Trigeminal Neuralgia

Trigeminal Neuralgia
Trigeminal neuralgia, also known as tic douloureux, sometimes is described as the most excruciating pain known to humanity. The pain typically involves the lower face and jaw, although sometimes it affects the area around the nose and above the eye. This intense, stabbing, electric shock-like pain is caused by irritation of the trigeminal nerve, which sends branches to the forehead, cheek and lower jaw. It usually is limited to one side of the face.

Although trigeminal neuralgia cannot always be cured, there are treatments available to alleviate the debilitating pain. Normally, anticonvulsive medications are the first treatment choice. Surgery can be an effective option for those who become unresponsive to medications or for those who suffer serious side effects from the medications.

The Trigeminal Nerve
The trigeminal nerve is the fifth of 12 pairs of cranial nerves in the head. It is the nerve responsible for providing sensation to the face. One trigeminal nerve runs to the right side of the head, while the other runs to the left. Each of these nerves has three distinct branches. ("Trigeminal" derives from the Latin word "tria," which means three, and "geminus," which means twin.) After the trigeminal nerve leaves the brain and travels inside the skull, it divides into three smaller branches, controlling sensations throughout the face:

The first branch controls sensation in a person's eye, upper eyelid and forehead.
The second branch controls sensation in the lower eyelid, cheek, nostril, upper lip and upper gum.
The third branch controls sensations in the jaw, lower lip, lower gum and some of the muscles used for chewing.
Prevalence and Incidence
It is reported that 150,000 people are diagnosed with trigeminal neuralgia every year. While the disorder can occur at any age, it is most common in people over the age of 50. The National Institute of Neurological Disorders and Stroke(NINDS) notes that trigeminal neuralgia is more common in women than in men. Additionally, there is evidence that the disorder runs in families, likely as a result of an inherited blood vessel formation. Hypertension and multiple sclerosis (MS) also are risk factors.

Causes
The pain associated with trigeminal neuralgia represents an irritation of the nerve. The cause of the pain usually is due to contact between a healthy artery or vein and the trigeminal nerve at the base of the brain. This places pressure on the nerve as it enters the brain and causes the nerve to misfire.

Other causes of trigeminal neuralgia include pressure of a tumor on the nerve or MS, which damages the myelin sheaths. Development of trigeminal neuralgia in a young adult suggests the possibility of MS.

Symptoms
Most patients report that their pain begins spontaneously and seemingly out of nowhere. Other patients say their pain follows a car accident, a blow to the face or dental surgery. Most physicians and dentists do not believe that dental work can cause trigeminal neuralgia. In these cases, it is more likely that the disorder was already developing, and the dental work caused the initial symptoms to be triggered coincidentally.

Pain often is first experienced along the upper or lower jaw, so many patients assume they have a dental abscess. Some patients see their dentists and actually have a root canal performed, which inevitably brings no relief. When the pain persists, patients realize the problem is not dental-related.

The pain of trigeminal neuralgia is defined as either Type I (sometimes also referred to as “classic”) or Type II (may also be called “atypical”) . With classic pain, there are definite periods of remission. The pain is intensely sharp, throbbing and shock-like and usually triggered by touching an area of the skin or by specific activities.Type II pain often is present as a constant, burning sensation affecting a more widespread area of the face. With atypical trigeminal neuralgia, there may not be a remission period, and symptoms are usually more difficult to treat.

Trigeminal neuralgia tends to run in cycles. Patients often suffer long stretches of frequent attacks followed by weeks, months or even years of little or no pain. The usual pattern, however, is for the attacks to intensify over time with shorter pain-free periods. Some patients suffer less than one attack a day, while others experience a dozen or more every hour. The pain typically begins with a sensation of electrical shocks that culminates in an excruciating stabbing pain within less than 20 seconds. The pain often leaves patients with uncontrollable facial twitching, which is why the disorder is also known as tic douloureux.

Attacks of trigeminal neuralgia may be triggered by the following:

Touching the skin lightly
Washing
Shaving
Brushing teeth
Blowing the nose
Drinking hot or cold beverages
Encountering a light breeze
Applying makeup
Smiling
Talking
The symptoms of several pain disorders are similar to those of trigeminal neuralgia. Temporal tendinitis involves cheek pain and tooth sensitivity, as well as headaches and neck and shoulder pain. This condition is called a "migraine mimic" because its symptoms are similar to those of a migraine. Ernest syndrome is an injury of the styomandubular ligament, which connects the base of the skull with the lower jaw, producing pain in areas of the face, head, and neck. Occipital neuralgia involves pain in the front and back of the head that sometimes extends into the facial region.

Diagnosis
Magnetic resonance imaging (MRI) can detect if a tumor or MS is irritating the trigeminal nerve. However, unless a tumor or MS is the cause, imaging of the brain will seldom reveal the precise reason why the nerve is being irritated. The vessel next to the nerve root is difficult to see even on a high-quality MRI. Tests can help rule out other causes of facial disorders. Trigeminal neuralgia usually is diagnosed based on the description of the symptoms provided by the patient.

Treatment
There are several effective ways to alleviate the pain, including a variety of medications.

Carbamazepine, an anticonvulsant drug, is the most common medication that doctors use to treat trigeminal neuralgia. In the early stages of the disease, carbamazepine controls pain for most people. When a patient shows no relief from this medication, a physician has cause to doubt whether trigeminal neuralgia is present. However, the effectiveness of carbamazepine decreases over time. Possible side effects include dizziness, double vision, drowsiness and nausea.
Baclofen is a muscle relaxant. Its effectiveness may increase when it is used with either carbamazepine or phenytoin. Possible side effects include confusion, depression and drowsiness.
Phenytoin, an anticonvulsant medication, was the first medication used to treat trigeminal neuralgia. Possible side effects include gum overgrowth, balance disturbances and drowsiness.
Oxcarbazepine, a newer medication, has been used more recently as the first line of treatment. It is structurally related to carbamazepine and may be preferred because it generally has fewer side effects. Possible side effects include dizziness and double vision.
Other medications include gabapentin, clonazepam, sodium valporate, lamotrigine and topiramate.

There are drawbacks to these medications other than side effects. Some patients may need relatively high doses to alleviate the pain, and the side effects can become more pronounced at higher doses. Anticonvulsant drugs may lose their effectiveness over time. Some patients may need a higher dose to reduce the pain or a second anticonvulsant, which can lead to adverse drug reactions. Many of these drugs can have a toxic effect on some patients, particularly people with a history of bone marrow suppression and kidney and liver toxicity. These patients must have their blood monitored to ensure their safety.