Delayed Hypersensitive Process in Subacute Subdural Hematoma.

The authors report 2 patients with subacute subdural hematoma (sASDH). An inflammatory process is known to be involved in the development of traumatic subdural effusion (TSE) evolving into chronic subdural hemorrhage (CSDH), but a similar event has not been previously described in acute subdural hematoma (ASDH) evolving into sASDH. In our cases, dexamethasone (DXM) and other conservative treatments were administered to our first patient with dramatic clinical outcome, and a postoperative pathologic examination of the neomembrane of the sASDH in the second patient was done, which showed marked inflammatory process with T-lymphocytes and neutrophils infiltration. The good response to DXM in the first patient and the definite laboratory result of the second patient and their radiologic presentations, as well as a review of relevant literature, suggest that a T-lymphocyte-mediated, delayed hypersensitive reaction triggered by undissolved blood clot may be the driving force of ASDH developing into sASDH, which starts after the seventh day, and peaked by the end of the second week of the clinical course.