Central Auditory Processing Disorder (CAPD)

Transcription

1 Central Auditory Processing Disorder (CAPD)

2 Brief Review of Neuroanatomy

3 Brief Review of Neuroanatomy

4 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?

5 Effects of Temporal Lobe Lesions on Dichotic Listening

6 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. Sound localization and lateralization 2. Auditory discrimination 3. Temporal aspects of audition including: temporal resolution, temporal masking, temporal integration and temporal ordering. 4. Auditory performance with competing acoustic signals 5. Auditory performance with degraded signals

7 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

8 WHAT ARE SOME OF THE BEHAVIORAL MANIFESTATIONS OF CAPD? 1. Difficulty hearing in noisy situations 2. Difficulty following long conversations 3. Difficulty hearing conversations on the telephone 4. Difficulty learning a foreign language or challenging vocabulary words 5. Difficulty remembering spoken information (i.e., auditory memory deficits) 6. Difficulty taking notes 7. Difficulty maintaining focus on an activity if other sounds are present child is easily distracted by other sounds in the environment 8. Difficulty with organizational skills 9. Difficulty following multi-step directions 10. Difficulty in directing, sustaining, or dividing attention 11. Difficulty with reading and/or spelling 12. Difficulty processing nonverbal information (e.g., lack of music appreciation) Source: Schminky & Baran (2000)

9 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

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

11 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)

12 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

13 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

14 Dichotic Digit Test Interpretation: The cut off norm is 90% and lower for 12 years to adult 7 years 7:11; 55% left, 70% right 8 years to 8:11; 65% left, 75% right 9 years to 9:11; 75% left, 80% right 10 years to 10:11; 78% left, 85% right 11 years to 11 years, 11 months; 88% left, 90% right Fairly sensitive to intra-cranial lesion 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

15 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

16 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 HZ Refer to the manuals provided

17 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

18 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)

19 Differential Diagnosis of CAPD (Jerger & Musiek, 2000) Behavioral Tests Electrophysiologic & Electroacoustic Tests Neuroimaging Studies

20 Behavioral Tests (Medwetsky, 2002) Based On The Particular Skill Span of Apprehension Lexical Decoding Phonologic Decoding Tolerance-Fading Memory Auditory Integration Sequencing Auditory Attention

21 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

22 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)

23 SSW Is a dichotic procedure Spondees are presented in an overlapped fashion: the 2 nd word of the 1 st spondee occurs at the same time as the first word of the 2 nd spondee Thus, one ear (leading ear) is presented with 1 st syllable in isolation (non-competing), followed by 2 nd syllable in a dichotic mode (competing). The other ear (lagging ear) begins with the 1 st syllable presented in the dichotic mode and finished with the 2 nd 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

24 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. 4 th edition (pp ) This test is sensitive to intra-cranial (temporal/cerebral) lesion Contralateral deficit if primary auditory areas involved Mixed results for brainstem lesions

25 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

26 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

27 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, 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%

28 Norms Based on Previous Scoring (Bellis, 2002) 7 years 7:11; 35% left, 80% right 8 years to 8:11; 39% left, 82% right 9 years to 9:11; 74% left, 90% right 10 years to 10:11; 88% left, 90% right 11 years to 11 years, 11 months; 90% both ears 12 years to adult: 90% both ears

29 Ear Advantage in Dichotic Tests

30 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)

31 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

32 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

33 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

34 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)

35 Binaural Integration Tests

36 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 Hz) is presented to one ear and the high pass band (e.g., 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

37 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

38 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.

39 MLD S o : Signal is presented binaurally with no interaural differences N o (or M 0 ): Noise (masker) is presented binaurally with no interaural differences (diotic). S m : Signal is presented to only one ear. N m : Noise is presented to only one ear. S π : Signal is presented to one ear 180 out of phase with the signal presented to the other ear. N π : Noise is presented to one ear 180 out of phase with the signal presented to the other ear. Monotic: N m S m Diotic: N o S o Dichotic: N o S π; N o S m; N π S π; N π S o; N π S m

40 MLD Listening Conditions

41 MLD

42 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 N o S π condition to as little as 0 db The largest MLDs are obtained when either the signal (S π N o ) or the noise (S o N π ) 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 Hz

43 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

44 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)

45 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)

46 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)

47 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.

48 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

49 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)

50 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

51 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

52 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, SSW

53 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

54 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

55 Summary of Behavioral Tests

56 Summary of Behavioral Tests

57 SSI-CCM SSI-ICM SSI-CCM: Ten-3 rd -order approximations of English Sentences Competing message consists of continuous discourse (Davy Crockett) 30 db HL (pure tone should be 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

58 Electrophysiologic Tests (Jerger & Musiek, 2000) Immittance audiometry Otoacoustic emissions Auditory brainstem response Auditory middle latency response (AMLR) Auditory late response (ALR) Mismatched negativity response (MMNR) Event-related response (ERP

59 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)