Abstract
PURPOSE: Sometimes chronic subdural hematoma can be developed following posttraumatic subdural
hygroma. The purpose of this study is to investigate its incidence, the duration required for their conversion,
and characteristic CT and MR findings of subdural hygroma and chronic subdural hamatoma.
MATERIALS AND METHODS: We studied 8 patients with persistent posttraumatic subdural hygroma which
consquently developed chronic subdural hamatoma. The patients were examined with CT initially and
foilowed-up with CT in 3 and MR in 5. We analyzed the location of the lesion, the change of the density or
signal intensity, the change of the size, and the degree of enhancement and mass effect.
RESULTS: The duration required for the formation of hematoma was 48-166 days (mean, 76 days). The characteristic
CT findings of subdural hygroma were a crescentric lesion with CSF density along the inner table without
contrast enhancement. The mass effect was minimal. The CT findings of chronic subdural hematoma were
higher density than that of hygroma in all cases, increase in thickness and size in 3 cases, and contrast
enhancement along the inner membrane of the hematoma in 5 cases. The signal intensities of the subdural
hygroma were identical to those of CSF on both T1 and T2 weighted images, whereas, those of chronic subdural
hematoma were higher.
CONCLUSION: The increased signal intensity on T1 weighted MR images and increased attenuation or contrast
enhancement of the lesion on CT may suggest the conversion of subdural hygroma into chronic subdural hematoma.