All You Need to Know About Auditory Processing Disorder

SYDNEY, Australia — Has your child been diagnosed with an auditory problem or a learning disability? Auditory processing disorder (APD) and learning disabilities (LD) are complex and can be intertwined conditions. 

At Tomatis® Australia, we came up with this article to give you a better understanding of your child’s condition. Let us share with you the facts about APD and LD. Browse through the blog as we present to you the various diagnostic tools and treatments.

What is auditory processing disorder?

Auditory processing disorder (APD) is also known as central auditory processing disorder (CAPD). APDs relate to impairments in detecting and focusing on the sources of sounds. People with APD have difficulty in determining the meaning of sounds. The disorder may be due to damage, faulty development, or disease of the central auditory nervous system.

APD is called King Kopetzky Syndrome, too. It’s a condition where a person with normal ear function has trouble hearing in noisy environments. 

Adults and children with APD hear what you are saying. Some of the spoken words, though, are heard differently. They understand what you are saying, but since they heard a different word, the meaning changes. It has nothing to do with intelligence. Instead, it’s hearing without listening. “It’s when the brain does not hear what the ears are hearing” often says Francoise Nicoloff, the Director and Senior Tomatis® Consultant at Tomatis® Australia

It is not known how APD was first used. In 1954, Myklebust observed some children with normal hearing couldn’t listen or focus on a particular sound. In a 2016 study, APD was estimated at 1.94 per 1,000 school-age children in the mid-Atlantic. The study also reveals that APD among children in private schools was twice higher than children in public schools.

• According to the National Center for Learning Disabilities, people with APD struggle with four auditory skills. 

1. Auditory discrimination: be able to distinguish the distinct and separate sounds in words, which are crucial for reading
2. Auditory figure-ground discrimination: be able to select sounds amidst a noisy environment
3. Auditory memory: be able to recall information from spoken words on a short- and long-term basis
4. Auditory sequencing: be able to understand and recollect the sequence of the sound of words
5. Others: Reading, spelling, and written expressions

• The British Society of Audiology suggested three types of APD:

1. Secondary APD: It may be linked to hereditary causes or external hearing damage. 
2. Acquired APD: It may be related to brain trauma such as infection or stroke. It can coexist with Alzheimer’s disease.
3. Developmental APD: It has no known cause but exists since birth among ordinary people. It may be considered as both a developmental and neurological disorder.

What is the link between APD and the middle ear? 

The auditory system changes sound waves picked up by the ear from the environment. It transforms these sounds into patterns of neural activity. It is then combined with information from various sensory organs such as the eyes, ears, nose, tongue, and skin. It also includes the vestibular and proprioception systems, responsible for balance and coordination. 

This complex process first starts at the external and middle ears that captures sound waves. It is amplified as it travels to the cochlea of the inner ear. It then breaks up into smaller units picked up by the sensory hair cells. These vibrations or frequencies and amplitude are encoded by the auditory nerve fibres that deliver the brain’s electrical activity.

People with APD usually have typical external, middle, and inner ear structures. The problem lies in processing or interpreting the information they hear. However, chronic ear infection in the middle ear, also called otitis media, may cause APD.

What is the connection between APD and the nervous system? 

The central auditory nervous system is composed of the cortex, midbrain, and nerve fibres of the brain stem. It processes information coming from the ears. The four functions include sound recognition, localisation, auditory attention, and recognition of pattern. 

APD occurs when the central auditory nervous system has problems translating the sounds being heard. APD, in this case, is caused by a neurological disorder instead of a developmental disorder.

Is APD a hearing loss?

APD is different from Hidden Hearing Loss (HLL) and Auditory Neuropathy Spectrum Disorder (ANSD).

• HLL refers to people with problems in hearing clearly, even if they have normal hearing functions. HHL is caused by a defect in the cochlea, a structure in the inner ear. Risks include aging, noise exposure, drugs harmful to the ear, and damage to the nerves outside the brain. 
• ANSD is an umbrella term for hearing disabilities manifested as trouble understanding speech clearly. It’s a condition where the ear detects the sound. The problem lies in sending the sound to the brain. 

