Results of upper airway radiography and ultrasonography predict dynamic laryngeal collapse in affected horses.
Authors: Fjordbakk C T, Chalmers H J, Holcombe S J, Strand E
Journal: Equine veterinary journal
Summary
# Editorial Summary: Upper Airway Imaging as a Diagnostic Tool for Dynamic Laryngeal Collapse Dynamic bilateral laryngeal collapse (DLC) in harness racehorses has proven difficult to diagnose outside the racing environment, typically requiring treadmill endoscopy performed with the characteristic poll flexion position used during competition. This case-control study of 50 harness racehorses (25 with endoscopically confirmed DLC and 25 controls) examined whether static radiographic and ultrasonographic measurements could predict collapse tendency by measuring laryngeal positioning and airway dimensions in both neutral and flexed head positions. Poll flexion triggered significantly greater rostral advancement of the larynx relative to the hyoid apparatus in affected horses compared to controls, and narrowed the laryngeal lumen width at the vocal fold level—two findings that correlated strongly with DLC diagnosis (odds ratios of 21.3 and 8.4 respectively when specific thresholds were exceeded). The practical implication is substantial: a thyrohyoid bone-to-thyroid cartilage distance of ≥12 mm during poll flexion, combined with dynamic airway narrowing on imaging, may enable practitioners to identify at-risk horses using readily available diagnostic imaging rather than relying solely on treadmill endoscopy, potentially streamlining pre-purchase screening and guiding decisions about training protocols or therapeutic intervention in suspected cases.
Read the full abstract on PubMed
Practical Takeaways
- •Radiography and ultrasonography in both neutral and flexed head positions can diagnose DLC at rest, avoiding need for costly treadmill endoscopy in some cases
- •Measure thyrohyoid distance and laryngeal lumen width during poll flexion as diagnostic indicators; distances ≥12 mm are highly suggestive of DLC
- •Understanding laryngohyoid conformation and how poll flexion mechanically narrows the airway helps explain why affected harness racehorses show exercise intolerance and guides treatment decisions
Key Findings
- •Poll flexion caused significantly greater rostral laryngeal advancement in DLC-affected horses compared to controls (P = 0.007)
- •Laryngeal lumen width at vocal fold level decreased more in DLC horses during poll flexion versus neutral position (P = 0.04)
- •Thyrohyoid bone to thyroid cartilage distance ≥12 mm in poll flexion had 21.3-fold increased odds of DLC (95% CI 3.65–124.8, P = 0.004)
- •Laryngeal lumen width narrowing during poll flexion relative to neutral position had 8.4-fold increased odds of DLC (95% CI 1.6–44.1, P = 0.012)