Botulinum toxin for the treatment of essential blepharospasm.

Twenty-six patients with essential blepharospasm were treated with botulinum toxin by injection. The onset of protractor weakness in all patients ranged from one to five days following treatment. Maximal weakness developed within 12 days. There was a variable and gradual return of protractor strength over eight to 29 weeks in most patients and, with it, a return of spasm. Twenty-five patients received some degree of functional relief following initial injection. In most patients, however, the post-injection result could not be stabilized and repeat injections have been necessary to control recurrent spasms. There was one treatment failure. Three patients treated by injection following previous neurectomy and myectomy appeared to have a reduced requirement for subsequent injections. Complications included transient ptosis in six patients and mild exposure symptoms in four patients. Extraocular muscle paresis did not occur. There were no systemic side effects from the botulinum toxin injections.