WASHINGTON – New evidence on the effectiveness of surgical options for trigeminal neuralgia points to greater safety and longer pain-free intervals when glycerol rhizotomy is used instead of balloon microcompression in patients with multiple sclerosis, as well as when the rhizotomy procedure is repeated, according to two studies reported at the meeting.
Rhizotomy vs. Microcompression
Trigeminal neuralgia occurs in about 2%-4% of patients with MS, said Dr. Grant W. Mallory, a fellow in neurological surgery at the Mayo Clinic, Rochester, Minn. Pain in these patients is more often bilateral than unilateral, and presents at a younger age than in the general population. While the majority of patients respond well to medical therapy with carbamazepine, some do require a surgical approach, he said.
Dr. Mallory and his mentor, Dr. Bruce Pollock, reviewed surgical outcomes and follow-up in 69 MS patients who underwent balloon microcompression and 68 who underwent glycerol rhizotomy during 1997-2010. The patients' mean age was 62 years. Their mean pain duration at baseline varied significantly, between 16 months in those undergoing microcompression and 55 months in those undergoing rhizotomy. Most patients had already undergone a prior procedure (87% of the microcompression patients and 48% of the rhizotomy patients).
The investigators defined an excellent outcome as being pain free and tapered off medications. A good outcome was freedom from pain with continued medication; a failed procedure was no pain relief, or pain recurrence within 1 month.
There was a nonsignificant trend for more patients to report excellent or good pain relief after rhizotomy than after microcompression (74% vs. 65%).
Overall, pain recurred in 86% of patients after a median time of 6 months; the overall median follow-up time was 13 months. Pain recurred significantly later after rhizotomy (mean of 7 months) than after balloon microcompression (5 months). This contributed to a significant difference in the percentage of patients who needed further surgical procedures: 36% with rhizotomy vs. 44% with microcompression. Patients undergoing their first procedure had a longer time to pain recurrence than did those who had a prior intervention (10 months vs. 4 months).
“Comparing our series [of MS patients] to historical controls in patients without MS, our cohort fared substantially worse with regard to initial response rate (69% vs. 90%),” Dr. Mallory said. Historical control patients also had a pain-free interval that was about twice that of patients with MS, he said.
Complications occurred significantly more often in patients treated with balloon microcompression than with rhizotomy (17% vs. 5%).
Although the study was not a randomized trial, Dr. Mallory said his mentor prefers the glycerol rhizotomy as a first-line invasive intervention in MS patients because of its low complication rate. If the patient is unable to tolerate the procedure under a local anesthetic, the surgeon may convert to a balloon microcompression under general anesthesia, Dr. Mallory said.
Benefits of Repeat Rhizotomy
Glycerol rhizotomy conferred greater benefit when it was repeated in patients with trigeminal neuralgia than when it was performed for the first time, according to a review of 547 patients conducted by Matthew Bender and his colleagues at Johns Hopkins University Medical Center, Baltimore.
Mr. Bender, a fourth-year medical student, reported that during 1998-2010, patients at the center who had undergone a prior rhizotomy were 21% less likely to have a failed procedure than were those who underwent an initial rhizotomy. These patients underwent 647 glycerol rhizotomies, including 504 first-time procedures.
The patients' mean age was 64 years, and their mean duration of trigeminal neuralgia was 7 years.
Ten patients in the repeat group and 13 in the initial group had previously undergone radiofrequency thermocoagulation. Other prior procedures included intracranial stereotactic radiosurgery (11 in the initial group and 1 in the repeat group), balloon microcompression (2 in the initial group), and microvascular decompression (19 in the initial group and 10 in the repeat group).
Rhizotomy led to at least 90% pain relief without medications for a significantly greater percentage of patients who had the procedure for a second time, compared with those who had it for the first time (74% vs. 65%). In 12% of the patients in each group there was at least 50% pain relief with minimal medications. Up to 50% pain relief with no medication change occurred in 10% of the initial group and 3% of the repeat group, whereas no pain relief occurred in 13% of the initial group and 10% of the repeat group.
The overall median time to treatment failure was similar between the first-time and repeat treatment groups (27 months vs. 19 months, respectively).