Laryngeal Features of External Superior Laryngeal Nerve Denervation: Revisiting a Century-Old Controversy

Abstract

A long-standing controversy exists regarding the laryngoscopic features associated with unilateral denervation of the external superior laryngeal nerve (ESLN). Recently, we modeled acute unilateral cricothyroid muscle paralysis by blocking the ipsilateral ESLN with lidocaine hydrochloride, and identified epiglottic petiole deviation to the side of paralysis during high-pitched voice production as a possible diagnostic sign. This study provides preliminary clinical evidence supporting the presence of petiole deviation in cases of ESLN denervation. Epiglottic petiole deviation to the side of weakness was present in electromyographically confirmed cases of unilateral partial or complete ESLN denervation, in isolation or in combination with denervation of other branches of the vagus nerve. In addition, a case of complete ESLN and recurrent laryngeal nerve (RLN) denervation showed return of the petiole to the midline 6 months after surgical reinnervation of the ESLN and RLN. Finally, petiole deviation was not present in isolated RLN paralysis — A finding suggesting that the diagnostic sign is uniquely associated with ESLN denervation. We concluded that deviation of the petiole to the side of cricothyroid muscle weakness during high-pitched voice production represents a potential diagnostic sign of unilateral ESLN denervation. Further research is necessary to determine factors that influence the expression and detection of this sign, as well as its diagnostic precision.