Ear diseases occur at all ages in dogs and cats. The diseases seen in young dogs and cats include congenital deafness, congenital deformations of the external ear, and acute bacterial, viral, and parasitic infections. Because congenital deafness, in particular bilateral deafness, is a severe handicap to the puppy or kitten and has serious consequences for die owner who was looking forward to training the young dog, early testing of hearing in young puppies is accentuated in this post.
Management of Ear Disease
As for all other diseases, management of ear disease starts with the taking of the history. For young dogs and cats the history of ear disease might well be short and plainly indicative of an acute problem with a circumscribed localization. Some exceptions are generalized juvenile pyoderma, demodicosis, and, in the cat, viral infections, for in these conditions the disease of the ear may be just a part of the clinical signs. Another aspect of the history in young dogs and cats is the relation between the onset of the disease and the change of environment, separation from litter mates, and starting of solitary life under new and different circumstances. Deafness is often only recognized when the puppy or kitten is separated from its playmates and placed in a new environment. The first steps in socializing with the new owner require communication, in which the human voice is the principal tool. Lack of response to commands may be interpreted as playfulness for awhile, but soon it dawns on the owner that the situation is not normal.
The clinical examination of the young dog or cat begins with a general impression of the animal’s alertness and mobility, its body weight, the condition of its coat, and any immediately obvious abnormalities. The general physical examination includes examination of respiratory movements, body temperature, pulse rate, skin and coat, mucous membranes, and lymph nodes, and it is supplemented by auscultation of the heart and lung sounds. Neurologic examination may be indicated when the ear disease involves the vestibular system, the facial nerve, or other cranial nerves.
The examination of the ear starts with inspection of the externally visible parts of the ear and adjacent structures. The pinnae of puppies may differ from those of older dogs in that initially all pinnae hang on the sides of the head, and at around the age of 6 weeks they begin to stand in those dogs in which the final ear carriage is standing. At the age of 4 to 6 months there may, however, be a temporary return to the puppy carriage of the pinnae. In kittens the pinnae stand within the first 2 weeks of life and are then relatively large for the head when compared with the adult cat. In dogs and cats the convex surface of the pinna is covered with hair at the age of 2 weeks. The external ear canal begins to open at the age of 2 weeks in dogs and at about the same age in cats. According to the results of hearing tests that we have performed, however, air-conducted hearing is not demonstrable in puppies before the age of 25 days.
Otoscopic examination of the ear canal and the tympanic membrane is in theory possible from the age of 25 days in dogs but is usually not requested before the age of 3 months or more. In the dog and the cat, examination is almost always possible without sedation or anesthesia. The key to success is gentle handling of the patient and avoidance of pressure on the lining of the ear canal, which is very sensitive. If the dog is not cooperative, an experienced assistant can restrain it in a sternal position; a cat can be taken under the arm and its head stabilized. The veterinarian then grasps the tip of the pinna and pulls it firmly in a lateroventral direction. The ear canal is thereby formed into a long, straight canal, with the axes of the vertical and horizontal parts coming into line with each other. The otoscope is then introduced under visual guidance, following the lumen of the ear canal and avoiding as much as possible any touching of the wall. To complete the examination, the pinna and the ear canal are maneuvered under visual control so that the otoscope, passively following the movements, will illuminate the different parts of the ear canal and the tympanic membrane.
In most cases of external ear canal disease, the ear canal will be found to be filled with cerumen or exudate. Cleaning the ear canal is the most important part of management of otitis externa and is essential in both diagnosis and treatment (). The cleaning must be complete and yet not irritating to the lining. The most effective way is with a forceful stream of water. This is best done using the Haeberle flusher (Haeberle GmbH Comp & Co, Stuttgart, Germany) designed for the cleaning or caloric testing of the human ear. The instrument is connected permanendy to a cold water supply pipe; the water in the reservoir is electrically heated and thermostatically controlled. The instrument produces a forceful stream of water at supply line pressure, and the thermostat is set to body temperature. The kitten or puppy is held in the same way, and its ear is kept in the same position as for otoscopic examination. The hand that held the otoscope now takes the handle of the flusher to introduce the stream of water into the canal. When the returning water is clean the animal is allowed to shake its head. This results in a dry ear canal and a dry tympanic membrane. The procedure can be repeated if necessary. Puppies and kittens do not like the procedure, but they can be calmed by an experienced assistant.
When the ear canal is clean and its lumen is sufficiently wide, the canal and the tympanic membrane can be inspected. The tympanic membrane is a transparent round membrane, but it appears to be oval because it is seen
through the otoscope at a 60° angle, the ventral part being farther away from the viewer than the dorsal part. The pars tensa, the tensed part, is transparent and slighdy blue or gray with radial striping. The dorsal part, the pars flac-cida, is pink, and it bulges slighdy when pressure in the middle ear is increased. The manu-brium of the malleus is a solid white structure in the pars tensa, bordered by small, bright red blood vessels. These characteristics are especially striking in young animals.
Selections from the book: “Veterinary pediatrics: dogs and cats from birth to six months”. Johnny D. Hoskins. (2001)