If your audiogram shows that your hearing thresholds are fine (lower than 20 dB) but still speech intelligibility is challenging, you may have auditory processing disorder (APD). Continue reading to learn more about APD.
Figure 1 - Auditory pathway
How does our auditory pathway work?
We hear with our ears but we perceive sound and understand words in our brain, a part of it called the auditory cortex. As you can see in Figure 1 above, the sound travels through the ear canal, vibrates the eardrum and the vibration is transferred to the labyrinth structure via the 3 little bones in the middle ear. The cochlea organ in the labyrinth structure transduces the vibration of the liquid inside into electrical signals and sends the signal to the auditory cortex via the vestibulocochlear nerve.
After some interaction on the path, the left and right signals arrive at the auditory centres in the brain where the sound is interpreted as music, words, etc.
What is APD?
Auditory processing disorder is a disorder of the auditory system that disrupts the way an individual's brain understands what they are hearing. This means that someone with APD does not have hearing loss, despite showing difficulty with hearing-related tasks. In other words, the patient's audiogram shows no hearing loss, but still, the patient has difficulty understanding words or the words need to be pronounced slower for the patient to understand them.
Auditory processing disorder (APD) often starts in childhood, but some people develop it later.
If you or your child have APD, you may find it difficult to understand:
people speaking in noisy places
people with strong accents or fast talkers
similar sounding words
spoken instructions
APD is not a hearing problem. People with the condition usually have normal hearing.
How can APD be diagnosed?
To test for auditory processing disorder (APD) you or your child may be asked to:
listen to speech with background noise
spot small changes in sounds
fill in missing parts of words
Other tests may include:
having electrodes on your head to measure how your brain reacts to sound
speech and language tests
memory, problem-solving and concentration tests
Testing for APD is not usually done on children under 7 years old.
The most popular tests were dichotic, monaural low-redundancy speech, and temporal processing tests. Treatment and management recommendations were usually customized for each patient based on deficits found in behavioural AP testing.
What causes APD?
It's not always clear what causes auditory processing disorder (APD).
Possible causes include:
regular ear infections
genetics
head injury
extreme fever
complications at birth
APD is often found in people with attention, language and learning difficulties, such as dyslexia and attention deficit hyperactivity disorder (ADHD).
Can APD be treated? How?
Auditory processing disorder (APD) is often considered a childhood condition that can disappear or significantly improve with therapy and early intervention. However, some children with APD never grow out of their symptoms. Schoolchildren with APD may be advised to wear a wireless earpiece that connects to a remote microphone worn by their teacher to reduce background noise.
Treatment of APD usually involves activities to improve listening and concentration. This is called auditory training. You can do it with a hearing specialist or on your own time online, but generally, the treatment is better received from a speech-language pathologist, educator, or audiologist.
Is APD one form of ADHD?
Attention deficit hyperactivity disorder (ADHD) and auditory processing disorder (APD) often occur together. Auditory processing may be a symptom of ADHD, and APD symptoms can mimic those of ADHD. Auditory processing disorder may affect attention, as well as executive function.
References
Auditory Processing Disorders: Assessment, Management, and Treatment
edited by Donna Geffner, Deborah Ross-Swain
Central Auditory Processing Disorder in School-Aged Children
A Critical Review - Anthony T. Cacace and Dennis J. McFarland
The Diagnosis and Management of Auditory Processing Disorder
David R. Moore
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