Subdural effusions: determination of contrast medium influx from CSF to the fluid accumulation by computed tomography as an aid to the indications for management.

In 46 patients with subdural effusions CSF dynamics and especially the influx of contrast medium from CSF to the subdural fluid accumulation was investigated by serial computed tomography (CT). In 16 cases the subdural effusion was of traumatic and in 30 cases of non-traumatic origin. The results allowed a subdivision of the patients into three groups. Group 1: patients without contrast medium influx into the subdural fluid accumulation; group 2: patients with delayed influx; group 3: patients with immediate influx. In group 1 patients the subdural effusion acted as a space-occupying process with absolute indication for surgical treatment. Also in group 2 patients the further course showed that a surgical indication was given, because the fluid accumulation did not resolve under conservative management but increased in size, and/or the neurological deficit worsened. In all group 3 patients the subdural effusions decreased and finally disappeared conservatively. Group 1 patients with effusions on traumatic origin generally had more severe injuries than the patients of the other groups. The investigations caused no serious complications. This diagnostic method proved to be a reliable means for early differentiation between the possibility of conservative management or the indication for operative treatment in cases with subdural effusions of different origin.