EQUINE VETERINARY EDUCATION / AE / JANUARY 2020
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was noted. No coughing or nasal discharge was evident during eating. Follow-up endoscopy was performed per nasum Day 5
post-operatively where DDSP was still evident. The soft palate, however, appeared to have a more normal dorsal outline apart from a dorsal protuberance on the right side. Repeat latero-lateral radiographs were also performed and these showed a normal outline to the caudal border of the soft palate (Fig 4). The gelding was discharged from the hospital 6 days post-operatively.
Outcome
Re-evaluation was performed at 4 weeks and again at 11 months post-operatively. The owners reported that the gelding had been much livelier and no respiratory noise, coughing or nasal discharge had been evident. Follow-up endoscopic examination at both 4 weeks and 11 months was performed pernasum and revealed the soft palate to be normally positioned relative to the epiglottis and the soft palate was normal in appearance (Fig 5).
Discussion
This report describes an unusual case of bilateral palatal cysts and to the authors’ knowledge this is the first description of laser ablation using a retrograde approach via a tracheotomy. This novel approach provided excellent visualisation of the caudal portion of the soft palate and may be a useful method of assessing the upper respiratory tract and accessing lesions for laser treatment when a conventional approach provides insufficient visualisation or surgical access utilising transendoscopic instruments. Lasers have expanded veterinary surgical capability by
facilitating minimally invasive surgery, allowing access to areas that would otherwise be unreachable and by interacting with tissue in ways that conventional instruments could not (Sullins 2002). The first veterinary use of a laser was reported in 1972 (Blikslager and Tate 2000). The development of commercially available and affordable lasers that can deliver thermal energy via flexible fibres has enabled a variety of transendoscopic surgical procedures to be developed. The minimally invasive nature of transendoscopic surgery has meant that laser has gained large-scale popularity for upper respiratory tract surgery (Orsini 2002). URT
Fig 5: Trans-nasal video-endoscopic view of the larynx at follow- up (11 months) showing a normal position of the soft palate and epiglottis. There was no residual deformity of the soft palate.
conditions that have been treated using transendoscopic lasers include: ablation of ethmoid haematomas and resection of masses (Sullins 2012), congenital or acquired tissue webs in the nasal passages, pharynx and larynx (Orsini 2002); stimulation of fibrosis of the caudal soft palate in horses with DDSP (Sullins 2012); correction of epiglottic entrapment (Parente 2002), resection of vocal cords (Ducharme et al. 2002), laryngeal ventricles and aryepiglottic folds (Orsini 2002); fenestration of the guttural pouch for management of tympany or to assist in the removal of chondroids (Sullins 2012); removal of subepiglottic and other cysts in the URT (Cramp et al. 2014) and resection of tissue in foals with choanal atresia (Ducharme 2012). Palatal cysts are relatively uncommon, with few reports in
the literature (Koch and Tate 1978; Haynes et al. 1990) and in this case, due to the young age of the horse, they were considered most likely to be congenital. More commonly cystic structures occur in the subepiglottic region and are usually congenital, being reported most frequently in young Thoroughbred and Standardbred racehorses (Fulton et al. 2012). Acquired cysts may develop as a sequela to inflammation or trauma (Sullivan and Parente 2003) but this is less common. Diagnosis in this group is potentially a function of their requirement for large aerobic capacity and the frequent nature of endoscopic examinations at an early age rather than being due to a specific breed predisposition, diagnosis being made most frequently at endoscopic examinations preceding yearling sales (Salz et al. 2013). Concomitant epiglottic entrapment has been reported in 20% (Tulleners 1991) and 36% (Salz et al. 2013) of cases according to two reports. Endoscopically cysts are visualised as pink and smooth, round to oval mucosal covered masses that sit below the epiglottis and are usually to one side of the midline (Fulton et al. 2012). In some cases, stimulation of swallowing or elevation of the epiglottis is needed to visualise the cysts (Blea and Arthur 2003). In this case, the cysts had a similar appearance but were difficult to fully evaluate without radiography and the ability to directly visualise the caudal border of the soft palate in detail. Surgical approaches via laryngotomy or pharyngotomy
Fig 4: Latero-lateral radiographic projection of the larynx after drainage and laser ablation of the cysts. A sharp, normal caudal border of the soft palate can be seen.
have been described to access masses in the URT (Haynes et al. 1990; Robertson 2007) and Robertson (2007) advocated surgical excision en bloc or drainage following excision of the caudal margin of the soft palate for
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