A prospective randomized double-blinded pilot study to examine the effect of botulinum toxin type a injection versus lidocaine/depomedrol injection on residual and phantom limb pain: Initial report

Objective: Botulinum toxin type A (Botox) injection has been used to manage pain. However, it remains to be proved whether Botox injection is effective to relieve residual limb pain (RLP) and phantom limb pain (PLP). Design: Randomized, double-blinded pilot study. Setting: Medical College and an outpatient clinic in Department of Physical Medicine and Rehabilitation. Participants: Amputees (n=14) with intractable RLP and/or PLP who failed in the conventional treatments. Interventions: Study amputees were randomized to receive 1 Botox injection versus the combination of Lidocaine and Depomedrol injection. Each patient was evaluated at baseline and every month after the injection for 6 months. Main Outcome Measure: The changes of RLP and PLP as recorded by VAS, and the changes of the pressure pain tolerance as determined by a pressure algometer. Results: All patients completed the protocol treatment without acute side effects, and monthly assessments of RLP, PLP, and pain tolerance after the treatment. The time trend in the outcomes was modeled as an immediate change owing to the treatment followed by a linear tread afterward. Repeated measures were incorporated using mixed effects modeling. We found that both Botox and Lidocaine/Depomedrol injections resulted in immediate improvements of RLP (Botox: P=0.002; Lidocaine/Depomedrol: P=0.06) and pain tolerance (Botox: P=0.01; Lidocaine/Depomedrol: P=0.07). The treatment effect lasted for 6 months in both groups. The patients who received Botox injection had higher starting pain than those who received Lidocaine/Depomedrol injection (P=0.07). However, there were no statistical differences in RLP and pain tolerance between these 2 groups. In addition, no improvement of PLP was observed after Botox or Lidocaine/Depomedrol injection. Conclusions: Both Botox and Lidocaine/Depomedrol injections resulted in immediate improvement of RLP (not PLP) and pain tolerance, which lasted for 6 months in amputees who failed in conventional treatments.