Clinically Significant Placebo Analgesic Response in a Pilot Trial of Botulinum B in Patients with Hand Pain and Carpal Tunnel Syndrome

Abstract

We conducted a pilot trial to assess the effect of botulinum toxin B on palmar pain and discomfort in carpal tunnel syndrome (CTS) patients. Design. Randomized, double-blind, placebo-controlled. Twenty ambulatory CTS patients. Intervention. Botulinum toxin B or placebo injections into three hypothenar muscles anatomically linked or attached to the carpal tunnel and its tentorium, that is, the Opponens Digiti Minimi and Flexor Digiti Minimi, located with electromyography (EMG), and the Palmaris Brevis Muscle, anatomically located without EMG. New York City hospital. Outcomes were measured with numeric ratings, with higher scores indicating worse outcomes. Daily, subjects recorded their 0-10 numeric ratings of overall pain levels and pain-related sleep disturbances. During weekly telephone calls, they reported their 0-10 ratings for overall pain, pain-related sleep disturbance, and CTS-related tingling during the night and day as experienced over the preceding 24 hours. For each of four clinic visits, we averaged each subject's ratings of nine quality of life indicators from the West Haven-Yale Multidimensional Pain Inventory (WHYMPI), each measured on a 0-6 numeric scale. Over the 13-week trial, compared to baseline scores, the following outcomes predominantly showed decreases of statistical significance (P < or = 0.050) or borderline significance (0.050 < P < or = 0.10) for weeks 2 through 8: overall pain per daily diary entries and per weekly telephone reports, and pain-related sleep disturbance in the placebo group per phone report and in the botulinum toxin B group per diary report. CTS painful night tingling and day tingling, as well as the average scores of the WHYMPI quality of life indicators, showed improvements with statistical or borderline significance for almost each follow-up week. Between-group analyses, however, demonstrated that at each follow-up week, there was no statistically significant difference between the two study groups regarding changes from baseline in any study outcome. Botulinum toxin B is not dramatically superior to placebo for the relief of CTS symptoms. Possible explanations of the improvements in each study group are explored.