Spasmodic Dysphonia and Laryngeal Sense

Abstract

Thirty-one patients with adduction spasmodic dysphonia who had received no treatment or only voice therapy received an injection of lidocaine into their vocal cords on one side. After injection, their conversational voice was evaluated and their larynx was observed by laryngoscopy every 10-60 minutes. All patients were observed to have weakness of the spasmodic motion of the vocal cords with voice improvement. Two patients showed weakness of the spasmodic motion of the vocal cords before the appearance of vocal cord palsy. Lidocaine is an anesthetic that anesthetizes the motor and sensory nerves. Spasmodic movement stopped while the motor nerves were paralyzed. Furthermore, before and after motor nerve paralysis, there was a time when only the sensory nerves were paralyzed. The voice and laryngeal motion improved at this time. The pathophysiology of spasmodic dysphonia may involve the mistakes in the processing of laryngeal sense and an unusual feedback mechanism in the cortex.