Protective glottic closure: biomechanical effects of selective laryngeal denervation

Glottic closure constitutes the primary mechanism for prevention of intradeglutitive and postdeglutitive aspiration. Laryngeal paralysis therefore exerts a considerable impact on deglutition, yet little is understood regarding the biomechanical effects of selective denervation on the laryngeal protective function. We measured the glottic closing force (GCF) in each of 6 male, 40-kg Yorkshire pigs 1) after selective unilateral superior laryngeal nerve (SLN) section; 2) after selective unilateral recurrent laryngeal nerve (RLN) section; and/or 3) after combined SLN-RLN section as both right and left SLNs were simultaneously stimulated to evoke the glottic closure response. Stimulation was provided through an oscilloscope with bipolar platinum-iridium electrodes, and the GCF was measured with a pressure transducer positioned between the vocal cords. Six repetitive measures of GCF were obtained before nerve section, and 6 after nerve section, in each subject. Unilateral SLN section reduced the GCF to 54.14% of control, RLN section reduced the GCF to 23.39% of control, and combined SLN-RLN section reduced the GCF to 22.67% of control. These findings underscore the profound differential effects exerted by isolated lesions on the glottic closure function.