VANCOUVER – A new American Academy of Neurology practice guideline on the efficacy and safety evidence for botulinum toxin treatment of blepharospasm, cervical dystonia, spasticity, and headache has updated the last recommendations published in 2008, but leaves some relevant clinical concerns and off-label uses unaddressed.
The 2016 update, published April 18 in Neurology, adds new individual evidence for the use of the four branded formulations of the two commercially available botulinum toxin serotypes, A and B, for the aforementioned indications rather than lumping all recommendations for botulinum toxin together as in the 2008 guidelines. However, questions remain on the differences between the different products in clinical practice, especially since the formulations show little clinical difference in head-to-head comparisons for some of the indications, especially for the serotype A formulations.
In a press briefing on the new guidelines at the annual meeting of the American Academy of Neurology, guidelines coauthor Dr. Mark Hallett noted that nothing really surprised the experienced 14-member committee that put the guidelines together. “The reason that we chose these four different diseases is because we already had the sense that they were going to change in the particular ways that they did. We didn’t know exactly, of course, what was going to happen, but we had a sense that there were sufficient data that it was worth looking at them.”
For blepharospasm, the totality of evidence suggests that onabotulinumtoxinA (onaBoNT-A; Botox) and incobotulinumtoxinA (incoBoNT-A; Xeomin) injections should be considered and are probably safe and effective (level B recommendation), while abobotulinumtoxinA (aboBoNT-A; Dysport) may be considered (level C) and is possibly effective. The evidence shows that incoBoNT-A and onaBoNT-A have equivalent efficacy and aboBoNT-A and onaBoNT-A are possibly equivalent. There was not enough evidence to determine the efficacy of rimabotulinumtoxinB for blepharospasm (rimaBoNT-B; Myobloc).
The rigorousness of clinical trials in evaluating the efficacy and safety of botulinum toxin has evolved since the Food and Drug Administration approved onaBoNT-A and incoBoNT-A to treat blepharospasm, but no new trials have been conducted to give it a higher level of recommendation despite their well-known magnitude of benefit, said Dr. Hallett, chief of the National Institute of Neurological Disorders and Stroke medical neurology branch and its human motor control section.
New evidence added to the already well-established data on the effectiveness of botulinum toxin for cervical dystonia suggest that onaBoNT-A and incoBoNT-A are probably safe and effective and should be considered. In addition, aboBoNT-A and rimaBoNT-B have already proven effectiveness and safety and should be offered. The lack of class I studies for onaBoNT-A and incoBoNT-A led to the lower level of recommendation for them despite an extensive clinical history of their use in cervical dystonia, the guideline committee wrote (Neurology. 2016 Apr 18. doi: 10.1212/WNL.0000000000002560).
In adults with upper-limb spasticity, all three serotype A formulations – onaBoNT-A, aboBoNT-A, and incoBoNT-A – are effective and safe in reducing symptoms and improving passive limb function. All three achieved level A evidence to recommend that they should be offered. One comparative trial showed enough evidence to say that onaBoNT-A is probably superior to tizanidine for reducing upper-extremity tone and should be considered before it. RimaBoNT-B has level B evidence to advise that it should be considered and is probably safe and effective. None of the formulations have enough data to determine their efficacy on active limb function.
Fewer trials have examined the safety and effectiveness of botulinum toxin formulations for reducing lower leg spasticity in adults. The guidelines panel found enough evidence to recommend that aboBoNT-A and onaBoNT-A are safe and effective and should be offered (level A). There were no trials with high enough level of quality to determine whether incoBoNT-A or rimaBoNT-B were effective for lower-leg spasticity. None of the four agents had enough evidence to support their ability to improve active function associated with lower-limb spasticity.
At the press briefing, guidelines first author Dr. David M. Simpson expressed hope that a more refined methodology for evaluating spasticity might be achieved in future trials of botulinum toxin to detect the potentially subtle effects the agents may have on certain patients who are more likely to achieve benefits in active limb function. Currently, trials use a standardized set of outcomes to try to detect differences in patients with wide-ranging severity of symptoms and types of injury that led to spasticity. Dr. Simpson is professor of neurology at Mount Sinai in New York, as well as director of the neuromuscular diseases division and director of the clinical neurophysiology laboratories.