The human larynx is a complex system. The movement of its various muscles make it possible for humans to speak and breathe. Nevertheless, respiratory and vocal problems can occur. They can be the consequences of absent or little vocal fold movement. In order to find out the original cause of the movement reduction, laryngeal electromyography (LEMG) is a useful diagnostic tool.
Indication for LEMG
A popular diagnosis for vocal fold movement reduction and resultant hoarseness is “paralysis of the recurrent laryngeal nerve”. However, it is not only the recurrent nerve that supplies the laryngeal muscles, also the superior laryngeal nerve does so. Consequently damages to the SLN can lead to vocal fold problems, too. Furthermore other reasons such as cricoarytenoid joint ankylosis, vocal fold fixation or the very rare luxation of the arytenoid cartilage should not be excluded either, especially if the immobile vocal fold(s) is (are) in an atypical paralysis position.
With stroboscopy one can also distinguish between neural damage and mechanical fixation, as it is possible to determine the vocal folds’ tonicity, which is reduced in case of neurogenic vocal fold movement reduction. Nevertheless, this method only delivers subjective diagnostic results.
LEMG in contrast is a useful tool for objective differential diagnosis. One can distinguish between mechanical fixation (normal EMG pattern) and vocal fold paralysis (abnormal LEMG pattern due to damaged nerves) and plan appropriate therapy in an early stage, about 10-14 days after vocal fold movement reduction occurrence.