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5/3/2004 Auditory Processing Disorders: Considerations for the Speech-Language Pathologist Dorothy A. Kelly, DA, SLP/CCC | |
| Introduction According to the American Speech-Language-Hearing Association (ASHA), central auditory processing disorder (CAPD/APD) is an observed deficiency in one or more of a group of mechanisms and processes related to a variety of auditory behaviors (1996). It involves difficulty in processing or interpreting verbal and/or nonverbal auditory stimuli usually in the absence of a peripheral hearing loss. APD may be associated with a lesion somewhere in the central auditory nervous system (CANS). According to Katz, it’s “What we do with what we hear.” (Katz, 1992). The purpose of this article is to advocate early and efficient identification of auditory processing difficulties in children. A multidimensional team approach will be suggested for early analysis during kindergarten, with follow-up at second grade. The goal of this program is to identify, assess and successfully intervene at the earliest possible time with maximal positive impact for the child. Children with APD Children with APD may experience difficulties with: 1) localizing sound sources; 2) comprehending the meaning of environmental sounds; 3) discriminating among sounds and words; 4) reproducing the pitch, rhythm, and melody of music; 5) distinguishing important sounds from other sounds; or 6) combining syllables to form words and sentences (Barr, 1976), and other deficits may be apparent too. APD can appear as the primary diagnosis or in combination with other disorders, such as learning disabilities, cluttering, or attention deficit disorder. Hearing loss (an acuity rather than perceptual problem) can complicate APD. Chermak and Musiek (1997) estimated that APD affected approximately 3% of the school-age population. Goldberg (1998) maintained that auditory processing deficits impacted 5% of children. Incidence estimates are higher for the special education population. The impact of APD upon language and language-dependent behaviors has been widely examined (Rampp, 1977; Cohen, 1980; Lasky and Cox, 1983; Sanger, Freed, and Decker, 1985; Tallal, 1990; Friel-Patti, 1994; Mody, Studdert-Kennedy and Brady, 1997; Cacace and McFarland, 1998). Although many clinicians agree that APD exists and can negatively affect language performance, there is disagreement concerning identification and intervention. Audiologists generally support a signal-based “bottom-up” model, while speech-language pathologists tend to advocate a “top-down” model. An integrated approach is consistent with the American Speech-Language-Hearing Association’s (1996) inclusive definition of APD, as well as its recommendations for assessment and intervention. Not all children who display APDs are diagnosed with APD. Many children with APD are misdiagnosed or not diagnosed at all. When APD presents as a secondary diagnosis, for example, to learning disabilities or attention deficit disorder, symptoms may be incorrectly associated with the primary diagnosis. Approximately 98% of children in the United States attend kindergarten before entering first grade (Zill, Collins, West, and Hausken, 1995). This population is increasingly diverse in ethnic background, income levels, and family status, and readiness. Factors that impact on preparedness include language abilities and auditory processing skills. Auditory processing is involved in many academic tasks. Some children with APD may experience difficulty reading aloud due to an inability to associate visual and auditory symbols. Difficulties with auditory discrimination are important to reading and spelling and may be due to “distortions” of speech sounds at the cortical level (Mencher, Gerber, and McCombe, 1997). Typical kindergarten screening protocols do not identify possible auditory processing difficulties. Screening of Auditory Processing Skills Screening of auditory processing skills is designed to identify children in need of more extensive auditory processing assessment. Screening materials may include checklists, questionnaires or other materials. Although it is generally agreed that children should not undergo full diagnostic evaluation for APD until age seven (or later), children who present at risk behaviors may be screened between ages five and seven. Multi-Dimensional Team Approach In general, a multi-dimensional team-based approach, which includes input from several knowledgeable and professional sources (parents, teachers, speech-language pathologist, audiologist, school nurse, and so on) is less likely to produce errors in identifying children with APD tendencies and APD. All children suspected of APD should undergo a comprehensive audiometric evaluation to determine if the suspect behaviors are due to peripheral hearing loss. Screening Tools To identify children at risk for APD, checklists used include: The Kindergarten Auditory Screening Test (Katz, 1971); The Auditory Perceptual Check List (Barr, 1976); Fisher’s Auditory Problems Checklist (Fisher, 1976); Checklist of Classroom Observations For Children With Possible Auditory Processing Problems (Sanger, Stick, and Smith, 1985); and, The Children''s Auditory Processing Performance Scale (Smoski, Brundt, and Tannahil, 1992). Keith (1999) identifies 10 behaviors of children with APD. These include, but are not limited to: difficulties with auditory discrimination; auditory figure-ground difficulties, and auditory memory. According to Keith (1999), children with APD may display some of these behaviors and are often candidates for APD testing. Additionally, other behaviors and attributes are associated with APD: having a family member with similar difficulties (Kinsbourne, 1983; Willeford and Burleigh, 1985); auditory distractibility; or hypersensitivity to