One probable cause of a structural anomaly is damage to the inner hair cells. These sensory cells found in the inner ear are responsible for sending information to the brain. Another probable cause is damage in the auditory neurons that bridges the inner hair cells to the brain.

What are the causes of APD?

The causes of ADP are unknown. Some of the probable causes are the following:

• Hereditary: Researchers said that there’s a probability that family history may cause obscure auditory dysfunction. 

Another study provided evidence suggesting that heredity causes APD. The measure used was for auditory processing skills, which were non-speech-based. It is vital in understanding and interpreting the meaning of spoken words. The neurological traits may be inherited from the father or the mother.

• Brain abnormalities: Researchers studied a young girl with listening, language, and learning problems. Their study reveals that preterm children with learning difficulties may suffer from auditory processing disorder. The researchers identified structural brain abnormalities due to complications during pregnancy or birth.
• Mild traumatic brain injury (MTBI): Researchers evaluated how people who suffered from MTBI understood spoken words amidst speech noise. The results show that 84% of people with MTBI reported difficulty in understanding speech-in-noise. 
• Ear problems: The middle ear can have issues such as a hole in the eardrum or an infection that doesn’t heal. It is called otitis media. If it persists for more than six weeks, it becomes chronic. The causes may vary from allergies, structural ear deformities to an immature immune system. 

A study shows that non-cholesteatomatous chronic otitis media affects the central auditory processing of teenagers. It’s a condition where there’s a non-cancerous skin growth in the middle ear. The most affected hearing mechanism was monaural low-redundancy. 

In children, otitis media negatively affected auditory abilities based on a study. The children who had otitis media and underwent surgery performed poorer than children who had no history of otitis media. Electrophysiological measures also showed changes in the brainstem response.

• Multiple sclerosis: Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system. Researchers in a study found that people with multiple sclerosis had central auditory processing defects. One of the results involved difficulty in discriminating speech in a noisy environment. Other auditory problems consisted of temporal resolution and auditory pattern, and the memory for the auditory task.
• Alzheimer’s Disease: Age-related CAPD is linked to loss of structure and function of brain cells. Or, as a coexisting disease, CAPD may increase the risk of mental deterioration. It occurs among people with early-stage Alzheimer’s disease.
• Premature birth: Researchers evaluated 82 premature children for CAPD. Their study shows that a higher number of premature children failed CAPD tests compared to full-term children.
• Lead poisoning: Lead poisoning happens when you breathe, eat, drink, or touch too much lead. It can damage your kidney and brain. The most common sources of lead poisoning are paint from walls, glazed dinnerware, and toys. Studies have shown that lead exposure impairs auditory function and perception.

What are the symptoms of APD?

Have you observed any of these symptoms from your child?

• Find it hard to understand spoken words, especially in a noisy environment
• May have a puzzled look when spoken to 
• May ask to repeat what’s been said
• Misunderstand words or may have a problem distinguishing similar sounding words
• Take more time to respond
• Can’t focus on what is being said
• Can’t understand rapid speech
• Can’t process complex instructions
• Can’t relate to a joke
• Can’t distinguish the tone of voice, inflection, connotations, or denotations
• May have problems with spelling, reading, language, and vocabulary 

What are the impacts of APD on learning?

APD may cause difficulties in communication, learning, and language functions. If left uncorrected, these handicaps may persist, which affects the quality of life. 

APD may exist independently or coexist with other disorders. It may also be linked to learning, language, listening, and speech difficulties. People with specific learning disorders (SLD) or difficulties in learning are 46% likely to have APD. 

There have been studies conducted over the years to investigate the impact of APD on learning. Earlier studies pointed out that there’s no connection between APD on cognitive development. However, there’s growing evidence in recent years that APD is linked to cognitive abilities.

• APD has little impact on verbal and non-verbal skills

A 2010 study aimed to determine if cognitive performance deficits are linked to auditory deficits. Twenty age-matched children with suspected APD participated in the study. All suspected APD children had listening/hearing problems. A control group consisting of 28 children also served as participants.

