[Promotive factors of chronic subdural hematoma in relation to age].

To reveal the pathogenesis of chronic subdural hematoma (CSDH), 256 patients with CSDH over 1 year of age were studied in relation to various traumatic or nontraumatic promotive factors of CSDH including arachnoid cyst, implantation of a cerebrospinal fluid shunt, secondary cerebral atrophy, coagulopathies and past history of acute subdural hematoma or effusion. All patients were grouped according to decade of age. The incidences of associated promotive factors were individually analyzed in each group. The incidences of associated promotive factors in the 1st, 2nd, 3rd, 4th, 5th, 6th, 7th, 8th, 9th decades of life were 71%, 89%, 56%, 33%, 9%, 11%, 8%, 8% and 5%, respectively. Thus, they were divided into two groups; youth (1st to 4th decade: n = 34) and elder (5th to 9th decade: n = 222). The incidences of associated promotive factors were 62% and 8%, respectively (P < 0.001). Severity of head injury received was also evaluated in these two groups. In the youth group, 15 out of 34 patients (44.1%) had received severe head injuries with loss of consciousness, while in the elder group, only 22 out of 222 patients (9.9%) had received severe head injuries (P < 0.001). The analysis was repeated after each group was divided into two subgroups regarding the coexistence of promotive factors. Among the youth group, 13 patients had no promotive factors and 21 had one or more promotive factors. In those without any promotive factor, 9 out of 13 had received severe head injuries with loss of consciousness, while in those with promotive factors, 6 out of 21 had received severe head injuries. On the other hand, majority of the elder group had not received severe head injuries irrespective of whether patients had promotive factors or not. The present study revealed that majority of young CSDH patient had some promotive factors or severe head injuries with loss of consciousness, and that majority of patients aged over 40 years had no promotive factors and did not receive severe head injuries.