Combined Stimulation Improves Pain, Not Outcome, in Migraine

Meg Barbor

October 09, 2015

NEW ORLEANS — Long-term pain reduction with combined occipital and supraorbital nerve stimulation for chronic migraine does not imply improved long-term functional outcome, a new study shows.

"Nowadays, neuromodulation has been established as a viable surgical treatment for primary headache; moreover, combined occipital and supraorbital nerve stimulation offers concordant stimulation to holocephalic pain," said Shannon W. Clark, MD, a neurosurgeon at Thomas Jefferson University Hospital in Philadelphia, Pennsylvania. "Therefore, there has been an anecdotally higher success rate than with occipital nerve stimulation alone."

"However despite the established efficacy, there is one unsolved problem for neuromodulation for headache, and that is the lack of functional outcome studies," she added. Because of the paucity of these types of studies, the correlation between pain efficacy and functional outcome is unknown.

Dr Clark presented their results here at the Congress of Neurological Surgeons (CNS) 2015 Annual Meeting.

Compromised Function

In addition to having severe daily headache, patients with chronic migraine who undergo surgery typically display compromised functional activity and depression. In this study, Dr Clark and her colleagues aimed to elucidate the potential functional outcome for combined stimulation for migraine and that outcome’s association with pain efficacy.

They conducted a retrospective chart review on a population of patients with chronic migraine who had both supraorbital and occipital nerve stimulators and also had preoperative and postoperative Migraine Disability Assessment Test (MIDAS) and Beck Depression Inventory (BDI) scores at 3-month intervals for long-term follow-up.

The MIDAS test comprises three scores: total MIDAS, which is the sum of five questions concerning work, school, and social activities missed in the past 3 months (the higher the number, the worse the total MIDAS); the MIDAS-A score, which simply asks, "How many days in the past 3 months did you have headache?"; and the MIDAS-B score, a visual analogue scale measuring average headache in the past 3 months (range, 0 to 10).

Outcome measures included short- and long-term efficacy evaluation, a preoperative and postoperative functional outcome comparison, and a long-term functional outcome analysis in the responder subgroup.

A total of 16 patients (12 women) with follow-up of 5 to 80 months (average, 44.5 months) were studied. Eight had a positive response (50% improvement in headache) at most recent follow-up.

"We found that at the short-term follow-up of 2 months, we had 75% efficacy, and at the long-term follow-up, which is the most recent follow-up, the efficacy dropped to 50%," said Dr Clark.

All four patients who converted from positive to negative responders did so within the first year of implantation; five of the negative responders had already had their device removed because of discomfort and/or device malfunction.

An inverse correlation between pain efficacy and disability status was also observed. "In other words, the predictive factor for lack of a positive response was patients' disability status," Dr Clark explained.

Improvement in Short-term Function

Investigators performed a short-term functional outcome univariate analysis. Despite suggestive trends, no statistical significance was reached with analysis of outcomes of total MIDAS, MIDAS-B, and BDI scores separately between the positive and negative responder groups.

"We were not able to reach any statistical significance, mainly because we only had 16 patients in the study, and the univariate analysis just had too much of a variance," she said. "There was more improvement in MIDAS-B in the positive responder group, but the P value was just not significant enough."

"So, we did a multivariate analysis in order to decrease the variance and study the functional outcomes in short term," she went on to explain. "When I say short term, I mean comparing the preoperative MIDAS and BDI versus the first postoperative MIDAS and BDI — and then we reached statistical significance."

A multivariate analysis of the perioperative functional metrics demonstrated that a positive response was significantly correlated with net improvements in total MIDAS, MIDAS-B, and BDI scores combined.

"So when these scores were analyzed together, patients that had positive response actually had significantly improved functional outcomes in the first 3-month postoperative period," Dr Clark added.

Statistical significance was not found when the authors conducted a multivariate analysis on long-term functional outcomes, so they performed a subgroup analysis on the eight positive responders and plotted out functional outcomes at each subsequent follow-up.

Total MIDAS and BDI scores increased during the follow-up period despite stable pain response. MIDAS-B scores also slightly increased as time progressed but did not increase as significantly as total MIDAS or BDI.

"We really can’t draw broad conclusions based on the small number of patients in this study, but it does provide a good foundation for building on future larger randomized trials," said session moderator Ashwin Viswanathan, MD, clinical assistant professor of neurosurgery at the University of Texas MD Anderson Cancer Center in Houston.

"It validates some of the things that we've known, which is combined supraorbital and occipital stimulation is an effective therapy for a segment of patients with migraines, but it’s just a question of identifying these patients preoperatively," he told Medscape Medical News.

Although Dr Clark and her co-investigators hypothesized that positive pain response to combined stimulation is correlated with improved functional outcomes, they found that long-term pain reduction did not imply improved long-term functional outcome. However, short-term improvement in functional outcome was observed with the use of combined stimulation for chronic migraine.

The researchers conclude that the functional status of migraineurs is likely affected by complex factors in addition to their perceived pain severity.

"Creating appropriate metrics of quality of life for stimulator populations remains a challenge," said Dr Clark. "And this is important in the future in order for us to assess functional outcomes."

Dr Clark and Dr Viswanathan have disclosed no relevant financial relationships.

Congress of Neurological Surgeons (CNS) 2015 Annual Meeting. Presented September 29, 2015.

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