Headshaking associated with a unique presentation of guttural pouches infection and otitis media in a Quarter Horse stallion: diagnosis, medical treatment and outcome

A 3-year-old Quarter Horse stallion was referred for headshaking (HS) syndrome of one month duration. The horse underwent complete HS workup. Physical examination revealed up-and-down head movements associated with nose snorting during lunging and riding, in the absence of other abnormalities at rest or in motion. Lameness, neurologic and behavioural evaluations were unremarkable. Endoscopic examination of the upper respiratory tract showed bilateral guttural pouches (GPs) inflammation. The mucosal surface was altered by the presence of areas of microbullous appearance coalescing into some bullae of larger diameter. A bacterial culture obtained by flushing, brushing and biopsy of the GP mucosa was positive for Serratia marcescens. Computed tomographic evaluation was indicative of: moderate bilateral GP inflammation, bilateral otitis media, and nuchal ligament enthesopathy, with uncertain significance. The horse was treated with antimicrobials according to the sensitivity test, systemic...