positive DSA were excluded from this analysis. Results: Perimesencephalic SAH was seen in 25 patients (45%); non-perimesencephalic bleeding patterns were seen in 31 (55%). All patients with perimesencephalic SAH presented with Hunt and Hess (HH) I, versus 45% HH I and 55% HH II-IV in those with non-perimecenphalic SAH. All patients with perimesencephalic SAH achieved modified Rankin score (mRS) 0 at discharge and 6-month follow-up, compared with 45% mRS 0 at discharge and 68% at 6-month follow-up in non-perimesencephalic SAH. Patients with perimesencephalic SAH presented a uniformly uncomplicated clinical course. Among nonperimesencephalic SAH patients there were 19 neurological/neurosurgical and 10 medical complications, two small aneurysms diagnosed at follow-up DSA, and one death. Conclusions: In this series, perimesencephalic SAH was associated with good clinical grades, consistently negative initial and follow-up angiograms, and an excellent prognosis. In contrast, non-perimesencephalic SAH was associated with a worse clinical presentation, higher complication rates, higher rates of true aneurysm detection on follow-up angiogram, and a poorer outcome.