Characterisation of palatal dysfunction after laryngoplasty

Dorsal displacement of the soft palate (DDSP) in the horse has been previously described as intermittent, typically occurring at fast exercise; or persistent, seen at rest. Dorsal displacement of the soft palate has recently been reported following laryngoplasty (LP) and can be associated with continued poor performance and respiratory noise.

The current study aimed to characterise the DDSP diagnosed post LP.

Cross-sectional study.

Owners/trainers of horses undergoing LP at one institution over 6 years were contacted to determine the horse's progress and willingness for re-examination. The horses were examined at the rest, walk, trot and canter with an overground exercising endoscope. A GPS-equipped watch was carried to obtain maximal exercising speeds. Videos of horses with DDSP were reviewed to determine frequency and duration of DDSP and swallowing events at the various gaits.

Exercising endoscopy was performed in 41 of the 89 horses that had undergone LP. Nineteen of the 41 horses were diagnosed with DDSP at exercise, of which 7/41 also had DDSP at rest. No difference was detected in the percentage of total time spent displaced at each gait (P = 0.67), or in the frequency of new DDSP events per minute between each gait (P = 0.10), or in the frequency of swallowing events per minute between each gait (P = 0.52). The majority of horses displaced at various times throughout each gait. Dorsal displacement of the soft palate was most commonly solely induced spontaneously and always corrected with a swallow. The maximum speed achieved was 8.3 m/s.

Dorsal displacement of the soft palate was common following LP and it appears to be induced at slower gaits than DDSP that has previously been described. It also occurred at various times throughout each gait and did not always occur persistently at rest.

These findings suggest horses undergoing LP may be more prone to DDSP and further investigations into the aetiology of post LP palatal dysfunction are warranted.