The American Academy of Neurology (AAN) has updated its 2008 guidelines on the use of botulinum toxin for spasticity, cervical dystonia, blepharospasm, and migraine headache, based on recent research. The revised guidelines were published online in the April 18 issue of Neurology.
The updated guidelines cover four neurological disorders: spasticity in adults, which is muscle tightness that interferes with movement, typically following a stroke, spinal cord damage, or other neurological injury; cervical dystonia, a disorder of the brain affecting the control of neck muscles, causing involuntary head tilt or neck movement; blepharospasm, a movement disorder that causes the eyes to close uncontrollably; and chronic and episodic migraine. Chronic migraine is defined as attacks that occur 15 or more days per month, with at least eight of those attacks having migraine features. In episodic migraine, attacks occur less often.
Botulinum toxin is produced by Clostridium botulinum bacteria. The drug blocks the release of substances at nerve endings, which leads to reduced muscle contraction and reduced transmission of pain signals. Four preparations of botulinum toxin are available in the United States, and they are not interchangeable. The updated guidelines assess each formulation separately for each condition. To develop the guidelines, researchers reviewed all available scientific studies on the topic.
The guidelines determined that botulinum toxin is generally safe and effective for treating spasticity in adults, cervical dystonia, blepharospasm, and chronic migraine, according to guideline author David M. Simpson, MD, of the Icahn School of Medicine at Mount Sinai in New York, New York.
A change from the earlier guidelines is the recommendation on chronic migraine. In 2008, not enough evidence was available to make a recommendation on the use of botulinum toxin for chronic migraine. Well-designed studies now support the effectiveness of onabotulinumtoxinA in reducing how often migraine headaches occur. However, these studies showed that the benefit from the drug was small. In the four weeks after the first treatments, the subjects had approximately 15% fewer days of headache compared with a placebo or dummy injection.
Spasticity has many causes, including multiple sclerosis, stroke, and head or spinal-cord trauma, according to the guidelines. For upper-limb spasticity, three of the drug formulations—abobotulinumtoxinA, incobotulinumtoxinA, and onabotulinumtoxinA—are effective in reducing excess muscle tone and should be offered. One formulation, rimabotulinumtoxinB, is probably effective and should be considered. For lower-limb spasticity, abobotulinumtoxinA and onabotulinumtoxinA are effective and should be offered.
For cervical dystonia, abobotulinumtoxinA and rimabotulinumtoxinB are effective and should be offered. OnabotulinumtoxinA and incobotulinumtoxinA are probably effective and should be considered.
Few well-designed studies have been conducted in subjects with blepharospasm. The updated guidelines state that onabotulinumtoxinA and incobotulinumtoxinA are probably effective and should be considered. AbobotulinumtoxinA is possibly effective and may be considered.
The 2008 guidelines also covered essential tremor, hemifacial spasm, and disorders of the voice. For those conditions, no new evidence was available at the time the guideline update was initiated that would change the conclusions, so they were not included in the update.
Source: AAN; April 18, 2016.