AIR-VENTRICULOGRAPHY PROVOKES AN ANTERIOR DISPLACEMENT OF THE 3RD VENTRICLE DURING FUNCTIONAL STEREOTAXIC PROCEDURES

The width of the third ventricle, the length of the anterior commissur e-posterior commissure line (AC-PC line), the spatial position of the midplane of the third ventricle, and the co-ordinates of the AC, the P C, and of 17 brain targets in the thalamus, hypothalamus and pallidum, were assessed on a pre-operative stereotactic computed-tomography (CT ) study and compared to measurements on intra-operative air-ventriculo graphy, using a non-invasive relocatable stereotactic frame. There wer e no significant differences in the length of the ACPC line, in the po sition of the midsagittal plane of the third ventricle, or in the vert ical or lateral co-ordinates of the AC, the PC and the cerebral target s, between measurements on CT and on air-ventriculography. However, th e width of the third ventricle was significantly larger, and the spati al positions of both AC and PC were significantly more anterior on air -ventriculography than on the CT study. This anterior dislocation of t he commissures was presumably due to the insufflation of air into the ventricles of patients being in the supine position during surgery.