What is Auditory Processing Disorder (APD)?
Auditory Processing Disorder (APD), also called Central Auditory Processing Disorder (CAPD), describes an impairment in processing sounds despite normal hearing sensitivity.
Our hearing relies on our main hearing organ, the cochlea, to receive auditory information and then relay this information via the nervous system to the brain for processing and understanding. APD occurs when there is a deficit (or lesion) in this relay or processing system (i.e., the problem is “central” in origin relative to the brain, hence why it’s sometimes called CAPD).
So APD can be present in people who have listening and learning difficulties due to a neurological problem beyond the cochlea, from the auditory nerves to the brain. For example, damage to both auditory cortices can render a person completely deaf even if the cochlea is undamaged.
APD may be present in isolation, or in combination with language disorders, Attention Deficit Hyperactivity Disorder (ADHD), auditory processing deficits, dyslexia, or learning disabilities.
The prevalence of APD is estimated to be approximately 5% of school-aged children. It is unclear if students “grow out” of APD or if the impact of APD decreases with age as those with APD learn and incorporate compensatory strategies.
Age-related central auditory processing disorders also occur in adults and is usually associated with difficulty hearing in noise, understanding what is said in the presence of competing speech, and difficulty following multi-step or complex directions.
Signs and Symptoms of Auditory Processing Disorder
APD is often quite individualized, but in general, the symptoms of APD usually include difficulty extracting important auditory information in everyday settings. This presents itself as many of the following listening behaviors:
- Normal or near-normal hearing sensitivity as measured on a traditional hearing test (audiogram) but difficulty with speech understanding and language comprehension. This indicates that APD is primarily an impairment of the central portion of the auditory system which includes the hearing portion of the central nervous system (auditory nerve and brain).
- Difficulty localizing sound
- Difficulty learning to read phonetically due to misunderstanding some speech sounds
- Difficulty learning or appreciating music
- Difficulty remembering the beginnings of long sentences by the end (poor auditory memory)
- Difficulty sequencing steps in a process (temporal processing)
- Having a hard time remembering strings of numbers
- Being more sensitive to loud sounds than others
- Exhibiting non-specific poor listening skills
- Difficulty understanding speech (also called auditory discrimination) in “degraded” conditions such as:
- Background noise (often called auditory figure-ground)
- Reverberation (large rooms, hard floors, high ceilings)
- People speaking quickly (often called speeded speech)
- People speaking with accents
While many people with APD are more distracted by background sounds than those without APD, APD is not exactly the same as ADHD. Likewise, while some people with Autism Spectrum Disorders (ASD) exhibit behaviors that look like APD, these are separate conditions and not always found together.
The prevalence of APD is estimated to be approximately 5% of school-aged children.
What Causes APD?
Since APD is a diverse group of difficulties, it doesn’t have a specific cause. APD has been found in people with the following risk factors and conditions:
- Brain injury (e.g., head trauma, infections like meningitis, etc.)
- Progressive neurological diseases like multiple sclerosis
- Seizure disorders
- Premature birth
- Exposure to cytomegalovirus (CMV) before birth
- Exposure to other drugs during pregnancy
- History of recurrent ear infections
- History of general, unspecified learning problems
APD is generally thought to be a developmental disorder. In many cases, a specific cause of APD cannot be identified, and this is often frustrating to families. However, carefully identifying strengths and weaknesses is more important to developing a plan than knowing exactly why the APD symptoms are present. Taking this approach also allows treatment teams to better track progress and adapt treatment plans as the patient’s auditory processing skills change and evolve.
Because APD is very complex, a team approach to diagnosis is important. It begins with a referral from your pediatrician or educational team. While there is no absolute “best practice,” the following professionals are typically involved in the evaluation:
Audiologist. Rules out peripheral (outer, middle, or inner ear) hearing loss, as well as documents baseline speech discrimination abilities in quiet. It is ideal for this audiologist to have specialty experience with pediatric audiology.
