[Perimesencephalic subarachnoid hemorrhage--an independent clinical picture of non-aneurysmatic subarachnoid hemorrhage with a benign course].

Two hundred seventy-three Patients with acute SAH were treated within the last 46 months (1.4.1991 to 31.1.1995). Diagnosis was made upon visible SAH on CT-scans or bloody spinal tap regardless of a negative CT-scan. These patients harbored 194 aneurysms, 25 AVM and cavernomas. Within the same time-period we treated 27 Patients without SAH but harboring vascular malformations (17 aneurysms, 10 AVM and cavernomas). In 30 patients (11%) no bleeding source was detectable. Fourteen of these patients (5.1%) had blood concentrated within the perimesencephalic cisterns on the CT-scans. On admission all of these 14 patients (8 men, 6 female, aged 30 to 63 years) were awake and without mentionable neurological deficit, equalling Hunt & Hess grade 1 (11 patients) and 2 (3 patients). Neither the initial nor control angiography revealed a vascular malformation as a bleeding source. MRI-scans performed for 11 patients did not reveal further etiological clues. During a follow-up interval of 3 to 48 months, none of these patients suffered a rebleeding. Vasospasm was not or only slightly present, no ischemia leading to neurological deficit. GOS reached 5 and Karnofsky-scale was 100 for all of these patients. We conclude that the perimesencephalic SAH is a homogeneous entity with a different natural course than the common aneurysmatic SAH. Probably leakage within the capillary or venous circulation causes this form of SAH with a benign clinical course. Further experience is required to determine whether control angiography is mandatory in these patents with a distinct CT appearance.