NORD gratefully acknowledges Jeffrey Cohen, MD, PhD, Director, Epilepsy Program & Clinical Neurophysiology, Beth Israel Medical, New York NY, for assistance in the preparation of this report.
Trigeminal neuralgia (TN), also known as tic douloureux, is a disorder of the fifth cranial nerve (trigeminal nerve). The disorder is sometimes broken down into type 1 and type 2. TN type 1 (TN1) is characterized by attacks of intense, stabbing pain affecting the mouth, cheek, nose, and/or other areas on one side of the face. TN type 2 (TN2) is characterized by less intense pain, but a constant dull aching or burning pain. Both types of pain can occur in the same individual, even at the same time. In some cases, the pain can be excruciating and incapacitating. If untreated, TN can have a profound effect on a person’s quality of life. In most cases, TN1 develops due to a blood vessel pressing against the trigeminal nerve, but sometimes no underlying cause can be identified (idiopathic). TN2 can be idiopathic, due to compression of the trigeminal nerve, or can occur due to a known underlying cause such as a tumor or multiple sclerosis. It is not known why one person gets symptoms of TN1 versus TN2; it may be due to the number of vessels (e.g. arteries, veins) or the degree of compression. TN can usually be managed through medications, surgery or injections.
There is no consensus or agreed upon classification system for TN. TN1 is also known as classical trigeminal neuralgia. TN2 was once known as atypical or symptomatic TN. However the term "atypical" trigeminal neuralgia has been inconsistently used for individuals who do not have TN1 and remains a vague, undefined term. Consequently, many researchers and patients have advocated eliminating the term "atypical TN", which remains a "wastebasket" diagnosis that serves no useful purpose and is often a disservice to patients. Symptomatic TN is often reserved for cases that develop because of multiple sclerosis. The term trigeminal neuropathic facial pain may be used for pain that results from unintentional injury to the trigeminal nerve, which can result from a variety of conditions including facial trauma, oral surgery, ear, nose and throat surgery, or stroke.
The most significant symptom of trigeminal neuralgia is recurring episodes of intense, short-lived spasms of pain of the lower portion of the face and the jaw. The nose is not infrequently affected. Much less often, the eyes and forehead are affected. In most cases, pain is limited to one side of the face (unilateral). The pain has been compared to a series of “electrical shocks” followed by a steady dull ache. The pain often starts and stops rapidly. Intense pain usually lessens rapidly (usually within several seconds), but the following dull aching pain may persist for as much as one to two minutes. For many individuals, pain is completely gone in between episodes. However, for some individuals, even some individuals with TN1, some degree of pain may persist.
Pain may be triggered by mild tactile stimuli including brushing one’s teeth, washing one’s face, shaving, drinking hot or cold drinks, chewing, talking, blowing one’s nose, a cool breeze, or a light touch to the face. Some episodes may occur without an apparent trigger (spontaneously). Consequently, episodes can occur repeatedly throughout the day. Episodes rarely occur during sleep. The frequency and severity of TN can vary dramatically from one person to another. One person may have as many as one hundred attacks in one day while another person may only have an occasional episode. Attacks typically stop for a period of time and then return. Over time, the pain tends to grow worse with fewer pain-free periods.
Pain may cause affected individuals to grimace, wince, or contort their heads. Skin on the affected side of the face may become flushed and the eye may tear. Some individuals also experience excessive salivation.
With TN2, facial pain is a constant dull or burning sensation and tends to affect a more widespread portion of the face than TN1. In some individuals, the pain will not go away even for short periods of time. The symptoms of TN2 tend to be more difficult to treat.
The pain associated with TN can be so severe that affected individuals avoid simple activities such as brushing one’s teeth and/or avoid social situations for fear of an impending attack. The disorder can cause profound psychological effects such as depression and anxiety.
The exact cause of trigeminal neuralgia is not fully understood. In most cases, the disorder results from a blood vessel pressing against the trigeminal nerve near the base of the brain. This compression may damage the nerve and cause excess bursts of neurological activity. The reason a blood vessel ends up pressing against the trigeminal nerve is not fully understood.
