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Letters to the Editor
January 2002

Use of Laryngeal Electromyography

Arch Otolaryngol Head Neck Surg. 2002;128(1):91-92. doi:10.1001/archotol.128.1.91

We have several significant concerns regarding the article titled "Prognostic Value of Laryngeal Electromyography [LEMG] in Vocal Fold Paralysis," which was published in the February 2001 issue of the ARCHIVES.1 There are several methodological flaws that limit the potential positive aspect of this article.

The use of Seddon's2 classification system is not appropriate for LEMG. To the modern electromyographer, Seddon's classification system is useful only for the interpretation of nerve conduction study findings. Neurapraxia is a condition in which stimulation of a motor nerve distal to a lesion produces a normal compound muscle action potential, whereas stimulation above a lesion produces little or no response. Axonotmesis is determined when low-amplitude compound muscle action potentials are recorded with nerve stimulation above and below a suspected lesion. Laryngeal electromyography cannot by itself differentiate these 2 processes with total clarity because there are no clinically useful motor nerve conduction studies available. In both examples noted above, LEMG could demonstrate identical decreased motor unit recruitment with attempted vocalization in proportion to the severity of the lesion. In cases involving axonotmetic injury, one would expect to see fibrillation (denervation) potentials at rest. However, our experience with LEMG is that the small laryngeal muscles do not fibrillate to the degree found in larger limb muscles.3 Fibrillations can vary in number and amplitude based on when they are recorded from the time of injury, and no data regarding mean onset time are presented in the article by Sittel et al.1