Section 6. Brain, Spinal Cord, and Nerve Disorders

Chapter 96. Cranial Nerve Disorders

Topics: Introduction | Internuclear Ophthalmoplegia | Palsies of Cranial Nerves That Control Eye Movement | Trigeminal Neuralgia | Bell's Palsy | Hemifacial Spasm | Glossopharyngeal Neuralgia | Hypoglossal Nerve Disorders

Trigeminal Neuralgia

Trigeminal neuralgia (tic douloureux) is pain due to malfunction of cranial nerve V (trigeminal nerve), which carries sensory information from the face to the brain and controls the muscles involved in chewing.

Trigeminal neuralgia usually occurs in middle-aged and older people, although it can affect adults of all ages. It is more common among women.

In most cases, the cause is unknown. A common known cause is an abnormally positioned artery that compresses the trigeminal nerve near where it exits the brain. Occasionally in younger people, trigeminal neuralgia results from nerve damage due to multiple sclerosis. Rarely, trigeminal neuralgia results from damage due to herpes zoster (a viral infection) or compression by a tumor.

Symptoms

The pain can occur spontaneously but is often triggered by touching a particular spot (called a trigger point) on the face, lips, or tongue or by an activity such as brushing the teeth or chewing. Repeated short, lightning-like bursts of excruciating stabbing pain can be felt in any part of the lower portion of the face but are most often felt in the cheek next to the nose or in the jaw. Usually, only one side of the face is affected. The pain usually lasts seconds but may last up to 2 minutes. Recurring as often as 100 times a day, the pain can be incapacitating. Because the pain is intense, people tend to wince, and thus the disorder is sometimes called a tic. The disorder commonly resolves on its own, but bouts of the disorder often recur after a long pain-free interval.

Diagnosis and Treatment

Although no specific test exists for identifying trigeminal neuralgia, its characteristic pain makes it easy for doctors to diagnose. However, doctors must distinguish trigeminal neuralgia from other possible causes of facial pain, such as disorders of the jaw, teeth, or sinuses and trigeminal neuropathy (which is often due to compression of the trigeminal nerve by a tumor or an aneurysm). For example, trigeminal neuropathy causes loss of sensation in the face and trigeminal neuralgia does not.

Because the bouts of pain are brief and recurrent, typical analgesics are not usually helpful, but other drugs, especially certain anticonvulsants (which stabilize nerve membranes), may be helpful. The anticonvulsant carbamazepine is usually tried first. Phenytoin or valproate may be prescribed if carbamazepine is ineffective or produces intolerable side effects. Baclofen (a drug used to reduce muscle spasms) or a tricyclic antidepressant (see Section 7, Chapter 101) may be used instead.

When trigeminal neuralgia results from an abnormally positioned artery, a surgeon separates the artery from the nerve and places a small sponge between them. This procedure usually relieves the pain for many years. If the cause is a tumor, the tumor can be surgically removed.

For people who have pain unrelieved by drugs and who may not be good candidates for surgery, a test can be performed to determine whether other procedures would be helpful. For the test, alcohol is injected into the nerve to temporarily block its function. If the pain is relieved by the alcohol, cutting the nerve surgically or with a radiofrequency probe (using heat) relieves the pain permanently. Alternatively, the nerve can be permanently destroyed by injecting a drug such as glycerol into it. However, these treatments are used as a last resort. They often provide only temporary relief--for months to a few years--and afterward, discomfort in the face recurs.