Quantification of muscle loss in the doxorubicin-treated orbicularis oculi of the monkey. Effect of local injection of doxorubicin into the eyelid.

Many neuromuscular diseases are characterized by involuntary and forceful muscle contraction. Doxorubicin has been shown to chemically remove the orbicularis oculi muscle after injection into the eyelid. The chemomyectomy effect of doxorubicin was quantified after injection of a 2-mg dose into the right lower eyelid. A significant loss of muscle was seen in the injected eyelids, with a mean loss of 87% of the summed cross-sectional area of all muscle fibers throughout representative cross-sections of the treated eyelids. This muscle loss was selective, with the greatest loss in the preseptal region of the orbicularis oculi. The authors found no differential loss of different muscle fiber types after doxorubicin treatment. This muscle loss was not accompanied by an increase in connective tissue, and surrounding eyelid structures were normal. The authors find that doxorubicin is a highly effective myotoxin and represents a novel permanent treatment for blepharospasm and related diseases because it is highly specific for muscle cells and is easy to localize within a given muscle.