A major new study involving 1,600 horses has provided fresh insight into the causes of sinonasal disease in horses, and the clinical signs that may be associated with different conditions.
Published in the Equine Veterinary Journal, the retrospective study brought together cases from 19 equine hospitals, with all horses undergoing computed tomography (CT) imaging.
Dental sinusitis caused by infection at the root of a tooth was by far the most common diagnosis, accounting for 693 cases, or 43.3% of all horses studied. Primary sinusitis was the second most common at 20.6%, followed by sinus cysts at 11.1%.
Researchers also identified associations between different conditions and the signs displayed by horses. Facial swelling was more commonly seen in horses with sinus cysts, tumours, trauma and fungal infections, while a foul smell from the nose was most strongly associated with dental sinusitis.
Obstruction of airflow through the nose was more common in horses diagnosed with sinus cysts, progressive ethmoid haematoma (PEH) and tumours.
Outcomes also varied depending on the underlying condition. Horses with sinonasal tumours and PEH had a significantly lower likelihood of being cured than horses with primary sinusitis.
The researchers conclude that equine sinonasal disease can have a wide range of underlying causes, which can influence both the clinical signs a horse displays and its likely outcome.
The findings also highlight the value of CT imaging in investigating horses with suspected sinonasal disease and helping veterinarians establish the underlying cause.
The study, Diagnosed causes of sinonasal disease in 1600 horses and associations with clinical signs, computed tomographic findings and case outcome, was first published on 8 September 2026 in the Equine Veterinary Journal.
