Objective: To evaluate safety, tolerability and efficacy of botulinum toxin type A for limb pain in advanced Parkinson´s disease (PD).

Background: Pain is a frequent symptom in PD and therapeutic alternatives are scarce. Evidence is limited and many of the frequently used treatments for pain can exacerbate other symptoms, including constipation, hallucinations, and confusion, especially in advanced stages of the disease. Botulinum toxin has been used to treat pain in other medical conditions in PD, and due to the local nature of the injections, should be better tolerated. 

Methods: A randomized, double blind cross over versus placebo study of botulinum toxin type A (BTXA) for limb pain (dystonia and rigidity) in advanced PD (Hoehn and Yahr 3-5, including post STN DBS) was conducted between November 2014 and December 2015. Fourteen subjects were included and 12 completed the trial. Subjects received individualized BTXA/Placebo dosing according to pain distribution in limbs. The primary outcome was a subjective measure of change in global pain on a Numeric Rating Scale at 4 and 12 weeks’ post injections and on a Visual Analogue Scale 12 weeks after treatment. Secondary outcomes included the percentage of responders (by at least 2 points reduction in NRS); Physician rated Clinical Global Impression, MDS-UPDRS and PDQ-39 scores, and adverse events.

Results: Treatment with BTXA (average dose = 241.66 U) produce a significant reduction in NRS 4 weeks after injections (- 1.75 points, range from -3 to 7, p=0,033). However, there was no significant difference compared to placebo (p=0,70). Participants with dystonic pain showed a greater reduction in NRS after 4 weeks when treated with BTXA (2.66 points versus 0.75 for placebo). However, comparing BTXA versus placebo there were no significant differences for any of the outcomes. All other secondary outcome was not significantly different. UPDRS III showed an increase of 7.54 points in the BTXA group. There were no significant adverse events.

Conclusions: Our results show that targeting BTXA injections were safe in patients with limb pain and advanced PD, however, the present study failed to show a significant effect when compared to placebo. Further studies may be focused in evaluating the effect of BTX particularly in dystonic pain.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/a-double-blind-randomized-placebo-controlled-study-of-botulinum-toxin-type-a-for-limb-pain-in-advanced-parkinsons-disease/