Botulinum toxin therapy. Botulinum toxin therapy has emerged as a treatment modality for a variety of spastic- or contracture-related muscle diseases. Its safety has been proven for long-term use in the treatment of benign essential blepharospasm, hemifacial spasm, and certain types of strabismus. Recent approval from the Federal Drug Administration should make botulinum toxin available for use in a greater number of patients. 