loud sounds; large differences between verbal and performance IQs (Musiek and Geurkink, 1980); academic underachievement; poor listening skills; phonological disorder; attention disorder; learning disability; language impairment; neurological insult; difficulty with directions; reading disorder; pervasive developmental disorder; difficulties with auditory closure; difficulties with rapidly produced speech; and hearing difficulties in the presence of a normal audiogram, among others. A history of recurrent otitis media is also associated with APD (Keith, 1995) as inconsistent auditory input may negatively affect the central auditory maturational process. Martin and Clark (2000) described minimal auditory deficiency syndrome, a language-learning condition associated with erratic auditory input. Among other effects, fluctuating hearing loss may affect a child’s categorical perceptions (Clarkson, Eimas, and Marean (1989; Werner and Marean, 1996). Screening in Kindergarten A screening protocol designed to identify children at risk for APD difficulties at the kindergarten level, appears desirable and reasonable. Kindergarten-based observations of verbal (e.g., can repeat an eight-syllable sentence; can follow a two-step command) and nonverbal (e.g., loud and soft tones; can identify long and short tones) auditory processing skills could help identify children with at risk behaviors for APDs. Such children may also be at risk for difficulties in reading, spelling, writing, and following directions, among other concerns related to language and academic functioning. For children identified as at risk at the kindergarten level, non-intrusive recommendations could be made. Auditory processing skills could be stimulated using computer programs designed to improve auditory discrimination, auditory memory, auditory closure skills, and so on. There are many opportunities during the typical class day for classroom teachers, music teachers, special educators, reading teachers and speech-language pathologists to provide helpful auditory experiences. These may include; listening games, rhythm activities, direction games, sound recognition activities discrimination and sequencing activities. These experiences may improve skills related to phonemic awareness, phonemic synthesis and blending, phonological processing and pre-reading skills. Second Grade Follow-Up Maturational gains are typically realized between kindergarten and second-grade, or between ages 5 and 7. A second-grade, rigorous analysis could be completed in second-grade for children who presented as at risk at the kindergarten level. By the time the child is in second grade, more input from teachers and other professionals is usually available regarding following directions, phonological/phonemic awareness, sound/symbol associations, auditory discrimination, tolerance to background noise, and other areas. Children who continue to display at risk behaviors at the second-grade level (or age seven) should be referred to an audiologist for a full comprehensive audiologic and APD evaluation. Thus, the main purpose of this protocol is to flag children who present at risk behaviors during kindergarten and make recommendations to parents and teachers, and then follow-up in second grade to re-evaluate. Wait and See In general, screening procedures of central auditory processing skills should be sensitive to neuromaturational factors. Many aspects of auditory perception develop as a function of maturation and experience. Some children identified with APD appear to eventually outgrow it (suggesting a neuromaturational profile). However, this does not imply that a “wait and see” attitude should be adopted. Critical time should not be wasted especially in view of what is known about neuroplasticity. Specifically, experience changes the brain’s architecture. The brain can rewire itself with appropriate stimulation. This is particularly true in young children. For example, there appears to be a window of opportunity between ages five and seven when foundation skills of reading are most easily learned (Kantrowitz and Underwood, 1999). Some children who display central auditory processing difficulties do not appear maturational in nature. Traumatic brain injury, aphasia, dyslexia, cluttering, and learning disabilities (and other diagnoses) are often associated with this group. Early identification of these children is important to facilitate neuroplasticity, as well as to provide targeted therapy and coping strategies. Milestones and Development of Auditory Attributes Screening protocols for APD skills should be sensitive to auditory developmental milestones. The following represents a brief summary of recent findings: Speech sound awareness and language-specific abilities are apparent within the first year of life (Kuhl, 1993). Newborns are not only capable of detecting auditory stimuli, but can also make gross discriminations on the basis of frequency and intensity. (Moffitt, 1971; Eimas, 1975; Eisenberg, 1976). Four- to 17 week-old infants can discriminate between the vowels {u} and {i}, and {a} and{I}. Two-month-old infants can discriminate between {ba} and {ga} (Roseberry-McKibbin and Hegde, 2000). The infant’s ability to discriminate sounds contained in languages other than their own appears to decline around age one (Roseberry-McKibbin and Hegde, 2000). However, according to Martin (1994), structures within the auditory nervous system continue to mature until age nine years. Many aspects of speech perception are mature by school-age (Olsho, 1985; Allen and Wightman, 1992). Siegenthaler (1969) maintained that children experienced the most significant gains in central auditory processing development between ages three and seven. According to Kendler (1995), very young children appear to process auditory information more generally (non-selectively) than older children. However, as they progress through childhood, they gradually increase their abilities to extract relevant information rapidly and efficiently. Wightman and Allen (1992) estimated that preschool-aged children were inattentive at least half of the time. Like other auditory skills, the ability to localize sound and process binaural cues appears to improve throughout infancy and preschool periods (Werner and Marean, 1996). According to Torgesen and Mathes (1998), by the beginning of kindergarten, children should be able to tell whether two words rhyme and these same children should be able to generate rhymes for simple words. At the kindergarten level, children should be able to blend sounds to make words (e.g., m+ a+ n=man) and to connect some sounds and letters (Wingert, 1999). Kraus, Burton-Koch, and McGee (1999) found that auditory discrimination skills are largely developed by age six. This finding is supportive of an earlier study by Templin (1957), which found that auditory discrimination skills mature early and are well established by ages six to seven. In the first and second grades children can count syllables in words (Wingert, 1999). Temporal processing abilities (e.g., gap detection, duration discrimination, and temporal integration) mature by about six years of age (Werner and Marean, 1996). Selective listening for tones in noise appears to mature by six to eight years of age (Greenberg, Bray, and Beasley, 1970). The Roswell-Chall Auditory Blending Test (1963) assessed a child’s ability to combine sounds to produce words when the sounds were presented orally (e.g., c-u-p/cup). The test was norm-referenced on children in first through fourth grades, as well as on older children who exhibited reading difficulties (Barr, 1976). Findings suggested that fundamental integration abilities are present in first grade. Sound/syllable associations approach adult levels after fifth grade. Some auditory perceptual skills mature later in childhood. Temporal acuity does not mature until age ten (Werner and Marean, 1996). Neuman and Hochberg (1983) discovered that the ability to identify consonants within reverberant environments continued to mature until age 13. In noise, these skills may mature between ages 13 and 15 years of age (Elliott, 1979). When reverberation is combined with noise, speech recognition is more challenging (Nabelek and Mason, 1981), and may not mature until the mid-to-late teens (Johnson, 2000). It appears that many central auditory processing skills (for speech and nonspeech stimuli) are largely functional by school-age (Kraus, Burton-Koch, and McGee, 1999). Therefore, a preliminary observation (without subsequent direct intervention) of basic auditory processing skills at the kindergarten level with possible follow-up at second-grade/age seven, appears appropriate. Observations of behaviors that mature later (e.g., auditory figure-ground skills) should be observed relative to the performance of peers. For example, parents and teachers may be asked how well the child functions in noise as compared to other children of the same age. Minor differences should not be considered significant. Psychological Issues Many children with auditory processing difficulties suffer from psychological “burn out” over time. Sustained academic failure, strained peer and family relationships, and pronounced frustration may result in depression. Some children grow to dislike school, exhibit low self-esteem, socially withdraw, or act out. Early identification and appropriate intervention may prevent some of these unfortunate results. Economic Considerations Early identification of children with central auditory processing difficulties has practical benefits, as well. Educational institutions are likely to realize considerable savings over time. The provision of “misguided services” is likely to continue longer than “appropriately designed” services. These expenditures include direct/indirect services (e.g., speech-language therapy) as well as those associated with the ripple effect (e.g., possible psychological services). Emergent Literacy Auditory processing skills, particularly auditory discrimination abilities, are associated with emergent literacy. Recognition, intervention and management of faulty auditory processing skills could strengthen early literacy skills. Phonological/phonemic awareness is also associated with emergent literacy. Such awareness involves an ability to detect rhymes and alliteration, segment and blend syllables, categorize sounds, sequence phonemes, and otherwise manipulate phonemes within words. This awareness is important to various aspects of literacy, especially reading. Catts (1993) maintained that metalinguistic abilities, including phonological awareness, were the best predictors of reading success. According to Gilbertson and Bramlett (1998), phonological measures were better predictors of at risk readers than other types of assessment. Temporal processing (i.e., perception of tonal patterns and sequences) is also associated with reading and spelling skills (Pinheiro, 1976). Cultural Bias Speakers perceive messages in terms of the phonological rules of their native language. Therefore, if the stimuli used i.e., phoneme contrasts, are not part of their phonological system, errors are bound to occur, which may not be auditory at all, but may represent a cultural difference (Shames, Wiig, and Secord, 1998). Without regard for a cultural bias, the speech-language pathologist may erroneously conclude that the child is delayed in auditory discrimination. When speakers of non-standard dialects are screened, the speech-language pathologist should be aware of these influences. Summary and Final Thoughts Early identification of auditory processing difficulties is warranted. 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