Pneumocephalus due to temporohyoid osteoarthropathy in a 16-year-old Friesian mare.

A sixteen-year-old Friesian mare was admitted to the university clinic with the following clinical signs: anorexia, weight loss, fever, bilateral nasal discharge, unilateral facial paralysis and a non-healing corneal lesion. Endoscopic examination of the upper airways showed thickening of the proximal portion of the right stylohyoid bone. Computed tomography imaging showed pneumocephalus due to grade 3 unilateral temporohyoid osteoarthropathy (THO) with fracture of the petrous temporal bone. The horse did not improve following medical treatment. Surgical intervention was declined by the owner and the horse was euthanized due to poor prognosis. Post-mortem examination confirmed the clinical diagnosis. The prevalence of temporal bone fractures is high in horses with severe THO. However, fracture extension into the cranial vault and pneumocephalus has not been described. This is the first reported case of pneumocephalus due to a fracture of the petrous temporal bone in a horse with THO.