EMG is an effective means of recording the electrical signals of muscle fibers as they contract. Specific patterns can be discerned which are diagnostic and predictive. Differentiating between a central or peripheral disorder as well as between an ongoing or recovering lesion is possible. After trauma to the recurrent nerve or the tenth nerve, the degree of injury can be assessed, and often, the program for recovery can be determined. Many new theraputic techniques have provided the impetus for more sophisticated diagnostic methods available in voice laboratories.
Precise evaluation is helpful in determining the best course of treatment for each patient.
In neurologic injuries, the degree of glottic incompetence will predict the value of arytenoid adduction as a supplement to vocal cord medialization. Electromyography has been helpful in these cases by detecting recovery earlier, and by identifying synkinesis which might be helped by botulinum toxin therapy. In cases of spasmodic dysphonia, the pre-treatment EMG establishes the degree of impairment and identifies the muscles most involved in the dystonia. This information has been useful especially in patients who do not respond to the usual doses of botulinum toxin. Additional resources are important for the evaluation of some voice disorder patients.