Clinico-Pathoanatomical Studies on the Genesis of the Chronic Subdural Hematoma

The chronic subdural hematoma here concerned is limited to a cystic type which consists of the outer and inner membrances. The classic osmotic theory of Gardner for the genesis of the hematoma has been questioned by various points. Recently, We clearly showed the absence of osmotic difference between the hematoma content and blood or CSF. To elucidate the genesis of the hematoma, we attempted clinicopathoanatomical studies on the hematoma and its membrane from 20 operated and 17 autopsied cases (average 55 years, 92% in male). The hematoma occurred unilaterally in 88% of the total cases. Anamnesis of trauma was obtained in 100% of the operated cases and in 62% of the autopsied cases. There was no detectable morphological difference in the hematoma membrane among these two groups. 1) By pathoanatomical analysis of the available cases, we propose that the chronic subdural hematoma may be formed by the following process. An old traumatic hemorrhage widely spread in the subdural space is organized from the dural side resulting in formation of a thin fibrous membrane on the dural surface (primary membrane). Multiple petecheal bleedings occur within the primary membrane probably due to breakage of highly congested venules in the membrane. These small bleeding foci confluent together leading splitting of the entire membrane. During this process, many intact blood vessels may be teared, creating a hematoma in the splitted membrane. The process may be progressive untill it forms an efficient size of a hematoma.