They took auditory tests using speech and non-speech methods. The cognitive assessment included tests on grammar, vocabulary, and non-verbal IQ. 

The study reveals that some of the children with suspected APD had genuine hearing deficits. Children with suspected APD scored lower than the control group. They performed poorer in verbal and non-verbal cognitive tests. 

But, children suspected of APD and those who genuinely had auditory deficits equally had poor cognitive abilities. Thus, the researchers concluded that with or without “the auditory deficit has little impact on the development of verbal and non-verbal skills.”

•  Poor auditory processing task is linked to cognitive deficit

A 2015 study aimed to examine if there’s a relationship between auditory processing, cognitive abilities, and functional deficits. Children aged 7-12 years old participated in the study. Fifty children comprised the control group, while 105 children took auditory processing and cognitive tests. Tests included auditory working memory, non-verbal intelligence, sustained attention, listening ability, and reading fluency.

Researchers found that children with AP assessment had poorer cognitive abilities than the controlled group. Out of the 105 children, those diagnosed with APD had significantly poorer cognitive abilities than other children who passed the tests.

A relationship between auditory processing and cognition existed based on correlation and regression tools. The researchers concluded that children with listening problems performed poorer in auditory processing tasks and cognitive tests.

• APD impacts verbal skills and spatial reasoning 

A 2018 study aimed to investigate the relationship between APD and SLD. The researchers selected participants from the Neuropediatric Unit, University of Brasilia Hospital. They were children who were reported to have SLD for at least a year. And they were monitored for at least six months. A total of 15 children as a control group and 41 children with SLD met the criteria.

The children underwent audiological evaluation, which related to attention and cognitive functions. These include tone audiometry, acoustic immittance measurement, assessment of acoustic reflex, and central auditory processing evaluation.

The same trained audiologist and neuropsychologist conducted all the tests. The children also took tests on verbal, non-verbal, and visuomotor skills to assess intelligence level.

The results of the study reveal that children with APD scored poorer on distractibility scales. They failed in arithmetic, coding, and labyrinth subtests. They also did poorly in visuomotor performance. This study concluded that children with APD had lower verbal and spatial reasoning performance.

What are the impacts of Auditory Processing Disorder on emotion and behaviour?

People with APD may experience negative emotions and behaviours. Anxiety, depression, and low self-esteem are only some of the psychological conditions. As a result, people with APD may have trouble communicating, socialising, and managing emotions. People with APD also have difficulty functioning at work or in school.

• APD link to mental disorders

A 2003 review of MEDLINE scientific journal aimed to determine the co-existence of CAPD with mental disorders. 

A total of 79 studies showed a relationship between CAPD and mental disorders. The specific conditions include learning disabilities (126), dyslexia (88), Alzheimer’s disease (39), Parkinson’s disease (29), and schizophrenia (175).  

The researchers concluded there’s substantial evidence proving the association between CAPD and mental disorders based on the review.

• APD and psychosocial difficulty and problems

A 2012 study investigated the link between APD and psychological and sociological status. Researchers enjoined 19 children with APD with an average age of 11.9 years old. Twenty children with no APD served as a control group. 

Parents of children with APD also participated in the study. They completed psychosocial questionnaires on how they perceived their children. It was in terms of behaviour and social skills. The results show that children with APD had greater psychosocial difficulty and problems. 

• APD and psychosocial consequences

A 2017 study aimed to investigate the psychological and social effects of APD. Children with APD and their parents participated in the qualitative cross-sectional study. The 10- to 12-year-old children and their parents totalled 13 in all. 

Researchers used semi-structured interviews to examine the emotional, educational, and social status of the children. The results reveal three themes on how APD impacted the psychological and social well-being of the children negatively. 

First, the children experienced internal problems. These are expressed behaviours and hidden thoughts. Second, the behaviours and thoughts manifested into external factors of dissatisfaction with support. Third, it affected the coping ability of the children and their parents.

