Ultrasonographic evaluation of Cricoarytenoideus lateralis muscle in Standardbred horse

Abstract

The cricoarytenoideus lateralis muscle (CALM) is an adductor of the arytenoid cartilages but is not directly involved in the pathogenesis of recurrent laryngeal neuropathy (RLN) as the abductor cricoarytenoideus dorsalis muscle (CADM) is. Nevertheless, the CALM is the first muscle to experience a neurogenic atrophy in the course of RLN and this feature explains its potential importance in RLN diagnosis. On 30 gelding and 30 female Standardbred horses weighing about 500 kg and aged between 3 and 9 years, an ultrasound examination of the larynx was performed in order to assess shape, size, and echogenicity of the CALMs. The mean width, thickness, and area of the muscle were respectively 1.42 cm, 1.23 cm, and 1.36 cm^2 for the right side and 1.40 cm, 1.21 cm, and 1.34 cm^2 for the left side. No differences were found in relation to sex, age, or difference between right and left muscle. Focal calcifications of thyroid cartilage prevented visualization of the muscles, especially in females.