Trigeminal neuralgia

Definition

Trigeminal neuralgia is a disorder of the trigeminal nerve that causes severe facial pain . It is also known as tic douloureux, Fothergill syndrome, or Fothergill's syndrome.

Description

Trigeminal neuralgia is a rare disorder of the sensory fibers of the trigeminal nerve (fifth cranial nerve), which innervate the face and jaw. The neuralgia is accompanied by severe, stabbing pains in the jaw or face, usually on one side of the jaw or cheek, which usually last for some seconds. The pain before treatment is severe; however, trigeminal neuralgia as such is not a life-threatening condition. As there are actually two trigeminal nerves, one for each side of the face, trigeminal neuralgia often affects only one side of the face, depending on which of the two trigeminal nerves is affected.

Demographics

There have been no systematic studies of the prevalence of trigeminal neuralgia, but one widely quoted estimate published in 1968 states that its prevalence is approximately 15.5 per 100,000 persons in the United States. Other sources state that the annual incidence is four to five per 100,000 persons, which would imply a higher prevalence (prevalence is the number of cases in a population at a given time; incidence is the number of new cases per year). In any case, the disorder is rare. Onset is after the age of 40 in 90% of patients. Trigeminal neuralgia is slightly more common among women than men.

Causes and symptoms

A number of theories have been advanced to explain trigeminal neuralgia, but none explains all the features of the disorder. The trigeminal nerve is made up of a set of branches radiating from a bulblike ganglion (nerve center) just above the joint of the jaw. These branches divide and subdivide to innervate the jaw, nose, cheek, eye, and forehead. Sensation is conveyed from the surfaces of these parts to the upper spinal cord and then to the brain; motor commands are conveyed along parallel fibers from the brain to the muscles of the jaw. The sensory fibers of the trigeminal nerve are specialized for the conveyance of cutaneous (skin) sensation, including pain.

In trigeminal neuralgia, the pain-conducting fibers of the trigeminal nerve are somehow stimulated, perhaps self-stimulated, to send a flood of impulses to the brain. Many physicians assume that compression of the trigeminal nerve near the spinal cord by an enlarged loop of the carotid artery or a nearby vein triggers this flood of impulses. Compression is thought to cause trigeminal neuralgia when it occurs at the root entry zone, a. 19–.39 in (0.5–1.0 cm) length of nerve where the type of myelination changes over from peripheral to central. Pressure on this area may cause demyelination, which in turn may cause abnormal, spontaneous electrical impulses (pain).

Compression is apparently the cause in some cases of trigeminal neuralgia, but not in others. Other theories focus on complex feedback mechanisms involving the subnucleus caudalis in the brain. Multiple sclerosis , which demyelinates nerve fibers, is associated with a higher rate of trigeminal neuralgia. Brain tumors can also be correlated with the occurrence of trigeminal neuralgia. Ultimately, however, the exact mechanisms of trigeminal neuralgia remain a mystery.

Trigeminal neuralgia was first described by the Arab physician Jurjani in the eleventh century. Jurjani was also the first physician to advance the vascular compression theory of trigeminal neuralgia. French physician Nicolaus André gave a thorough description of trigeminal neuralgia in 1756 and coined the term tic douloureux. English physician John Fothergill also described the syndrome in the middle 1700s, and the disorder has sometimes been called after him. Knowledge of trigeminal neuralgia slowly grew during the twentieth century. In the 1960s, effective treatment with drugs and surgery began to be available.

The pains of trigeminal neuralgia have several distinct characteristics, including:

• They are paroxysmal, pains that start and end suddenly, with painless intervals between.
• They are usually extremely intense.
• They are restricted to areas innervated by the trigeminal nerve.
• As seen on autopsy, nothing is visibly wrong with the trigeminal nerve.
• About 50% of patients have trigger zones, areas where slight stimulation or irritation can bring on an episode of pain. Painful stimulation of the trigger zones is actually less effective than light stimulation in triggering an attack.
• The disorder comes and goes in an unpredictable way; some patients show a correlation of attack frequency or severity with stress or menstrual cycle.

