Temporohyoid Osteoarthropathy in 33 Horses (1993–2000)

Abstract

A retrospective study of the medical records of 33 horses was performed to determine the clinical and diagnostic abnormalities associated with temporohyoid osteoarthropathy. Data collected from medical records included signalment, presenting complaints, history, physical examination findings, laboratory data, results of diagnostic imaging studies, and treatments. Follow-up information was obtained from a review of case records; by telephone conversation with the owner, veterinarian, or trainer; or by both methods. Of 33 horses with temporohyoid osteoarthropathy, 29 presented with facial nerve (cranial nerve VII) deficits and 23 presented with vestibulocochlear nerve (cranial nerve VIII) deficits. Guttural pouch endoscopy was more reliable than radiography for diagnosis. Of horses with unilateral clinical signs, 22.6% actually had bilateral disease. Magnetic resonance imaging and computed tomography identified the lesions in all horses in which these tests were performed. Of 30 horses for which follow-up information was obtained, 20 (67%) were alive. Eight horses were euthanized and 1 died because of problems associated with temporohyoid osteoarthropathy. Nineteen of 20 surviving horses (95%) were considered by the owner or trainer to be suitable for athletic use. Twelve surviving horses (60%) had residual facial nerve deficits; 11 horses (55%) had residual vestibulocochlear nerve deficits. Horses with temporohyoid osteoarthropathy have a fair prognosis for return to some type of athletic function, but there is risk of acute death. The majority of horses would be expected to have some residual cranial nerve dysfunction, and it could take a year or longer for maximal improvement to occur.

Differential Diagnosis and Management of Cranial Nerve Abnormalities

“…[6][7][8][9][10] This condition should be a primary differential in all horses with acute onset of vestibular dysfunction, with or without ipsilateral facial nerve paralysis. The onset of neurologic dysfunction in horses with temporohyoid osteoarthropathy represents an acute manifestation of a chronic, proliferative process involving the bones surrounding the inner ear, particularly the stylohyoid and petrous temporal bones.…”

“…It is difficult to identify the actual fracture due to overlapping structures and minimal displacement of 104 Section II / Clinical Equine Neurology media), or nonseptic degenerative arthrosis due to mechanical stress on the joint. 7,[8][9][10] This condition is observed in adult horses with no breed or gender predilection.…”

“…Clinical signs of facial nerve paralysis may precede vestibular signs or may not appear for several days after the onset of vestibular disease. 7 Damage to either nerve may be the result of hematoma, callus, infection, or direct laceration by fracture fragments. Corticosteroid therapy should be considered on a case by case basis.…”

“…In some instances, CT (see Figure 8.5) or magnetic resonance imaging may be necessary to detect bony proliferation and fracture. 7,9 Medical therapy for temporohyoid osteoarthropathy includes broad-spectrum antibiotic therapy to prevent meningitis and treat primary or secondary otitis-media interna. Potentiated sulfa antimicrobials, ampicillin (2 mg/kg, IM, q 12 h or q 8 h), and chloramphenicol (15-25 mg/kg PO, q 6 h) have been recommended when culture and sensitivity cannot be obtained.…”

Central Nervous System Trauma

“…[11][12][13][14] Forces applied to this immobilized joint can cause fractures of the skull of which a common sequela is damage to the vestibular apparatus or cranial nerve VII. Another sequela is extension of infection in the middle/inner ear to the brainstem, additional cranial nerves, or hindbrain.…”