TRANSORAL ELECTROMYOGRAPHIC RECORDINGS IN BOTULINUM TOXIN-INJECTED RAT LARYNGES

Objective assessment of muscle function following botulinum toxin inje ctions in laryngeal muscles is difficult in human subjects. We develop ed a rat laryngeal model for the study of botulinum toxin injection. A new laryngoscopic technique has made it possible to observe the rat l arynx endoscopically and to obtain electromyographic measurements duri ng and after injection of toxin. The electromyographic interference pa ttern, fibrillation potentials, and vocal fold movement were used for analyzing dose and volume effects of injected toxin. We conclude that the lowest dosage able to produce the maximal duration of functional l aryngeal impairment is 0.07 U in a volume of 0.4 mu L. This model will enable us to obtain physiologic and histologic parameters that can be used to assess the selection of optimal treatment regimens with botul inum toxin for the treatment of patients with spasmodic dysphonia.