Abstract
To investigate whether the development of chronic subdural hematomas from posttraumatic subdural collections is a common occurrence, 40 cases of posttraumatic subdural collections of low density observed in two hospitals were followed with CT scans in the 30-month period between June 1, 1977 and Dec. 31, 1979. Their clinical courses were devided into three groups.
(1) Among 40 patients with posttraumatic subdural collections of low density, eight subsequently developed chronic subdural hematomas. Five bilateral subdural collections evolved into bilateral chronic subdural hematomas. When the subdural collections were unilateral, the resulting hematomas developed at the site of the original collections. In five of these cases, CT scans at intermediate dates demonstrated a stage when the subdural collections had increased density but were not expanding. From these non-expanding subdural collections of increased density, expanding chronic subdural hematomas evolved in 2 weeks to 1 month. (2) In 10 cases, the subdural collections showed increased density at later dates but were eventually resolved without evolving into chronic subdural hematomas. (3) In the remaining 22 cases, the subdural collections were resolved without apparent increase in density.
It was noted that the subdural collections remained at a uniformly low-density at least for the first month after the initial head injury and the increase in density occurred thereafter.
The nature of these posttraumatic subdural collections of low density, which seem to be precursors of chronic subdural hematomas, are discussed. They appear to be posttraumatic subdural hygromas.
