Congenital deafness and its recognition

Sensory function in neonatal dogs and cats is primarily tactile, olfactory, and gustatory. The visual and auditory senses, although partially functional at birth, exhibit significant postnatal development: in the dog, the eyes do not open until a puppy is 8 to 10 days of age, the ear canals do not open until it is 12 to 13 days of age, and mature system function up through the cortex is not present until it is 3 months of age or older.(18,22) Similar delays are seen in the cat. As a result, disorders of these systems frequently escape early detection. Deafness can be described as (1) congenital or late onset, (2) hereditary or acquired, and (3) conductive or sensorineural.(14,15) The most commonly occurring deafness forms in dogs and cats are congenital hereditary sensorineural deafness, late-onset acquired sensorineural deafness, and late-onset acquired conductive deafness. Distinguishing between hereditary and acquired deafness is generally not possible without breeding trials, although an assumption of hereditary deafness can be made in breeds with a high prevalence of deafness. The most common form of deafness in young dogs and cats is congenital hereditary sensorineural deafness, with acquired conductive and acquired sensorineural deafness appearing on rare occasions.