Postoperative CT appearance in chronic subdural hematomas

Postoperative CT appearances in 65 cases of chronic subdural hematomas were evaluated in terms of patient's age, preoperative neurological symptoms and CT findings, final outcomes, and so on. All of the cases were treated with trepanation and irrigation. CT appearances were divided into four different types as follows; Type Ia: No abnormal findings in the subdural sapce, Type Ib: The same as above except for a linear high density suggestive of thickened outer membrane, Type II: Persistence subdural fluid collection and widened cortical sulci which indicate underlining brain atrophy, Type III: Remaining hematoma and/or density changes during follow-up period. Although the mean age of the patients in type Ib was higher than those in type Ia and reexpansion of the brain appear to delay in type Ib and preoperative CT in type Ib tended to show mixed density, final outcome in both groups were excellent. Characteristics in type II were that most of cases were in the eighth decade, preceding head injury was unclear, preoperative psychiatric symptoms and disturbance of consciousness were common and postoperative improvement of the symptoms was not satisfactory compared to other types. Aged patients as in type Ib and type II and thick hematomas of over 2 cm depth with mixed or high density tended to show type III postoperatively. All of the nine patients who required reoperation were included in this type. The present study indicates that thick hematomas with sizable mass effect and mixed or high density in the aged must be carefully treated, such as with placement of the subdural drainage or keeping the patient in the Trendelenburg position, to facilitate postoperative reexpansion of the brain. (author)