Pharyngeal Paralysis in Horses
Pharyngeal paralysis refers to paralysis of the upper throat (pharynx). The paralysis makes swallowing difficult or impossible. It may be caused by a nervous system disorder (for example rabies, equine protozoal myeloencephalitis, or botulism) or other disease that causes collapse, obstruction, or malfunction of the pharynx. Conditions such as poisoning, head trauma, and tumor formation may dramatically affect function of the pharynx in many species. Disorders of the guttural pouch can also lead to pharyngeal paralysis. In some instances, the condition may be partial or one-sided (for example, guttural pouch disease) and the horse may be able to swallow, although complications may occur.
In general, pharyngeal paralysis results in severe problems with swallowing; food, water, and saliva come back out through the mouth and nose. Other signs include coughing, trouble breathing, excessive drooling, and teeth grinding. Collapse of throat tissues may cause breathing difficulties. Affected animals are at risk of pneumonia from inhaling food and liquid (aspiration pneumonia), dehydration, and circulatory and respiratory failure. Signs of this include fever, coughing, and choking. This condition may be fatal. In many cases, emergency surgery to provide an airway (tracheostomy) must be done before any more detailed analysis of the condition can be performed.
Veterinarians typically diagnose pharyngeal paralysis based on the horse's history and a physical examination. Additional tests, including blood tests, skull and chest x-rays, endoscopy (a flexible tube with a tiny camera at the end), ultrasonography, computed tomography, and magnetic resonance imaging (MRI), may be necessary to determine the underlying cause. In general, treatment for pharyngeal paralysis is directed toward relieving signs. If the paralysis is caused by another disorder, treatment of that disorder may help correct the problem. Treatment may include drugs to control inflammation, antibiotics to control the complications of aspiration pneumonia, the draining of pharyngeal abscesses (if they are present), and alternative routes of nutrition, such as a feeding tube. Intravenous fluids and medications are often necessary because the horse may be unable to swallow. The outlook depends on the underlying cause. The outlook for a pharyngeal abscess is good, whereas it is uncertain for guttural pouch disease. If the horse does not improve after 4 to 6 weeks of treatment, the outlook is poor, and euthanasia should be considered. Your veterinarian will consider the welfare of the animal when recommending a course of treatment.
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