Trigeminal neuralgia, aka tic doloroux, is an excruciatingly painful illness in which the afflicted feels sudden pangs of pain in the face. The pains usually last only moments, but are among the most severe pains humans can feel. Pain usually is provoked by touching a "trigger-zone," typically near the nose or mouth. Sometimes even the acts or drinking or eating stimulate the trigger-zone and produce the pain; in these cases, the patients will frequently avoid nourishment, and thereby risk dehydration or starvation. Fortunately, medications such as carbamazepine usually control the pain.
In particularly severe cases, or when medication does not work well, surgical treatment is required. A variety of operations have been devised, all of which involve the trigeminal nerve-the cranial nerve which carries sensation from the face to the brain. The current concept of the mechanism of trigeminal neuralgia is that it results from compression ot the trigeminal nerve by a blood vessel where the nerve enters the brain.
In the operation depicted here, the brainstem is exposed through an opening in the skull behind the ear. The brain is gently retracted, exposing the trigeminal nerve and brainstem. The first view
shows the brain retracted to the right, and the trigeminal nerve coursing to the left, where it enters an opening in the left side of the patient's skull. A small artery - about 1mm diameter - is compressing the front of the nerve just as it enters the brainstem. Sometimes one can actually see a notch in the nerve made by the artery. The second view
shows the artery after it has ben lifted away from the nerve and the nerve has been protected with a small teflon pledget, which keeps the artery from moving back to its original position. This protection allows the nerve to restore its myelin "insulation", and thus prevents the spread of impulses in the nerve which previously caused terrible pain when just a light touch of the trigger zone could cause a massive nerve discharge.
These illustrations attempt to show the usefulness of the operating-microscope, which provides the surgeon with binocular vision and excellent lighting through an exposure only a little over a centimeter wide. Although surgeons have exposed this part of the brain for at least fifty years, with the use of the operating-microscope over the last twenty years, the operations have become more safe and thorough.