Trigeminal Neuralgia (TN)

What is trigeminal neuralgia?

Trigeminal Neuralgia (TN), also called tic douloureux, is a condition that affects the trigeminal nerve (the 5th cranial nerve), one of the largest nerves in the head. TN is primarily known for the intense level of pain it causes. The trigeminal nerve is responsible for sending impulses of touch, pain, pressure and temperature to the brain from the face, jaw, gums, forehead and around the eyes. The disorder is more common in women than in men and rarely affects anyone younger than 50.

What are the symptoms of trigeminal neuralgia?

TN is characterised by a sudden, severe, electric shock-like or stabbing pain typically felt on one side of the jaw or cheek. The attacks of pain, which generally last several seconds and may be repeated one after the other, may be triggered by talking, brushing teeth, touching the face, chewing or swallowing. The attacks may come and go throughout the day and last for days, weeks or months at a time, and then disappear for months or years.

What causes trigeminal neuralgia?

The exact cause of TN is not known. However, certain factors - such as physical nerve damage and stress - can trigger the beginning of the painful attacks. Nerve damage may occur as the nerve passes from the openings in the skull to the muscles and tissue of the face. As the damage compresses the nerve, the nerve cells shed a protective and conductive coating known as myelin. Myelin acts as an insulator. Without this insulation, information from nerves would be transmitted inefficiently. This may result in weakness, sensory loss or other neurologic dysfunction. Damage may also be the result of a biochemical change in the nerve tissue itself or an abnormal blood vessel compressing the nerve as it exits from the brain. In almost all cases, an excessive burst of nervous activity from a damaged nerve causes the painful attacks.

In people without TN, blood vessels are usually not in contact with the trigeminal nerve root entry zone. Though pulsation of vessels upon the trigeminal nerve root do not visibly damage the nerve, the irritation from repeated pulsations may lead to changes of nerve function and delivery of abnormal signals to the trigeminal nerve nucleus. Over time, this may cause hyperactivity of the trigeminal nerve nucleus which results in the generation of TN pain.

Psychological stress can be the cause as well as the outcome of TN. In clinical studies, patients have been known to report TN following major stress like divorce, the death of close family members, a job change, or unhealthy family relationships.

How is trigeminal neuralgia treated?

Medications are the first line of treatment for TN and include drugs such as Carbamazepine (Tegretol®), Phenytoin (Dilantin®), Gabapentin (neurontin®), and Baclofen. There is also a controled trial using Lamotrignine (Lamcital®). Many of the medications used to treat TN are those originally designed to treat seizures. The anti-seizure agents in these medications suppress excessive nerve tissue activity. If pain becomes more frequent and severe, increased doses of medications are required. This may lead to intolerable side effects and/or inadequate pain control. Since TN is extremely painful, but not life threatening, the goal of therapy is to minimize the dangerous side effects.

If medications do not adequately control TN that progressively worsens, surgical procedures are considered to be the next line of treatment. The surgical procedures considered may include either microvascular decompression (MVD) surgery; alcohol or glycerol injections into the trigeminal nerves; gamma-knife treatment; or some form of nerve injury procedure (rhizotomies). A neurosurgeon can perform MVD surgery if the doctors can successfully determine the cause of the disorder to be compression of an artery on the trigeminal nerve deep inside the skull.

The major disadvantage to surgery is that it requires a neurosurgical operation — with all its complications — to get access to the root of the trigeminal nerve. The success rates of the surgical procedures vary according to the experience of the surgeon or the anaesthetist.

What do we know about heredity and trigeminal neuralgia?

The exact role of heredity regarding TN remains unclear. However, estimates suggest that roughly 5 percent of TN patients have a history of other family members who have had the disorder. Familial TN has been noted to be more common in women, mostly in women older than 50 years. This has led to speculation that there is a dominant pattern of genetic transfer.