Central Auditory Processing Disorder (CAPD)

Transcription

Central Auditory Processing
Disorder
(CAPD)
Brief Review of Neuroanatomy
Brief Review of Neuroanatomy
Dichotic Listening

Kimura (1961):
contralateral pathways
are stronger & more
numerous than
ipsilateral
During dichotic listening
the ipsilateral pathways
are suppressed by
contralateral pathways
Right ear advantage
(REA) is usuaaly
apparent in dichotic
listening. Why?
Effects of Temporal Lobe Lesions
on Dichotic Listening
What Is Central Auditory
Processes?

Katz, Stecker & Henderson (1992) described
central auditory processing as "what we do with
what we hear."
Central auditory processes are the auditory system
mechanisms and processes responsible for the
following behavioral phenomena (ASHA 1996)
1.
2.
3.
4.
5.
Sound localization and lateralization
Auditory discrimination
Temporal aspects of audition including: temporal
resolution, temporal masking, temporal integration and
temporal ordering.
Auditory performance with competing acoustic signals
Auditory performance with degraded signals
What is CAPD?

CAPD is an observed deficiency in one or more of
the ASHA (1996) listed behaviors (see previous
slide)
CAPD can result from dysfunction of the
processes that are dedicated to audition, as well
from more global deficits (e.g., language deficits,
memory deficits, and attention deficits)
The prevalence of CAPD in children is estimated
to be between 2 and 3% (Chermak & Musiek,
1997), with it being twice as prevalent in males
WHAT ARE SOME OF THE BEHAVIORAL
MANIFESTATIONS OF CAPD?
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Difficulty hearing in noisy situations
Difficulty following long conversations
Difficulty hearing conversations on the telephone
Difficulty learning a foreign language or challenging vocabulary
words
Difficulty remembering spoken information (i.e., auditory memory
deficits)
Difficulty taking notes
Difficulty maintaining focus on an activity if other sounds are present
child is easily distracted by other sounds in the environment
Difficulty with organizational skills
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) Source: Schminky & Baran (2000)
Diagnostic Problem

(Jerger & Musiek, 2000)
Other types of childhood disorders may
exhibit similar behaviors, e.g., attention
deficit hyperactivity disorder (ADHD),
language impairment, reading
disability,autistic spectrum disorders
Some audiological test battery may fail to
distinguish CAPD from children with other
problems
Other confounding factors, e.g., lack of
motivation, attention, cooperation and
understanding
Differentiation Between CAPD
& ADHD

Read Chermark et al., 1999.
Only 2 (i.e., inattention & distractibility) of
the 11 most frequently cited behaviors
reported as common to both condition
Screening For CAPD

Screening by Questionnaire: observation of suspect
behaviors via questionnaires (Jerger & Musiek, 2000)

Fisher's Auditory Problems Checklist (Fisher 1985) for Kdg.
to grade 6
Screening Instrument for Targeting Educational Risk by
Anderson 1989 (S.I.F.T.E.R) for grade 1 & above
Children’s Auditory Processing Performance Scale (CHAPPS)
by Smoski, 1990
Screening by Test (Jerger & Musiek, 2000).

A dichotic digit test (Musiek, 1983)
A gap-detection test
SCAN-A (Keith, 1986)
Dichotic Digit Test

One of the more commonly used tests in Dichotic Speech Tests
is the Dichotic Digits test (Musiek, 1983)
Number 1-10 excluding 7 is used
Presentation level: 50 dB re: SRT
The child is asked to listen to four numbers presented to the
two ears at comfortable listening levels (50 dB SL re:SRT)
In each test item two numbers are presented to one ear and
two numbers are presented to the other ear. For example, in
this figure, 5 is presented to the right ear at the same time 1 is
presented to the left ear.
Then the numbers 9 and 6 are presented simultaneously to the
right and left ears
Dichotic Digit Test

Child is asked to repeat all numbers heard and a
percent correct score is determined for each ear and
compared to age-appropriate norms
The minimum patient age should be 7 years
Test administration time: 4-5 minutes minutes

Advantages:

Good validity
Short administration time
Resistive to effect of peripheral loss
Little linguistic load
Digits are easily transferred to picture-pointing task
Moderately high sensitivity to brainstem, cortical, and interhemispheric lesions
Dichotic Digit Test

