Atypical chronic subdural hematoma requiring craniotomy for treatment

The authors report three cases of rare atypical chronic subdural hematoma showing specific CT findings and requiring craniotomy for treatment. They were all males aged 57 to 79 (mean: 68) years old; none had had a history of head trauma, and the chief complaint was invariably hemiparesis. On a plain CT, the hematoma was irregular in shape and was imaged as an inhomogeneous density without a niveau. On an enhanced CT, however, the inner margin of the hematoma was thick and markedly enhanced. In addition, the inner and outer membranes adhered to each other at a few points to present a multilocular form which the present authors named the ''tenting sign.'' Craniotomy revealed that the hematoma was a mixture of clot and liquid hematoma. Moreover, the hematoma was imaged as a single cavity, with the inner membrane of the hematoma being raised in the form of a canopy or tent and adhering to the outer membrane to present a characteristic structure. This characteristic CT sign suggests mixed components of the hematoma and the necessity for craniotomy. (author)