Equis ISSN 2398-2977

Epiglottis: persistent frenulum

Contributor(s): Tim Brazil, Nicola Menzies-Gow

Introduction

  • Cause: congenital band of tissue on the ventral aspect of the epiglottis to tongue.
  • Signs: young foal with nursing difficulties - dysphagia, oronasal reflux, cough; aspiration pneumonia - tachypnea, pyrexia, weakness.
  • Diagnosis: endoscopy.
  • Treatment: surgical transection of the frenulum.
  • Prognosis: good with early diagnosis; poor with advanced pneumonia.

Pathogenesis

Etiology

  • Larynx is formed from several embryonic structures:
    • Mucosa - endodermal.
    • Cartilage and muscles - mesenchymal (within 3rd, 4th and 5th branchial arches).
  • There are several embryonic processes that may contribute to frenulum formation:
    • During proliferation of the laryngeal epithelium there is temporary occlusion of the lumen, then vacuolization and recanalization reforms the lumen.
    • The epiglottis and the caudal portions of the tongue are formed from the hypobranchial eminence of the 3rd and 4th branchial arches; the epiglottis and tongue then gradually migrate apart.
    • A variation in the closure of the thyroglossal duct (cf subepiglottic cysts   Epiglottis: cyst - subepiglottic  ).
    • Fibrosis of the glossoepiglottic fold and hyoepiglotticus muscle.
  • Note that membranous pharyngeal and laryngeal bands reported in humans do not resemble the epiglottic frenulum in foals.

Pathophysiology

  • Persistent band of fibrous tissue from epiglottis to base of tongue → prevents normal action of epiglottis during swallowing → dorsal displacement of soft palate → aspiration and reflux of milk during nursing.
  • Aspiration of milk → pneumonia.

Timecourse

  • Clinical signs evident in first few days of life.

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Dixon P M & Collins N (2004) The equine epiglottis. Equine Vet Educ 16 (6), 299-301 VetMedResource.
  • Yarborough T B et al (1999) Persistent frenulum of the epiglottis in four foals. Vet Surg 28, 287-291 PubMed.


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