Guttural pouch
The condition predisposes young horses to infection, often including severe swelling and often requires surgery to correct.
The opening into the pharynx is called the nasopharyngeal ostium, which is composed of the pharyngeal wall laterally and a fibrocartilaginous fold medially.
The glossopharyngeal, vagus, accessory and hypoglossal nerves;[citation needed] the sympathetic trunk leaving from the cranial cervical ganglion; and the internal carotid all cause a mucosal fold indent within the medial compartment, visible when viewed endoscopically.
[5] The function of the guttural pouches has been shown with experimental data to participate in the rapid cooling of arterial blood destined for the brain and surrounding structures.
In other words, the horse's guttural pouches are 'brain-cooling devices', cooling blood within the internal carotid arteries during hyperthermia that occurs during heavy exercise.
These guttural pouch microvascular plexuses, engulfing the internal carotid arteries, are typical of countercurrent heat exchangers recognised in other animal species, supporting the data that guttural pouches participate in selective brain cooling, even at lower air flow rates.
[11] If the drainage tract becomes blocked for any reason, the mucous secretions can accumulate and cause the pouch to distend, producing a visible and palpable protrusion behind the mandible.
Clinically apparent symptoms include painful swelling of the parotid area and recurrent infected nasal discharge, and in severe circumstances, difficulty breathing and abnormal head carriage may be observable.
Radiographic examination of the area will show an opaque fluid line in the pouch and if a retropharyngeal lymph node is involved, it may reveal a mass.
[13] In mild, acute cases of empyema, a saline or polyionic solution lavage is often performed via an endoscope or catheter repeatedly until the exudate drains.
The specific cause of guttural pouch tympany is not known, but it is suspected that it is more common when there are defects of the plica salpingopharyngeus, and/or the pharyngeal orifice where they act as a one-way valve that does not allow air to escape.
Treatment protocols may include, but are not limited to, surgical intervention and in cases where surgery is not an option, insertion of a transnasal Foley balloon catheter in an attempt to remodel the pharyngeal orifice.
[13] Clinical signs include unilateral or bilateral epistaxis due to erosion of the artery walls,[13] nasal discharge and cranial nerve dysfunction.
[22] Treatment typically consists of topical as well as systemic antifungal medication, paired with surgery to occlude or embolise affected arteries.
Horses that experience dysphagia or other forms of nerve dysfunction as a result of GPM have a poorer prognosis that those who have not exhibited those symptoms.