Interpretation:

The cut off norm is 90% and lower for 12 years to adult

Fairly sensitive to intra-cranial lesion

7 years – 7:11; 55% left, 70% right
8 years to 8:11; 65% left, 75% right
11 years to 11 years, 11 months; 88% left, 90% right
Contralateral in right temporal lobe lesion
Bilateral in left temporal lobe lesion
Sensitive to inter-hemispheric lesion (corpus callosum)
Sensitive to brain stem lesion
Resistant to mild-moderate cochlear lost
The Gap Detection Test

Gap detection is a hearing test that measures the
ability to resolve differences in time
Three noise bursts, with one of them having a
silent interval ("gap") in it are presented
The task is to pick the one with the gap
Depending on the response, the gap may
become longer or shorter or totally undetectable
The computer program may be used to
automatically track the responses and calculate
the smallest gap that can be detected
The Gap Detection Test

Interpretation

A normally-hearing person may detect 1-2 msec gap if the stimuli
are presented at a comfortably loud level
person with CAPD may have a significantly greater gap detection
threshold
A standard test developed by Keith (2000) can be used; Random
Gap Detection Test (RGDT)

Several pairs of tonal or click stimuli are presented to listener, who is
required to indicate whether one or two sounds are heard
Subtest 1 is a practice consisting of 500 Hz tone pairs with
interstimulus interval (ISIs) presented in ascending order from 0-40 ms
Subtest 2 is the standard test with random ordering of ISI from 5004000 HZ
Refer to the manuals provided
SCAN-A

Screening Test for auditory Disorders (SCAN,
Keith, 1986)
For children between 3-11 years
Four subtests

Filtered words
Auditory figure ground (speech in noise)
Competing words (recall two or more competing
words – divided attention)
Competing sentences (revised, Keith, 2000)
Administered at MCL
Test time: approximately 20 minutes
SCAN-A-B-C

Disadvantages

Bellis (1996) found alarming false positives
and false negatives for the test
The passing score in all subtests should not
be taken as evidence that further
evaluation is unnecessary, but rather be
viewed in light of other data (Bellis, 1996)
Differential Diagnosis of CAPD

Behavioral Tests
Electrophysiologic & Electroacoustic
Tests
Neuroimaging Studies
Behavioral Tests (Medwetsky, 2002)
Based On The Particular Skill

Span of Apprehension
Lexical Decoding
Phonologic Decoding
Tolerance-Fading Memory
Auditory Integration
Sequencing
Auditory Attention
Span of Apprehension

Tests how much information can be retained
in short term/working memory

Test of Auditory-Perceptual Skills (TAPS-R;
Gardner, 1996) – Auditory Numbers Forward
(ANF)

This test evaluates how much information a child can
hold in conscious, short-term/working memory for
familiar items such as numbers, familiar words, or
everyday direction
Has been normed for children ages 4-12
Can provide scaled score, percentile, and age-equivalent
scores
Lexical Decoding

Ability to process information both
accurately and quickly using lexical
(word) items

Staggered Spondaic Word Test (SSW, Katz
& Ivey, 1994)
Competing Sentence Test (CST; Willeford
& Burleigh, 1994)
SSW

Is a dichotic procedure
Spondees are presented in an overlapped fashion: the 2nd
word of the 1st spondee occurs at the same time as the
first word of the 2nd spondee
Thus, one ear (leading ear) is presented with 1st syllable
in isolation (non-competing), followed by 2nd syllable in a
dichotic mode (competing). The other ear (lagging ear)
begins with the 1st syllable presented in the dichotic mode
and finished with the 2nd syllable presented in isolation
Each ear serves as the leading ear for half of the test
presentations
Presentation level: 50 dB SL re: SRT/PTA
Test time: 8 minutes
Normed for ages 5-69 years
SSW

Test outcome

Error scores are calculated for each ear in both
the competing and non-competing modes
Corrections can be applied to account for hearing
loss
Many error patterns can be identified, interested
students can refer to Katz & Ivey (1994) in
Handbook of Clinical Audiology. 4th edition
(pp.239-255)
This test is sensitive to intra-cranial
(temporal/cerebral) lesion

