Postural displacement of the brain: feasibility of using CT for determination of stereotaxic coordinates.

Ten patients were studied with computed tomography (CT) in an attempt to determine if CT could be used preoperatively to establish stereotaxic coordinates for an operation and to find out more about how postural changes affect the position of the brain. Certain well defined cerebral structures were chosen as anatomic landmarks, and their relation to the skull determined with the patient in the supine, lateral, and prone positions. An external helmet fixation system was used to ensure consistent and reproducible CT slices. No displacement of the brain structures was observed in any of the positions, so it may be assumed that it is feasible to use CT-generated preoperative stereotaxic coordinates for reference during an operation, regardless of the patient's position. Four of the 10 patients were examined after lumbar intrathecal administration of metrizamide (200 mg I/ml). This small amount of positive contrast material did not seem to influence the position of the brain.