One of the many things I’m involved with online is running the London Pain Consortium twitter account, and recently someone got in touch asking about botox treatment for complex regional pain syndrome (CRPS), so I decided to write a wee post summarising what is published on the subject. Please note: I am not a doctor, or a CRPS specialist! Just a bog standard pain researcher, with experience in systematic reviews…
I found 4 publications, 2 case study format, and the other 2 involving between 14 and 37 patients. 3 of these reported that botulinum A toxin (Botox) improved symptoms when injected into trigger points and other areas affected by CRPS… sounds promising, but it’s important to also look at the quality of the study before deciding to trust what it is claiming. I have an inherent distrust in case studies – for one thing, they rarely feature qualitative outcomes measures, relying more on subjective descriptions of patient condition, and for another, they are a good example of publication bias, i.e. people prefer to share the positive rather than negative. It’d be very unusual to read a published case study describing a failed treatment – the fact is, pain is such a complex condition that many treatments will only work in very narrowly defined populations, so without good information on who was treated (age, sex, weight, medical history), how they were treated (dose, injection spot, frequency), and how any changes were assessed (pain & quality of life questionnaires, sensory testing, VAS scales), it’s difficult to say how relevant or accurate their statements are.
Looking at the 4 publications again, taking into account quality of evidence presented by the study, as well as whether they said it worked or not, shows a different picture. As I mentioned, 2 were case studies:
- The first, published in 2009, described 4 teenage patients in good detail, but failed to mention the dose, or use objective measures in reporting changes after the treatment
- The second, published in 2010, described 2 adult patients, and used VAS scales to objectively measure the effect of the treatment
The third paper, is from the authors of the second case study above, and was the only study to involve a control group, or use multiple methods of assessing pain. They looked at 14 patients, with 5 different tests, but had to call the study short due to poor tolerance of the treatment. (I imagine they planned the pilot study on the basis of the case study reported above.)
The final paper, published in 2011, was completely upfront in stating its limitations – it was done retrospectively from patient records, and had no control group, meaning it’s impossible to exclude the possibility that the reported positive results are due to the placebo effect (a well known issue in clinical trials for pain conditions), or say how it compares to another, more established drug.
In summary, my evaluation of the literature above suggests caution – although many seem positive, the quality of the studies is low, but until someone does a high quality study, it won’t be used as a standard treatment. One of the problems in the pain field in general, and with CRPS in particular, is that clear diagnosis is often difficult, and results in patient populations which may have little in common.
I’m going to look at the evidence from the pre-clinical studies next, and do a follow-up blog to see whether that has anything to add to this discussion.
As always, questions & comments welcome :)
- Syndrome of fixed dystonia in adolescents-short term outcome in 4 cases. Majumdar et al., 2009
- Botulinum toxin A (Botox) for treatment of proximal myofascial pain in complex regional pain syndrome: two cases. Safarpour & Jabbari 2010
- Botulinum toxin A for treatment of allodynia of complex regional pain syndrome: a pilot study. Safarpour et al., 2010
- Intramuscular botulinum toxin in complex regional pain syndrome: case series and literature review. Kharkar et al., 2011