A first step towards objective grading of equine laryngeal function.
Authors: Hardwick Josephine, Ahern Benjamin, Franklin Samantha
Journal: Veterinary journal (London, England : 1997)
Summary
Inconsistency among veterinarians when grading resting laryngeal function has long hampered clinical communication and research standardisation in equine medicine; Hardwick and colleagues addressed this by developing a diagnostic decision tree (DDT) that operationalises the Havemeyer grading system with objective, measurable criteria to eliminate ambiguity. Using videoendoscopic recordings previously assigned unanimous grades by three experienced observers, the authors created a branching algorithm that guides assessment through a series of binary decisions, establishing precise cut-off values—notably that maintained full left arytenoid cartilage abduction requires ≥0.2 seconds duration to differentiate grade II.2 from the fugacious abduction of grade III.1, and that incomplete abduction is stratified by the 45° threshold from vertical midline. Frame-by-frame video analysis at known frame rates is essential for applying the DDT, positioning it as a reproducible, verifiable alternative to subjective grading. For practitioners involved in pre-purchase examinations, performance evaluation, or longitudinal monitoring of recurrent laryngeal neuropathy, this approach promises more reliable documentation and enables meaningful comparison of cases across different clinicians and time points. The authors suggest this DDT represents a practical foundation for future computer-assisted assessment, which could further standardise laryngeal evaluation across the equine industry.
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Practical Takeaways
- •When evaluating laryngeal endoscopy videos, use frame-by-frame playback at known frame rates and apply this decision tree to achieve more consistent, objective grading of laryngeal function across cases.
- •The critical distinction between grades III.1 and II.2 depends on whether arytenoid abduction is maintained for at least 0.2 seconds—use this as your timing benchmark during video review.
- •This standardized approach reduces subjective interpretation and improves communication with referring veterinarians by providing consistent, evidence-based laryngeal grades.
Key Findings
- •A diagnostic decision tree (DDT) was developed by codifying the Havemeyer grading system with objective definitions to reduce inter-observer disagreement in equine laryngeal function grading.
- •Full left arytenoid cartilage abduction maintained for ≥0.2 seconds is defined as grade II.2 or better, while abduction maintained for <0.2 seconds is classified as grade III.1.
- •Arytenoid abductor deficit is subdivided based on abduction angle from vertical midline: ≥45° classified as grade III.2 and <45° as grade III.3.
- •The DDT uses frame-by-frame video analysis with known frame rates to provide objective, standardized grading and could serve as a foundation for computer-assisted laryngeal function assessment.