Stimulation of the face, lips, or gums, such as talking, eating, shaving, tooth-brushing, touch, or even a current of air, may trigger the severe knifelike or shocklike pain of trigeminal neuralgia, often described as excruciating. Trigger zones may be a few square millimeters in size, or large and diffuse. The pain usually starts in the trigger zone, but may start elsewhere. Approximately 17% of patients experience dull, aching pain for days to years before the onset of paroxysmal pain; this has been termed pretrigeminal neuralgia.

The pain of trigeminal neuralgia is severe enough that patients often modify their behaviors to avoid it. They may suffer severe weight loss from inability to eat, become unwilling to talk or smile, and cease to practice oral hygiene. Trigeminal neuralgia tends to worsen with time, so that a patient whose pain is initially well-controlled with medication may eventually require surgery.

Diagnosis

Trigeminal neuralgia is a possible diagnosis for any patient presenting with severe, stabbing, paroxysmal pain in the jaw or face. However, the most common causes of facial pain are dental problems and diseases of the mouth. Trigeminal neuralgia must also be differentiated from migraine headaches and from other cranial neuralgias (i.e., neuralgias affecting cranial nerves other than the trigeminal). Many persons with trigeminal neuralgia see multiple physicians before getting a correct diagnosis, and may have multiple dental procedures performed in an effort to relieve the pain.

There is no definitive, single test for trigeminal neuralgia. Imaging studies such as computed tomography (CT ) scans or magnetic resonance imaging (MRI) may help to rule out other possible causes of pain and to indicate trigeminal neuralgia. High-definition MRI angiography of the trigeminal nerve and brain stem is often able to spot compression of the trigeminal nerve by an artery or vein. Trial and error also has its place in the diagnostic process; the physician may initially give the patient carbamazepine (an anticonvulsant) to see if this diminishes the pain. If so, this is positive evidence for the diagnosis of trigeminal neuralgia.

Treatment team

Many different sorts of health care professionals may be consulted by patients with trigeminal neuralgia, including dentists, neurologists, neurosurgeons, oral surgeons, and ear, nose, and throat surgeons. A referral to a neurologist should always be sought, as trigeminal neuralgia is essentially a neurological problem.

Treatment

Treatment is primarily with drugs or surgery. Drugs are often preferred because of their lower risk, but may have intolerable side effects such as nausea or ataxia (loss of muscle coordination). The two most effective drugs are carbamazepine (an anticonvulsant often used in treating epilepsy ), used for trigeminal neuralgia since 1962, and gabapentin . Drugs are prescribed initially in low doses and increased until an effective level is found. Other drugs in use for trigeminal neuralgia are phenytoin, baclofen, clonazepam, lamotrigine topiramate , and trileptal.

Carbamazepine, which inhibits the activity of sodium channels in the cell membranes of neurons (thereby reducing their excitability), is deemed the most effective medication for trigeminal neuralgia. Unfortunately, it has many side effects, including vertigo (dizziness ), ataxia, and sedation (mental dullness). This may make it harder to treat elderly patients, who are more likely to have trigeminal neuralgia. Carbamazepine provides complete or partial relief for as many as 70% of patients. Phenytoin is also a sodium channel blocker, and also has adverse side effects, including hirsutism (increased facial hair), coarsening of facial features, and ataxia.

For patients whose pain does not respond adequately to medication, or who cannot tolerate the medication itself due to side effects, surgery is considered. Approximately 50% of trigeminal neuralgia patients eventually undergo surgery of some kind for their condition. The most common procedure is microvascular decompression, also known as the Jannetta procedure after its inventor. This involves surgery to separate the vein or artery compressing the trigeminal nerve. Teflon or polivinyl alcohol foam is inserted to cushion the trigeminal nerve against the vein or artery. This procedure is often effective, but some physicians argue that since other procedures that disturb or injure the trigeminal nerve are also effective, the benefit of microvascular decompression surgery is not relief of compression but disturbance of the trigeminal nerve, causing nonspecific nerve injury that leads to a change in neural activity.