Speech-Language Pathologist (SLP). Evaluates overall language function to help identify if any other issues exist that may mimic APD. SLPs are also able to assist with reading and memory skills development.
Educational Psychologist. Provides a comprehensive evaluation of language-based brain function called a neuro-psychological evaluation. This evaluation helps identify areas of weakness in the organization of information in the brain, as well as the patient’s ability to prioritize and allocate brain resources to interpret, retain, and filter information. This group of skills is often called executive functioning, and is often impacted by APD.
Due to the multidisciplinary nature of APD evaluation and treatment, university training programs in communication disorders offer a unique opportunity to not only have all the right people in the room, but also to have access to research and treatment protocol development. To find an accredited communication disorders program near you, check out this list of CAA Accredited Programs in the United States.
APD evaluations generally take several visits and involve primarily language-based listening tests. Some examples include:
- Repeating a string of numbers (Auditory Digit Span Recall) to evaluate working memory.
- Repeating words or sentences in background noise.
- Repeating words or sentences that have been artificially sped up.
- Repeating numbers or words that differ between the two ears (Dichotic Listening).
- Evaluating how the brain manages sounds from both ears individually and together (binaural integration).
- Repeating and labeling tones of different pitches (Pitch Pattern Sequencing).
In some cases, measurements of brain activity similar to an EEG (Electroencephalogram) called Auditory Evoked Potentials are made to better identify how the patient’s brain behavior differs from average to help shape the treatment plan.
When seeking evaluation for APD, be sure to ask each clinician to describe their experience and approach to APD.
One challenge of APD evaluation is that, because many of the tests are based on language, the patient needs to have fairly well developed language skills to perform them. In general, APD evaluations are most accurate after about the age of 5 or 6, and many tests are most valid after age 7.
The results of an APD evaluation are often more like a list of strengths, weaknesses, and strategies to compensate for them than a definitive diagnosis and prescription for a “fix.”
Pediatric audiologists are instrumental in the diagnosis and ongoing treatment strategies for APD.
Treating Auditory Processing Disorder
Based on the patterns of auditory processing identified in the APD evaluation, the treatment team—which, in addition to the evaluation team, includes teachers and family members—will develop a series of exercises to address each of the APD weakness areas. Think of this as a personal trainer’s program for getting the listening brain in shape.
Treatment can take several forms including formal therapy sessions with a Speech-language pathologist. This is called auditory training.
Developing and learning to use more effective communication strategies to minimize the impact of APD is also very important. These can include:
- Speaking in shorter sentences
- Reducing background noise when possible
- Using “multimedia” learning including listening, visual aids, and other prompts to facilitate memory and understanding
- Classroom modifications to reduce background noise and echo (reverberation)
- Use of assistive technology such as low-gain hearing aids, remote microphones, and media streamers especially in noisy environments.
As stated above, living successfully with APD is more about adaptation and compensation than curing the underlying disorder. Because this usually requires a lot of effort, having support is helpful. The following websites may provide additional information and resources beyond the scope of this article.
American Academy of Audiology consumer page on APD
Resources designed for consumers.
American Speech-Language Hearing Association’s page on APD
This webpage is geared mostly toward professionals and educators and may be a bit technical.
Success for Kids with Hearing Loss
Although not specifically geared toward APD, this website is a comprehensive collection of resources developed and curated by well-respected educational audiologist Karen Anderson who has decades of experience helping families of kids with listening challenges that impact education and development.
When the Brain Can’t Hear: Unraveling the Mystery of Auditory Processing Disorders
Teri James’s Bellis, PhD, is one of the world's foremost experts on the evaluation and treatment of APD. Available on Amazon, this book is designed to be accessible and understandable to non-professionals.
Finding success with APD
APD isn’t something that can be “cured,” but with persistence, consistency, and optimism, most families challenged by APD find ways to reduce frustration and improve the health of the family communication ecosystem. With ongoing consistent work, it is possible for those with APD to live successful and fulfilling lives.