This equine study aimed to evaluate the use of transcutaneous ultrasound of the left cricoarytenoideus dorsalis muscle (LCAD) and right cricoarytenoideus dorsalis muscle (RCAD) to diagnose recurrent laryngeal neuropathy (RLN).
This research was titled, “External transcutaneous ultrasound technique in the equine cricoarytenoideus dorsalis muscle: Assessment of muscle size and echogenicity with resting endoscopy” and was authored by Satoh, M.; Higuchi, T.; Inoue, S.; Miyakoshi, D.; Kajihara, A.; Gotoh, T.; and Shimizu, Y.
A total of 164 Thoroughbreds underwent resting endoscopy without sedation and were graded using the 4-grade Havermeyer system. Horses with resting grades 1 and 2 with no history of abnormal respiratory noise acted as controls, and horses with resting grades 3 and 4 with a history of abnormal respiratory noise at exercise were deemed to be clinically “affected” by RLN.
Following endoscopy, the horses were sedated and transcutaneous ultrasonography of the larynx was performed. The axial plane thickness, cross-sectional area and echogenicity of the LCAD and RCAD were measured, and the LCAD:RCAD ratios in thickness and area compared between controls and affected horses.
Thickness and area of the LCAD showed a negative correlation with resting laryngeal grade. In contrast, the thickness of the RCAD showed a positive correlation with resting laryngeal grade. Increasing RCAD thickness was found in horses with resting grades 3.II and 4, while increasing RCAD cross-sectional area was found in horses with grade 3.II. LCAD was more hyperechogenic than RCAD in resting grades 3 and 4.
Bottom line: Assessment of the CAD using transcutaneous ultrasonography might be a useful technique in determining whether to perform nerve graft or laryngoplasty.
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