Impairment or loss of hearing power is more commonly the result of organic changes. Very rarely deafness depends upon certain constitutional disturbances, there being an entire absence of all symptoms indicative of inflammation.

Certain drugs such as quinine, taken in very large doses, and persisted in for a long time, have been known to induce deafness. In young dogs this is generally transitory, but in older the impairment may be permanent.

The more common cause is otitis, media or interna, or some organic change in the auditory nerve, possibly induced by blows on the head, or sympathetic with disease of the brain.

In very rare instances a catarrhal inflammation of the middle ear may be excited and subside without the occurrence of purulent changes, leaving a chronic irritation which eventually causes a thickening of the drum membrane, and impaired hearing power in the affected ear.

Accumulations in the external passage may cause deafness, at first mechanically, and ultimately by pressure inducing disease, and permanent injury of the parts acted upon. Some puppies are imperfect at whelp, the sense of hearing being entirely absent.

Treatment

Excepting in cases where the deafness is due to accumulations in the external ear, the results of treatment will prove negative. If congenital, positively nothing can be done. If the drum membrane has been perforated, a Judicious treatment of otitis will favor a closing of the opening, and the hearing power will in a measure be restored.

The deafness of old dogs admits of little or no improvement. Catarrhal inflammation of the middle ear generally results in a chronic disease very difficult to cure, and for which there is no treatment which will promise much. When organic nerve deafness exists, the condition is due to paralysis and should be treated as such. Where the cause is obscure or due to evident constitutional disturbances, efforts should be made to tone up the system, thereby improving the general health. Where deafness is suspected the ears should be well syringed and then carefully examined.