Blepharospasm and related facial movement disorders.

The variable clinical features and the relatively good response of blepharospasm to botulinum-toxin type A are now well established. The etiology and pathophysiology of blepharospasm and related facial movement disorders are still poorly understood. Genetic and histopathologic studies over the last year have contributed to our understanding of this disease. The most significant progress has been made in the electromyographic studies of the the levator palpebrae and orbicularis oculi muscles. Subclassification based on the electromyographic abnormalities of these two muscles have begun to improve our understanding of the variable responses to botulinum-toxin type A. Further electromyographic studies may help identify the best sites of injection for optimal response and differentiate patients requiring limited or complete myectomy. The development of the limited myectomy has provided excellent functional and cosmetic results with quick recovery times in selected patients.