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Letters to the Editor
January 2002

In reply

Arch Otolaryngol Head Neck Surg. 2002;128(1):91-92. doi:

Drs Munin and Rosen have raised some concerns concerning (1) our classification of neural damage, (2) our definitions of electrophysiologic findings, and (3) our way of grouping subsets for statistical analysis. There is no doubt that Seddon's1 classification system is less than perfect for LEMG. Hopefully, every laryngeal electromyographer is aware of the restrictions that Drs Munin and Rosen describe. However, to classify electrophysiologic findings according to Seddon in order to describe a diagnosis has been clinical routine for years in many centers. Our goal was to test the reliability of this approach using the current standard of practice, since data concerning the prognostic value of LEMG have been lacking so far.

My coauthors and I agree with Drs Munin and Rosen that we might have difficulty with interpreting our electromyographic recordings in a blinded fashion, mainly because we are convinced that reading still pictures of LEMG can never make sense anyway. Laryngeal electromyography is a dynamic examination, the results of which can be interpreted in a meaningful fashion only when oscillographic presentation of potentials, the sound these potentials are generating, and the behavior of the patient (for the identification of artefacts) are offered simultaneously. As Drs Munin and Rosen correctly point out, there is a great variability of potentials. Recording of potentials is influenced by many parameters; therefore, often there are eletrophysiologic readings that do not look as ideal as in textbooks.

To classify vocal fold mobility is difficult and prone to investigator bias. Therefore, my colleagues and I defined complete recovery only as completely restored vocal fold mobility. Following Drs Munin and Rosen's suggestion, and grouping all cases with completely free and substantially recovered mobility, would certainly improve the figures for the negative and positive prognostic values of LEMG. However, we believe that data calculated on that basis would be biased beyond control and therefore might be considered useless.

References
1.
Seddon  H Three types of brain injury.  Brain.1943;66:237-288.Google Scholar
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