Trigeminus stereoguide: an instrument for stereotactic approach through the foramen ovale and foramen jugulare.

The author describes a new, fully stereotactic instrument for the percutaneous treatment of tic douloureux. The principle is to place the instrument in such a position around the patient's head that the foramen ovale lies at the midpoint for a spherical system consisting of a cylinder part and a 90 degrees arch with an electrode carrier. The foramen can then be reached from a suitable bone-free direction, either through the cheek or inframandibularly. The position of the foramen ovale is calculated from lateral and axial radiograms and defined with x, y, and z coordinates. The instrument can also be used for the percutaneous treatment of glossopharyngeal neuralgia.