Contralateral deficit if primary auditory areas involved
Mixed results for brainstem lesions
CST

25 pairs of sentences with 6-7 words are
simultaneously presented in dichotic manner
All the sentences have similar duration, word
length and semantic content
Normed for ages 5 years through adulthood
Presentation level:

target ear (test ear) 35 dB SL re: SRT
Non-test ear receives competing sentences at 50
dB SL re:SRT
10 paired sentences for each test condition
CST

Outcome and interpretation

Sentences are generally scored as correct if the
meaning and content of the sentence was
identified appropriately
The scores are then compared to age norms for
the better and poorer ears
Abnormal competing sentence tests performance
has been reported in patients with temporal lobe
lesions (Musiek, 1983), predominantly in the ear
contralateral to the lesion
Other Scoring Methods (Musiek)

Each of the 10 target
sentences is assigned a
value of 10 points and is
divided into quadrants, each
worth 2.5 points or 25% of
total sentence score
The child’s response is
scored in terms of quadrants
correct. Each sentence will
have maximum score of
10% with possible scores of
7.5, 5. 2.5 and 0% scores.
The maximum total score of
100% for 10 sentences

Target: I think we’ll have
rain today
Competing: There was frost
on the ground
Responses:

I think we’ll have rain
today; Score: 10%
I think we’ll have frost
today; score 7.5%
There was rain today; 5%
There was frost today;
2.5%
There was frost on the
ground; o%
Norms Based on Previous Scoring
(Bellis, 2002)

7 years – 7:11; 35% left, 80% right
11 years to 11 years, 11 months; 90% both ears
12 years to adult: 90% both ears
Ear Advantage in Dichotic
Tests
Phonologic Decoding

Encompasses a broad range of skills that can
be divided into two main areas:

Phonological awareness: the ability to think about
and manipulate the speech segments of a
language (Swank & Catts, 1994)
Phonics: the ability to represent individual speech
sounds through the use of symbols (e.g., letters)
In this category we only discuss Phonemic
Synthesis Test (PST; Katz & Harmon, 1982)
PST

Assesses the ability to blend individual phonemes to
form the target word
Consists of 25 test words presented phoneme by
phoneme for each word
Words are presented one sound at a time to the
child, who will then blend the sounds into words
It evaluates discriminations, sequencing and/or
sound blending
Norms available down to 6 years of age
Highly predictive of the ability to read words
Also closely associated with articulation, spelling, and
receptive language (Katz & Harmon, 1982)
Administration time: 15 minutes
PST

The following outcomes can be determined
through careful analysis of the error patterns:

More errors on the initial phoneme: associated with
tolerance-fading memory (ability to retain/recall earlier
presented information successfully) because of an
inability to retain earlier presented information
More errors on the vowel and final phonemes:
associated with phonologic decoding difficulty (an
ability to process phonemes accurately and quickly)
Reversals: associated with sequencing or
organizational difficulty
Auditory Integration

Includes:

Binaural integration of acoustic stimuli: integrating
signals transmitted separately to each ear
Inter-hemispheric transfer of auditory-linguistic
information (assessing ear dominance)
Integration of auditory-linguistic information
across processing regions (segmental and
suprasegmental)
Integration of information between modalities:i.e.,
auditory-visual integration
Binaural Integration

It is sensitive to brainstem lesions and it is
the initial stage of processing. It includes:

Integration of different intensity and temporal
information of one signal source from the two ears
(e.g., localizing a sound)
Integration a portion of one signal presented to one
ear and a complementary portion presented to the
other ear and to combine the two portions to derive a
target stimulus (also called binaural fusion)
Two tests will be discussed in this category:

Binaural fusion (BF, Matzker, 1959)
Masking Level Difference (MLD, Hirsh, 1948; Licklider,
1948)
Binaural Integration Tests
BF

Is a measure in which words, usually monosyllables, are
pass-band filtered into a low-pass band and a high pass
band
A low pass band (e.g., from 500-800 Hz) is presented to
one ear and the high pass band (e.g., 1815-2500 Hz) to
the other ear
Recognition of either band in isolation is poor
Normal listeners are capable of fusing the two pass-bands
when they are presented binaurally with a high level of
accuracy
Patients with brain stem lesions (Palva & Jokinem, 1975;
Smith & Resnick, 1972) and some patients with temporal
lobe disorder (Lynn & Gilory, 1972) have poor BF scores
BF