Other surgical procedures are performed, some of which focus on destroying the pain-carrying fibers of the trigeminal nerve. The most high-tech and least invasive procedure is gamma-ray knife surgery, which uses approximately 200 convergent beams of gamma rays to deliver a high (and highly localized) radiation dose to the trigeminal nerve root. Almost 80% of patients undergoing this procedure experience significant relief with this procedure, although about 10% develop facial paresthesias (odd, non-painful sensations not triggered by any external stimulus).

Clinical trials

As of mid-2004, one clinical trial related to trigeminal neuralgia was recruiting patients. This study, titled "Randomized Study of L-Baclofen in Patients with Refractory Trigeminal Neuralgia," was being carried out at the University of Pennsylvania, Pittsburgh, and was sponsored by the FDA Office of Orphan Products Development (dedicated to promoting the development of treatments for diseases too rare to be considered profitable by pharmaceutical companies). Its goal is to test the effectiveness and safety of the drug L-baclofen in patients with refractory (treatment-resistant) trigeminal neuralgia. The contact is Michael J. Soso at the University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, 15261, telephone (412) 648-1239. Forms of baclofen have been used for the treatment of trigeminal neuralgia since 1980.

Prognosis

Trigeminal neuralgia is not life threatening. It tends, however, to worsen with time, and many patients who initially were successfully treated with medication must eventually resort to surgery. Some doctors advocate surgery such as microvascular decompression early in the course of the syndrome to forestall the demyelination damage. However, there is still much controversy and uncertainty about the causes of trigeminal neuralgia and the mechanism of benefit even in those treatments that provide relief for many patients.

Resources

BOOKS

Fromm, Gerhard H., and Barry J. Sessle, eds. Trigeminal Neuralgia: Current Concepts Regarding Pathogenesis and Treatment. Stoneham, MA: Butterworth-Heinemann, 1991.

Zakrzewska, Joanna M., and P. N. Patsalos. Trigeminal Neuralgia. London: Cambridge Press, 1995.

PERIODICALS

Brown, Cassi. "Surgical Treatment of Trigeminal Neuralgia." AORN Journal (November 1, 2003).

Mosiman, Wendy. "Taking the Sting out of Trigeminal Neuralgia." Nursing (March 1, 2001).

OTHER

Komi, Suzan, and Abraham Totah. "Understanding Trigeminal Neuralgia." eMedicine. April 30, 2004 (May 27, 2004). <http://www.emedicine.com/med/topic2899.htm>.

ORGANIZATIONS

Trigeminal Neuralgia Association. 2801 SW Archer Road, Gainesville, FL 32608. (352) 376-9955; Fax: (352) 376-8688. [email protected]. <http://www.tnasupport.org/>.

Larry Gilman

Trigeminal Neuralgia

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 tooth-brushing 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

Resources

ORGANIZATIONS

Chronic Pain Outreach. 822 Wycliff Ct., Manassas, VA 22110. (703) 368-7357.

National Chronic Pain Outreach Association, Inc. P.O. Box 274, Millboro, VA 24460-9606. (540) 997-5004.

National Institute of Neurological Disorders and Stroke. P.O. Box 5801, Bethesda, MD 20824. (800) 352-9424. 〈http://www.ninds.nih.gov/index.htm〉.

Trigeminal Neuralgia Association. P.O. Box 785, Barnegat Light, NJ 08006. (609) 361-1014.

KEY TERMS

Multiple sclerosis— A progressive disease of the central nervous system in which the coverings of nerves in the brain and spinal cord are destroyed.

trigeminal neuralgia (tic douloureux) n. see neuralgia.