The ears listen, and the brain hears. Children with Central Auditory Processing Disorder (CAPD) may have perfectly good hearing when tested, but their brain does not properly process sounds into meaning. These childrendo not understand what is being said as well as they should. They may not learn as well as their peers, especially in large noisy classrooms and homes. They may understand only portions of what is being or behave as if they understand but lose track of conversations.When more than one person is talking, talking quickly, or in incomplete sentences, understanding becomes even more difficult. Issues also arise when there is too much background noise, or the conversation is high in emotional content.
Children with CAPD can lose confidence and develop feelings of insecurity, since they are often criticised or punished for their failure to understand. They may doubt their ability to overcome their learning difficulties. As a result, they can become isolated, withdrawn, and depressed. Others become bored and restless. To dishuise their deficits, it is not uncommon for children with CAPD to become disruptive, cynical, argumentative, and even aggressive. Such behaviours can appear as difficulties paying attention or following instructions, and for this reason many children with CAPD are misdiagnosed with ADHD.
SOME OF THE BEHAVIOURAL SYMPTOMS OF CAPD?
Below is a list of common behavioural symptoms noted in children with CAPD. Many of these behaviours are not unique to CAPD, but common to those with other deficits including attention deficits, hearing loss, behavioural problems, dyslexia, and other learning difficulties. Therefore, one should not assume that the presence of any of these symptoms indicates CAPD. Instead, these symptoms should be considered a risk-factor requiring further testing:
- Difficulty hearing in noisy situations
- Difficulty following long conversations
- Difficulty hearing conversations on the telephone
- Difficulty learning a foreign language
- Difficulty with challenging vocabulary
- Difficulty remembering spoken information (i.e., auditory memory deficits)
- Difficulty taking notes
- Difficulty maintaining focus on an activity if other sounds are present
- Difficulty with organisation
- Difficulty following multi-step directions
- Difficulty in directing, sustaining, or dividing attention
- Difficulty with reading and/or spelling
- Difficulty processing nonverbal information (e.g., lack of music appreciation)
Definitive diagnosis of a central auditory processing disorder cannot be made until specialised auditory testing is completed and other aetiologies have been ruled out.
HOW IS CAPD ASSESSED AT THE CLINIC?
CAPD is assessed with tests designed to assess various auditory brain functions. However, before testing begins, it is important that the patient receive a routine hearing test. An audiologist must rule out any physical hearing problems. An audiologist assesses the ability of the ear to detect a normal range of frequencies, from low tones to high tones, without loss of sensitivity. We can make a referral to an Audiologist experienced in assessing children.
At BNC, our central auditory function tests fall into two major categories: Behavioural tests and Electrophysiological tests.
The tests that we use depend on several factors including the child’s age, native language, cognitive status, and specific auditory deficits. Central auditory processing assessments are not generally appropriate for children with significant developmental delays and cognitive issues.
A brief overview of the CAPD tests at BNC is provided below, along with an abbreviated description of a few representative subtests that also used for CAPD diagnosis.
Electrophysiological tests measure the brain's response to sounds. A cap with built in sensors is placed on the child’s head to measure the brain’s electrical activity, arising from the central nervous system in response to an auditory stimulus (e.g., a clicking sound, or two tones of different frequency). The sounds are delivered to the ear and the electrical responses recorded.
To detect CAPD, some clinicians examine responses low in the brain (auditory brainstem response), whereas others assess functioning higher in the brain (middle latency responses, late auditory evoked responses, auditory cognitive or P300 responses). Either way, results on these tests are compared to age-appropriate norms to determine if any abnormalities exist.
SCAN-3A SCREENING TEST FOR AUDITORY PROCESSING DISORDERS.
SCAN identifies children with auditory processing disorders who may benefit from intervention. The 20-minute test is administered to children age 5-11. There are three subtests including low pass filtered words, auditory figure ground and competing words.The SCAN A: A Test for Auditory Processing Disorders in Adolescents and Adults was designed for individuals over 11 years. This instrument includes an additional subtest that uses competing sentences as stimuli.
MONAURAL LOW-REDUNDANCY SPEECH TESTS
Due to the complexity ofthe neural pathways in the auditory system, and the redundancy of acoustic information in spoken language, a healthy listener can recognise speech even when parts of the speech signal are missing. However, this ability is often compromised in CAPD. Monaural low-redundancy speech tests are designed to assess an individual's ability to achieve auditory closure when information is missing. The speech stimuli used in these tests are modified by changing one or more characteristics of the speech signal: frequency, timing (phase), or amplitude characteristics. The test items are presented to each ear individually and the child is asked to repeat the presented words. From here,a‘percent correct score’ is derived for each ear before being compared to age-appropriate norms.
DICHOTIC SPEECH TESTS
In these tests different speech items are presented to both ears (either simultaneously or in an overlapping manner).The child is asked to repeat everything that they have heard (divided attention) or to repeat whatever is heard in one ear (directed attention). The more similar and closely aligned the test items are acoustically, the more difficult the task becomes.
Another commonly used test for CAPD is the Dichotic Digits test. Here the child is asked to listen to four numbers presented to both ears at a comfortable listening level. Two numbers are presented to one ear and two numbers are presented to the other ear. For example, in Figure One, the number 5 is presented to the right ear, and at the same time, the number 1 is presented to the left ear. Then the numbers 9 and 6 are presented simultaneously to both ears. The child is asked to repeat all the numbers that they have heard and a ‘percent correct score’ is determined for each ear (once again compared to age-appropriate norms).