Stridor and focal laryngeal dystonia.

Fibreoptic laryngoscopy in 6 patients with laryngeal stridor showed immobile vocal cords in a paramedian position but no other local cause. Thus a diagnosis of Gerhardt's syndrome, usually ascribed to paralysis of vocal-cord abductor muscles, was made in 3 patients who had no other signs or symptoms of dystonia, and in 3 patients who had multifocal dystonia. Electromyography (EMG) showed evidence of overactivity of vocal-cord adductors, with no evidence of denervation in the abductor muscles. Botulinum toxin injection of the overactive thyroarytenoid muscles abolished stridor. These clinical and EMG findings indicate that Gerhardt's syndrome is not caused by paralysis of vocal-cord abductors, but represents a focal laryngeal dystonia which may be treatable by botulinum toxin injections of vocal-cord adductor muscles rather than by arytenoidopexy or tracheostomy.