Ultrasound-guided biopsy of the cricoarytenoideus lateralis muscle: technique and safety in horses

Reasons for performing study: Current diagnosis of recurrent laryngeal neuropathy (RLN) depends upon disease recognition in the clinically affected horse. Biopsy of the intrinsic laryngeal muscles may provide a method to identify the changes in fibre-type composition that occur in RLN before clinical signs become apparent.

Objective: To develop an ultrasound-guided biopsy technique of the left cricoarytenoideus lateralis muscle (CALM) and evaluate its efficacy and safety in vivo.

Study design: A longitudinal descriptive study.

Methods: Six standing horses underwent ultrasound-guided biopsy of the left CALM. Frozen muscle cores were obtained with a breast biopsy tool. Serial endoscopic, ultrasonographic and physical examinations before and for 8 weeks after the biopsy were assessed for iatrogenic trauma. Histologies of representative muscle core cross-sections were analysed for the total number of muscle fibres obtained with each biopsy.

Results: There were no immediate complications of the procedure and the left CALM was harvested in all instances. Biopsy samples had an average weight of 0.043 g (range = 0.023-0.077 g) and contained 3418 fibres in cross-section (range = 711-7143). Laryngeal endoscopic grade did not change significantly between prebiopsy and the end of the 8 week follow-up. The left CALM had significantly greater echogenicity than the right throughout the study (P<0.001), but there was no difference between the prebiopsy CALM echogenicity and that at completion of the study.

Conclusions: Ultrasound-guided biopsy of the left CALM is safe and well tolerated, providing a minimally invasive method to obtain muscle from healthy horses. This new technique may be applicable in research and clinical settings.