Alterations in the intracranial venous sinuses in spontaneous nontraumatic chronic subdural hematomas.

Occlusion of the cerebral venous system is frequently associated with intraparenchymal or subarachnoid hemorrhage. There are few reports of cerebral venous thrombosis associated with nontraumatic chronic subdural hematoma (CSH). We aimed to evaluate the intracranial venous system in patients with spontaneous nontraumatic CSH and to identify alterations in their venous sinuses. In this study, eight patients with spontaneous, nontraumatic CSH were followed for a 7-year period (mean: 2.2 years, range: 1-7 years). Neuroradiological images were taken at the onset of symptoms and during follow-up. Venous angiography or magnetic resonance venography was used to evaluate the cerebral venous system of patients. In all patients, medical or surgical treatments were based on clinical symptoms. In seven of the eight patients, the CSH was in the left hemisphere, whereas one patient had bilateral CSH. In one of the eight patients, thrombosis of the transverse sinus and sigmoid sinus was found, but recanalization was observed at follow-up. In a further three patients, the superior sagittal sinus, the straight sinus, and the vein of Galen were markedly reduced in diameter compared to normal or were not visible at presentation, but normal flow was observed at follow-up. In the remaining four patients, the transverse sinus was not observed at symptom onset or during long-term follow-up. A nontraumatic CSH can occur secondary to a venous thrombosis or it can be associated with the inability to image some of the venous sinuses. Venous flow was restored at long-term follow-up. Increased intravenous pressure is thought to be the pathogenic factor that causes a nontraumatic CSH.