Trigeminal Neuralgia

Trigeminal neuralgia is relatively rare, with an estimated 45,000 people in the United States and an estimated one million people worldwide suffering from the disorder. Advanced age is a major risk factor for trigeminal neuralgia – it rarely affects anyone younger than age 50. Hypertension and multiple sclerosis are also risk factors, and the disorder affects more women than men. The most effective, yet also the most invasive treatment for this condition is open surgery.

Researchers at the University of California, Los Angeles, recently analysed the efficacy of linear accelerator radiosurgery to treat trigeminal neuralgia over a 10-year period. The results of this study, The UCLA Experience with LinearAccelerator Radiosurgery for Trigeminal Neuralgia: An Evolution of Treatment Planning and Dose Prescription, will be presented by Zachary A, Smith, MD, 3:33 to 3:45 pm on Tuesday, April 17, 2007, during the 75th Annual Meeting of the American Association of Neurological Surgeons in Washington, D.C. Co-authors are Alessandra Gorgulho, MD, Nikita Bezruky, MS, Nzhde Agazarayan, PhD, Michael Selch, MD, and Antonio A.F. De Salles, MD, PhD.

Stereotactic radiosurgery delivers a single, highly concentrated dose of ionizing radiation to a small, precise target – in the case of trigeminal neuralgia – to the site where the trigeminal nerve leaves the brainstem. It is noninvasive and avoids many of the risks and complications of open surgery and other treatments. Over a period of time and as a result of radiation exposure, the slow formation of a lesion in the nerve interrupts transmission of pain signals to the brain.

In this major study, 164 patients were treated at UCLA between August 1995 and December 2005, and of those, 120 were evaluated at a minimum of six months post surgery. The patients mean age was 65 years. Twenty-two patients had secondary or atypical pain related to a separate disease process or “non-classic” symptoms (bilateral facial pain, pain outside the trigeminal nerve distribution). Thirty-eight patients had undergone prior procedures.

Initially, 15 patients were treated with a low-dose radiation (70 Gy) and 30 percent isodose-line (IDL) radiation at the brainstem. Sixty-nine patients received doses of 90 Gy, with the same percentage of brainstem radiation. In the final 23 patients, the percentage of brainstem radiation was increased to 50 percent, but the overall dose to the nerve remained the same. The results were based on follow-up examination and questioning of 120 patients after radiation treatment. Patients were asked to grade the quality of their pain relief, as well as any degree of numbness that they experienced after the radiosurgery. The following outcomes were noted:

•Regardless of history, 82 patients (68.3 percent) experienced excellent/good pain relief at a mean follow-up of 19.1 months (6-70.6 months).
•Patients experienced relief an average of 2.98 months (immediate-12 months) post surgery.
•Fifteen patients (12.5 percent) experienced recurrent pain.
•Fifty-six (90.3 percent) of 62 patients with idiopathic trigeminal neuralgia without prior procedures experienced significant relief.
•In 69 patients treated with 90Gy and 30 percent IDL at the brainstem, 50 (72.4 percent) had significant relief, and 44.9 percent had subjective numbness.
•In 27 patients with a similar dose, but with 50 percent IDL at the brainstem, 23 (85.2 percent) had excellent/good relief.
•Subjective numbness was experienced in 77.8 percent of patients, which was in general mild, with an average of 2.3 using a 1-5 scale.
•There was no anesthesia dolorosa, facial weakness, or gait disturbance.

“During the course of 10 years of treatment at UCLA, we modified the way we treated this disorder using new parameters and doses as we learned more about patient outcomes. What we concluded is that radiosurgery is a safe and effective treatment option for trigeminal neuralgia, with less risks than other surgical methods, which is especially important for older or frail patients,” stated Dr. Smith.

“However, the radiation dose applied to the brainstem has important implications for efficacy as well as side effects. A larger brainstem dose may yield a higher degree of pain relief, but additionally may lead to an increased rate of numbness,” added Dr. Smith.

Source: Newswise © 2007 Newswise. All Rights Reserved.