Abstract: A stereotaxic apparatus comprises a ring with head clamps and an arch-shaped plate adapted to carry a stereotaxic instrument and dovably joined to a bushing by means of a guide member attached to the bushing. The bushing is mounted on a bar so as to be movable along the bar and rotable thereabout, with the bar being disposed radially relative to the arch defining the shape of the plate, and being joined to the ring by means of a spatial hinge having two degrees of freedom and mounted on the ring so as to be movable therealong. The extremity of the stereotaxic instrument is positioned at a point being the projection of the curvature center of the arch defining the shape of the plate on the axis of the bar.

Abstract: A method for guiding a stereotaxic instrument at a target point in an intracerebral cavity comprising fixing detachable roentgenocontrast markers with respect to the patient's cranium, then effecting contrast roentgenography and determining the relative position of the markers and intracerebral reference points. Subsequently, the position of a target point with respect to the intracerebral reference points is determined and a physical model of the intracerebral cavity is constructed to include the points simulating the markers and a point simulating the target point. A stereotaxic apparatus is installed on the patient's head, the detachable roentgenocontrast markers are again fixed with respect to the patient's cranium, the position of the detachable markers with respect to the stereotaxic apparatus is identified and the positions of the detachable roentgenocontrast markers with respect to the stereotaxic apparatus are set-up in the model of the stereotaxic apparatus.