Orbicularis muscle pathology after botulinum toxin injection.

A 49-year-old woman underwent 1 year (six injections) of botulinum toxin treatments for essential blepharospasm. When she became dissatisfied with the need for repeat injections, she elected to undergo an orbicularis muscle stripping procedure for control of spasms. Pathologic examination of the orbicularis muscles showed only minimal degenerative changes. Botulinum toxin injection into the orbicularis is known to provide only temporary relief of essential blepharospasm. This may be because the resulting orbicularis atrophy is insufficient to maintain permanent control of these spasms.