Introduction: Angiogram-negative subarachnoid hemorrhage (SAH) accounts for up to 20% of all spontaneous SAH. Much of the angiogram-negative SAH literature includes perimesencephalic hemorrhage which is well known to have a much better outcome than aSAH. The incidence of rebleeding in non-perimesencephalic pattern of bleeding is between 0-12% with reports of significantly fewer other complications.We therefore sought to compare the complications and clinical outcomes of: angiogram-negative SAH with non-perimesencephalic pattern of blood (NPAN-SAH) to angiogram-positive SAH (AP-SAH).

Methods: A prospectively accrued spontaneous SAH database of 1674 patients between April 2006 and December 2013 was analysed. All patients with diffuse SAH and two consecutive negative digital subtraction cerebral angiograms were included. Patients adjudicated to have perimesencephalic SAH pattern based on their Hidjra subscores were excluded. Patients were followed for the primary poor outcome (mRS 3-6) at 3 month. Secondary outcomes included rebleeding, vasospasm, seizures, and infarctions. Multivariable logistic regression was used to assess the relationship between outcomes in NPAN-SAH to angiogram-positive SAH (AP-SAH).

Results: Of 1674 SAH patients, 191 (11%) were found to have negative angiograms and of these, a total of 83 patients (4.9%) were adjudicated to have NPAN-SAH. Patient demographics and clinical characteristics were similar across the groups, except patients with NPAN-SAH were more frequently female, and had diabetes. In the univariate analysis NPAN-SAH was less likely to be associated with poor outcome (mRS 3-6) compared to AP-SAH [OR 0.53, 95% CI (0.31 - 0.92) p<0.026]. After adjusting for Fisher grade, sex, and diabetes, or Hunt & Hess Grade =3, the multi-variable logistic regression model showed that NPAN-SAH patients were less likely to develop vasospasm, but were equally associated with poor outcome, rebleeding, seizure, cerebral infarction or death.

Conclusions: NPAN-SAH accounts for almost 5% of all patients who present with diffuse SAH. Although the risk of vasospasm may be lower, patients with NPAN are equally associated with poor outcome, infarction, and death as compared to patients with AP-SAH hence caution should be applied. Furthers studies may be necessary to further clarify these findings

Patient Care: It will help guide our management of non-perimesencephalic pattern of blood (NPAN-SAH) to angiogram-positive SAH which accouns for around 5% of all SAHs.

Learning Objectives: We therefore sought to compare the complications and clinical outcomes of: angiogram-negative SAH with non-perimesencephalic pattern of blood (NPAN-SAH) to angiogram-positive SAH (AP-SAH).

References: Lin et al. Neurocrit Care (2012) 16:389–398, Rinkel GJ et al. Lancet 1991;338:964–8. Whiting J et al Neurosurg Focus. 2009;26:E21.