trigeminal neuralgia

Trigeminal Neuralgia

Trigeminal neuralgia is a facial pain syndrome consisting of sharp, lancinating pain in the face. The pain is often described as shock-like stabs of pain. The pain is only on one side of the face and may be elicited by touching trigger points in the skin of gums. There is no associated numbness (unless there is co-existing multiple sclerosis). Often there may spontaneous remissions from pain lasting weeks to years. Interestingly this pain usually responds to carbamazepine (Tegretol), an oral anticonvulsant medication.

trigeminal nerve.jpg (21828 bytes) Trigeminal neuralgia is usually caused by compression of the sensory (trigeminal) nerve within the skull by a small artery or vein at the point where the nerve joins the brain stem. Sometimes a small, benign tumor compressed the nerve, causing jolts of electrical shock –like pain to radiate into the face. A few percent of tic patients suffer from multiple sclerosis. In this case the inflammatory response affecting the brain also involves the trigeminal nerve, causing paroxysmal pain.

Tic douloureaux is unique among pain disorders because nearly all treatments work for a period of time. Over the years peripheral nerve avulsion, heating, cooling, compressing, decompressing, chemical ablation, and irradiation have all enjoyed varying degrees of success. Because of the effectiveness of carbamazepine (Tegretol), its use is usually the first level of treatment. Other anticonvulsants may be tried, but these are not usually as effective. When oral medication fails to control this dreadful pain, other surgical measures are quite effective:

Glycerol Injection

Injection of glycerol into the gasserian ganglion is a simple and effective treatment. Using a brief, intravenous anesthetic a needle is introduced into the nerve in the base of the skull and a small amount of glycerol injected. The treatment only takes a few minutes. Eighty-five percent of patients achieve immediate pain relief and persisting numbness in the face is unusual and infection is rare. Recurrence rates are relatively high: about ½ will recur over 3 to 4 years. Re-injection may be performed, but glycerol injections become less effective after several are performed.

Radiofrequency Rhizotomy

This procedure, first described by Sweet is similar to glycerol injection. A needle-electrode is introduced through the face into the nerve in the skull base, once again using a brief anesthetic. A high frequency (radiofrequency) current heats the needle tip, selectively destroying pain nerve fibers and preserving touch sensation nerve fibers. Patients develop some sensory loss. About 98% of individuals have early success with a 20% recurrence rate after a few years. Marked numbness of the eye is an unusual hazard and infection is rare. The procedure can be repeated.

Balloon Compression of Gasserian Ganglion

In this treatment a small balloon catheter is introduced through the needle into the nerve in the skull base. With the patient anesthetized the balloon is briefly inflated to compress the nerve and then removed. Initial pain relief is high: 93% and pain recurrence similar to radiofrequency treatment, about 20% over a few years. Numbness in the face, unfortunately is high (72%). Infection again is a hazard.

Microvascular decompression

Dr. Peter Jennetta established cause of tic douloureaux when he confirmed earlier observations that these patients usually had a small artery or vein compressing the nerve in the posterior skull. He developed microvascular decompression as an effective treatment. Under general anesthesia a small window of bone is removed from behind the ear to gain entry to the lower brain stem and trigeminal nerve. Under a microscope the surgeon separates the blood vessel from the nerve and places a cushion of Teflon cotton between them. An overnight stay in the intensive care unit and a few days hospitalization are required. Initial pain relief is found in 83% of patients; facial numbness is rare and 10 year recurrence rate is 15%. Rare complications are deafness, cerebrospinal leak and other complications of open surgery

Gamma Knife Therapy

Gamma Knife radiosurgery can successfully treat tic pain. A single, non-invasive morning treatment has resulted in excellent pain relief in 58%; good pain relief in 36% and failed pain relief in 6%. Transient facial numbness is rare. Long term recurrence rates are unknown. This treatment is a suitable alternative to anticonvulsant therapy and compares favorably to other treatments.

Read the personal experience of a patient during and after her Gamma Knife treatment submitted to the Trigeminal Neuralgia Association, San Diego Support Group.

figure: MRI scan through the trigeminal nerves showing a Gamma Knife radiosurgical plan with a
4 mm "shot" (yellow circle) to the affected nerve. The opposite nerve is also well seen.

Comparative results of various procedures for trigeminal neuralgia.

	MVD	RF Lesion	Glycerol Injection	Balloon Compression	Gamma Knife
pain relief	83%	98%	85%	92%	80%
recurrence	15%	20%	54%	21%	?
sensory loss	2%	98%	60%	72%	5%

references:

Taha JM, et al. Comparison of surgical treatments for trigeminal neuralgia: reevaluation of radiofrequency rhizotomy. Neurosurg 1996; 38:865-871.
An excellent review of the results of all contemporary surgical treatments.

Barker FG, et al.Long term outcome of microvascular decompression for trigeminal neuralgia. NEJM 1996; 334, 1001.
A ten year follow up of over 1300 of Dr. Jannetta's MVD patients.

Kondziolka D, et al. Stereotactic radiosurgery for trigeminal neuralgia: a multi-institutional study using the gamma unit. J Neurosurg 1996; 84:940-945.
The first large experience of GK radiosurgery for TN.