Laryngeal Paralysis / Lar Par / fetch dvm360 conference March 2023 / Dr. Shadi Ireifej / VetTriage скачать в хорошем качестве

Laryngeal Paralysis / Lar Par / fetch dvm360 conference March 2023 / Dr. Shadi Ireifej / VetTriage

Acquired laryngeal paralysis is more commonly seen than the congenital form and is a common cause of upper airway obstruction in large and giant breed dogs. It has been diagnosed in cats and small breed dogs as well. One quarter of all dogs are affected with some degree of laryngeal paralysis or paresis. Of all patients with upper airway obstruction, 5% of them are secondary to laryngeal paralysis. Differential diagnoses include cervical penetrating wounds (dogfights), strangulating trauma, surgical trauma (ventral slot procedure, thyroid gland surgery, and tracheal surgery), infection (retropharyngeal abscess formation, rabies virus infection), granuloma formation, neoplastic disease (thyroid carcinoma, thymoma, lymphosarcoma), paraneoplastic disease, central nervous system disease, laryngeal myopathy, or a generalized neuromuscular disorder of the intrinsic laryngeal muscles (polyneuropathy, polyradiculoneuritis, polymyopathy, myasthenia gravis, etc.). Dogs presenting with laryngeal paralysis typically have insidious and progressive clinical signs that extend over months to years. The clinical signs and their respective percent incidence include inspiratory laryngeal strider (100% incidence), exercise intolerance (90%), dysphonia (70%), gagging and coughing (60%), expiratory laryngeal stridor (55%), hyperthermia/heatstroke (30%), vomiting, dysphagia, dyspnea, cyanosis, and syncope. On physical examination, the laryngeal region may be auscultated with and without mild laryngeal compression before and after exercise. In 85 to 100% of affected dogs an increased respiratory noise is heard, especially during inspiration. The respiratory rate is normal in only a few dogs before exercise but all dogs develop an increased rate after exercise. Inspiratory dyspnea make cause secondary regurgitation, esophageal disease, gagging, retching, and an elongated soft palate. Dogs with unilateral disease are rarely symptomatic. The left side is more commonly affected in dogs, horses, and people. This is due to the recurrent laryngeal nerves longer course and fewer nerve fibers than the right recurrent laryngeal nerve. Bilateral disease is more common than unilateral and occurs in 81 to 100% of cases. Laryngeal paralysis can be symmetric or asymmetric. Over the course of this disease these clinical signs progress from intermittent to consistent as laryngeal paresis progresses to flaccid paralysis and disease becomes bilateral. The signs worsen with exercise, excitement, and increased ambient temperature due to increased oxygen demands leading to greater inspiratory effort and greater negative pressure that draws the arytenoid cartilages and vocal folds medially. The arytenoid cartilages and vocal fold failed to abduct, remaining in a paramedian position. This results in a decreased glottic opening, causing impaired inspiration, and an upper respiratory obstruction. Increased resistance to airflow develops and the resulting turbulence is observed as inspiratory laryngeal stridor. During times of stress or exercise the air flow is increased through the larynx causing a decrease in intraglottic pressure. This pulls the arytenoid cartilages and vocal fold across the lumen further, increasing the resistance to inspiratory gas flow and causes arytenoid cartilage mucosal trauma. This exacerbation of an already present upper airway obstruction causes concurrent laryngeal inflammation, edema, tonsillitis, and weakening of the cartilages, and an expiratory dyspnea. A vicious cycle then forms. The most common causes of acquired laryngeal paralysis is idiopathic, a diagnosis of exclusion, making up 89% of cases. In people, 30% of laryngeal paralysis cases are deemed idiopathic. It is becoming more evident that neuromuscular disease may play a monumental role in what has previously been thought of as an idiopathic condition. This is a disease of older dogs averaging nine years of age and ranging from 9.5 to 12.2 years of age. Older animals are four times as likely to develop laryngeal paralysis than younger animals. Neutered males appear to be predisposed. Reported ratios of male to female are 3.7:1, 3:1, and 1:1. There is a direct relationship to age, body weight, and body condition score. Commonly affected breeds including the Labrador Retriever (35 to 73% incidence), Golden Retriever, St. Bernard, Irish Setter, Afghan Hound, Chesapeake Bay Retriever, and Great Dane. The Labrador retriever and Rottweiler are twice as likely to be affected and the Labrador retriever is the most commonly affected breed. A diagnosis of laryngeal paralysis is made based on history, signalment, clinical signs, and visualization of the affected arytenoid cartilages. Diagnosis based on clinical suspicion carries a 91.6% sensitivity and 98.5% specificity. Most common surgical treatment techniques is unilateral arytenoid cartilage lateralization (cricoarytenoid and/or thyroarytenoid laryngoplasty, also known as a laryngeal “tieback” procedure).