Laryngeal Electromyography (LEMG)
LEMG Offers Earlier and Better Diagnosis for Voice Patients
The Johns Hopkins Voice Center at GBMC's Milton J. Dance Head and Neck Center offers laryngeal electromyography (LEMG), a specialized, interdisciplinary diagnostic test used to assess nerve activity and recovery potential of the larynx in cases of vocal cord motion impairment. LEMG is designed to evaluate the integrity of the muscles and nerves of the larynx by recording action potentials (electrical activity) generated in muscle fibers.
Impaired motion of the vocal cords can result from many causes, including viral infection, cancer, neuropathy, neurological diseases, and nerve injury following surgical trauma. In the past, clinicians could only observe patients over a several-month period in order to determine whether a vocal cord was partially or completely paralyzed. If a nerve problem was suspected, prognosis and expected recovery could not be directly ascertained, and patients often had to wait six months or more before a definitive intervention (such as surgery) was recommended. Now, recovery potential can be more directly studied with laryngeal electromyography.
The laryngeal electromyography interdisciplinary team at GBMC includes an otolaryngologist/ head and neck surgeon, neurologist, and speech pathologist.
The otolaryngologist begins by placing small electrodes in some of the muscles that move the vocal cords. Electrical responses are recorded from these muscles (in response to a series of voice tasks evoked by the speech pathologist), and analyzed by the neurologist. The procedure takes about thirty minutes to complete.
Laryngeal electromyography is useful in evaluating patients with vocal cord paralysis, as well as other vocal cord disorders, such as spasmodic dysphonia, vocal tremors, and the symptoms of progressive neurological diseases (e.g., myasthenia gravis). In cases of vocal cord motion impairment, the potential for recovery can be inferred, often indicating that there are signs of recovery in spite of a lack of apparent clinical improvement. On the other hand, some patients who show no evidence of recovery may benefit from earlier surgical intervention aimed at improving their voice.
Laryngeal electromyography can also be used to pinpoint the site of the lesion in patients with unexplained vocal cord paralysis. During the procedure, patients' responses are correlated with their symptoms to determine which nerves are affected. "If both the superior and inferior laryngeal nerves are affected, this would imply that the nerve was damaged higher up than the level of the larynx" says Dr. Dan Pinheiro. "Alternatively, abnormal responses on both sides of the larynx may represent a more diffuse process, such as a virally induced neuropathy."
Referrals for LEMG
Patients may be referred to the MJ Dance Center to have the LEMG performed by our team, including, the otolaryngologist/head and neck surgeon, neurologist, and the speech pathologist. For further information and scheduling please call (443) 849-2087.
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