Branchial Remnant Cysts in Horses: 7 Cases
ACVIM 2008
R.D. Nolen-Walston1; E.J. Parente1; K.A. Kalck2; F.M. Andrews2; J.E. Madigan3; J.B. Engiles1
1New Bolton Center, University of Pennsylvania School of Veterinary Medicine, Kennett Square, PA, USA; 2College of Veterinary Medicine, University of Tennessee, Knoxville, TN, USA; 3School of Veterinary Medicine, University of California, Davis, CA, USA

The branchial arches are the embryologic origin of multiple structures of the mammalian head and neck. In horses, there are several studies of 4th branchial arch anomalies which present as laryngeal cartilage malformations, but only isolated cases of branchial cysts have been described. This retrospective multicenter study aims to identify and characterize the presentation, clinical characteristics, treatment, outcome, and histology of suspected branchial cysts in horses.

An email survey of diplomats of the ACVIM and ACVP identified 7 cases of branchial cysts. There was no sex or breed predilection, and age at presentation was bimodal, with 3/7 cases presenting at <6 months of age, and the remaining 4 at >8 years of age (range 9-21 years). The younger group presented for respiratory distress or stridor, whereas the older horses typically were evaluated for esophageal obstruction. A firm, non-painful, spherical mass was palpable in the throatlatch region in all patients (right-sided in 6/7). Sonographic examination typically revealed an encapsulated mass 3-10cm in diameter, containing minimally echoic fluid and frequently small spherical, hyperechoic bodies, with aspirates consistent with chronic hemorrhage. Six cases were treated via surgical excision. Of these, one was euthanized intraoperatively due to severe laryngeal anomalies, and the remainder survived to discharge. Post-operative complications were common, and included seroma (3/5), pneumonia, and laminitis. Preliminary histology and immunostaining for pancytokeratin markers confirmed squamous to ciliated pseudostratified columnar epithelial cyst lining in multiple cases, consistent with branchial cysts described in humans. At follow-up right recurrent laryngeal neuropathy was identified in 4 cases.

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Rose Nolen-Walston


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