Botulinum toxin treatment of spasmodic dysphonia

Abstract

Dystonia is a chronic neurological disorder of central motor processing characterized by task-specific action-induced muscle spasms. It may be generalized or limited to one functional group of muscles. When it affects the larynx, it is usually focal, or isolated to that organ. In the vast majority of cases, laryngeal dystonia affects connected speech, although there are rare cases of breathing dystonia. Laryngeal dystonia, termed “spasmodic dysphonia” (SD) by otolaryngologists, typically begins in the mid-30s and is more common in women (63%).1 Approximately 8 of 10 affected individuals have adductor SD, which causes inappropriate glottal closure, producing characteristic harshness, strain, and strangled breaks in connected speech. Abductor SD, in contrast, causes inappropriate glottal opening that produces hypophonia and breathy breaks. Because of compensatory maneuvers or mixed dystonic features, voice patterns encountered clinically may not always be typical or easy to discern. However, the classification of spasmodic dysphonia into abductor and adductor types is central to botulinum toxin (BTX)∗ treatment.