Hearing impairment and auditory processing disorders can look very similar on the surface. To understand the difference, it helps to know what hearing is. We learn as kids that hearing is one of the five senses. But it’s a complex process—picking up sound and attaching meaning to it.
Hearing loss, or hearing impairment, is a problem with one or more parts of the ear that interrupts the way sound travels through the hearing system up to the brain. Someone who has hearing loss might be able to hear most sounds, hear only some sounds or possibly nothing at all. To understand hearing loss, it helps to know how the ear works. So, how do we hear?
The ear is divided into three main parts:
- The outer ear picks up the sound waves. Sound travels down the ear canal, hits the eardrum and causes it to move or vibrate.
- The middle ear is a closed space behind the eardrum. It is normally filled with air, but sometimes fluid collects there, too. When sound waves hit the eardrum, it vibrates, moving three tiny bones. These bones move sound along into the inner ear.
- The inner ear organ is called the cochlea. Vibrations travel from the middle ear to the cochlea, which sends sound information as electrical signals to your hearing nerve. This nerve sends the signals to your brain, which recognizes and interprets them into meaningful speech.
Even the slightest flaw along this pathway to the brain can cause a hearing loss.
- Conductive hearing loss happens when there is a problem with the outer or middle ear. Ear infections and earwax are problems that keep sounds from being conducted to the inner ear. Conductive hearing losses are usually mild and temporary because in most cases medical treatment can help.
- Sensorineural hearing loss happens when the cochlea in the inner ear isn’t working properly. Part of it is damaged, possibly by illness, noise exposure or even normal aging. Sensorineural loss is almost always permanent, and in kids it impacts speech, learning and development.
So how does hearing loss differ from an auditory processing disorder (APD)?
APD is not the inability to hear. It’s the inability to interpret, organize, or analyze what’s heard. All the parts of the hearing pathway are working well. But parts of the brain are not.
Some symptoms of APD in children are very similar to the symptoms of a hearing loss. So they’re often confused. But they’re not the same thing.
Hearing loss can be detected very early. Some infants can be diagnosed right after birth. Some symptoms of childhood hearing loss:
- Child does not react to loud sounds.
- Child is unable to detect where a sound is coming from, for example, turning the head toward the person speaking.
- Child is not responding to his own name by 6 months.
- Babbling does not develop into recognizable speech sounds or into words by age 2.
- Child may start showing frustration and acting out aggressively.
- Child frequently asks “what?” when spoken to.
Unlike hearing loss, APD cannot be diagnosed in infancy. Experts have different opinions on when a child’s brain is mature enough to be diagnosed with APD. Some say as early as 4 years and others say not until 12. But the majority of experts say 6 is the earliest, and that it’s best to wait until a child is 7 or 8 years old. This is because children develop at different rates.
Symptoms of APD include:
- Unusual sensitivity to loud sounds
- Difficulty understanding speech in noisy environments
- Difficulty following directions, especially directions with more than one step
- Difficulty telling the difference between similar-sounding speech sounds such as pat and bat
- Difficulty with spelling, reading and understanding information presented verbally
- Frequently saying “huh?” or “what?” when spoken to
It’s important to remember that neither hearing loss nor APD can be accurately diagnosed by checking through a list of symptoms. So, where do you start?
Diagnosing either hearing loss or APD requires a multidisciplinary team of consultants:
- The pediatric ear, nose and throat (ENT) doctor will assess any medical problems with the hearing pathway, such as ear infections, etc.
- An audiologist will test hearing sensitivity to determine if there is a hearing loss. She will administer the series of tests that will determine if APD is present.
- The speech-language pathologist (SLP) will test developmental milestones in speech and even written language.
- The teacher or an educational expert will look at academic difficulties.
- A psychologist will evaluate cognitive functioning.
Hearing loss and APD may have some symptoms in common. But the treatment options are very different. That’s why it’s a good idea to work with professionals who are trained to recognize the difference.