Pharyngeal paralysis is generally a disease of the central or peripheral nervous system. Symptoms of pharyngeal paralysis include dysphagia, nasal discharge of food, ptyalism, coughing, and upper respiratory tract noise. Diagnosis is based on clinical signs, endoscopic examination (rhinolaryngoscopy), and diagnostic imaging (eg, radiography and CT). Treatment is mainly symptomatic; however, treatment options can include medical and surgical management. Prognosis for affected animals is fair to guarded.
Pharyngeal paralysis may be the result of a central or peripheral nervous system disorder or may develop secondary to severe local disease that may cause collapse, obstruction, or malfunction of the pharynx. Of CNS disorders, rabies is the most important of viral causes of encephalomyelitis, although perhaps not the most frequent. Toxicoses affecting the CNS including lead toxicity, head trauma, infections with intracranial abscessation, and neoplasia may also result in pharyngeal paralysis in many species.
Courtesy of Dr. Jan Hawkins.
Peripheral causes of pharyngeal paralysis include pharyngeal trauma and abnormalities of the pharynx, particularly involving the guttural pouch of horses. Disorders of the guttural pouch resulting in pharyngeal paralysis include guttural pouch mycosis, guttural pouch empyema, guttural pouch neoplasia, and osteoarthropathy of the temporohyoid joint. Equine protozoal myeloencephalitis can also cause pharyngeal paralysis in some affected horses. The extent of pharyngeal paralysis is variable, depending on whether the abnormality is unilateral or bilateral and central versus peripheral. Unilateral lesions may result in partial pharyngeal malfunction. For example, horses with guttural pouch disease may be able to swallow but may still develop clinical signs of dysphagia (eg, nasal discharge of food or water, coughing).
Clinical Findings and Lesions of Pharyngeal Paralysis in Animals
Courtesy of Dr. Jan Hawkins.
Clinical signs of pharyngeal paralysis include dysphagia with oral or nasal discharge of food, water, or saliva. Other clinical signs include coughing, dyspnea, ptyalism, or bruxism. Affected animals are at risk of inhalation pneumonia, dehydration, and shock. Affected animals frequently have one or more clinical signs, including pyrexia, retching, and signs compatible with esophageal obstruction. Severely affected animals may die or should be considered for euthanasia. Animals with dyspnea may require an emergency tracheostomy before any clinical diagnostic techniques can be performed.
Diagnosis of Pharyngeal Paralysis in Animals
Clinical signs
CBC and serum biochemical analysis
Diagnostic imaging, typically plain radiography and CT
Postmortem examination in patients that die or are euthanized
History and clinical signs are usually diagnostic for pharyngeal paralysis. A baseline CBC and serum biochemical analysis should be performed. Affected animals be hemoconcentrated due to dehydration, have electrolyte and acid-base disturbances, and may exhibit prerenal azotemia. Serologic testing, skull radiographs, thoracic radiographs to evaluate for aspiration pneumonia, endoscopy, ultrasonography, CT scan, and MRI (if available) are all valuable aids to determine whether the underlying cause is central or peripheral. The use of CT and MRI has particular value in evaluating CNS causes of pharyngeal paralysis in small animals. Animals suspected of having rabies should be handled appropriately.
Treatment of Pharyngeal Paralysis in Animals
Courtesy of Dr. Jan Hawkins, Purdue University.
Identification of the underlying cause
Administration of antimicrobial and anti-inflammatory drugs
Intravenous fluid therapy with or without partial or total enteral or parenteral nutrition
Surgical management (eg, ceratohyoidectomy in horses with temporohyoid osteoarthropathy
Treatment protocols for pharyngeal paralysis vary depending on the underlying cause. Treatment generally includes the administration of antimicrobial and anti-inflammatory medications. Because of the patient's inability to swallow normally, intravenous administration is preferred. Animals with hemoconcentration or other indicators of dehydration should be administered intravenous fluids. If the animal is unable to eat without aspiration, extraoral or parenteral nutrition should be strongly considered. Extraoral alimentation with pharyngostomy, esophagostomy, or nasogastric tubes or temporary rumenostomy in ruminants can be an economical and effective way to provide nutritional support. Other treatments include local treatment for pharyngeal abscesses.
The prognosis for pharyngeal paralysis varies depending on the underlying cause. The prognosis for pharyngeal abscessation can be favorable, whereas the prognosis for guttural pouch disease can be guarded. In general, if affected animals do not improve after 4–6 weeks of symptomatic treatment, the prognosis is poor and euthanasia should be considered.
Key Points
An accurate diagnosis is crucial to obtaining a successful outcome.
Supplemental nutrition is required in many cases because affected animals are unable to ingest food normally.
Prognosis is guarded to poor in most cases.
For More Information
Also see pet health content regarding pharyngeal paralysis in horses.
