Recurrent laryngeal nerve transposition in guinea pigs

Improved control of prosthetic voice aids for laryngectomees might be possi ble to obtain with residual laryngeal motor nerve signals. We were able to recover motor signals from the recurrent laryngeal nerve (RLN) by transposi ng it into the ipsilateral denervated stemohyoid muscle (SH) in 8 guinea pi gs. Reinnervation was monitored by electromyographic recordings from surfac e and intramuscular needle electrodes in awake animals. Within 4 to 14 week s after surgery, all animals demonstrated laryngeal-like motor activity in the reinnervated SH, including activity during respiration, sniffing, swall owing, and/or vocalizing. After 3 to 6 months, the animals were reanestheti zed, and nerve stimulation and section experiments confirmed the RLN as the source of reinnervation in all cases. In several animals, activity of the RLN-innervated SH was demonstrated to be correlated with that of contralate ral laryngeal muscles. Histochemical analysis of the SH indicated a unilate ral transformation from mostly fatigable to mostly fatigue-resistant fiber types ipsilateral to the RLN transposition, a phenotype more typical of lar yngeal muscles. Thus, RLN transposition at the time of laryngectomy may be a method for salvaging laryngeal control signals that could be used to cont rol prosthetic voice devices.