Cranial Anatomy - Trigeminal Neuralgia

What is Trigeminal Neuralgia?

Trigeminal neuralgia or tic douloureux is sometimes 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 is usually limited to one side of the face.

Although trigeminal neuralgia cannot always be cured, there are treatments available to alleviate the excruciating pain. Anticonvulsive medications are normally 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 and the other 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 your brain and travels inside your skull, it divides into three smaller branches, controlling sensations throughout your face:

• The first branch controls sensation in your eye, upper eyelid and forehead.
• The second branch controls sensation in your lower eyelid, cheek, nostril, upper lip and upper gum.
• The third branch controls sensations in your jaw, lower lip, lower gum and some of the muscles you use for chewing.

Prevalence and Incidence

Advanced age is a major risk factor for trigeminal neuralgia. The disorder is more common in women than in men and rarely affects anyone younger than age 50. Hypertension and multiple sclerosis are also risk factors. Trigeminal neuralgia is relatively rare. An estimated 45,000 people in the United States and an estimated one million people worldwide, suffer from trigeminal neuralgia.

While inheritance has not been conclusively established, there is evidence that trigeminal neuralgia is tied to family history. According to the Trigeminal Neuralgia Association, 4.1 percent of patients with unilateral trigeminal neuralgia and 17 percent of patients with bilateral trigeminal neuralgia report a family history of the disorder.

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 normal artery or vein and the trigeminal nerve at the base of your brain. This places pressure on the nerve as it enters your brain and causes the nerve to misfire.

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

What symptoms can it cause?

Most patients report that their pain begins spontaneously out of nowhere. Other patients say that 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 is often first experienced along the upper or lower jaw and 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 classic or 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. Atypical pain is often present as a constant, burning sensation affecting a more diffuse 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 less than 20 seconds, with an excruciating stabbing pain. The pain often leaves patients with uncontrollable facial twitching, which is why the disorder is also known as tic douloureux.

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. 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 tumour or multiple sclerosis is irritating the trigeminal nerve. However, unless a tumour or multiple sclerosis is the cause, imaging of the brain will seldom reveal the precise reason why the nerve is being irritated. The vessel abutting 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 is usually diagnosed based on the description of the symptoms provided by the patient.

Treatment

Years ago trigeminal neuralgia was not well understood and treatment was nearly nonexistent. Today, there are several effective ways to alleviate the pain, including a variety of medications. 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 efficacy over time. Some patients may need a higher dose to reduce the pain or may need 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.

Surgery

If medications have proven ineffective in treating trigeminal neuralgia, there are several surgical procedures which may help control the pain. Surgical treatment is divided into two categories: percutaneous (through the skin) and open. In general, percutaneous approaches are preferred in older or medically frail patients, in patients with multiple sclerosis, or in individuals who have failed to attain pain relief from the open approach. The open approach is recommended for younger and healthier patients. All of the procedures have varying success rates and some side effects, such as recurrence of pain and facial numbness.

Click here for Trigeminal Neuralgia Association - Support Group Meeting September 2011

Click here for Trigeminal Neuralgia Association - Newsletter March 2011