[Subacute subdural hematoma--reexamination of mechanism by CT and MRI findings].

ABSTRACT

We have already reported about the importance of establishing the concept of subacute subdural hematoma. But the mechanism by which this disease develops has not as yet been elucidated fully. In one case of subacute subdural hematoma, we were able to perform CT and MRI over time and obtained findings which were of use in studying the mechanism of development. The case was a 56-year-old male. He developed with seizure. CT on admission revealed acute subdural hematoma and subarachnoid hemorrhage. But neurological deficits were absent. So he was treated conservatively. On the 16th hospital day there appeared seizure, anisocoria and an increase in the mass sign due to subdural hematoma was noted on CT, so a diagnosis of subacute subdural hematoma was made. Cerebrospinal fluid was considered accountable for the increase in the mass sign judging from the findings of CT and MRI each performed over time. It was surmised that subdural effusion developed concurrently in the subacute stage. Three conditions, namely, presence of (1) arachnoid tear, (2) clots, (3) no intracranial hypertension are considered important as the mechanism by which subacute subdural hematoma develops.