Some researchers believe that the specific injury to the trigeminal nerve involves damage to, or loss of, the myelin sheath from nerve fibers (demyelination) causes the symptoms. The myelin sheath is the fatty covering of nerve cells and fibers. Some researchers believe that damage to the myelin sheath results in increased electrical activity in the trigeminal nerve, which triggers the pain regions of the brain.
In rare cases, tumors may press against the trigeminal nerve. Multiple sclerosis is also sometimes cited as a cause of TN due to deterioration of the myelin sheath. In many cases, no underlying cause of TN can be identified (idiopathic).
The trigeminal nerve is one of the 12 pairs of nerves that arise from the underside of the brain. The trigeminal nerve has three main branches. Each of these three branches further splits into multiple smaller branches. The ophthalmic or upper branch provides sensation to the area of the eyes, forehead, front of the head and the scalp. The maxillary or middle branch provides sensation to cheeks, around the nose, top lip, upper jaw, and teeth and gums. The mandibular or lower branch provides sensation to the bottom lip, lower jaw, and teeth and gums. TN pain can result from one or more of these three branches. However, the middle or lower branches are affected more often than the upper branch.
Trigeminal neuralgia affects females slightly more often than males. Although the exact incidence is unknown, approximately 10,000-15,000 new cases occur each year in the United States. The disorder most frequently affects individuals more than 50 years of age. However, cases can occur in younger adults as well. In younger individuals, the cause is often idiopathic, but when compared to older adult cases are more likely to be caused by damage to the central nervous system as in individuals with multiple sclerosis. Although extremely rare, TN can occur in children.
A diagnosis of trigeminal neuralgia is based upon identification of characteristic symptoms, a detailed patient history, and a thorough clinical evaluation. TN should be suspected in individuals with facial pain affecting one side of the face. Because there is no specific diagnostic test for TN, physicians rely on individual’s personal history and description of symptoms when considering a diagnosis of TN.
One published set of guidelines for diagnosing TN is from the International Headache Society.
For classical TN:
For symptomatic TN:
Certain imaging techniques such as magnetic resonance imaging (MRI) can be used to assess for or rule out underlying causes of TN including tumors or multiple sclerosis. An MRI uses a magnetic field and radio waves to produce cross-sectional images of particular organs and bodily tissues. However, it is difficult to see a blood vessel pressing against the trigeminal nerve root through a "routine" MRI.
Facial pain experts may order a "targeted" MRI, which usually means using a high resolution MR(3T), with special attention paid to the trigeminal nerve. This test may be performed with or without gadolinium, a contrast agent that is used to enhance the scanning results and supply a more detailed picture of tissues such as the brain or blood vessels. On some MR machines this is called FIESTA sequences. This means that 1 millimeter thin sections are taken, in a coronal plane, without any skips in between images, through the entire course of the trigeminal nerve. This results in a high likelihood of finding the offending vessel. This targeted method often yields an identified cause even in individuals who have been told that they have a normal MRI (routine study).
Specific therapeutic procedures and interventions for TN may vary, depending upon numerous factors, such as disease severity; underlying cause (if known); the presence or absence of certain symptoms; an individual’s age and general health; and/or other elements. Decisions concerning the use of particular drug regimens, surgical therapies, and/or other treatments should be made by physicians and other members of the health care team in careful consultation with the patient based upon the specifics of his or her case; a thorough discussion of the potential benefits and risks, including possible side effects and long-term effects; patient preference; and other appropriate factors.
The initial therapy for individuals with TN is usually the use of medications, particularly the anti-seizure medications (anti-convulsants), carbamazepine or oxycarbazepine. When used in the early stages, these drugs are generally effective in reducing pain of affected individuals. Most people begin with a low dose that is gradually increased until the pain goes away. The exact dosage needed for each individual will vary. Despite its initial effectiveness, the benefits of these drugs may lessen over time. As with most drugs, carbamazepine can be associated with side effects. Oxycarbazepine, which is a newer medication that is related to carbamazepine, is generally associated with fewer side effects than carbamazepine.
