Laryngeal paralysis

Laryngeal paralysis in animals is a condition in which the nerves and muscles that control the movements of one or both arytenoid cartilages of the larynx cease to function, and instead of opening during inspiration and closing during swallowing, the arytenoids remain stationary in a somewhat neutral position. Specifically, the muscle that causes abduction of the arytenoid cartilage, the cricoarytenoideus dorsalis muscle, ceases to function. This leads to inadequate ventilation during exercise and during thermoregulatory panting as well as incomplete protection of the airway during swallowing. Laryngeal paralysis in animals is a condition in which the nerves and muscles that control the movements of one or both arytenoid cartilages of the larynx cease to function, and instead of opening during inspiration and closing during swallowing, the arytenoids remain stationary in a somewhat neutral position. Specifically, the muscle that causes abduction of the arytenoid cartilage, the cricoarytenoideus dorsalis muscle, ceases to function. This leads to inadequate ventilation during exercise and during thermoregulatory panting as well as incomplete protection of the airway during swallowing. One of the most common forms of laryngeal paralysis develops in geriatric medium to large breed dogs, in particular the Labrador retriever, but also some other breeds. This had been traditionally known as idiopathic largyngeal paralysis ('ILP': idiopathic means 'of unknown cause'), and was believed to be a result of a condition affecting the nerves of the larynx (bilateral mononeuropathy of the recurrent laryngeal nerves). However investigations into ILP by two groups in Michigan and Tennessee between 2005 - 2013 showed that the condition was not limited to, or specifically a result of, dysfunction of the laryngeal nerves. Instead it was the most visible symptom of a slowly progressing polyneuropathy of old age, which also affected other nerves in the body. This finding, now generally believed correct following further research, has led to the proposed renaming of this type of laryngeal paralysis from 'Idiopathic laryngeal paralysis' ('ILP') to 'Geriatric onset laryngeal paralysis polyneuropathy' ('GOLPP'). Animals affected by laryngeal paralysis have reduced tolerance for exercise and heat and an increased risk of aspiration pneumonia. The condition is not generally regarded as causing pain, other than physical distress and anxiety caused by any difficulty in breathing or emotional distress from any difficulty with physical movement. Where laryngeal paralysis is related to a general progressive polyneuropathy, as in GOLPP, the nervous system will gradually degenerate causing increasing difficulty in management of the limbs (especially rear limbs), swallowing and breathing, and eventually in most cases euthanasia. Laryngeal paralysis is fairly common in large breed and geriatric dogs, particularly in the Labrador retriever, is rarely found in cats, and can also occur in horses where it is referred to as roaring, roarer's syndrome, or medically as laryngeal hemiplegia or recurrent laryngeal neuropathy (RLN). Laryngeal paralysis can be unilateral or bilateral depending upon dysfunction of one or both arytenoid cartilages. In most cases, the cause of laryngeal paralysis is unknown or idiopathic. However, the disorder may arise secondary to general neuropathies, generalized neuromuscular diseases, muscular diseases, neoplasia either in the cervical (neck) region or the cranial mediastinum, or trauma. This acquired form occurs predominantly in middle-aged to old large breed or giant breed dogs such as the Labrador Retriever, golden retriever, Siberian Husky, Newfoundland, and St. Bernard. Usually these dogs are born with a normal larynx, but over time the nerves and muscles that control the laryngeal cartilages lose function. Laryngeal paralysis may also be congenital in some breeds (e.g. Bouvier des Flandres, Dalmatians, Siberian huskies, and bulldogs), appearing in dogs between two and six months of age. Affected puppies may have difficulty swallowing and breathing, they may gag frequently, and their bark often sounds abnormal. In Dalmatians it is part of another condition called 'laryngeal paralysis-polyneuropathy complex.' Affected puppies should not be used for breeding. Choke collars are not thought to be a significant risk factor for this disorder. However, after LP is diagnosed it is usually recommended to stop using a collar or anything else around the dog's neck and to switch to a harness instead. Signs of laryngeal paralysis include voice change (the dog's bark becomes hoarse-sounding), gagging or coughing (often during or after eating or drinking), exercise intolerance, inspiratory stridor (noisy breathing on inspiration), difficulty breathing, and in severe cases cyanosis or syncope (fainting). Secondary problems may also occur, including aspiration or edema in the lungs, though often the problem remains an upper respiratory problem. Affected dogs are vulnerable to heat stroke and heat exhaustion due to their limited ability to cool themselves down by panting, but the disorder itself can be mistaken for heat stroke.