Ultrasonography detects early laryngeal muscle atrophy in an equine neurectomy model.

Heather J Chalmers,Jeff Caswell,Norm G Ducharme,Richard J Piercy,Laurent Viel,Justin Perkins,David Goodwin

doi:10.1002/mus.24785

Heather J Chalmers, Jeff Caswell + Show 5 more

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https://doi.org/10.1002/mus.24785

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Abstract

A unilateral neurectomy model was used to study the relationship between histologic and ultrasonographic tissue characteristics during muscle atrophy over time. This investigation was an in vivo experimental study in an equine model (n = 28). Mean pixel intensity of ultrasonographic images was measured, a muscle appearance grade was assigned weekly, and muscles were harvested from 4 to 32 weeks. Minimum fiber diameter, fiber density per unit area, percent collagen, percent fat, and fiber type profile were measured from muscle cryosections and correlated with the ultrasonographic parameters. A significant relationship was identified between collagen content, minimum fiber diameter, and ultrasonographic muscle appearance by as early as 8 weeks. There was no apparent association between fat content of muscle and the ultrasonographic appearance of atrophy before 28 weeks. Early muscle atrophy before fatty infiltration is detectable with ultrasound. The effect of muscle collagen content on echointensity may be mediated by reduced fiber diameter.

Highlights

Diagnostic imaging modalities are at the forefront of the emerging field of non-invasive tissue characterization and offer expanding potential as a non-invasive way to assess muscle
Neurectomy resulted in ultrasonographically-visible muscle atrophy that was minimally apparent at 4 weeks and became progressively more evident at each time point thereafter
A significant increase was not apparent until 14 weeks postneurectomy in the right lateral cricoarytenoid (LCA) muscle compared to the left (P=0.001) (Figure 3C) and until 18 weeks post-neurectomy in the right posterior cricoarytenoid (PCA) muscle compared to the left (P=0.043) (Figure 3C)

Summary

Introduction

Diagnostic imaging modalities are at the forefront of the emerging field of non-invasive tissue characterization and offer expanding potential as a non-invasive way to assess muscle. There is need for detailed study of the relationship between the histologic and ultrasonographic findings of muscle tissue in health and disease. The ultrasonographic appearance of muscle has been characterized as having increased echogenicity, while with certain myopathies no such change is observed.[1] The reason(s) for altered appearance of muscle under conditions of neurogenic atrophy are understood incompletely. Several authors have hypothesized that the increase in echogenicity is the result of fat and fibrous tissue infiltration.[2,3,4,5] Isolated attempts have been made to correlate muscle echogenicity and histologic parameters with mixed results; the relative effects of fat and collagen content have been inconsistent in the models studied

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