The analgesic effect of botulinum-toxin A on postwhiplash neck pain

The effectiveness of botulinum neurotoxin type A (BTXA) injections in relieving the neck pain and reduced motion that evolve after whiplash injury (WI) has been controversial.

To test the long-term efficacy of a tender point injection of BTXA in relieving neck pain in patients with WI.

Twenty patients with cervical myofascial pain, 2 to 48 weeks after WI, were randomly assigned to receive either 200 U of BTXA or placebo at 4 tender points and were seen during the follow-ups 3, 6, 9, 12, and 24 weeks after the injections. Outcome measures included the intensity of pain as evaluated by a 10-cm Visual Analog Scale (VAS) and a 5-point Verbal Rating Scale (VRS), quality of life as evaluated by the SF-36 questionnaire, treatment efficacy as per the global assessment of the physician and patient, intensity of pain in response to mechanical pressure, range of cervical motion, and use of other therapies and their adverse effects.

A time-dependent improvement in all the parameters was found in both groups, which was consistently larger in the BTXA-treated group, but mostly not at a significant level. Significant differences between the groups were found only in the percentages of patients who achieved 50% or more of reduction in intensity (VAS and average VRS) at 24 weeks (50% vs. 0%, P>0.05 and 70% vs. 11%, P>0.05, respectively). Systemic adverse effects tended to be more common in the BTXA-treated group (40% vs. 0%, P=0.07).

Study results suggest that BTXA treatment has some efficacy when administered within 1 year of the WI. However, a large, well-designed clinical trial is needed to draw final conclusions.