Clinician: Equine Ear Infections Might Spread to TMJ
Swelling and pain in the upper jaw between the eye and the ear might indicate an infection in the temporomandibular joint (TMJ) area. And it’s possible that the infection initially started as a middle ear infection that moved down into the TMJ, researchers recently reported.

Veterinarians can use standing robotic cone-beam computed tomography (CBCT) of the head to detect these simultaneous infections and, in some cases, can treat them through standing arthroscopy, said Kyla Ortved, DVM, PhD, Dipl. ACVS, ACVSMR, Jacques Jenny Endowed Term Chair of Orthopedic Surgery at the University of Pennsylvania’s New Bolton Center, in Kennett Square, Pennsylvania.

In comparison to standard CT, CBCT does not rely on a closed gantry (the circular “tunnel” where technicians place the part of the body to be scanned). Instead, CBCT images are collected using a robotic arm that rotates around the horse’s head, capturing focused images from radiography (X rays) directed through a cone in a way that allows for 3D imaging. “Three-dimensional imaging (with a CT scan) is invaluable when examining complex structures like the skull, especially when you are trying to diagnosis an unusual disease,” Ortved said.

Standing Arthroscopy Successful in Treating Ear and TMJ Infection

Arthroscopy in the standing, sedated horse can provide a safe way to explore, clean, and treat TMJ infections, at a lower cost than the same surgery under general anesthesia, said Ortved, citing the case of a Thoroughbred with otitis media (middle ear infection) and a TMJ infection.

“The technique was very well tolerated by (this) horse and did not present any further technical challenges,” she said. “I think it is definitely a good option in amenable horses that tolerate standing sedation well.”

The 15-year-old gelding was unable to open his mouth for four days and had pain around his jaw when people touched it, she said. He had marked swelling in the temporomandibular area on just the right side and a fever of 102 to 103°F (normal for an adult horses is 99-101.5°F). Despite treatment with antibiotics and anti-inflammatories, the horse got worse, so Ortved decided to X ray and ultrasound his head.

The imaging showed swelling around the TMJ area on the right side of the head, as well as swelling and increased fluid in the joint itself. After culturing samples to confirm a bacterial infection, the veterinary team ran a CBCT on the horse’s head. It showed that the horse had evidence of a right middle ear infection in addition to septic arthritis of the right TMJ. “There’s evidence in humans that otitis media can cause infection of the TMJ through local spread of bacteria,” said Ortved. “It seems possible that this occurs in some horses, as well.”

Her group’s standing CT system has revealed a few other cases suggesting simultaneous middle ear infection and “I think we are starting to see the connection between middle ear infection and extension of the infection to the temporohyoid articulation or the TMJ more commonly because we’re doing more head CTs,” she said.

Horses can theoretically develop middle ear infections by getting bacteria either in their ear canals or throats, which connect to their ears via an auditory tube, Ortved explained.

Owners might not always notice a middle ear infection, she added. But they’re not likely to miss a “true infection” of the TMJ. “True infections of the TMJ generally carry very noticeable clinical signs, including pain, swelling, and difficulty eating,” she said. “Some horses do get osteoarthritis of the TMJ without any infection, and these horses can be much less painful and more difficult to diagnose.” Even so, TMJ osteoarthritis appears to be relatively uncommon in horses, said Ortved.