Evoked electromyographic technique for quantitative assessment of the innervation status of laryngeal muscles.

OBJECTIVES: The purpose of this study was to develop a minimally invasive, noninjurious evoked electromyographic technique that could accurately quantitate the level of innervation of laryngeal muscles with recurrent laryngeal nerve stimulation. METHODS: A four-phase study was conducted in 24 canines, including 1) identification of the best stimulation-recording configuration, 2) statistical analysis of sensitivity and accuracy, 3) evaluation of safety, and 4) identification of the laryngeal muscle(s) that contribute to the evoked response. RESULTS: The results demonstrated that an entirely noninvasive technique is not feasible. The stimulating cathode must be invasive to ensure discrete activation of the recurrent laryngeal nerve, whereas both recording electrodes should remain on the surface with one overlying the thyroid ala. This configuration proved to be highly accurate, with an error rate of only 6% to 7%, and with sensitivity sufficient to detect a signal in a nerve with fewer than 1% of the axons intact. There was no evidence of nerve injury in any animal over the course of 350 stimulus needle penetrations. By use of neuromuscular blockade to identify those muscles generating the surface response, the thyroarytenoid muscle was found to be the primary contributor, whereas the posterior cricoarytenoid muscle was uninvolved. CONCLUSIONS: This evoked electromyographic technique could provide quantitative information regarding the extent of muscle innervation during denervation and regeneration in case of laryngeal paralysis.

Palatal adhesion: the treatment of unilateral palatal paralysis after high vagus nerve injury.

BACKGROUND: Resection of skull base tumors commonly necessitates intraoperative sacrifice of lower cranial nerves at the level of the jugular foramen. Sequelae of unilateral vagus nerve loss include ipsilateral laryngeal paralysis, ipsilateral palatal and pharyngeal paralysis, and velopharyngeal incompetence (VPI) marked by hypernasal speech and nasopharyngeal reflux of liquids during swallowing. METHODS: Palatal adhesion (PA), a procedure whereby the unilaterally paralyzed palate is attached to the posterior pharyngeal wall, decreases the size of the velopharyngeal port and minimizes the symptoms. This study assessed the outcome of PA in 31 patients with VPI secondary to proximal vagus nerve injury. RESULTS: PA decreased postoperative nasality in 96% of patients. Nasopharyngeal reflux was significantly improved in 83%. Three patients (11%) had minor wound breakdown postoperatively, all of which healed completely with conservative management. CONCLUSION: PA offers a favorable result with minimal concomitant morbidity and is recommended for patients with VPI secondary to unilateral proximal vagus nerve paralysis.