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Botulinum-induced changes in monkey eyelid muscle. Comparison with changes seen in extraocular muscle
J D Porter1, S Strebeck, N F Capra
1Department of Anatomy and Neurobiology, University of Kentucky Medical Center, Lexington 40536-0084.
Archives of Ophthalmology (Chicago, Ill. : 1960)
|March 1, 1991
Summary
Botulinum toxin type A causes temporary, non-specific muscle fiber atrophy in eyelid muscles of monkeys. These structural changes in the orbicularis oculi muscle are reversible, unlike those in extraocular muscles.
Area of Science:
- Neurology
- Muscle Physiology
- Ophthalmology
Background:
- Botulinum toxin type A is used to treat conditions like strabismus and focal dystonia.
- Understanding its effects on different muscle types is crucial for optimizing treatment outcomes.
Purpose of the Study:
- To evaluate the structural alterations in the orbicularis oculi muscle after botulinum toxin type A injection in adult monkeys.
- To compare the effects of botulinum toxin type A on eyelid muscles with its known effects on extraocular muscles.
Main Methods:
- Adult monkeys received injections of botulinum toxin type A into their eyelids.
- Orbicularis oculi muscles were examined using light and electron microscopy at survival times ranging from 7 to 84 days.
Main Results:
- Nonselective atrophy of nearly all muscle fibers was observed.
- Botulinum toxin type A induced nonspecific alterations across all three orbicularis oculi fiber types.
- Muscle structural changes were reversible with no long-term consequences noted.
Conclusions:
- Botulinum toxin type A induces reversible, non-specific atrophy in eyelid muscles, contrasting with fiber type-specific changes in extraocular muscles.
- Differences in fiber type composition and motor control likely explain the varied responses between eyelid and extraocular muscles.
- The efficacy of botulinum toxin treatments may depend on the specific muscle's anatomy and functional properties.