Botulinum toxin injection in the treatment of vocal fold paralysis associated with multiple sclerosis: a case report

Botulinum toxin has been demonstrated clinically to be an effective treatment for a variety of laryngeal problems, most notably spasmodic dysphonia. As in other movement disorders, the theory behind the injection of this substance in the larynx has been a weakening of the vocal fold musculature to relieve uncoordinated and spasmodic movement of the vocal folds, presumably rebalancing the forces within the intralaryngeal musculature. Recently, this concept was applied to help reposition the arytenoid cartilage in acute and longstanding anteromedial cricoarytenoid dislocations. This same concept may apply to the paralyzed vocal fold. In support of this idea, a number of investigators have shown that immobile, clinically paralyzed vocal folds may still have partial voluntary motor unit activity. This voluntary activation may not produce clinically evident movement but may be sufficient to produce tone within the fold. If the voluntary motor units in the abductor musculature of the paralyzed fold are weakened with botulinum toxin, the continued pull of the functioning adductor musculature may be sufficient to medialize the paralyzed fold. This idea has been supported by animal experiments, which have shown that botulinum toxin may affect the ability of the fold to rebalance itself. With this evidence in mind, a patient with fold immobility secondary to multiple sclerosis was treated in an attempt at laryngeal rebalancing, using botulinum toxin to medialize the fold. However, instead of simply having the fold return fixed to the midline, the patient regained normal laryngeal mobility and voice. While it is unclear whether the botulinum toxin alone was responsible, the coincidence of this occurrence certainly requires reporting. This paper is a report of the first successful treatment of vocal fold paralysis using botulinum toxin to treat vocal fold fixation in a patient with multiple sclerosis.