What is the role of botulinum toxin in pain management for neuromuscular disorders?

Updated: Mar 11, 2019
  • Author: Heather Rachel Davids, MD; Chief Editor: Elizabeth A Moberg-Wolff, MD  more...
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Previous studies of conditions with involuntary muscular contractions have provided some indirect evidence of the analgesic effects of botulinum toxin. A summary of a MEDLINE search for clinical studies with the headings "botulinum toxin," and "pain" performed from 1966 to September 2005 resulted in more than 40 studies that included "pain" within the article title or abstract.

In the report, pain response to treatment with botulinum toxin was cited within the context of treatment for a number of conditions, including tennis elbow, chronic anal fissure, pain attributed to mastectomy and hemorrhoidectomy, headaches (including migraine), piriformis syndrome, facial pain, myofascial pain, temporomandibular joint syndrome (TMJ), low back pain, chronic prostatic pain, and whiplash. [8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24]

Variables in these studies included dosing, concentration, injection techniques, use of concurrent therapeutic modalities, varying diagnoses, and chronicity of neurologic dysfunction. Some patients treated for disorders that included involuntary muscle contraction (eg, dystonia) also reported benefits in pain reduction in muscles injected with botulinum toxin. Variables in the studies cited included the presence or absence of concurrent therapy, diagnoses, length of time since onset of pain, dosing and concentration, and methodology for measurement of outcome. [25]  In 2016, the US Food and Drug Administration approved onabotulinumtoxinA to decrease the severity of stiffness in ankle and toe muscles among adults with lower limb spasticity. [26]

Another review of botulinum toxin studies was performed by the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology. [27] Evidence of the toxin's effectiveness was examined for a variety of conditions, including chronic tension-type headache, episodic migraine, chronic daily migraine, [28] and chronic low back pain.

According to the subcommittee's report, the evidence indicated that botulinum toxin may be useful in the treatment of lower back pain but that it is probably not effective against episodic migraine and chronic tension-type headache. The report also stated that the available evidence was not strong or consistent enough to determine botulinum toxin's usefulness in the treatment of chronic daily headache (primarily, transformed migraine).

A German report also investigated botulinum toxin's effectiveness against tension-type headache. [29] In a double-blind, randomized, placebo-controlled study, researchers compared the number of headache-free days experienced by patients 4 weeks prior to injections of BoNT-A with the number of such days occurring 4-8 weeks after treatment. The number of headache-free days increased for the study's placebo and nonplacebo groups, but the difference in increase between the 2 groups was not significant.

The researchers did find, however, that in comparison with the placebo group, the patients who received BoNT-A injections experienced a significant reduction in the duration of their headaches.

A study by Naik et al reported that the use of botulinum toxin to treat painful cutaneous leiomyomas was associated with improved quality of life and with a trend toward improved pain at rest. [30]

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