There are a number of commercial BF tests
available:

The Ivey BF test, which uses spondees and is
included in the Willeford central test battery
(Willford & Burleigh, 1985)
The NU-6 BF test (Wilson & Mueller, 1984): uses
monosyllabic words to reduce linguistic
redundancy, thereby increasing sensitivity
The CVC-BF task (Wilson, 1994): uses initial
consonant-vowel nucleus-final consonant word
list. The carrier phrase and vowel segments are
presented to one ear, and the consonant
segments to the other ear
MLD

Many experiments have shown that the
threshold for detecting a signal masked by
noise is lower when the noise and signal are
presented in a particular way to both ears.
Before describing the experiments you have
to become familiar to different terminology
that is used in these types of experiments.
MLD

So: Signal is presented binaurally with no interaural
differences
No (or M0): Noise (masker) is presented binaurally with no
interaural differences (diotic).
Sm: Signal is presented to only one ear.
Nm: Noise is presented to only one ear.
Sπ: Signal is presented to one ear 180° out of phase with
the signal presented to the other ear.
Nπ: Noise is presented to one ear 180° out of phase with
the signal presented to the other ear.
Monotic: NmSm
Diotic: NoSo
Dichotic: NoSπ; NoSm; NπSπ; NπSo; NπSm
MLD Listening Conditions
MLD
MLD

Binaural advantage occurs only when the stimuli are in
some way different at the two ears (dichotic)
We can define MLD as difference in masked threshold
between dichotically presented stimuli and signals that are
presented monotically (or diotically).
The size of the MLD varies from as large as about 15 dB
for NoSπ condition to as little as 0 dB
The largest MLDs are obtained when either the signal
(SπNo) or the noise (SoNπ) is opposite in phase at the two
ears
MLD is largest for low frequencies-about 15 dB for 250
Hz- and decreases for higher frequencies until a constant
of about 3 dB is maintained about 1500-2000 Hz
MLD

In clinic MLD is performed for 500 Hz and it is
defined as the difference in threshold between
the in-phase and out-of-phase conditions
For 500 Hz, the MLD should be greater than 7 dB
and is usually around 12 dB
Abnormal performance on the MLD is consistent
with brainstem disorder (Hannley et al., 1983;
Hendler et al., 1990; Lynn et al., 1981)
Care must be taken in interpreting MLD results in
the presence of hearing loss at 500 Hz
Interhemispheric Transfer of
Auditory-Linguistic Information

It test the efficiency of transfer of auditory-linguistic
information between the two hemispheres of the brain
It is a dichotic test
Acoustic stimuli are transmitted most efficiently to the
hemisphere contralateral to the stimulated ear
Language processing center resides in the left hemisphere
in most individuals (Bhatnagar & Andy, 1995), therefore,
stimuli presented to the left ear must ultimately cross over
from right to left via corpus callosum
Corpus callusum is one of the last cortical structures to
reach physical maturity
A right ear advantage is usually observed in children until
age 11 (Pinheiro & Musiek, 1985)
Tests for Interhemispheric Transfer
of Auditory-Linguistic Information

The dichotic tests that can be used for
this category are:

Dichotic Digits Test (DDT; Musiek, 1983)
Staggered Spondaic Word (SSW)
Competing Sentence Test (CST)
Integration Across Processing
Regions

Perception of speech entails processing of both
linguistic content (lexicon, semantic, syntax and
suprasegmental information (stress, intonation,
duration pattern)
The linguistic contents are mostly processed in
the left hemisphere and suprasegmental
information are mostly processed in the right
hemisphere (Musiek & Lamb, 1994)
Two tests will be discussed here:

Pitch Pattern Sequence (PPS, Pinheiro, 1977)
Duration Pattern Sequence (DPS; Musiek et al., 1990)
PPS

Has a high sensitivity
Administration time: 10 minutes
Children & adult version (not good for children ≤ 8 yrs)
It is composed of 120 test sequences
Each sequence containing three tone bursts
In each sequence two of the tone bursts are of the
same frequency, whereas the third is of a different
frequency
The tone bursts include

