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Written by

Dr Karen H Simpson Dr Karen H Simpson is a consultant in anaesthesia and pain medicine, Leeds, UK

Research update: Botulinum toxin A for treating neuropathic pain in patients with spinal cord injury

Published 4 August 2017

Pain specialist and joint editor Dr Karen H Simpson discusses the results of a randomised controlled trial of botulinum A for treating neuropathic pain in spinal cord injuries

Li G, Lv CA, et al.
A randomized controlled trial of botulinum toxin A for treating neuropathic pain in patients with spinal cord injury
Medicine (Baltimore) 2017;96(20):e6919.

Central neuropathic pain can occur from a variety of causes, for example post-stroke, multiple sclerosis and after spinal cord injury (SCI).1 Botulinum neurotoxin, derived from Clostridium botulinum, has  previously been used therapeutically for focal dystonia, spasticity and chronic migraine, and its potential as a treatment for neuropathic pain has grown.2 

The mechanism of action of botulinum toxin in neuoropathic pain is still far from clear. Recent opinions on the mechanism behind the antinociceptive effects of botulinum toxin suggest that it inhibits the release of peripheral neurotransmitters and inflammatory mediators from sensory nerves.2 Botulinum toxin has seven antigenically different serotypes (A–G). Its main mechanism of action is the inhibition of acetylcholine (ACh) release at pre-synaptic nerve terminals, which results in a reduction of muscle fibre activity and muscle weakness that lasts for a few months.2

Aside from blocking the release of ACh, it has been suggested that botulinum toxin, particularly botulinum toxin A (BTA), may inhibit the release of local nociceptive neuropeptides, such as substance P, calcitonin gene-related peptide and glutamate, as well as the expression of the transient receptor potential vanilloid 1.2 Through this process, BTA may inhibit neurogenic inflammation and peripheral sensitisation. Botulinum toxin is generally well tolerated with few reported irreversible medical adverse effects. When a small amount of BTA enters the circulatory system, systemic or regional complications can occur, for example antibody formation and possible immune-related complications. However, to develop antibodies, large amounts of botulinum toxin are required.2

The authors of this interesting study from China assessed the effect of BTA for treating neuropathic pain in patients with SCI. Forty-four patients with SCI with neuropathic pain were randomly assigned to the intervention (BTA) group and the placebo group. Those in the intervention group received BTA 200 U subcutaneous injection, once daily for eight weeks, to the painful area, whereas those in the placebo group were given a saline placebo. The primary outcome was measured using the visual analogue scale (VAS). The secondary outcomes were measured using the short-form McGill Pain Questionnaire (SF-MPQ), and World Health Organization quality of life (WHOQOL-BREF) questionnaire. Assessments were performed before and after 4 and 8 weeks of intervention.3

Forty-one subjects completed the study. Those who had BTA showed a greater decrease in the VAS score after week 4 and week 8 of treatment when compared with placebo. Significant differences in the SF-MPQ and WHOQOL-BREF were also found between the two groups, with the BTA group doing better than the placebo group. This study, while small, demonstrated the potential for BTA to be useful in managing of neuropathic pain in patients with SCI. However, ideal dosage regimens remain unknown and require further study.3  


  • Dr Karen H Simpson is a consultant in anaesthesia and pain medicine, Leeds, UK

References

  1. Santos Garcia JB, Barbosa Neto JO, et al. Revista Dor. São Paulo 2016;17 (Suppl 1):S67–71.
  2. Oh H-M, Chung ME. Toxins (Basel) 2015; 7(8): 3127–3154.
  3. Li G, Lv CA, et al. Medicine (Baltimore) 2017;96(20):e6919.


Date of preparation: August 2017; MINT/PAEU-17041