Long-term model of induced canine phonation.

Experimental induced phonation in the dog has been used in short-term studies by several investigators and has proved quite useful in laryngeal research. In this study a long-term canine phonation model is described that uses permanently implanted electrodes on the superior and recurrent laryngeal nerves. A serial induced phonation model has not been previously reported and is needed for laryngeal research in which voice results are a primary end point. Inexpensive, reliable, nontoxic electrodes were designed and fabricated. The laryngeal nerves were found to be quite susceptible to injury, necessitating a series of changes in electrode design. Electrode durability and laryngeal nerve viability improved with each design modification; the final design gave a recurrent laryngeal nerve viability rate of 100% at 6 weeks, 83% at 9 weeks, and 73% at 12 weeks. Induced phonation was successfully produced on a repeated basis by stimulating the recurrent laryngeal nerves while passing air through the larynx, in 22 (95.6%) of 23 animals. Stimulation of the superior laryngeal nerves increased vocal fold length and tension but was not required for phonation. Technical aspects of chronic implantation and stimulation of the laryngeal nerves are discussed. The development and successful long-term implantation of electrodes on the laryngeal nerves and their use in repeated induced phonation have not been reported previously.