A low frequency tone (880 Hz)

A high frequency tone (1122 Hz)
An interstimulus interval of 200 msec.
PPS

Six different sequences can be generated
(i.e., high-high-low, high-low-high, high-lowlow, …)
The sequence are typically presented at 50
dB Sl re: SRT
The patient is asked to verbally describe each
sequence heard (can also hum in case of
children)
Percent correct identification scores are
derived for each ear
PPS Outcome

Patients with compromise of the auditory areas of
either hemisphere or of the interhemispheric
pathways (i.e, corpus callosum) have difficulty
describing the monaurally presented test sequence
(Musiek et al, 1994)
If the patients can not describe the sequence verbally
but can hum the sequence, it is most likely corpus
callosum lesion (observed in confirmed cases of
posterior commissurotomies, Musiek et al., 1984)
Therefore, in a verbal response some processing of
stimuli occurs in both hemispheres
A cut off score of 78% for young , normal hearing
adult (Musiek, 1994)
DPS

Similar to PPS
The patient is asked to verbally describe the
sequences heard; long-short-long
The frequency of the tones is maintained at 1000
Hz and the duration of the tones is varied (250
msec and 500 msec)
In each sequence two of the three tones have
the same duration and the third one if of a
different duration
The presentation level: 50 dB re:SRT
Percent correct identification scores are derived
for each ear
DPS Outcome

The test is highly sensitive to cerebral
lesion (86%, Musiek et al., 1990) with
most of the cochlear hearing loss (92%)
showing normal performance
A cut off score of 73% for young ,
normal hearing adult (Musiek, 1994)
Not appropriate <9 years of age
Auditory-Visual (AV)
Integration

AV integration will help hearing impaired
individuals to integrate both visual (lip
reading) and auditory cues to perceive the
speech.
It also helps to associate sounds and symbols
(phonics) which is essential when learning to
read and spell
Tests:

Lindamood Auditory Conceptualization Test
(Lindamood-Charles-H; Lindamood-Patricia-C,
19790
SSW
Lindamood Auditory
Conceptualization Test

Designed to measure a student's level of
auditory functioning.
Skills measured parallel those basic to
spelling and reading
Subject manipulates wooden blocks of
various colors to indicate his or her
conceptualization of speech sound patterns
delivered by examiner
Age Range: AGE 2-17, Adults
Testing Time: 10 minutes
Summary of Behavioral Tests

If you want to be less affected by the
influence of language and cognitive
processes (e.g., memory, attention)
then you have to select those test
battery that have little linguistic load,
e.g., nonsense syllables or digits
Always adhere to a test battery concept
SSI-CCM SSI-ICM

SSI-CCM:

Ten-3rd-order approximations of English Sentences
Competing message consists of continuous discourse (Davy Crockett)
Message @ 30 dB HL (pure tone should be normal @500-2000 Hz)
The competing varies from 30 dB HL (o S/N) to 70 dB HL (-40 dB S/N)
Sntences have to be identify by number on the sentence lists in front of the
patient
Score is in percent correct for each ear. CCM score is considered to be
either the core obtained in most difficult condition (-40 S/N) or the average
of the S/N
Degree of asymmetry between ears are better indicator of central auditory
dysfunction
Adults with normal hearing tends to perform around 100% in all conditions
as do most listeners with brainstem lesion
People with temporal problem tend to do worse in ear contralateral to the
lesion
Electrophysiologic Tests

Immittance audiometry
Otoacoustic emissions
Auditory brainstem response
Auditory middle latency response (AMLR)
Auditory late response (ALR)
Mismatched negativity response (MMNR)
Event-related response (ERP
Auditory Neuropathy

Can exhibit symptomatology similar to CAPD (Read Linda
Hood paper)
Auditory neuropathy affects the normal synchronous
activity in the auditory nerve, without affecting the
amplification function in the inner ear
Patients with auditory neuropathy often complain that
they can hear sounds, but cannot understand speech
Psychophysical tests indicating that these patients' poor
speech recognition is due to a severe impairment in their
temporal processing abilities
These characteristics are observed on clinical audiologic
tests as normal otoacoustic emissions (OAEs) in the
presence of an absent or severely abnormal auditory
brainstem response (ABR)