Otitis media is an infection of the eardrum and the cavity of the middle ear, including the three bony ossicles. Most cases are caused by an outer ear infection that involves the eardrum and then progresses to the middle ear. In fact, about 50 percent of cases of chronic external otitis are associated with otitis media. Bacteria can also gain entrance to the middle ear through the opening of the auditory tube that connects the middle ear to the nasopharynx. Occasionally, the infection is blood-borne.
The early signs of otitis media are the same as those of external otitis. However, as the middle ear becomes infected the pain increases dramatically. The dog often tilts her head down on the affected side, holds it as still as possible, and exhibits increased pain sensitivity when her head is touched or her mouth is opened. Hearing can be affected, but the loss may not be noticed unless both ears are involved.
An otoscopic examination performed after the dog has been sedated or anesthetized reveals a bulging eardrum. If the drum is ruptured, pus may be seen draining from the middle ear. X-rays occasionally show fluid or inflammatory tissue in the middle ear cavity.
Injury to a branch of the facial nerve that crosses the eardrum causes drooping of the upper lip and ear on the affected side. Another sign of facial nerve injury is Homer’s syndrome, a symptom complex of the eye that consists of a small pupil, drooping upper eyelid, protrusion of the nictitating membrane, and retraction of the eyeball into the orbit.
Treatment: This involves thoroughly cleansing and flushing the ear, as described for external otitis. If the eardrum is intact but bulging, pus and fluid in the middle ear can be aspirated by your veterinarian using a syringe and needle. This reduces pressure and relieves pain.
The exudate is cultured. Oral antibiotics are started and can be changed pending the results of sensitivity reports. Antibiotics are continued for at least three weeks, or until the problem resolves. Recurrent or chronic otitis media may require middle ear surgery.
Prevention: Most cases of otitis media can be prevented by treating ear canal infections at an early stage. This is why it is so important to take your dog to a veterinarian as soon as you suspect an ear problem.