Glottal closure in the hemiparalyzed canine larynx.

Although compensation of voice with unilateral recurrent laryngeal nerve paralysis is commonly held to be the result of the unaffected vocal fold crossing past midline, or overcrossing, this mechanism of compensation has rarely been documented accurately. Beagle dogs were used to create a model of another proposed mechanism of compensation, known as midline drift. Six animals underwent sectioning of the left recurrent laryngeal nerve. One week later, three of the dogs underwent removal of the left posterior and lateral cricoarytenoid muscles. The effects of these procedures were studied by subjective assessment, direct laryngoscopy, and sound spectrographic analysis. Results indicate that glottal closure was improved after the second surgical procedure. The clinical implications of the results are discussed and compared with other manners of compensation hypothesized in the literature.