Trigeminal neuralgia (TN) is a pain disorder of the face and mouth characterized by sharp, lancinating, electrical or stabbing sensations most frequently involving the mid and lower face. Almost always this occurs on only one side. Not uncommonly it can mimic dental problems and in many patients it is only after unsuccessful tooth extractions or root canal treatments are performed that the correct diagnosis of TN is made. Bouts of pain can become more frequent, prolonged and severe as time passes. The potential incapacitating nature of the disease is evident in many patients who are unable to talk or eat during periods of discomfort. Many people with TN can identify triggering mechanisms that cause the pain such as brushing the teeth, swallowing, shaving, stroking the face and smiling. In some cases wind blowing against the face can be intolerable. While there are various theories as to the cause of TN, it is generally felt that most cases are caused by a blood vessel (usually an artery) compressing the trigeminal nerve, the nerve responsible for feeling in the face and mouth) where it enters the brainstem. Pulsations of the artery cause, over time, erosion of the covering of the nerves (myelin) resulting in a short circuiting of the electrical impulses (ephaptic transmission), resulting in pain.
Most patients with TN are initially treated with medications. These can be very effective at controlling the pain. Common medications include Tegretol, Trileptal, and Neurontin. When medications are not effective or when the side effects are poorly tolerated by the patient, alternative treatment options should be considered.
Glossopharyngeal neuralgia, which is similar to trigeminal neuralgia, is a rare disorder characterized by episodes of pain located in the oropharynx on one side, typically in the region of the tonsil. The pain usually is repetitive and frequently has a jabbing or electrical quality. The discomfort may originate in or radiate to the ear and consequently can be confused with geniculate neuralgia. Attacks may be triggered by swallowing or stimulation of the tonsil. Athough remissions may occur for months or even years, recurrence is common.
Most cases of glossopharyngeal neuralgia are idiopathic, meaning there is no identifiable cause. Less commonly, it may be related to prior surgery, tumors, or vascular compression of the glossopharyngeal nerve. Treatment is usually directed at the cause when possible. When an underlying cause is not identified, various medications, the same that are used to treat trigeminal neuralgia such as carbamazepine and gabapentin, may be effective. In most cases, however, surgery is required to treat the condition. This usually takes the form of intracranial exposure for vascular decompression and division of the ninth cranial nerve (glossopharyngeal nerve) and the upper rootlets of the tenth cranial nerve (vagus nerve).
• Microvascular Decompression Surgery: In most patients the preferred surgical treatment is known as a microvascular decompression (MVD) procedure. A small incision is made behind the ear and a nickel sized opening in the skull allows visualization of the area of the trigeminal nerve and brainstem, the cerebello-pontine angle (CPA). Using a high powered microscope and endoscopes the blood vessel compressing the trigeminal nerve is lifted and a small pad or sponge is placed between it and the nerve, acting as a shock absorber. The pulsations of the artery are no longer eroding the covering of the nerve. Excellent pain relief is achieved in more than 90% of properly selected patients. Hospitalization is usually 2 days.
• Percutaneous Rhizotomy: An alternative procedure is some patients is to pass a needle into the bundle of trigeminal nerves (Gasserian Ganglion) before the nerves separate and go to the face. Once inserted into the bundle the pain fibers are “deadened” by heating them (radiofrequency lesion), bathing them in alcohol (glycerol injection) or compressing them with a balloon. In all cases good pain reief can be achieved. This is an outpatient procedure.
• Stereotactic Radiosurgery (SRS): Highly focused radiation using the Gamma Knife (GK) is an excellent treatment modality for many patients with TN who are not felt to be candidates for conventional surgery or do not desire the more invasive procedures. This outpatient procedure requires placement of a special frame (stereotactic frame) on the head. An MRI scan is performed to precisely localize the trigeminal nerve as it enters the brainstem. Radiation is then focused on this site for approximately one hour. The frame is removed from the head and the patient can go home. Beneficial effects of the radiation are typically seen 1 to 3 months following the treatment.