Although they don’t tend to garner as much attention as infectious neurologic diseases, vestibular diseases (those that pertain to the balance mechanisms) are common and important causes of neurologic problems in horses. At the 2013 Western Veterinary Conference, held Feb. 17-21, Laurie Beard, DVM, MS, Dipl. ACVIM, associate clinical professor at Kansas State University’s College of Veterinary Medicine, described the two most common vestibular diseases in horses: temporohyoid osteoarthropathy (THO) and skull fractures.

Beard used case studies to present a review of the clinical signs, diagnostic methods, and treatment options for the two disorders. She explained that some clinical signs are common among the different vestibular disease, including:

  • Head tilting;
  • Nystagmus (involuntary movement of the eyeballs);
  • Circling;
  • Ataxia (incoordination);
  • Strabismus (misalignment of the eyeball from its normal position); and
  • Facial nerve paralysis.

Temporohyoid Osteoarthropathy

Beard explained that THO is a chronic, bony growth on the stylohyoid bone in the temporohyoid joint associated with the skull and located near the middle ear and guttural pouch, which results in ankylosis (joint fusion). The disorder’s cause is unknown.

According to Beard, clinical signs of THO include:

  • Acute onset neurologic dysfunction;
  • Unilateral (one sided) facial and/or vestibular nerve dysfunction or paralysis;
  • Discharge—blood, purulent exudates, or spinal fluid—from the ear;
  • Dysphagia (diffic