Archive Case #241: Equine Temporohyoid Osteoarthropathy

Clinical Clues

1. A horse develops a head tilt and asymmetry of one side of its face over a few days.
2. The same side has reduced ear and eyelid movement, while the horse remains alert.
3. Examination finds peripheral vestibular dysfunction alongside facial-nerve weakness; limb strength is preserved.
4. Otoscopy shows no obvious external-ear disease, but deeper ear disease remains a possibility.
5. Guttural-pouch endoscopy shows enlargement of the proximal stylohyoid bone near its joint with the skull.
6. CT demonstrates proliferation and fusion at that articulation, supporting equine temporohyoid osteoarthropathy.

Diagnosis

Equine Temporohyoid Osteoarthropathy

The paired facial and vestibular deficits localise near the petrous temporal region; enlarged stylohyoid bone on endoscopy and fused, proliferative temporohyoid articulation on CT support equine temporohyoid osteoarthropathy. Otitis media/interna can mimic peripheral vestibular disease, and head trauma or central disease remain considerations until imaging localises the lesion. Remember: In a horse with head tilt and facial weakness, inspect the guttural pouch and temporohyoid joint; normal outer-ear findings do not exclude deeper disease.

Educational Use

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