Postoperative subdural fluid collections in neurosurgery.

After introduction of computed tomography (CT) scanning, subdural fluid collections (SFCs) have been more frequently detected. We encountered 1013 operated cases in which CT scans were performed at an early postoperative stage. Postoperative SFC occurred in 165 of the 1013 operated cases (17%). The incidence of SFC was highest in aneurysm surgery (47%), followed by neurovascular decompression (27%) and brain tumor surgery (22%). In aneurysm surgery, preoperative ventricular dilatation seemed to promote the occurrence of SFC. In tumor surgery, SFC occurred more frequently when the tumor existed in the sellar region. The SFCs decreased or disappeared in most cases on sequential CT scans, but increased in 27 cases. In the latter, maximum thickness of the SFC was seen between 20 and 30 postoperative days. Nineteen of the 27 cases had preoperative ventricular dilatation. Operation for SFC was performed in four cases with clinical symptoms and signs. Three of 169 cases developed into chronic subdural hematomas.