Background: The cause of perimesencephalic nonaneurysmal SAH or PMH is not known. Earlier studies reported a possible contribution of a primitive variant of the BVR in the pathogenesis of PMH. We compared the variants of BVR in a case control study between patients with PMH and aneurysmal SAH by studying the venous phase of the DSA.
Methods: Two observers reviewed the DSAs of 59 patients with PMH and 59 patients with aneurysmal SAH. The variants of BVR were classified into (1) normal continuous: BVR is continuous with the deep middle cerebral vein and drains mainly into the VG; (2) normal discontinuous: drainage anterior to uncal veins and posterior to the VG; and (3) primitive variant: drainage into veins other than the VG.
Results: One hundred eighteen patients were enrolled, with a mean age of 49 +/- 12 years. There were 31 men and 28 women in each group. Patients with PMH were older than patients with aneurysmal SAH (52 vs 46, P = .01). Primitive variants were found in 21% on the left side and 29% on the right side (P = .27). There was no association between PMH and the presence of a primitive variant on the left (25% in PMH vs 19% in aneurysmal SAH, P = .65) or on the right side (31% in PMH vs 30% in aneurysmal SAH, P = .92) in univariate analysis. After correction for age and sex, variants on neither side were associated with PMH (OR: 1.4, P = .53 for left variants and 1.2, P = .67 for right variants).
Conclusions: In this large controlled study, we were unable to confirm a contribution of a primitive variant of the BVR in the pathogenesis of PMH.