What is the role of botulinum A toxin in the treatment of benign essential blepharospasm (BEB)?

Updated: May 20, 2019
  • Author: Robert H Graham, MD; Chief Editor: Edsel Ing, MD, MPH, FRCSC  more...
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Answer

Botulinum A toxin is regarded as the most effective treatment of choice for the rapid but temporary treatment of orbicularis spasm. [40, 41, 42, 43, 44, 45, 46, 47, 48, 49] More than 95% of patients with blepharospasm report significant improvement with use of the toxin. The toxin interferes with acetylcholine (ACh) release from nerve terminals, causing temporary paralysis of the associated muscles. Botulinum A toxin is the product of the bacteria, Clostridium botulinum (a large anaerobic, gram-positive, rod-shaped organism). Two of the commercially available botulinum A preparations include onabotulinumtoxinA (Botox) and incobotulinumtoxinA (Xeomin). AbobotulinumtoxinA (Dysport) may also be effective. [50]

Once injected, the toxin rapidly and firmly binds at receptor sites on cholinergic nerve terminals in a saturable fashion. The toxin is internalized through the synaptic recycling process. Paralysis of muscle is a result of the inhibition of the release of vesicular ACh from the nerve terminal. It is assumed that the toxin attaches to the ACh-containing vesicles in the nerve terminal and prevents calcium-dependent exocytosis.

The paralytic effect is dose related, with a peak of effect at 5-7 days after injection. Patients typically note the onset of relief 2.5 days after injection, with a mean duration of relief from symptoms of 3 months. More than 5% of treated patients have sustained relief for more than 6 months, although some patients require injections as often as monthly. It takes as much as 6-9 months for the injected muscles to recover from the effects of the toxin, and, occasionally, muscles do not fully return to their preinjection level of function. Some have suggested that the development of antitoxin antibodies or the progressive atrophy of muscle may account for variations in the dose response curve, but no studies have supported these findings.

Tear breakup time (TBUT), lissamine green staining, and Ocular Surface Disease Index (OSDI) scores have all been shown to be improved after botulinum toxin injection. [51]


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