[Pathogenesis of chronic subdural hematoma].

In a retrospective examination, the developmental process of chronic subdural haematomas (CSDH) was investigated by means of sequential CT studies. All CSDHs were found to arise from subdural hygromas by means of encapsulation and bleeding into the hygroma content: hypodense, isodense and "mixed" hyper/hypodense CSDHs were shown to develop due to this mechanism. It is suggested that low intracranial pressure represents the main factor for membrane formation and the development of CSDH of traumatic as well as non-traumatic origin. It is hypothesised that CSDHs are space-filling rather than space-occupying and represent some sort of adaption process to intracranial hypotension. The developmental process described is well suited to explain specific features of CSDH, including membrane formation and the latent interval.