Laryngeal Hemiplegia in a Cat - Video-assisted Arytenoid Lateralization

Abstract

Background: Laryngeal paralysis is a respiratory disorder characterized by a complete or partial failure in the ability to abduct the arytenoid cartilage, which can be either unilateral or bilateral. Direct observation of the lack of movement under controlled conditions is diagnostic, and videolaryngoscopy can be a helpful tool. This condition is well described in dogs; however, but it is rare in cats, and unilateral arytenoid lateralization is the surgical procedure of choice for correcting this condition. This report presents a unique approach to laryngeal hemiplegia in a cat, describing the diagnosis by videolaryngoscopy and correction by video-assisted arytenoid lateralization. 

Case: A 4-year-old mixed-breed female cat was examined owing to respiratory noises; however, the cat showed no improvement with clinical treatment. Laryngotracheoscopy was performed using a 5 mm and 30° optic for the assessment of laryngeal movement, which was then replaced by a 2.9 mm and 30° optic mounted on a 3.4 mm working channel for tracheoscopy. Moderate to severe edema of the arytenoid mucosa and rima glottis, eversion of the laryngeal saccules causing mild to moderate collapse of the larynx, absent right arytenoid movement, and subtle left arytenoid movement were observed. Given the diagnosis, the chosen course of action was unilateral arytenoid lateralization, accompanied by laryngoscopic monitoring for the correction of laryngeal paralysis. Surgical access was made ventral to the junction of the left maxillary and linguofacial veins. The dorsal border of the thyroid cartilage was pulled ventrally by a support suture. The remaining left dorsal cricoarytenoid muscle was identified, and the cricoarytenoid joint was partially dislocated to facilitate the passage of sutures around the left caudal border of the cricoid cartilage. The closure of the cricoarytenoid sutures was monitored in real-time through laryngoscopy to assess the tensioning and confirm the lateralization of the arytenoid cartilage. This was achieved using a 2.9 mm, 30° optic mounted on a 3.4 mm working channel. 

Discussion: The absence of arytenoid abduction during inhalation leads to increased resistance to airflow and consequently, to the presentation of clinical signs such as stridor, cyanosis, inspiratory dyspnea, and exercise intolerance. The patient in this report had stridor and experienced difficulty in breathing, which was initially misattributed to other pathologies. The use of doxapram induces deeper breathing and more pronounced abduction of the patent cartilages, without affecting those that are paralyzed, and therefore, helped in confirming arytenoid paralysis. However, its use is associated with adverse reactions including an increase in the depth of breathing, tachycardia, hypertension, and cardiac arrhythmias. In this case, the patient had transient tachypnea. Surgical treatment through bilateral arytenoid lateralization is not recommended owing to the risk of aspiration pneumonia. Instead, unilateral arytenoid lateralization is the preferred procedure in cats, for both unilateral and bilateral laryngeal paralysis. However, even with surgical treatment, a small likelihood of aspiration remains throughout the lifetime of the patient, which, up to this point, has not occurred in this case. This case stands out from other previously reported ones because, in addition to the diagnosis of laryngeal paralysis made via videolaryngoscopy, the surgical procedure for the correction was also video-assisted. This ensured appropriate suture tension, achieving moderate abduction of the arytenoid cartilage without excessive tension, which could lead to post-surgical laryngeal dysfunction. We conclude that video-assisted monitoring of arytenoid lateralization in cats is potentially useful for the success of the procedure. 

Keywords: arytenoidplasty, laryngoscopy, stridor. 

Título: Hemiplegia laríngea em gato - lateralização de aritenoide videoassistida 

Descritores: aritenoideplastia, laringoscopia, estridor.