Ear

The ears of cats and dogs are composed of three regions: the external ear, the middle ear, and the inner ear.

The external ear is formed by the pinna, the vertical canal, and the horizontal canal.

The middle ear consists of the tympanic membrane (drum), the tympanic cavity (bulla), and eustachian tubes which connect the middle ear to the pharynx.

The inner ear is formed by auditory ossicles, bony labyrinth, and the semi-circular canal.

A bony septum divides the cat’s tympanic bulla into two chambers. Ear and facial nerves enter the middle ear close to this septum. Because of this reason, cleaning of the bulla in cats is more challenging than in dogs. This may require a two-stage procedure under the same general anaesthesia. In these cases, ventral access to the bulla would be preferred to a lateral one (dogs).

The facial nerve runs very close to the horizontal ear canal on its way out of the skull in both cats and dogs. This nerve controls muscles of the face, lachrymal glands, the closing of the eyelid, and lip retractions.

(Hill’s Pet Products, 2006).

Clinical Signs

(Hill’s Pet Products, 2006).

Chronic inflammation, masses, and recurrent otitis cause significant discomfort for the patient. Ear shaking, purulent discharge, head tilt, reduced hearing, constant ear scratching, and neurologic signs may be detected.

Treatment

Total Ear Canal Ablation (TECA) and Bulla Osteotomy

The TECA and Bulla Osteotomy are surgeries performed on the ear pinna and bulla for the treatment of chronic and end-stage otitis, recurrent resistant ear bacterial infection, masses (lumps) in the ear canal, traumas of the ear canal, or deep infection of the bulla.

The vertical and horizontal ear canals are surgically removed, and the bulla (ear bone cavity) is widened with special bone forceps and gently cleaned. In dogs, the cleaning of the bulla is performed through lateral access, whereas in cats, ventral access may be preferred because of the two chambers. The external ear pinna is not touched, maintaining a good cosmetic outcome. However, in very rare cases, this may fold forward.

The outcome of the surgery is excellent, with a significant improvement in the patient's quality of life.

After the TECA is performed, the hearing of the patient results reduced if compared with a pet with normal ears. The amount of hearing loss is very similar to a dog with occlusion of the ear canal because the presence of lumps, pus, discharge, or narrowing of the ear canal leads to a significant reduction in hearing. Although comparable hearing loss, the TECA has the benefit of being free from discomfort and pain, and it improves the patient's quality of life.

Complications

Possible complications of the surgery include infection with the formation of an abscess, nerve paralysis, and bleeding during surgery. Infection is mainly treated with antibiotics; however, if the infection starts from the bulla or if there is an abscess formation, a review surgery may be required. The facial nerve injury could be temporary or permanent. In most cases, this resolves in 4 weeks, and eye drops will be applied to prevent dry eyes until complete blinking. In very rare cases, permanent paralysis may occur, which will require eye drop medication for life. Bleeding during surgery is another rare complication.

Bleeding is not life-threatening; however, because of the very narrow space, this will not allow good visualisation of the anatomical structures. In this case, the bleeding is controlled with ice-cold saline, digital pressure, or bone wax. Once the bleeding stops, the surgery will carry on. If it is not possible to control the bleeding, the ear will be packed with sterile swabs, and the surgery will be continued the following day; fortunately, this complication is extremely rare.

Overall the surgery has a very low risk, providing excellent relief from pain and discomfort for the patient.

Reference

Hill’s Pet Products (2006). Hill’s Atlas of Veterinary Clinical Anatomy. Topeka, USA: Veterinary Medicine Publishing Company.