Recurrent laryngeal nerve afferents and their role in laryngospasm.

Airway protection is a critical and phylogeneticaly old function of the larynx. Therefore, the sensory supply to the larynx is extensive, including afferent nerve endings in the mucosa, muscles, and joints. The majority of afferent fibers are in the distribution of superior laryngeal nerve (SLN). The afferents of the recurrent laryngeal nerve (RLN) have been infrequently studied in humans. Laryngospasm is defined as a prolonged occlusion of the glottis caused by contraction of the intrinsic laryngeal muscles. It is a wellknown potential hazard of any type of laryngeal or pharyngeal surgery. Laryngospasm is more likely in the presence of excessive secretions or in patients who are extubated in an inappropriate plane of anesthesia. Laryngospasm has been observed in 0.87% of all patients undergoing general anesthesia, and in 1.74% of children 0 to 9 years of age.’ Laryngospasm is more common when the larynx is instrumented during a procedure. Laryngospasm can be differentiated from reflex laryngeal closure, which is shorter in duration, and can be elicited by a wider variety of stimuli. According to Suzuki and Sasaki,’ laryngospasm is elicited only by repetitive suprathreshold stimulation of SLN afferents. We recently obtained evidence for the presence of RLN afferents and showed their possible role in laryngospasm. Two cases form