Pharyngeal paralysis is generally a disease of the central or peripheral nervous system. Clinical signs 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 or CT). Treatment consists mainly of supportive care; however, treatment options can include medical and surgical management. The prognosis for affected animals is fair to guarded.
Pharyngeal paralysis can result either from a central or peripheral nervous system disorder or secondary to severe local disease that might cause collapse, obstruction, or malfunction of the pharynx. Of CNS disorders, rabies is the most important viral cause of pharyngeal paralysis (due to encephalomyelitis), although perhaps not the most frequent.
Toxicoses that affect the CNS, including lead poisoning, head trauma, infections with intracranial abscessation, and neoplasia, can result in pharyngeal paralysis in many species. In addition, some neonatal foals are dysphagic secondary to hypoxic ischemic encephalopathy or pharyngeal weakness (commonly recognized in Friesians). Many of these foals regain normal function after a period of supportive care.
Peripheral causes of pharyngeal paralysis in horses include pharyngeal trauma and abnormalities of the pharynx, particularly involving the guttural pouch. 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 cause pharyngeal paralysis in some horses.
The extent of pharyngeal paralysis varies, depending on whether the abnormality is unilateral or bilateral and central or peripheral. Unilateral lesions can result in partial pharyngeal malfunction. For example, horses with guttural pouch disease might be able to swallow but might still develop clinical signs of dysphagia (eg, nasal discharge of food or water, coughing).
In cattle, retropharyngeal abscesses can cause dysphagia. These abscesses can develop secondary to iatrogenic trauma (eg, balling gun injury), ingestion of foreign bodies, or lymph node abscesses. In small ruminants and pigs, otitis media or interna can lead to dysphagia. In ruminants, listeriosis can cause dysphagia and abnormal mentation.
Clinical Findings and Lesions of Pharyngeal Paralysis in Large Animals
Clinical signs of pharyngeal paralysis include dysphagia, with oral or nasal discharge of food, water, or saliva. Other clinical signs include coughing, dyspnea, ptyalism (see ), or bruxism. Affected animals are at risk of aspiration pneumonia, dehydration, and hypovolemic shock.
A Quarter Horse yearling colt with ptyalism and feed present at the nares.
Courtesy of Dr. Jan Hawkins.
Animals with pharyngeal paralysis frequently have one or more clinical signs, including pyrexia, retching, and signs compatible with esophageal obstruction. Severely affected animals might die or should be considered for euthanasia. Patients with dyspnea might require an emergency tracheostomy before any clinical diagnostic techniques can be performed.
Diagnosis of Pharyngeal Paralysis in Large Animals
Clinical signs
CBC and serum biochemical analysis
Endoscopy of the upper respiratory tract and/or pharynx
Diagnostic imaging, typically plain radiography and CT, ultrasonography, or MRI
Postmortem examination
History and clinical signs are usually diagnostic for pharyngeal paralysis. A baseline CBC and serum biochemical analysis should be performed. Affected animals might show hemoconcentration as a result of dehydration, might have electrolyte and acid-base disturbances, and might exhibit prerenal azotemia.
Serological testing, skull radiography, thoracic radiography to evaluate for aspiration pneumonia, endoscopy, ultrasonography, CT, and MRI (if available) are all valuable aids to determine whether the underlying cause of pharyngeal paralysis is central or peripheral. CT and MRI can be helpful in evaluating causes of pharyngeal paralysis.
Animals suspected of having rabies should be handled appropriately.
Treatment of Pharyngeal Paralysis in Large Animals
Identification of underlying cause
Antimicrobial and anti-inflammatory drugs
IV fluid therapy
Nutritional support
Surgical management, if indicated
Pearls & Pitfalls
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Treatment protocols for pharyngeal paralysis vary depending on the underlying cause. Treatment generally includes the administration of antimicrobial and anti-inflammatory medications. When possible, aspirates should be obtained to submit samples for microbial culture and susceptibility testing. Aspirates can be obtained with the aid of ultrasonography or CT.
Standing surgical placement of an esophagostomy tube for extraoral alimentation in a horse.
Courtesy of Dr. Jan Hawkins.
Because patients with pharyngeal paralysis cannot swallow normally, IV administration of medications is preferred. Animals with hemoconcentration or other indicators of dehydration should be administered IV fluids.
If the patient is unable to eat without aspirating, extraoral or partial or complete parenteral nutrition should be considered. Extraoral alimentation with pharyngostomy, esophagostomy (see ), or nasogastric tubes, or with temporary rumenostomy in ruminants, can be an economical and effective way to provide nutritional support.
Other treatments for pharyngeal paralysis include surgical drainage of pharyngeal abscesses.
The prognosis for pharyngeal paralysis varies depending on the underlying cause. For patients with pharyngeal abscessation, the prognosis can be favorable; for patients with guttural pouch disease, the prognosis is usually guarded. In general, if affected animals do not improve after 4–6 weeks of supportive care, the prognosis is poor and euthanasia should be considered.
Key Points
An accurate diagnosis of pharyngeal paralysis is crucial for a successful outcome.
Supplemental nutrition is required in many cases because affected animals are unable to ingest food normally.
The prognosis is guarded to poor in most cases.
For More Information
Auer JA, Stick JA, Kümmerle JM, Prange T, eds. Equine Surgery. 5th ed. Elsevier; 2019.
Fubini SL, Ducharme NG, eds. Farm Animal Surgery. 2nd ed. Elsevier; 2017.
Also see pet owner content regarding pharyngeal paralysis in horses.
