Large CT study maps causes and outcomes in equine sinonasal disease
Bottom line
Sinonasal disease in horses is a broad category, but this new multicenter dataset gives clinicians a much larger map of what they're actually seeing in practice. In a retrospective series of 1,600 horses with CT-confirmed sinonasal disease from 19 clinics across the UK, continental Europe, and the US, dental sinusitis linked to apical infection was the most common diagnosis, accounting for 693 cases, or 43.3%. Primary sinusitis was next at 329 cases, followed by sinus cysts at 178 and progressive ethmoid haematoma at 100. The dataset, published September 3, 2026, examined how diagnosis related to clinical presentation, CT findings, treatment, and outcome, and found that sinonasal neoplasia and progressive ethmoid haematoma carried markedly worse cure rates than primary sinusitis. (datadryad.org)
Why it matters: For equine veterinarians, the study reinforces two practical points: first, that dental disease remains the leading driver of sinonasal pathology in referred horses, and second, that CT is central to sorting out a problem list that often looks similar on physical exam. Merck’s current review notes that unilateral nasal discharge, facial swelling, epiphora, and inspiratory noise are common across sinus disorders, while CT is especially useful for identifying affected compartments and subtle dental pathology. In the treatment-outcome data tied to this case series, primary, dental, and mycotic sinusitis all had complete cure rates above 79%, while cure fell to 40.4% for progressive ethmoid haematoma and 7.3% for sinonasal neoplasia. (merckvetmanual.com)
What to watch: Watch for the peer-reviewed publication and any companion analyses that further break down which CT patterns and clinical signs best predict diagnosis, prognosis, and treatment selection across these 1,600 cases. (datadryad.org)
Key facts
- Study type
- Retrospective multicenter case series
- Sample size
- 1,600 horses
- Case confirmation
- CT-confirmed sinonasal disease
- Sites
- 19 clinics across the UK, continental Europe, and the US
- Most common diagnosis
- Dental sinusitis associated with apical infection
- Most common diagnosis count
- 693 cases (43.3%)
- Next most common diagnosis
- Primary sinusitis, 329 cases
- Other common diagnoses
- Sinus cysts, 178 cases; progressive ethmoid haematoma, 100 cases
- Outcome finding
- Sinonasal neoplasia and progressive ethmoid haematoma had markedly worse cure rates than primary sinusitis
A newly released multicenter study of 1,600 horses with CT-confirmed sinonasal disease offers one of the largest datasets yet on how these cases present, what causes them, and how they fare after treatment. The headline finding is straightforward: dental sinusitis associated with apical infection was the most common diagnosis, representing 693 of 1,600 cases, or 43.3%. The study also linked specific diagnoses with different outcomes, with primary, dental, and mycotic sinusitis showing the strongest cure rates, while sinonasal neoplasia and progressive ethmoid haematoma performed much worse. (d197for5662m48.cloudfront.net)
The work builds on a long line of equine sinus research from some of the same investigators, but at a much larger scale. Earlier published series of 277 horses found a more mixed diagnostic distribution, with primary sinusitis, dental sinusitis, cysts, neoplasia, and progressive ethmoid haematoma all contributing meaningful shares of disease. More recent CT-based work has emphasized that equine sinonasal disease is often more anatomically complex than radiographs or endoscopy alone suggest, especially when nasal structures and harder-to-access sinus compartments are involved. (pubmed.ncbi.nlm.nih.gov)
According to the Dryad dataset and related preprint material, data came from 21 contributors at 19 equine clinics in the UK, continental Europe, and the US. Cases included 1,457 horses with unilateral disease and 143 with bilateral disease. Beyond the 693 dental sinusitis cases and 329 primary sinusitis cases, the diagnosed causes included 178 sinus cysts, 100 progressive ethmoid haematomas, 90 traumatic sinusitis cases, 65 mycotic sinusitis cases, 57 confirmed sinonasal neoplasms, and 29 suspected neoplasms without histology, plus smaller numbers of fistulas, non-neoplastic growths, sinus pneumocele, mucocele, and infected suturitis. (datadryad.org)
The treatment and outcome findings add clinical weight. In the linked treatment analysis, outcome data were available for 926 horses, of which 69.7% were recorded as cured, 17.0% as partially cured, and 13.5% as not cured. Dental sinusitis had one of the best complete cure rates at 79.7%, and oral extraction in those cases was associated with a higher likelihood of cure; among 324 horses with outcome data after oral extraction, 83.6% were reported cured. By contrast, progressive ethmoid haematoma had a complete cure rate of 40.4%, and sinonasal neoplasia just 7.3%. The multivariable model also found both PEH and sinonasal tumors were significantly less likely to achieve cure than primary sinusitis. (d197for5662m48.cloudfront.net)
That prognosis gap fits with what equine clinicians already see at the case level. Merck’s veterinary reference notes that many sinus diseases share overlapping signs, including unilateral mucopurulent or bloody nasal discharge, facial swelling, epiphora, and inspiratory noise, making imaging important for sorting out etiology. It also highlights CT’s value in identifying involved compartments and subtle periapical dental disease, both of which matter when deciding between lavage, sinoscopy, standing surgery, extraction, or more guarded conversations with pet parents. (merckvetmanual.com)
Published expert commentary specific to this new paper was limited at the time of writing, but the broader literature points in the same direction. Prior reviews and CT studies have described CT as a major advance for equine sinonasal diagnosis because it avoids superimposition, improves surgical planning, and detects concurrent nasal conchal bulla or sphenopalatine involvement that may explain treatment failures or persistent discharge. That context helps explain why a large CT-confirmed cohort is clinically meaningful: it reflects not just what diseases occur, but how modern referral centers are actually resolving ambiguous sinus cases. (pmc.ncbi.nlm.nih.gov)
Why it matters: For veterinary professionals, especially equine practitioners and referral hospitals, the study sharpens expectations around both prevalence and prognosis. If nearly half of referred CT-confirmed cases are dental in origin, dental workups need to stay front and center in chronic unilateral discharge, facial swelling, or malodor cases. At the same time, the poor cure rates reported for sinonasal neoplasia and PEH support earlier escalation to advanced imaging and earlier client counseling when those diagnoses are suspected. The data also reinforce that “sinusitis” can be too narrow a label, because concurrent nasal disease and multi-compartment involvement may shape both treatment choice and outcome. (d197for5662m48.cloudfront.net)
What to watch: The next step is the formal peer-reviewed publication of the 1,600-case diagnostic analysis and any companion papers that translate these data into more usable clinical predictors, such as which combinations of signs and CT findings most strongly point to dental disease, cysts, PEH, or neoplasia, and which treatment pathways consistently deliver the best outcomes across centers. (datadryad.org)