A Prospective Study on the Incidence, Patterns and Premorbid Conditions of Traumatic Subdural Hygroma

Sohn, Il Tae; Lee, Kyeong Seok; Doh, Jae Won; Bae, Hack Gun; Yun, Il Gyu; Byun, Bark Jang

Abstract

The origin and clinical importance of subdural hygroma(SDG) are still uncertain. Its pathogenetic mechanism and natural history have not yet been settled. Although the incidence of traumatic SDG has been reported to be 5-20% of posttraumatic space-occupying lesions, the true incidence has not been documented in prospective study. Therefore, authors have tried to determine the incidence of traumatic SDG prospectively during past six months. Serial computed tomography(CT) or magnetic resonance imaging(MRI) studies were done in all patients who were admitted to our department after head injuries. Data on the age, sex, Glasgow coma scale(GCS) on admission, and initial CT findings were collected and analyzed to determine the true incidence, pattern and premorbid conditions for the development of traumatic SDG. Serial CT or MRI scans were performed on the date of admission, the second to sixth hospital day, and the seventh to fourteenth hospital day. Study population consisted of 115 patients, excluding 31 expired, discharged, or transferred patients within a week. Subdural hygroma was noted in 42(35.6%) patients. It shared 45.2% of posttraumatic mass lesion. More than half (54.7%) of patients aged 40 or more had subdural hygromas. They were generally delayed lesions, due to the fact that most of them(81%) were observed at four days or more after the injury. All hygromas were located at the frontal or fronto-temporo-parietal regions. Bilaterality was seen in 54.7%. SDGs occurred earlier when the age of the patients were 40 years old or more(p=0.037). It occurred earlier when the initial CT scans were normal, when there was no accompanying traumatic intracranial lesions, and high GCS on admission. However, these differences were statistically not significant(p>0.05). These results suggest that the premorbid conditions for the development of subdural hygroma were sufficient potential subdural space and separation of the dural border cell layer, although former seemed to be more important that the later. Osmotic dehydration in the aged victims should be serially reevaluated, because the subdural hygroma may develop when the intracranial pressure is excessively low.