A Brainstem Auditory Evoked Response (BAER) Test determines whether sound waves are picked up by the ear and transferred neurologically to the brain for interpretation. Eight percent of Dalmatians are born bilaterally (both ears) deaf. Twenty-two percent are born unilaterally (one ear) deaf. The average person would not recognize a unilaterally deaf, or uni as we call them, Dalmatian. Unis make great pets, but we do not believe they should be breed.
The puppy is usually sedated and does not feel any pain. Because the BAER test does not hurt, it can be performed without sedation. During the test, earphones are placed in the puppy's ears while electrodes measure the puppy's brain activity when sound (about 70 db) is administered. If the puppy hears, the brain makes all sorts of activity and you get a wavy line (kind of like a seismograph machine measuring the ground's activity during an earthquake). If the puppy cannot hear, the brain makes little or no activity and you get a flat or straighter line. Each ear is done individually.
This is "Emma" being BAER Tested at Oakland Veterinary Referral Service.
This is the BAER Test machine. If you look closely at the screen, you can see two wavy lines. This shows the pup hears in both ears. Below are copies of two actual BAER tracings. The left tracing is of a bilateral hearing pup. On the right is a tracing of a unilateral hearing pup. Notice the top line on the tracing on the right. It indicates the deaf ear.
As you can see, this test requires some very specialized equipment. This is not a test that can be performed by any veterinarian. There is no home test. Although many experienced breeders have found ways to assess their puppies at home. Reputable breeders ALWAYS follow thru with a BAER test to confirm their findings. Even experience breeders can be surprised by a uni they thought was a full hearing dog.
BAER Testing Sites
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