Some patients with intracranial aneurysms have a reduced type III/type I collagen ratio. A case-control study.

A reduced production of type III collagen has been reported in previous studies to be associated with intracranial aneurysms. The purpose of this prospective case-control study was to assess the possible role of a reduced type III collagen production as a risk factor for having an intracranial aneurysm. The study group consisted of 41 consecutively admitted patients with intracranial aneurysms. Intracranial aneurysms were demonstrated by intraarterial digital subtraction cerebral angiography or during operation. The control group consisted of 41 healthy volunteers matched for age and sex. Fibroblasts were cultured from skin biopsies from patients and control subjects, and the type III/type I collagen ratios were determined. The type III/type I collagen ratios in the controls ranged from 5.5 to 19.8%, with a median ratio of 10%, and none had a ratio below 5.5%. The type III/type I collagen ratios in patients ranged from 1.1 to 25.1%, with a median ratio of 10.5%, and eight patients (19.5%) had a low (< 5.5%) ratio (p = 0.005, Fisher's exact test). Our findings support the hypothesis that a reduced production of type III collagen may contribute to the formation of intracranial aneurysms in some patients.