Veterinarians are often confronted by frustrated pet owners claiming that their pet is going deaf! Now, whether this is a valid claim or rather an actual ploy conceived by a defiant subject will not be known until a thorough ear examination is performed. A pet’s apparent inability to perceive sounds can result for a number of reasons.
First, there might be impedance to the sound waves traveling through the ear. An external ear canal clogged with wax and debris can certainly be the culprit, as can constrictive swelling of the ear canal caused by otitis externa. Torn or ruptured eardrums can also diminish the effective transmission of sound waves to the middle and inner ears.
Interestingly, some researchers feel that a dog’s eardrums are not altogether necessary for efficient conduction of sound waves; rather, sound waves permeating the bony, air-filled tympanic bullae directly fulfill a major portion of this conductive function. Regardless, researchers do know that sound waves must pass through the middle ear cavity before reaching the inner ear, and that fluid or inflammation secondary to otitis media can lead to diminished hearing.
Besides interference with the transmission of sound waves, deafness in dogs and cats can also be caused by developmental defects or damage involving the actual nerve endings within the inner ear. Congenital nerve deafness has been reported in some breeds, including dalmatians, collies, and rottweilers. Nerve deafness can also be inherited in some cats. This type of induced deafness is seen primarily in white cats with blue eyes.
Certain drugs, such as the aminoglycoside antibiotics, are well known for their adverse effects on the hearing function in dogs and cats. Chronic, untreated bacterial and fungal infections within the middle and inner ears can undoubtedly lead to nerve deafness, as can certain viral organisms.
Diagnosis of nerve deafness is based on history and special hearing tests. One such test, the brainstem auditory evoked response test (BAER), measures the brain’s response to auditory stimuli and is quite helpful in the detection of hearing defects, determining the extent of any defect, and pinpointing its location.
Unfortunately, no known treatment exists for true nerve deafness. Hearing aids designed especially for dogs are now commercially available, and may help improve hearing in select instances. Most deaf pets will adapt to their condition with time. However, because of inherent dangers associated with environmental hazards, deaf dogs and cats should not be allowed outdoors unless closely supervised or maintained on a leash and harness.
First, there might be impedance to the sound waves traveling through the ear. An external ear canal clogged with wax and debris can certainly be the culprit, as can constrictive swelling of the ear canal caused by otitis externa. Torn or ruptured eardrums can also diminish the effective transmission of sound waves to the middle and inner ears.
Interestingly, some researchers feel that a dog’s eardrums are not altogether necessary for efficient conduction of sound waves; rather, sound waves permeating the bony, air-filled tympanic bullae directly fulfill a major portion of this conductive function. Regardless, researchers do know that sound waves must pass through the middle ear cavity before reaching the inner ear, and that fluid or inflammation secondary to otitis media can lead to diminished hearing.
Besides interference with the transmission of sound waves, deafness in dogs and cats can also be caused by developmental defects or damage involving the actual nerve endings within the inner ear. Congenital nerve deafness has been reported in some breeds, including dalmatians, collies, and rottweilers. Nerve deafness can also be inherited in some cats. This type of induced deafness is seen primarily in white cats with blue eyes.
Certain drugs, such as the aminoglycoside antibiotics, are well known for their adverse effects on the hearing function in dogs and cats. Chronic, untreated bacterial and fungal infections within the middle and inner ears can undoubtedly lead to nerve deafness, as can certain viral organisms.
Diagnosis of nerve deafness is based on history and special hearing tests. One such test, the brainstem auditory evoked response test (BAER), measures the brain’s response to auditory stimuli and is quite helpful in the detection of hearing defects, determining the extent of any defect, and pinpointing its location.
Unfortunately, no known treatment exists for true nerve deafness. Hearing aids designed especially for dogs are now commercially available, and may help improve hearing in select instances. Most deaf pets will adapt to their condition with time. However, because of inherent dangers associated with environmental hazards, deaf dogs and cats should not be allowed outdoors unless closely supervised or maintained on a leash and harness.
Post a Comment