Dr Paul Michael Peloso, who works as a director of clinical research at Merck, in New Jersey, USA states:
"It's always important to look carefully at evidence from clinical trials to see whether a treatment is more effective than a placebo, and this is particularly important when treatments have known adverse effects. It is possible that BoNT did give some benefits that were not measured in the trials, or that it could help highly particular types of neck pain, but we would need some much more carefully conducted trials to reveal this. Based on current evidence we have no reason for supporting the use of BoNT as a stand-alone therapy for neck pain, but we do suggest that researchers consider further study to clarify whether the dose can be optimized for neck pain."
Almost all injections of BoNT are not without risk, and patients may experience muscle tenderness or pain, weakness, or a general sense of being unwell. A few have anaphylactic reactions and there are reports that some have died.
Some of the trials specifically compared the effects of either giving the toxin or a placebo injection of saline to two different groups of people with neck pain. The researchers could see no difference between the two groups either at 4 weeks or 6 months. Similarly adding BoNT to physiotherapy was no more effective than adding either an anaesthetic or saline.
Botox is now also a common treatment for muscles affected by the upper motor neuron syndrome, for muscles with an impaired ability to effectively lengthen. Muscles affected by the Upper Motor Neuron Syndrome frequently are limited by weakness, loss of reciprocal innervation, decreased movement control and hypertonicity (including spasticity). Joint motion may be restricted by severe muscle imbalance related to the Upper Motor Neuron Syndrome, when some muscles are markedly hypertonic, and lack effective active lengthening. Injecting an overactive muscle to decrease its level of contraction can allow improved reciprocal motion, and so improved ability to move and exercise.