A 17 year-old thoroughbred gelding was referred for evaluation of an acute onset of vestibular disease, characterized by right-sided head tilt and ataxia. The signs progressed to include right ear droop, ptosis, and muzzle pull to the left (right facial nerve paralysis). A tentative diagnosis of right-sided temporohyoid osteoarthropathy was made and was confirmed by endoscopy and radiographs. Euthanasia was elected based on poor prognosis for complete recovery and a post-mortem CT scan and tympanocentesis were performed.