Simple determination of the foramen in trigeminus coagulation.

The object is to achieve a high degree of precision in the determination of the foramen ovale in managing trigeminus neuralgia stereotactically as well as by free-hand penetrations. We carried out exact measurements on lateral skull x-rays of 55 corpses and 25 patients. With the aid of a design and several plain x-ray films we drew connecting-lines between fixed, easily determined points of the skull. The middle of the foramen ovale coincides with the dissecting point of these 3 co-ordinates, the maximal deviation of 2 mm is clinically negligible compared with the total width of the foramen. The average distance of the foramen from the midline as measured on the basic projection is 2.8 cm +/- 2 mm. The puncture technique and the thermocontrolled coagulation of the trigeminus branches are discussed.