Pain from trigeminal and post-herpetic neuralgia is often debilitating. Pharmacotherapy and neurosurgery are the two main treatment approaches with medical management being the main approach as it carries lower risk. However, systemic medication is not without side effects which can themselves be problematic. Botulinum toxin type A (BoTN-A) is a neuromuscular blocker that demonstrated positive effects in patients with neuropathic pain.

The aim of this review was to determine the efficacy of BoTN-A when used as a treatment in patients suffering from trigeminal neuralgia (TN) or post herpetic neuralgia (PHN).

Methods

Searches were conducted in the Cochrane Library, Medline and the Web of Science databases. Randomised controlled trials ( RCTs) comparing BoTN-A with placebo in in patients with painful neuralgia (trigeminal, occipital, glossopharyngeal, and post- herpetic), and at least one clinical endpoint were considered. Studies conducted in children ( ≤ 18 years) and not available in English were excluded. 3 reviewers screened studies for inclusion abstracted data and assessed risk of bias using the Cochrane tool. The primary outcomes were baseline and post treatment intensity of pain and patients reporting pain relief of 50% or greater.

Results

• 6 studies were included
• 2 studies assessed BoTN-A used in PHN and 4 in TN.
• 5 studies were considered to be at unclear risk of bias and 1 at high risk of bias.
• All individual studies showed a statistically significant difference in post treatment pain between the BoTN-A and placebo groups.
• Pooled results showed
  • a difference in post-treatment pain intensity of -3.009 (95% confidence interval -4.566 to -1.453; P < .001) in favor of BoTN-A compared with placebo in managing TN or PHN
  • Patients treated with BoTN-A were 2.89 times more likely to have a “50% reduction of pain or more” compared with patients treated with placebo. Relative risk = 2.89; (95%CI; 1.73-4.85) P < .001

Conclusions

The authors concluded:-

This systematic review with meta-analyses provides moderate evidence for the use of BoTN-A in the management of chronic neuralgias. The authors of this review also found a limited number of case reports and open-label studies that showed favorable outcomes. There is a need to do further well-designed, randomised, placebo-controlled, double-blinded studies for the use of BoTN-A for treating neuropathic pain.

Comments

This well conducted systematic review was only able to include six small RCTs with 2 focusing on post herpetic neuralgia and 4 on trigeminal neuralgia. While the results suggest positive benefits from the use of BoTN-A the fact that the included studies have mainly an unclear or high risk of bias indicates that the findings should be interpreted cautiously. It also needs to be highlighted that all the included studies have been compared with placebo only. While BoTN-A has a good safety profile more well conducted and reported trials are needed and probably some direct comparisons with current medial approaches should be included to clarify therapeutic approaches for these conditions

Links

Primary paper

Shackleton T, Ram S, Black M, Ryder J, Clark GT, Enciso R. The efficacy of botulinum toxin for the treatment of trigeminal and postherpetic neuralgia: a systematic review with meta-analyses. Oral Surg Oral Med Oral Pathol Oral Radiol. 2016 Jul;122(1):61-71. doi: 10.1016/j.oooo.2016.03.003. Epub 2016 Mar 15. Review. PubMed PMID: 27260275