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Basics ⬇

Outline

BASICS

Overview!!navigator!!

  • Fungal infection which usually affects 1 GP, but bilateral lesions are possible (20%)
  • Clinical signs relate to damage to the arteries and nerves underlying the GP mucosa
  • Spontaneous epistaxis in a resting horse usually is the first sign

Signalment!!navigator!!

  • More common in mature horses but also reported in foals
  • No breed, sex, genetic, or geographic predisposition
  • Not contagious

Signs!!navigator!!

  • Epistaxis—reason for consultation in 74% of horses affected by mycosis; not related to exercise; severity varies from a mild, unilateral, blood-tinged nasal secretion to fatal hemorrhage. Bleeding may be bilateral with severe hemorrhage. Premonitory bleeding often, but not always, precedes fatal hemorrhage
  • Dysphagia—results from lesions involving the vagus, glossopharyngeal, or hypoglossal nerve
  • Other neurologic deficits—abnormal respiratory noise (laryngeal hemiplegia, dorsal displacement of the soft palate, pharyngeal collapse), facial paralysis, and Horner syndrome
  • Less commonly observed—headshaking, abnormal head posture, visual disturbances, neck stiffness (parotid pain, septic arthritis of the atlanto-occipital joint)
  • May be asymptomatic

Causes and Risk Factors!!navigator!!

  • No evidence of initiating factor predisposing to growth of opportunistic fungi in the affected GP. Aspergillus fumigatus is the most frequently isolated fungus
  • Erosion of the arterial wall by fungus will cause epistaxis; internal carotid will be affected in 2/3 cases. The external carotid or 1 of its branches will be affected in 1/3 cases
  • Fungus can also cause nerve damage either by inflammation and infiltration of nerves by mycelium or by diffusion of fungal toxins. Nerve damage can also result from sequestration of nerves in scar tissue. Cranial nerves (VII, IX, X, XI, XII) and their branches, cranial cervical ganglion, and sympathetic trunk may be affected

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

  • Epistaxis—exercise-induced pulmonary hemorrhage, ethmoid hematoma, head trauma, foreign bodies, upper airway neoplasia, longus capitis muscle rupture, and coagulopathy
  • Dysphagia—esophageal obstruction, megaesophagus, fracture of the hyoid apparatus, inflammatory reaction, pharyngeal mass, empyema or tympanism of the guttural pouch, central nervous system affections

CBC/Biochemistry/Urinalysis!!navigator!!

  • Hypoproteinemia and anemia in cases of significant blood loss
  • Leukocytosis and hyperfibrinogenemia in cases of aspiration pneumonia

Imaging!!navigator!!

Endoscopy

  • Critical for diagnosis, but risky in case of epistaxis
  • In case of bleeding from pharyngeal orifices or nostril, prepare surgical facilities and scope the horse in the induction stall. The endoscope should not be introduced into the GP in case of active bleeding as this could dislodge the thrombus. Large amount of blood in the GP may preclude visualization of affected nerves and arteries
  • If no bleeding seen from pharyngeal orifices, perform a thorough examination of both GPs to determine which vessels are affected. Mycotic lesions appear as a diphtheritic membrane on the surface of the mucosa. No relationship exists between lesion size and severity of the clinical signs
  • In cases of dysphagia or abnormal respiratory noise, examine for food material, pharyngeal collapse, laryngeal hemiplegia, soft palate displacement

Treatment ⬆ ⬇

TREATMENT

  • The first goal is to prevent spontaneous fatal hemorrhage and the treatment is surgical. Perform arterial occlusion as soon as possible. In life-threatening emergency, ligature of the common carotid artery may in some cases prevent fatal bleeding. However, this does not eliminate completely the risk of fatal hemorrhage due to retrograde blood flow
  • The aim is to stop blood flow distally and proximally to the lesion. Different techniques of internal occlusion have been described—balloon catheter occlusion (first described technique, high complication rate), transarterial coil or nitinol plug embolization under fluoroscopic guidance (less invasive, low complication rate, specialized equipment)

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

Medical treatment provides doubtful results.

Contraindications/Possible Interactions!!navigator!!

  • Use α2-agonists with caution if epistaxis; they may worsen hemorrhage by increasing the arterial pressure
  • Possible irritating or neurotoxic effect of topical drugs

Follow-up ⬆ ⬇

FOLLOW-UP

  • Surgical treatment in cases of epistaxis provides an excellent prognosis for survival (84%)
  • Guarded prognosis for recovery of neurologic dysfunction (50%)
  • Rare spontaneous regression
  • 50% have fatal hemorrhage if left untreated

Miscellaneous ⬆ ⬇

MISCELLANEOUS

Abbreviations

GP = guttural pouch

Suggested Reading ⬆ ⬇

Lepage OM, Picot-Crézollet C. Trans-arterial coil embolization in 31 horses (1999–2002) with guttural pouch mycosis: a 2-year follow-up. Equine Vet J 2005;37:430–434.

Author(s) ⬆

Author: Perrine Piat

Consulting Editors: Daniel Jean and Mathilde Leclère

Acknowledgment: The author and editors acknowledge the prior contribution of Vincent J. Ammann.