[X-ray studies of the brain as a basis for stereotaxy (author's transl)]

All attempts to reconstruct the topography of the brain in the living from studies of animal material are handicapped by technical difficulties. The best method is to compare exact X-ray pictures, which have been taken under stereotactic conditions. From a large collection of such X-rays the authors have composed contours of the internal table of the skull and of the ventricles, which best match the brains, selected for the Schaltenbrand-Bailey sterotactic atlas. For practical purposes these contours were combined with the transparent overlays for the nomenclature and the border lines of the different parts of the basal ganglia, which have been used in the myelin sections part of the atlas. A comparison of our sagittal series with the new X-ray findings shows, that the sagittal schemata of the atlas represent an extreme variation in the position of the Meynert axis and of the contours of the 4th ventricle. We have chosen a new axis system for the hindbrain, which corresponds to the average of our brains in constructing a new set of typical overlays for the atlas. The contour of the posterior fossa had to be completed. An independent axis system dor the structures of the 4th ventricle was developed, consisting of the base of the 4th ventricle, and a tangent, to the upper contour of the pons. In sterotactic procedures the axis systems for the forebrain and the hindbrain should be used independently. The results obtained are the basis for a new series of lantern slides which can be projected against the X-ray pictures with the Würzburg stereotactic equipment. In the course of this investigation we discovered a source of error. When air enters the puncture hole of the dura, the brain may sink back, so with the patient lying on his back, all structures may shift a few millimeters towards the occipital region. When the patient is lying on his side, as during an approach to the amygdala through the planum temporale, the ventricular system may collapse, so that almost no air is visible in the ventricles and the 3rd ventricle may appear to be in the lower hemisphere, the dislocation being more than 5-8 mm. But filling the ventricle with air through the ventricular catheter is sufficient to blow up the brain and to restore the normal topography.