Definition

Trigeminal neuralgia is a disorder of the trigeminal nerve (the fifth cranial nerve) that causes episodes of sharp, stabbing pain in the cheek, lips, gums, or chin on one side of the face.

Description

The trigeminal nerve, which is divided into three branches, is responsible for chewing, for producing saliva and tears, and for sending facial sensations to the brain. When this nerve breaks down for some reason, it can trigger brief but agonizing sizzles of pain on one side of the face.

This condition is unusual in those under age 50 and more often occurs after 70. Women are three times more likely to have the condition than are men. When trigeminal neuralgia does occur in younger people, it is often associated with multiple sclerosis.

The pain, while brief, is so severe that the sufferer often can't do anything else while the attack lasts. People with this pain often wince or twitch, which is where trigeminal neuralgia gets its French nickname tic douloureux, meaning "painful twitch."

Causes and symptoms

The origin of trigeminal neuralgia is not certain, but scientists believe it may be caused by degeneration, pressure, or irritation of the trigeminal nerve. Some doctors believe the pain may be triggered by pressure from a nearby abnormally-formed artery lying too close to the nerve.

Any part of the three branches of the trigeminal nerve may be affected. Neuralgia of the first branch leads to pain around the eyes and over the forehead; the second branch causes pain in the upper lip, nose and cheek; the third branch causes pain on the side of the tongue and lower lip.

The first episodes are usually fairly mild and brief, and it may be minutes, hours, or weeks before the next attack. However, attacks tend to occur in clumps that may last for weeks at a time. As the sufferer ages, the episodes become more frequent and painful, until the person begins to live in constant fear of the next one.

The momentary bursts of pain usually begin from the same spot on the face each time. The pain can be triggered by touching the area, washing, shaving, eating, drinking, or even talking. Even a cool breeze across the face can set off an attack. Pain is more severe at the ends of the affected nerve, especially over the lip, chin, nostrils, or teeth.

Diagnosis
Diagnosis is usually made by eliminating other problems that could cause similar pain in teeth, jaw, head, or sinuses. Because patients with the condition tend to avoid trigger points, avoiding chewing, shaving, touching or washing their faces can be a clue to diagnosis of trigeminal neuralgia.

Treatment

It is not easy to treat trigeminal neuralgia. Pain can be suppressed by a range of medicines, including the anti-epilepsy medicines carbamazepine (Tegretol) or phenytoin (Dilantin). These drugs slow down the nerve signals at certain nerve terminals, which eases the pain. However, these drugs cause a wide range of side effects, including nausea, dizziness, drowsiness, liver problems, and skin allergies. Some people develop resistance to the drugs or they can't tolerate the high dosage needed to control the discomfort. If the medicines are stopped, the pain usually returns.

If drug treatment fails, surgical treatment to block pain signals from the nerve may be effective. Radio-frequency waves, gamma rays, or glycerol injections can deaden the nerve (and hence the pain). An operation that frees the nerve from whatever is compressing it (blood vessel or tumor) can permanently relieve pain, but this major neurosurgical procedure carries its own risks and complications. Alternatively, a new procedure seeks to place a cushioning sponge between the nerve and a pulsating artery wrapping around it to soothe the irritated nerve.

Prognosis

Although the pain is momentarily incapacitating, it's not life-threatening. As the person ages, the attacks can be expected to occur more and more frequently.

Prevention

While the condition itself can't be prevented, there are a number of things patients can do to avoid triggering attacks:

• wash with cotton pads and warm water over the face

   

   

• rinse the mouth with water after eating, if toothbrushing triggers pain

   

   

• eat and drink food and beverages at room temperature

   

   

• chew on the unaffected side

   

   

• eat soft foods, if eating is becoming a problem

Neuralgia-inducing Cavitational Osteonecrosis (NICO) has been described in medical literature since 1976 and is known under a number of names including: Ratner bone cavities, alveolar cavitational osteopathosis, Robert's bone cavity, trigger point bone cavity, interference field and, most commonly, NICO. In cases of NICO it is claimed that small areas of bone in the upper or lower jaw become infected or inflamed and die, producing neuralgia-like pain. Most often, no sign of inflammation appears on X-ray. NICO is said to appear after tooth extraction, jaw surgery, endodontic therapy or crown preparation and is speculated to be the result of a long-standing low-grade infection.

The pain felt is constant and is often burning and cramping, much like atypical facial pain symptoms. Usually there are trigger points immediately over the areas of infected jawbone that will produce pain when pressed. NICO can cause "referred pain" in that the neuralgia-like symptoms are "referred" to other parts of the face, intraoral cavity and head.

Some cases of NICO appear to be caused or aggravated by infection. Others speculate that minor trauma from extractions, root canal and other dental procedures are common initiators of NICO but believe this only happens in people already susceptible because of a pre-existing blood clotting disorder. Some believe that NICO can develop when blood vessels are injured in the area, resulting in poor circulation which in turn can lead to bone death.

It is difficult to diagnose this problem as the pain symptoms often are similar to other conditions such as Myofascial Pain Disorder (MPD), Temporal Mandibular Joint (TMJ) problems, atypical facial pain, trigeminal neuralgia, phantom toothache, or headache. X-rays of the jawbone most often appear normal. However, a bone biopsy of the affected area can show positive signs of jawbone inflammation.

Discussion
NICO is not generally accepted as a cause of Trigeminal Neuralgia by most medical and dental professionals. It is possible that NICO is involved in some cases of facial neuralgia, especially atypical facial pain. One long-term study has reported considerably or totally reduced pain in 74% of facial neuralgia patients who had jawbone curettage. However, the pain returned for about 30% of these patients, of whom most had been diagnosed with either TN or atypical facial pain.

In dental circles there appears to be two distinct schools of thought on NICO. Some medical and dental professionals consider NICO a controversial diagnosis. Not only do they not consider it a possible cause of trigeminal neuralgia or other facial neuralgias, they also doubt the condition exists as a disorder. They point to data suggesting bone cavitations are found routinely in cadaver jawbones, casting doubt on the theory that bone cavities cause facial neuralgias.

Other dentists believe NICO is the culprit in many facial pain syndromes and that these painful conditions can be cured by jawbone curettage (scraping and removing infected tissue). They point to studies that show a high success rate for jawbone curettage. Some of these dentists believe that root canals and mercury fillings are partly responsible for NICO.

What research is being done?
Within the NINDS research programs, trigeminal neuralgia is addressed primarily through studies associated with pain research. NINDS vigorously pursues a research program seeking new treatments for pain and nerve damage with the ultimate goal of reversing debilitating conditions such as trigeminal neuralgia. NINDS has notified research investigators that it is seeking grant applications both in basic and clinical pain research.