Branchial remnant cysts of mature and juvenile horses.
Authors: Nolen-Walston R D, Parente E J, Madigan J E, David F, Knafo S E, Engiles J B
Journal: Equine veterinary journal
Summary
Branchial remnant cysts (BRC) are embryological remnants that present with a bimodal age distribution in horses, affecting both foals and mature animals, though historically documented only in young stock. This retrospective case series of eight horses revealed two distinct clinical presentations: foals (aged 1–10 months) presented with respiratory stridor and visible masses, whilst mature horses (8–21 years) presented with dysphagia, oesophageal obstruction, or retropharyngeal swelling, with masses typically located on the right side or dorsal aspect, ranging from 3–35 cm in diameter. Ultrasonography was diagnostically valuable, characteristically showing thick-walled cysts with hypoechoic fluid and dependent hyperechoic clot material, findings supported by radiography and endoscopy; cytological examination revealed chronic haemorrhage in 75% of cases and squamous epithelial cells in one case, with histopathology confirming epithelium-lined cysts lacking smooth muscle or thyroid tissue. Of five cases managed surgically, all developed right laryngeal hemiplegia post-operatively, a significant complication rate necessitating careful pre-operative assessment and informed consent. Practitioners should expand their differential diagnoses for retropharyngeal masses in mature horses to include BRC and recognise that whilst surgical excision may relieve airway obstruction or dysphagia, recurrent laryngeal nerve injury represents a substantial risk requiring client discussion and post-operative monitoring.
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Practical Takeaways
- •Branchial remnant cysts should be considered in the differential diagnosis for mature horses presenting with throat latch masses, dysphagia, or retropharyngeal swelling—not just in foals as previously reported
- •Ultrasonography is a useful diagnostic tool showing characteristic thick-walled cysts with fluid and clots; definitive diagnosis requires squamous epithelium identification via cytology or histopathology
- •Surgeons should counsel owners that right laryngeal hemiplegia is a frequent complication of BRC excision due to proximity to the recurrent laryngeal nerve, with potential impacts on athletic performance
Key Findings
- •Branchial remnant cysts occur in horses with bimodal age distribution: 5 mature horses (8-21 years) and 3 foals (1-10 months old)
- •Clinical presentation differs by age: mature horses presented with dysphagia/oesophageal obstruction (2/5) or retropharyngeal swelling (3/5), while foals presented with respiratory stridor and visible masses
- •Right-sided (5/8) or dorsal (2/8) retropharyngeal masses of 3-35 cm diameter were palpable; ultrasonography showed thick-walled cysts with hypoechoic fluid and dependent hyperechoic masses
- •Post-operative right laryngeal hemiplegia occurred in 4/5 surgically treated cases, representing a common complication of surgical excision