Acute posttraumatic subdural hematomas: "intradural" computed tomographic appearance as a favorable prognostic factor

Posttraumatic acute subdural hematoma carries a high postoperative mortality rate. Preservation of subarachnoid spaces in preoperative computed tomographic (CT) scans may be interpreted as a favorable prognostic factor.

Thirty-one cases of posttraumatic acute subdural hematoma operated on consecutively, with an interval from trauma to surgery of less than 4 hours and a Glasgow Coma Scale score of less than 8, were reviewed. The immediate and long-term results were evaluated with reference to preoperative CT images, distinguishing cases with preserved subarachnoid spaces from the others.

In 5 of the 31 cases, preoperative CT scans showed intact subarachnoid spaces and the absence of blood in the cerebrospinal fluid. These cases presented a much better postoperative course than did the others.

The presence of intact subarachnoid spaces in CT scans for patients with acute subdural hematomas may be interpreted as an extremely favorable prognostic factor; this may be attributed to the protective effect of the integral visceral membrane of the hematoma, which prevents the diffusion of neurotoxic and vasoactive substances into the subarachnoid spaces. This group of hematomas was classified as "intradural," with reference to the concept of the "subdural compartment" described in studies conducted using an electron microscope.