Postural displacements of the brain--on the feasibility of using CT for determination of stereotactic coordinates

Ten patients were studied with CT. In order to achieve consistent and reproducible CT slices an external helmet fixation system was used. Certain well defined cerebral structures were chosen as anatomical landmarks and their relationship to the skull determined with the patient in supine, lateral and prone positions. No displacements of brain structures could be observed. The results show the feasibility of using the same coordinates for intracranial structures at CT and at operation irrespective of the position of the patient's head at these procedures. Four of these patients were examined after lumbar intrathecal administration of 5 ml metrizamide (200 mgJ/ml). This small amount of positive contrast does not seem to influence on the position for the brain.