This study was performed to apply the evoked electromyographic (EMG) test to the larynx and to find out whether or not this test is useful for diagnosis of patients with recurrent laryngeal nerve paralysis. As a result, it was considered that the present test was useful for the following:
1. Diagnosis of the site of lesion: The decision is easily made whether the recurrent laryngeal nerve is damaged alone or together with the superior laryngeal nerve, and on the site of damages along the recurrent laryngeal nerve in some cases.
2. Determination of prognosis: The cases showing no evoked wave may not recover completely. For the cases showing an evoked wave, information on prognosis can be obtained from the degree of changes in latency and evoked wave form.
3. Indication of the state of nerve regeneration: The evoked EMG test is able to reveal the state of reinnervation of the paralyzed laryngeal nerve as well as and even earlier than the ordinary EMG test.