A 9 year old Arabian mare presented to the Cornell Equine and Nemo Farm Animal Hospital (ENFAH) Internal Medicine Service for evaluation of weight loss, ataxia and facial nerve deficits. Acute onset of ataxia and facial nerve paralysis had been noticed one week prior to presentation. Signs included deviation of the muzzle to the right side, left sided ear droop and lagophthalmos, and dropping feed, accompanied by weight loss and ataxia. The mare was treated with rest, intravenous fluids, flunixin meglumine, and dexamethasone with no significant response prior to presentation at Cornell.
On presentation the mare was dull but alert and responsive. She was mildly hypothermic and mildly tachypneic with a poor body condition score (2/9). She had muzzle deviation to the right, lagophthalmos and ptosis of the left eye and a left ear droop. There was occasional horizontal nystagmus bilaterally with the fast phase to the right. Sensation of both pinnae and the face was present. A corneal ulcer and mucopurulent discharge were detected on the left eye, as well as reduced tear production. The mare presented with grade 3/5 vestibular ataxia. Point-of-care bloodwork revealed a stress leukogram and no other significant abnormalities. Clinical signs were strongly suggestive of cranial nerve VII (facial nerve) and VIII (vestibulocochlear nerve) dysfunction. Primary differentials included brainstem disease, temporohyoid osteoarthropathy (THO), guttural pouch mycosis, and traumatic injury. Bilateral guttural pouch endoscopy was performed to narrow down the differential list and severe thickening and arthritic changes were seen in the left stylohyoid bone. This, together with the clinical signs and neurolocalization, was indicative of unilateral temporohyoid osteoarthropathy. A ceratohyoidectomy was performed along with a tarsorrhaphy and sub-palpebral lavage (SPL) placement in the left eye.
This presentation will review the clinical signs, diagnosis and treatment of temporohyoid osteoarthropathy in horses. Prognosis and common complications will also be discussed.