Vocal Fold Paresis: A Well-Recognized Condition of Ambiguous Significance

In this age of increasing reliance on diagnostic technologies to better see pathologies of the body, there is a confounding problem of seeing too much, with too little understanding of what one is seeing and whether what one sees poses a problem.

In the world of laryngology, vocal fold paresis falls into this diagnostic problem area. With the aid of electrophysiological investigations, vocal fold paresis (or partial or incomplete paralysis) is now a recognized clinical condition that is seen as belonging on a continuum of neurogenic dysfunction along with vocal fold paralysis. Although vocal fold paralysis was once thought to be an all-or-nothing phenomenon, as noted by Lucian Sulica, MD, in a recent review article (Curr Opin Otolaryngol Head Neck Surg 2007;15:159-62), improved diagnostics have now shown that there are variable degrees of nerve function of the vocal folds. What distinguishes vocal fold paresis from vocal fold paralysis is both the degree of nerve dysfunction and mobility of the vocal folds.

According to Dr. Sulica, Associate Professor in the Department of Otorhinolaryngology at Weill Cornell Medical College in New York, who moderated a miniseminar on this topic at the 2008 annual meeting of the American Academy of Otolaryngology-Head and Neck Surgery, vocal folds in patients with vocal fold paralysis may still demonstrate some evidence of nerve function, but the vocal fold is completely immobile. In patients with vocal fold paresis, the vocal folds themselves retain substantial mobility, he said, but the muscles of the vocal fold in these patients receive incomplete motor nerve input.

Despite this recognition that vocal fold paresis exists, there remains the problem of meaning. Part of this is the lack of agreement on an exact definition of what vocal fold paresis is, and its natural history. Part of this is the real thorny problem of distinguishing what is normal from what is pathology on laryngeal examination.

How to Determine the Meaning of What Is Seen

Diagnosis of vocal fold paresis is done by identifying the one vocal fold that does not move as well as the other, according to Mark S. Courey, MD, Director of the Division of Laryngology at the University of California, San Francisco. However, no one’s larynx is totally symmetric at baseline, he said. Therefore, the big trick is to determine if the asymmetric movement is due to a true nerve injury or just a congenitally asymmetric larynx.

Put another way, although laryngeal examination may show asymmetric movement of the vocal folds, determining whether this is a problem is not easy.