NEUROSURGERY ARTICLES

TRIGEMINAL NEURALGIA

by Mark Linskey, M.D.

Trigeminal neuralgia (TN) is a facial pain syndrome that affects the distribution of the trigeminal nerve; cranial nerve 5. Typical TN is a sudden shock-like, electric, or sharp-stabbing pain, that resolves as suddenly as it starts. Early on, the pain lasts only seconds and between episodes, the patient is pain-free. As things progress, the pain can last longer and background constant symptoms can develop. The pain usually arrives in an unpredictable manner, but also can be triggered by simple occurrences such as a cold wind on the face, brushing teeth, washing face, putting on make-up, talking, or even chewing. Standard neurological examination is usually normal, but careful testing can reveal subtle sensory reduction in the center of the lower face in up to one-third of patients. The likelihood of decreased facial sensation increases with syndrome duration and with surgical attempts at treatment. Spontaneous periods of symptom disappearance, or remission, lasting up to 6 months are common in up to 50% of patients. However, recurrence is the rule as the syndrome is slowly progressive in severity, frequency, and area of the face affected. TN pain is so excruciating that the patient will abruptly stop anything they are doing, and usually hold themselves immobile until it passes.

TN must be distinguished from other facial pain syndromes, including temporomandibular joint syndrome, post-herpetic neuralgia, cluster headache, and nerve damage pain. Approximately 98% of cases are thought to be caused by vascular compression of the trigeminal nerve, breaking down the insulation of the nerve, as it enters the lower portion of the brain. The remaining 2% of patients include those with: multiple sclerosis, tiny brain stem strokes, or patients with tumors, cysts, or vascular problems near the lower brain. MRI scanning is useful to rule out these alternative causes. However, it does not rule in, or rule out, vascular compression as a cause of the pain.

Initial therapy involves anti-seizure medications to raise the threshold for stimulation of the trigeminal system. Carbamazepine (Tegretol) and oxcarbazepine (Trileptal) have been proven to be the most effective drugs for the treatment of TN. Oxcarbazepine is currently preferred due to a more favorable toxicity and side effect profile, but lacks the long-term proof that it will continue to work as well as carbamazepine. Other medications often tried include Dilantin, Neurontin, and Baclofen, among many others. Approximately 95% of TN patients will initially respond to anti-seizure medicines. Unfortunately, some are intolerant of side effects, some have unpredictable drug reactions, and the remainder tend to gradually become resistant to higher and higher doses as the syndrome progresses. Approximately 56% of patients will fail carbamazepine therapy for one of these reasons over a period of 16 years. Despite these observations, it remains a sad truth that most TN patients have undergone several dental procedures over a period of several years before the correct diagnosis is made. The average TN patient has suffered with the syndrome for greater than 5 years and has seen 2-4 neurologists before they are finally referred to a neurosurgeon.

In experienced hands, surgical alleviation of blood vessel compression of the trigeminal nerve leads to initial cure with no pain and no medications in approximately 80% of patients. This success remains durable at 70% of patients for up to 20 years, which is the longest period observed so far. Other important palliative treatment options include procedures that selectively and partially damage parts of the nerve root. These include heat (percutaneous radiofrequency lesion), chemicals (percutaneous glycerol rhizotomy), mechanical crush (percutaneous balloon compression), or highly concentrated radiation (Gamma Knife Stereotactic Radiosurgery - GKSR). Palliative means that these methods provide relief of symptoms without curing the syndrome, since they do not address the syndrome cause. In essence, they are trading the risk of facial numbness and, more rarely, nerve damage pain, for relief of the pain syndrome.

The definition of success is the most critical factor in comparing procedure results. Patients can often be confused by reports where success is defined less strictly than being pain-free with or without the need for medications. All four palliative procedures are initially effective in about 65-80% of cases, pain-free with or without medications at 1 year. However, because they do not treat the cause of the syndrome, they each have an annual recurrence rate of approximately 6-10% per year, so that by 5 years after treatment this number drops to approximately 50%. The need for repeat palliative intervention is common. Currently, GKSR appears to have the lowest rate of treatment- related numbness, and avoids invasive procedures. Unfortunately, it is not immediately effective, usually requiring 6-8 weeks before pain relief is experienced.

The best treatment option for a given patient is very individual-specific. It centers upon each patient's age, clinical situation, personal goals, priorities, fears, and degree of risk tolerance. Patients are usually best served by referral to a neurosurgeon experienced in all aspects of TN care early in their course so that the personal issues involved, as well as best timing for surgical intervention can be carefully considered without time pressure. Excellent information for patients can be obtained from the national Trigeminal Neuralgia Association (TNA) as well as from the local TNA support group in Orange County currently led by Mrs. Linda Benson (octngroup@yahoo.com). Dr. Linskey at the Department of Neurological Surgery at UCI is one of only 14 physicians nationally from all specialties currently serving on the Medical Advisory Board for the TNA and has extensive experience treating TN patients. He trained at the University of Pittsburgh under Peter Jannetta, who developed and championed microvascular decompression, as well as L. Dade Lunsford who is an expert in radiofrequency lesioning, glycerol rhizotomy and Gamma Knife radiosurgery. Dr. Linskey is able to offer all four procedures for selected patients. Appointments can be made by calling 714-456-6392.

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