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23b I s with the same procedures. For example, in the case of studies of the duration of collagen or fat as an injectable agent for medialization, reports vary from a few months to years [32-37]; however, the endpoint in determining the outcome of injectables in many studies is voice quality. It is very likely the differences in outcomes between studies are due to the random percentage of patients who happen to have spontaneous recovery of nerve function after their injections. Patients who have good voice due to neural recovery, even synkinetic recovery, could be erroneously judged as having had a permanent response to an injection even if the substance had been completely resorbed.

Surgeons who do not use LEMG can also suffer from the lack of understanding in the underlying pathophysiology as they try to evaluate unsatisfactory results of procedures. It might be that a medialization failed to provide an excellent voice because the surgeon was not aware of a contralateral paresis. The surgeon might be guided by his visual exam to do a revision medialization with a similar poor result, rather than perform a medialization on the contralateral paretic side.

The LEMG allows the treating physician to discover the mechanism of disease before treatment, even if it sometimes does not affect treatment choice. The validity of outcome measures is lost without accurate treatment indications. The advancement of laryngology depends upon the refinement of our empirical treatment and study to include an objective evaluation of the neurophysiology of immobility and dysmotil-ity. It is recommended that all laryngologists work to develop a good program of LEMG so that clinical decisions and treatment outcomes can be evaluated with an understanding of the underlying mechanism of disease.

Philosophy of LEMG

Laryngeal electromyography offers the best diagnostic examination to evaluate the pathophysiology of vocal fold dysmotility. With experience, an otolaryngologist can gather information that can affect treatment planning and operative decisions. The findings of LEMG

can also help the practitioner evaluate the outcomes of therapies with an understanding of the specific disease process. This understanding can lead to a tremendous improvement in both diagnostic and therapeutic skills of the individual practitioner, and overall, can significantly advance the field of laryngology as studies of therapeutic outcomes are related to specific diagnoses.

Case Examples

Case 1

A 37-year-old man presented with an 18-month history of weak voice. There was not particular event at the onset of his voice difficulties. He had undergone numerous examinations with the findings of a normal laryngeal exam. Video-stroboscopy in our clinic demonstrated normal mobility; however, in one short sequence, there was a suggestion of increased amplitude of the mucosal wave on the left side. Laryngeal EMG was performed and demonstrated the presence of "few motor units firing fast" (Fig. 5.8). No fibrillations or positive sharp waves were found that would indicate ongoing denervation and no polyphasic potentials were found that would indicate ongoing reinnervation. Based on these findings and a normal CT scan, the patient agreed to a vocal fold medialization with resolution ofhis voice fatigue.

Case 2

A 33-year-old man presented to clinic with a 2-week history of voice loss without an antecedent event. Examination showed a hoarse, breathy voice with a strobe exam demonstrating left true vocal fold atrophy with bowing and incomplete glottic closure. The LEMG at 1 month after the onset of symptoms showed findings of many motor units firing slowly in the left TA muscle. Examination of the left CT muscle also demonstrated normal motor units with a decreased rate of firing (Figs. 5.9, 5.10). These findings were judged to be consistent with an upper motor neuron lesion. Both an MRI and neurological examinations were normal. Based on the results of the LEMG, the patient received speech therapy as his only intervention. The patient returned at 4 months with a significant improvement in his voice. The LEMG demonstrated a rate near normal with good recruitment (Fig. 5.11).

16:19:25 Fig. 5.8. Few motor units firing fast indicating aperipheral recurrent nerve injury.

Fig. 5.9. This EMG is 1 month after the onset of the patient's hoarseness. The upper channel in this tracing is a signal from a microphone recording the patient's voice. The second channel shows normal motor units firing slowly in the left TA muscle, indicative of a central nervous system injury.
Fig. 5.10. This EMG is 1 month after the onset of the patient's hoarseness. The upper channel in this tracing is a signal from a microphone recording the patient's voice. The lower channel shows normal motor units firing slowly in the left CT muscle, indicative of a central nervous system injury.

Fig.5.n.This EMG ofthe left TA is 4 months after the onset of the patient's hoarseness. At this time the patient reported significant improvement ofhis voice and was again able to sing. The EMG tracing demonstrates improved recruitment with an increased rate of firing when compared with the tracing at 1 month (see Fig.5.9).

References

1. Weddell G, Feinstein B, Paattle R (1944) The electrical activity of voluntary muscle in man under normal and pathological conditions. Brain 67:178242

2. Golseth JG (1950) Diagnostic contributions of the electromyogram. CalifMed 73:355-357

3. GolsethJG(i957) Electromyographicexamination in the office. CalifMed 87:298-300

4. Faaborg-Andersen K, Buchthal F (1956) Action potentials from internal laryngeal muscles during phonation. Nature 177:340-341

5. Buchthal F (1959) Electromyography of intrinsic laryngeal muscles. Q J Exp Physiol 44:137-148

6. Hiroto I, Hirano M, Tomita H (1968) Electromyographic investigation of human vocal cord paralysis. Ann Otol 77:296-304

7. Maronian N et al. (2003) Electromyographic findings in recurrent laryngeal nerve reinnervation. Ann Otol Rhinol Laryngol 112:314-323

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