Guttural Pouch

Guttural Pouch/Graphic Western Horse Magazine

What is a guttural pouch? It is not really that easy to define a horse's guttural pouch. It is understood where it is located and how the anatomy presents; however, much of what a guttural pouch does remains somewhat of a mystery. The horses's guttural pouch is an "air-filled out-pouching of the auditory or Eustachian tube. While all mammals have auditory tubes, not all have these pouches. Horses, mules and donkeys have the largest, with one pouch lying on each side of the back of the throat." The Mysterious Guttural Pouch The pouches contain arteries, some cranial nerves: facial, glossopharyngeal, vagus, accessory, and hypoglossal.

Update: "Guttural pouch empyema (pus collection), mycosis (fungal disease), and tympany (swelling from air accumulation).

With guttural pouch diseases, the vagus and glossopharyngeal nerves running through the medial compartment (that is, the larger of the two segments of the guttural pouch) can become inflamed or even paralyzed, resulting in nasopharyngeal collapse and pDDSP.

'Caution must be used when using resting endoscopy to diagnose intermittent DDSP because even with a history of noise during exercise, studies show that veterinarians only correctly predict intermittent DDSP (iDDSP) in 50% of cases,' said Ducharme. 'Even identification of an ulcer on the caudal free edge (back) of the palate, a flaccid epiglottis, and induction of DDSP by either swallowing or nasal occlusion are not reliable indicators of iDDSP.'

If a horse has an ulcer on the caudal free edge of the soft palate, he might have a subepiglottic ulcer/granuloma or intermittent epiglottic entrapment-when the loose skin located on the bottom of the epiglottis (hence, sub-) flips over, covering the epiglottis like a slipper.

Based on Ducharme's comprehensive review of the available literature, he deemed resting endoscopy an appropriate diagnostic technique for laryngeal hemiplegia. Primarily caused by neuropathy of the left recurrent laryngeal nerve, roaring occurs when the left arytenoid cartilage droops into the airways at the entrance to the trachea (i.e. voice box). Ultrasound examination of the muscles associated with laryngeal function also appears to be highly valuable; however, ultrasound should not replace resting endoscopy, he said, because other obvious lesions can easily be missed. Examples include arytenoid chondromas (rare benign cartilaginous tumors) and subluxations (partial dislocation), abnormal movements of the arytenoid cartilages, inflammation of the epiglottis (called epiglottitis), epiglottic abscess, and subepiglottic ulceration..." (theHorse, By Stacey Oke, DVM, MSc Feb 28, 2017)

Disease of the Guttural Pouch

Since guttural pouches are not sterile, have a thin membrane, and because they have a connection to the Eustachian tubes - middle ear, pharynx, the rear of the mouth and nasal passages, the larynx and esophagus, the guttural pouch can become diseased.

• Guttural pouch tympany/a birth defect.
• Pus collection in pouches (empyema)
• Fungal infection (mycosis/Aspergillosis most common fungi.)
• Inflammation of the middle and inner ear

Theories About Other Uses of Horse's Guttural Pouch

It was once thought that perhaps the guttural pouch functioned as a regulator for pressure changes. However, now it is thought that the guttural pouch acts as a cooling device for the horse's brain..."Researchers now believe that heat is removed from the exercising horse's brain via transfer from the blood to the air in the guttural pouch and then out through the pharynx. This mechanism also provides a clue as to why diseases occur in this anatomical area and why those diseases can be deadly..." The Mysterious Guttural Pouch

Diagnosis of Guttural Pouch Disease:
Clinical Signs:

• Nasty, nasal discharge
• Painful swelling in the parotid area (side of the face)
• Stiff head carriage and harsh breathing
• Fever
• Depression
• Anorexia
• Epistaxis (nose bleed)
• Dysphagia (difficulty in swallowing)
• Rhinititis/nasal discharge/dyspnea (shortness of breath)
• Acute enteritis (inflammation of the small intestine)
• Bleeding in horses with mycosis
• Colitis caused from invading aspergillus in intestinal mucosa
• Locomotal disturbances/from spread of infection to brain
• Visual disturbances/from spread of infection to optic nerve
• Diagnosis is determined by endoscopic examination of the guttural pouch
• Radiographs of the pharynx will demonstrate a fluid line in the guttural pouch and may allow the clinician to identify an associated retropharyngeal mass

Treatments:

• Lavage-Rupturing the abscess
• Surgical drainage
• Tracheotomy
• Endoscopic removal depending on severity
• Systemic and topical antimicrobial therapy accompanies treatments
• Embolization of the internal carotid artery

Guttural Pouch disease is a really nasty problem. It is imperative that your vet be called immediately before many complications may arise as the disease progresses.

For More Information:

Western Horseman Magazine/January 2001. An excellent reference article.