Transmucosal electrical stimulation of laryngeal muscles.

A new technique is described that enables discrete activation of individual laryngeal muscles by electrical stimulation across overlying mucosa. In 15 dogs, we defined six distinct motor points by transmucosal stimulation at 3 mA while observing the resulting characteristic position of the arytenoid and true vocal cord. Five dogs were then paralyzed with succinylcholine in order to simulate bilateral vocal cord paralysis. Application of a 3-mA stimulus at each motor point yielded no motion of the cords, but when the current was increased to 20 mA, characteristic responses were elicited. In five other dogs, botulinum toxin was injected directly into laryngeal muscles. Stimulation was used in an attempt to quantify the degree of neuromuscular blockade. In the last group of five dogs, we simulated cricoarytenoid arthritis by scarifying the joint. The extent and nature of the joint's impairment could be demonstrated by stimulation. Transmucosal stimulation appears promising as a clinical technique for correlating particular vocal cord movements and thresholds of activation with specific laryngeal disorders. Additionally, such a technique may be useful in clarifying how each laryngeal muscle acts upon the cricoarytenoid joint.