Electromyography and the immobile vocal fold
Laryngeal EMG has become a useful tool for the otolaryngologist in the four decades since the pioneering work of Faaborg-Anderson and Buchtal. It is able to distinguish between mechanical limitation and denervation in an immobile vocal fold. In the paralyzed vocal fold, it can guide workup by pointing to the site of the lesion. In the hands of a circumspect clinician, it can provide clinically valuable information regarding prognosis. Useful application of laryngeal EMG must rest on the basic fact that it isa qualitative test. Because of factors like sampling error, interfering signal from neighboring muscles, difficulties in needle placement, and our in-complete understanding of reinnervation physiology, the boundary between sophisticated, subtle interpretation and overreading is particularly difficult to distinguish. EMG diagnosis is based on patterns of abnormalities over time and, like other tests, requires interpretation in a clinical context. As in any such undertaking, there is no substitute for good judgment and experience. The most important benefit of clinical use of laryngeal EMG may be that it has catalyzed and broadened interest in laryngeal neurophysiology in the same way that stroboscopy has focused attention on the structure and function of the vocal fold lamina propria. The continuing refinement of electrodiagnostic approaches to the larynx that has resulted, including quantitative, single-fiber. and vector laryngeal EMG, and evolving methods of nerve conduction testing will continue to yield important insights into mechanisms of neural control that are likely to drive developments in the treatment of vocal fold paralysis in the future.