Additional anti-seizure medications that have been used to treat TN in smaller studies or case reports include topiramate, gabapentin, pregabalin, clonazepam, phenytoin, lamotrigine, and valproic acid.
Over time, in many cases, these drugs may become less effective or ineffective. When one anti-seizure drug loses effectiveness, another anti-seizure medication may be tried. More than one anti-seizure medication may be necessary to control pain in an affected individual. Eventually, anti-seizure medications may stop providing relief.
Muscle relaxants, such as baclofen, may also be used. Such medications may be used alone or in conjunction with anti-seizure medication. Tricyclic antidepressant medications such as amitriptyline and nortriptyline can dampen pain transmission in individuals with TN2. Common pain relievers such as opioids are generally ineffective in TN1, but may provide some relief in TN2.
If medications fail to control pain or become ineffective, surgery is recommended. There are several different surgical techniques that have been used to treat individuals with TN. Surgical techniques are generally not used unless other therapies have failed or become ineffective. The decision to undergo surgery to treat TN can depend on several factors. Some physicians and individuals in the TN community believe that surgical interventions should occur sooner rather than later. There is evidence that affected individuals have a better response to microvascular decompression if the surgery is done within seven years of the initial diagnosis rather than later. Surgery should be considered early in an individual who does not have an adequate response to the two front-line medications, whether these medications are used in succession or in combination. An inadequate response can be defined as incomplete pain relief affecting activities of daily living or requiring such high doses of medication to relieve the pain that the side effects limit functioning.
Decisions concerning the use of a particular surgery, drug regimens, and/or other treatments should be made by physicians and other members of the health care team in careful consultation with parents or a patient based upon the specifics of the individual case; a thorough discussion of the potential benefits and risks, including possible side effects and long-term effects; patient preference; and other appropriate factors.
One of the most common procedures to treat TN1 is microvascular decompression, also known as the Janetta procedure. This procedure involves moving the blood vessel that is pressing against the trigeminal nerve and inserting a soft cushion between the nerve and the vessel. This allows the trigeminal nerve to recover, eventually relieving the pain. Microvascular decompression can result in sustained pain relief of greater than 10 years in some cases. This procedure is the only non-destructive one that will leave trigeminal nerve function intact, but the procedure is the most invasive and carries a small risk of serious complications. During the procedure, the physician makes a small incision behind the ear on the same side of the head where the pain is located and creates a small hole in the skull to gain access the trigeminal nerve and the blood vessels that are compressing it.
Another possible treatment is stereotactic surgery, which includes procedures known as Gamma Knife and CyberKnife. These procedures employ a highly concentrated beam of ionizing radiation that is delivered to a specific target at the root of the trigeminal nerve. The radiation creates a lesion near the nerve root that disrupts the transmission of pain signals to the brain. Pain relief may be delayed, however, by up to several weeks or months. Additionally, in approximately 50% of individuals, pain returns within three years. These procedures are the least invasive surgical techniques for treating individuals with TN and can be repeated if pain recurs.
Three additional procedures involve damaging the trigeminal nerve to interrupt the transmission of pain signals to the brain. These procedures are percutaneous balloon compression, percutaneous glycerol rhizotomy, and percutaneous stereotactic rhizotomy. They involve the insertion of a needle through the cheek and into the trigeminal nerve. Percutaneous balloon compression involves inserting a tiny balloon in the trigeminal nerve near the area where the pain fibers are located. The balloon is inflated, damaging the nerve fibers. Then the balloon is deflated and removed. Percutaneous glycerol rhizotomy involves injecting glycerol, a chemical compound, into the trigeminal nerve to damage the nerve. Percutaneous stereotactic rhizotomy, also known as radiofrequency lesioning, involves uses an electrode to apply heat to damage nerve fibers.
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