Venous and cerebrospinal fluid outflow in patients with brain swelling and oedema

67 patients with benign intracranial hypertension (BIH) and 44 with normal pressure hydrocephalus (NPH) were examined by employment of infusion tests. Brain swelling (decrease of ventricular size with normal or increased brain tissue density) was a characteristic feature of BIH. It may result from venous outflow disturbances leading to vascular engorgement. But later, the process appears to be independent from the increase of the dural sinus pressure. This was normal in patients with BIH and NPH. Despite absorption disturbances there was a strong positive correlation in NPH between cerebrospinal fluid- and dural sinus pressure, while in BIH such a correlation was absent. The data confirm a pathogenesis of brain swelling in BIH as an obstacle to venous outflow at the level of the bridging veins and venous lacunae, however, not at the level of the dural sinuses.