This disease is thought to be caused by an underlying neuromuscular disorder of the cricopharyngeus muscle, etiology unknown. Swallowing normally involves three phases (oropharyngeal, esophageal, and the gastroesophageal) and it is in the middle esophageal phase, when the upper esophageal sphincter fails to relax that the disorder manifests. Failure for this muscle to relax can be caused by asynchrony or achalasia.
Cricopharyngeal achalasia occurs when the upper esophageal sphincter fails to relax or when there is asynchrony between contraction of the pharynx during swallowing and relaxation of the sphincter.
Clinical signs frequently develop in pups at or soon after weaning, with characteristic dysphagia, frequent swallowing, gagging, regurgitation and nasal reflux/discharge. These dogs appear clinically healthy unless there is secondary aspiration pneumonia or emaciation.
Diagnosis is one of exclusion of other causes and use of fluoroscopic swallowing studies (using liquid barium or barium soaked kibble) to make a definitive confirmation of the disorder, showing disturbances to normal bolus formation and contraction of the pharyngeal muscles.
Treatment for this condition is either the transection or the complete removal of the muscles that surround the esophagus in this region (cricopharyngeal myotomy); specifically the cricopharyngeus muscle, the thyropharyngeus muscle, or both.
Complications arising from both of these surgical procedures may occur if concurrent aspiration pneumonia or malnutrition are not addressed prior to surgery, and include fibrosis, recurrent laryngeal paralysis, esophageal perforation, recurrence of dysphagia, and pharyngocutaneous fistula.
In dogs with achalasia complicated by myasthenia gravis, laryngeal paralysis and esophageal stricture, surgery may not be indicated and conservative medical therapy with prednisolone may be warranted.
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