Role of motor unit number estimate electromyography in experimental canine laryngeal reinnervation

Abstract

Laryngeal electromyography has been used clinically to differentiate neuromuscular pathology from other causes of vocal fold immobility such as arytenoid dislocation, tumor invasion, or cricoarytenoid joint fixation. Electromyography has also been used to predict the prognosis for nerve recovery in laryngeal paralysis. Existing electromyographic techniques either record activity with voluntary motion or study nerve conduction. In this study a new technique, motor unit number estimation, a commercially available quantitative method of electromyographic analysis, is used to study the progress of recovery of vocal fold function after recurrent laryngeal nerve injury. Four dogs underwent transection and immediate reanastomosis of selected branches of the adductor and abductor branches of the recurrent laryngeal nerve on 1 side; the opposite side served as a control. Baseline electromyographic and videolaryngoscopic studies were performed. These measures were then repeated in a longitudinal fashion every 6 weeks after denervation. The motor unit number estimation technique indicated a return of motor unit numbers with time, along with estimates of their size. This was consistent with the expected progress of laryngeal reinnervation. These data and their predictive value for nerve recovery will be discussed.

Estimation of the number and size of motor units in intrinsic laryngeal muscles using morphometric methods

“…In this respect, morphological studies on MU number and size should contribute to the understanding of the actions of laryngeal muscles in humans. In a previous study conducted on dogs, in which MU number was first estimated in response to electrical stimulation of the recurrent laryngeal nerve and then confirmed by anatomical methods using the same animals (Peterson et al, 1999), MU number was smaller in TA muscle compared with PCA muscle, similar to the present findings. English and Blevins (1969), using morphological methods, reported a combined MU size of 30 for all the laryngeal muscles.…”

“…By placing the stimulating electrode directly on the recurrent laryngeal nerve, Peterson et al (1999) estimated the number and size of MUs in laryngeal muscles of dogs by an EMG method and the results correlated well with their own results obtained by histological methods. However, the use of electrophysiological methods for the estimation of MU number and size in the human ILMs is technically difficult since it requires general anesthesia for adequate surface recording and optimal nerve stimulation .…”

Laryngeal adductor function in experimental models of recurrent laryngeal nerve injury

“…10 The adductor muscles, for their protective glottic closure reflex function, have a majority of fast-twitch, type II muscle fibers. 11,12 At low stimulation frequencies (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) Hz), the slow-twitch abductor PCA muscle predominates, and there is little or no net adduction. As the frequency is increased, the fast-twitch adductor muscles take over, and the vocal fold begins to adduct, reaching a force plateau at 70 to 100 Hz.…”

Motor unit number estimate as a predictor of motor dysfunction in an animal model of type 1 diabetes

“…MUNE is computed from the ratio between maximum muscle CMAP divided by the average surface motor unit potential. Although MUNE technique is increasingly used in clinical and experimental studies of amyotrophic lateral sclerosis (ALS), it is rarely used in other peripheral nerve disorders, including diabetic neuropathy (6,18,26,34).…”