Kuhlmann, J.J.KuhlmannVan der Vekens, E.E.Van der VekensKoch, C.C.Koch0000-0002-4574-6952Klopfenstein Bregger, M. D.M. D.Klopfenstein Breggerde Preux, M.M.de PreuxBrünisholz, H. P.H. P.Brünisholz2025-10-232025-10-232025-09-19https://boris-portal.unibe.ch/handle/20.500.12422/221413A 17‐year‐old Swiss Warmblood mare presented with signs of left‐sided facial nerve paralysis and was diagnosed with left‐sided temporohyoid osteoarthropathy (THO). A partial ceratohyoidectomy was performed in the standing, sedated mare to treat this condition. Despite surgery and an initial improvement of clinical signs, the horse showed a sudden worsening of facial nerve paresis and additional ataxia grade 4/5 (modified Mayhew scale) 7 months after surgery. Cone‐beam computed tomography revealed new bone formation and partial fusion of the left basihyoid and ceratohyoid bone, and this was considered responsible for the clinical deterioration. Therefore, a total ceratohyoidectomy was performed under general anaesthesia. Intraoperatively, pseudoankylosis of the basihyoid–ceratohyoid joint was confirmed. After the second surgery, the horse showed clinical improvement within 2 days after surgery. The remaining grade 1/5 ataxia and facial paresis showed further progressive improvement during the 8 months follow‐up after the second surgery.en600 - Technology::630 - Agriculturearticle10.48620/9203110.1111/eve.70000