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.
Trigeminal neuralgia (TN), also called tic douloureux, is a chronic pain condition that causes extreme, sporadic, sudden burning or shock-like face pain. The pain seldom lasts more than a few seconds or a minute or two per episode. The intensity of pain can be physically and mentally incapacitating.
TN pain is typically felt on one side of the jaw or cheek. Episodes can last for days, weeks, or months at a time and then disappear for months or years. In the days before an episode begins, some patients may experience a tingling or numbing sensation or a somewhat constant and aching pain.
The attacks often worsen over time, with fewer and shorter pain-free periods before they recur. The intense flashes of pain can be triggered by vibration or contact with the cheek (such as when shaving, washing the face, or applying makeup), brushing teeth, eating, drinking, talking, or being exposed to the wind.
TN occurs most often in people over age 50, but it can occur at any age, and is more common in women than in men. There is some evidence that the disorder runs in families, perhaps because of an inherited pattern of blood vessel formation. Although sometimes debilitating, the disorder is not life-threatening.
Atypical features may coexist with some of the previously described symptoms. These atypical features may include a constant pain that is not always triggered by light touch. Patients with constant pain and TN are sometimes diagnosed as having atypical trigeminal neuralgia.
Approximately 14,000 people develop TN each year in the United States; about 140,000 people have the condition. Trigeminal neuralgia is more common in patients with multiple sclerosis.
The disorder is characterized by episodes of intense facial pain that last from a few seconds to several minutes or hours. The episodes of intense pain may occur paroxysmally. To describe the pain sensation, patients may describe a trigger area on the face so sensitive that touching or even air currents can trigger an episode; however, in many patients the pain is generated spontaneously without any apparent stimulation.
It affects lifestyle as it can be triggered by common activities such as eating, talking, shaving and brushing teeth. Wind, high pitched sounds, loud noises such as concerts or crowds, chewing, and talking can aggravate the condition in many patients. The attacks are said by those affected to feel like stabbing electric shocks, burning, pressing, crushing, exploding or shooting pain that becomes intractable.
Individual attacks usually affect one side of the face at a time, lasting from several seconds to a few minutes and repeat up to hundreds of times throughout the day. The pain also tends to occur in cycles with remissions lasting months or even years. 10-12% of cases are bilateral, or occurring on both sides.
This normally indicates problems with both trigeminal nerves since one serves strictly the left side of the face and the other serves the right side. Pain attacks are known to worsen in frequency or severity over time, in some patients. Many patients develop the pain in one branch, then over years the pain will travel through the other nerve branches.
The most frequent cause of trigeminal neuralgia is a blood vessel pressing on the nerve near the brain stem. Over time, changes in the blood vessels of the brain can result in blood vessels rubbing against the trigeminal nerve root. The constant rubbing with each heartbeat wears away the insulating membrane of the nerve, resulting in nerve irritation.
TN may be part of the normal aging process but in some cases it is the associated with another disorder, such as multiple sclerosis or other disorders characterized by damage to the myelin sheath that covers certain nerves.
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.
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.
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.
In addition to a thorough history and physical examination, magnetic resonance imaging (MRI) of the brain is recommended. This procedure helps identify a brain tumor in the rare cases in which it is present along with TN. It may also help to diagnose multiple sclerosis. Often when the MRI is performed, some contrast material is injected into the vein so that the appearance of a small tumor, blood vessel, or other structures in the brain can be enhanced and made easier to detect.