Special features of subarachnoid hemorrhage of unknown origin: a review of a series of 179 cases.

OBJECTIVES

The aim of this study was to work out the special features of subarachnoid hemorrhage (SAH) of unknown origin in respect of diagnostic evaluation, clinical course, and outcome in a large cohort of patients.

METHODS

We reviewed the data of 179 patients with SAH of unknown origin during 1991 and 2008. The differentiation between perimesencephalic (PM-SAH) and non-perimesencephalic SAH (NON-PM-SAH) was done under consideration of the bleeding pattern on CT scanning.

RESULTS

Among 1226 treated patients with spontaneous SAH over a time period of 17 years, a bleeding source remained undetected on first digital subtraction angiogram (DSA) in 179 patients (16.7%)--47 PM-SAH (26.3%) and 132 NON-PM-SAH (73.7%). The clinical signs of patients with PM-SAH were less marked compared to those with NON-PM-SAH, equally to the Hunt and Hess grade. magnetic resonance imaging (MRI) and MR angiography had 100% negative findings for non-aneurismal bleeding sources in all patients. Second DSA revealed a bleeding source in the NON-PM group in 10.8%. The clinical course of the patients with NON-PM-SAH showed a significantly higher rate of complications and a mortality of about 10%. The outcome was excellent in the PM group, in contrast to a fatal course in 13 cases in the NON-PM group.

DISCUSSION

PM-SAH imposed with a mild clinical course and an excellent outcome, without severe complications. In contrast to this, NON-PM-SAH has a significant higher rate of dreaded complications and mortality. It is crucial to make an exact diagnosis of PM-SAH, considering CT scanning during the first 24 hours after occurrence of symptoms and the radiological features.