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 treatme nt for a variety of laryngeal problems, most notably spasmodic dysphonia. A s in other movement disorders, the theory behind the injection of this subs tance in the larynx has been a weakening of the vocal fold musculature to r elieve uncoordinated and spasmodic movement of the vocal folds, presumably rebalancing the forces within the intralaryngeal musculature. Recently, thi s concept was applied to help reposition the arytenoid cartilage in acute a nd 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 paral yzed vocal folds may still have partial voluntary motor unit activity. This voluntary activation may not produce clinically evident movement but may b e sufficient to produce tone within the fold. If the voluntary motor units in the abductor musculature of the paralyzed fold are weakened with botulin um 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 b otulinum toxin may affect the ability of the fold to rebalance itself. With this evidence in mind, a patient with fold immobility secondary to multipl e sclerosis was treated in an attempt at laryngeal rebalancing, using botul inum toxin to medialize the fold. However, instead of simply having the fol d return fixed to the midline, the patient regained normal laryngeal mobili ty and voice. While it is unclear whether the botulinum toxin alone was res ponsible, the coincidence of this occurrence certainly requires reporting. This paper is a report of the first successful treatment of vocal fold para lysis using botulinum toxin to treat vocal fold fixation in a patient with multiple sclerosis.