Histopathological study of venous aneurysms in patients with dural arteriovenous fistulas.

Object. Of all intracranial dural arteriovenous fistulas (DAVFs), those with cortical venous drainage associated with cortical venous ectasia or varices are predisposed to an aggressive course and produce progressive neurological symptoms or hemorrhages. The authors undertook a histological examination of venous aneurysms and arterialized veins in the proximity of these aneurysms that had been surgically removed in patients with DAVFs. Methods. Surgical specimens were obtained in eight patients. The excised venous aneurysms and the arterialized veins in their proximity were stained using hematoxylin and eosin, van Gieson's elastic, and Masson's trichrome stain. Immunostaining was also performed for alpha smooth-muscle actin, desmin, and factor VIII antigen. Five of the patients had presented with venous hypertension, and three had intracranial hemorrhages. The arterialized vein obtained in the proximity of the venous aneurysm exhibited local irregular intimal thickening; the internal elastic lamina (IEL) was grossly preserved. All venous aneurysms in patients with venous hypertension manifested medial thickening and local intimal thickening with loss of IEL: the thickness of the wall was relatively uniform. In contrast, the wall thickness of venous aneurysms in patients with hemorrhage was extremely irregular and there was no clear delineation between the media and the intima. In media with complete disappearance of IEL, there was scant muscle tissue. Conclusions. Degenerative changes in venous aneurysms in patients with hemorrhage were much greater than in patients with venous hypertension, possibly because hemorrhages result from a more complicated interplay of anatomical, hemodynamic, and degenerative factors.