How hearing works

The ears hear sound. The sound signals pass along nerves to the brain. The part of the brain that controls hearing is the central auditory system. It interprets the signals as sound. Then the brain mixes these signals with signals from other parts of the brain.

This process is very complex. The brain must ignore certain background sounds. At the same time, the brain highlights important sounds, such as the speech in a conversation. Several parts of the brain must work together. It's how we pay attention to and understand sounds.

In some cases, part of this process goes wrong. A problem happens between the ear and the the brain's central auditory system. Certain kinds of sounds become hard to interpret.

What causes CAPD?

Researchers are still trying to understand what causes CAPD. An increased risk for CAPD may be genetic. In some cases, a specific problem may cause it. This problem may be:

• Exposure to a toxic substance, such as lead.

• A brain tumor.

• A brain injury.

• Repeated ear infections.

• Autoimmune diseases, such as multiple sclerosis.

In most cases, the cause of CAPD is not known.

Signs of CAPD

A child with CAPD may show a variety of problems with listening. For example, you may notice that your child often asks what you mean. Or they may ask you to repeat what you’ve said. Children with CAPD may have problems with:

• Understanding speech in a noisy environment.

• Following directions.

• Maintaining their attention.

• Understanding rapid speech.

• Telling the difference between similar speech sounds.

• Telling where a sound comes from (localize a sound).

• Paying attention in lecture classes.

• Language, learning, and reading.

Your child may not have all of these signs.

Diagnosing CAPD

Even if your child has signs of CAPD, they might not have it. Many of these signs are like those of other disorders. A health care provider trained in hearing problems (audiologist) can diagnose CAPD. The provider uses several methods to figure out a child’s hearing problem.

The audiologist may give a series of tests in a soundproof room. Your child will be asked to listen to a set of sounds and then respond to them in some way. The tests might assess your child’s:

• Basic hearing.

• Use of sound in both ears.

• Ability to tell where a sound comes from (localize a sound).

• Ability to tell the difference between sounds (sound discrimination).

• Ability to distinguish competing sounds.

• Ability to make out poor-quality sounds.

In some cases, an audiologist may measure the brain’s response to sound. An example is the auditory brainstem response test. This uses electrodes placed on your child’s head. They are connected to a computer, which records brain activity when a sound is heard. This test is also known as the brainstem auditory evoked response. It can check the nerve pathways and help locate the problem. These tests work best in children 7 years of age and older. This is often the earliest age that an audiologist will diagnose CAPD.

Other health care providers may also help assess your child. A speech-language pathologist (SLP) can assess your child’s language and speech issues. A psychologist can assess your child’s mental and psychological health. An ear nose and throat specialist or a neurologist may be able to help. And your child’s teacher might have insights on learning problems.