• APD and anxiety

A 2017 study aimed to assess the association between auditory test results, APD symptoms, and psychological status. Twenty-two adults participated in the study who reported listening difficulties. They all had a normal hearing but had trouble understanding words in a noisy environment. They were suspected of having APD.

The participants underwent auditory tests. These include the Japanese hearing-in-noise, auditory psychological, gaps-in-noise, and auditory memory tests. They also took tests to assess their psychological characteristics. These are the Attention Deficit Hyperactivity Disorder Ration Scale-IV, Tokyo University Egogram test, and Pervasive Development Disorder Autism Society Japan Rating Scale. 

All participants had low scores in at least one of the auditory tests. Thus, they were suspected of suffering from APD. Some of the participants exhibited a psychological characteristic of AC-dominant. It is associated with focusing and restraining emotions. It influences how they perceive their condition. And they constantly become anxious and complain about their listening problem. The neurological basis of APD isn’t clear. But anxiety was evident as a psychological characteristic of people with APD.

What are the impacts of Auditory Processing Disorder on speech and language?

APD has been incorrectly linked with an intellectual disability or mental retardation. People with APD are not intellectually challenged. However, they have difficulty learning, reading, speaking, and writing. It results in poor grades for school children, which has nothing to do with intelligence or mental ability.

• APD and speech

• • A 2104 study aimed to understand the link between APD and language development. Seventy-five children aged 6 to 12 years old participants were divided into three groups. The first group consisted of 25 children with specific language impairment (SLI). The second group was composed of 25 children with APD. And the third group of 25 children had typical development (TD).

The children went through tests, namely the speech-in-noise, dichotic test, and pitch pattern sequencing test. Results reveal that children with APD and SLI performed poorer than children with TD. Children with APD, though, performed better than children with SLI. This study may indicate a difference between APD and SLI in terms of neural processing.

• • Central APD was shown to influence the severity of the speech-sound disorder in children. Researchers concluded this in a 2016 study. Children aged seven to ten years old with speech-sound disease participated in the study. They were divided into two groups based on the results of their central auditory processing evaluation.

The results reveal that children who probably had central APD also had greater severity of speech disorder.

• APD on learning and reading 

In a 2009 study, researchers assessed the coexistence of APD with language and reading disorders. Participants in the study were 68 children with suspected APD. They had nonverbal IQ scores of 80 and higher as validated by the attention, auditory, language, memory, and reading tests.

Results reveal that 72% of the children had APD. The researchers concluded that APD coexists with learning and reading disorders.

• APD on writing

A 2009 study aimed to explore the effects of APD on reading, speaking, and writing skills. First and second-grade school children participated in the study. A total of 67 children were divided into two groups—the first group composed of 41 children without APD. At the same time, the second group comprised 27 children suspected of APD.

An Observational Rating Scale was used to evaluate the children’s reading, speaking, and writing skills. The researchers found that APD is associated with or can result in problems in writing skills.

Is auditory processing disorder related to ADHD?

APD and attention deficit hyperactive disorder (ADHD) are two different conditions. Both conditions are brain-based but have slightly different symptoms. APD refers to the inability to recognise subtle differences in sound. On the other hand, ADHD exhibits difficulty in paying attention or staying focused.

However, studies show APD and ADHD can overlap. Given the coexistence, medical professionals need to come up with a comprehensive diagnosis to recommend proper interventions.  

Does your child have APD and ADHD? It is best to seek consultation from a psychologist, educational therapist, and speech-language pathologist. Or you can call us at Tomatis® Australia at 1300 233 572.

Do people with APD need special education?

Among many interventions, speech therapy is the primary treatment for APD. But children with APD may also be supported with a special education plan. A parent like you and teachers work together to develop an Individualized Education Program (IEP).

An IEP includes adjustments in your child’s physical environment in school. The location of the desk may be placed in a corner. Or it can be away from windows or entrances where noises are louder. Teachers can spend more time giving instructions to your child. And the teacher can provide more time to your child to answer questions and test papers. Visual aids may be helpful, too, in helping your child cope with learning.