INJECTION OF DOXORUBICIN INTO RABBIT EYELID DOES NOT RESULT IN LOSS OF FACIAL MOTOR-NEURONS

In both laboratory and clinical studies, injection of doxorubicin dire ctly into the eyelid results in Permanent muscle loss of the majority of fibers within treated eyelids. A first clinical trial of this techn ique in blepharospasm and hemifacial spasm patients has been performed . All patients who completed a full course of doxorubicin treatment sh owed a permanent decrease in eyelid strength, with over 50% of these p atients requiring no further treatment. Doxorubicin is known to be car ried by retrograde axonal transport to the brain and is a known neurot oxin. This raises the question of the effect of these treatments on th e facial neurons which innervate the orbicularis oculi muscle in the e yelids. The effect on the number of facial neurons present after injec tion of doxorubicin into the eyelid of rabbits was determined using bo th HRP and dil retrograde labeling techniques. Despite the extensive a nd permanent muscle loss caused by the doxorubicin treatments, there w as no measurable loss of facial neurons on the doxorubicin treated sid es. Dil was shown to be myotoxic at high concentrations and amplified the myotoxic effect of doxorubicin. Lack of neuronal loss may offer as surance of clinical safety to the facial motor neurons of muscle spasm patients who receive doxorubicin injections into their eyelids.