Portuguese Version

Year:  2004  Vol. 70   Ed. 3 - (22º)

Relato de Caso

Pages: 427 to 432

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The effectiveness of the auditory training in the central auditory processing disorder: a case study

Author(s): Lorena Kozlowski 1,
Gislaine M. R. Wiemes 2,
Cristiana Magni 3,
Angela L. G. da Silva 4

Keywords: auditory system, auditory training, central auditory processing, central auditory processing disorders

Abstract:
The objective of this study is to present the effectiveness of auditory training in the evaluation of a 9 year-old individual with a learning disorder, which have been evaluated through objective and behavioral tests, including audiometric test, imitanciometry, auditory brain response, P300 and central auditory processing evaluation. The diagnosis of Central Auditory Processing Disorder (CAPD) was confirmed by a normal performance on an audiometric test battery and an increased P300 latency time and the central auditory processing evaluation, which have shown the presence of a severe hearing processing disorder, characterized by the alteration of decoding, integration and memory process, and significant difficulties, particularly in selective attention and auditory closure. Auditory training to enhance development of the altered hearing abilities was conducted for four months. The progress observed in P300 latency time and the hearing processing disorder was still present but now at a moderate level at the end of the study. Also, this improvement was more significant in the integration process and showed an improvement in the auditory closure. It is concluded that the effectiveness of the auditory training through the development of the hearing abilities could be verified through the P300 and behavioral tests.

INTRODUCTION

For the past two decades, professionals dedicated their attention to identifying central auditory processing disorders in children with learning disorders in order to find the most appropriate therapeutic method.
Central auditory processing (CAP) refers to mechanisms and processes performed by the auditory system responsible for the following behavioral phenomena 1:

 Sound localization;
 Sound discrimination;
 Auditory recognition;
 Temporal auditory aspects (resolution, masking, integration and temporal sequencing);
 Auditory performance with competitive acoustic signs;
 Auditory performance in unfavorable acoustic situations.

These mechanisms and processes are applicable to verbal and non-verbal stimuli and can affect different areas, including speech and language.
Central auditory processing disorders (CAPD) can be defined as deficiency of one or more of the areas above described 1.

Many children during literacy process present difficulties to learn how to read and write and are referred to Otorhinolaryngologists, Neuropediatrics, Speech Therapist, Audiologist and other professionals related to childhood development and school learning. These children may present CAPD, manifesting different clinical problems, especially concerning comprehensive language and learning process.

LITERATURE REVIEW

Children with many different school problems, including difficulty to learn how to read, show abnormalities in central auditory processing tests, being that these affections are frequently suggested as the cause of learning disorders.

According to ASHA1 there is a causal relation between language problems and CAPD, especially concerning understanding of oral language.

According to Chermak and Musiek2 there is strong correlation between oral understanding, auditory treatment and vocabulary. Subjects who have CAPD manifest deficit of grammar morphology, metalinguistic deficit and problems to produce /r/ and /l/. Different abnormalities can be found in writing (inversion of letters, right/left orientation problems, dysgraphy, difficulty to understand reading, difficulty to learn how to read and write), being that school performance is normally worse in reading, grammar, spelling and mathematics.

Gillet3 stated that there are three important auditory processes in learning how to read: discrimination of isolated phonemes, discrimination of phonemes in words and auditory closure. Reading comprises visual symbols overlapped with auditory language already acquired, being that CAPD can influence reading acquisition.

The diagnosis of CAPD can be performed by different strategies 4:
 Clinical history;
 Non-audiological tests: linguistic performance and auditory behavior tests;
 Audiological tests: audiometry and specific CAP tests (monotic, dichotic and binaural interaction);
 Objective test: immittanciometry;
 Electrophysiological tests: otoacoustic emissions, medium and long latency evoked potentials (N1 P2, P3 and MMN).

In many situations, upon assessing CAP, we can observe abnormal results in behavioral tests and in P300. In children aged 8 to 10 years that present attention deficit and hyperactivity in school activities, P300 showed latency with values higher than 358ms of latency 5. It was also observed that children with school complaints and abnormal auditory processing presented latency of P300 higher than children without school problems of the same age range 6. Therefore, P300 can be considered a screening instrument to select cases that should be assessed with behavioral tests, which involve verbal and non-verbal stimuli.

Among the test with verbal stimuli, we can include SSW (Staggered Spondaic Word) created by Jack Katz, in 1962, in the United States. This test aims at assessing central hearing, determining the site of dysfunction in cases of suspected cerebral or brainstem damage. By means of this test it is possible to analyze how speech signal clues are being used to recognize, analyze, interpret and understand spoken message, as a result of auditory skills involved in the process.

Tests such as SSW support clinical practice of many related areas, such as Speech Therapy, psychology and psychopedagogy, because they can indicate the level of auditory pathway maturation, including the periodical assessment in longitudinal follow up of the child; they can identify progressive neurological diseases, assess improvement of auditory skills when there is administration of drugs, support description of auditory disorders, clarify the definition of central dominance for language, in addition to indicating whether the auditory canal is really an important route for learning 7.

In Portuguese, some adaptations from the original tests have been published. In 1986, Borges adapted the test using disyllable words and in 1993, Machado used monosyllable idiomatic expressions, which were also named spondaic 8, 9.

Another test that has been used to demonstrate presence of central auditory dysfunction in children is Speech in Noise test. The main objective is to measure performance-intensity function, comparing speech recognition with and without noise. The test has been frequently used to demonstrate difficulties in hearing speech in the presence of background noise, in cases of suspicion of learning difficulties, being described as useful to measure selective attention and auditory closure, skills related to disorders associated with cognitive factors. There is no definite standardization in this test, allowing use of different types of speech stimuli, different types of noise and forms of presentation 10.

Recent studies 11, 12 demonstrated that specific techniques for auditory training can positively influence temporal auditory process of subjects that present learning and language disorders. It means that auditory skills can be improved with training and that better performance in auditory function is directly related with the capacity to modify the central nervous system.

Auditory plasticity can be defined 13 as modification by means of improvement of nervous cells based on the influence of the environment, which causes behavioral changes. Many studies in animals and human beings 13 demonstrated the evidence of auditory cortical plasticity through functional reorganization and these alterations are the result of neural responses to auditory stimuli. Therefore, diagnosis of CAPD can guide the most appropriate type of auditory training to be employed.

The present study aims at presenting efficiency of CAPD therapy through monitoring with auditory behavioral and electrophysiological tests. Speech and audiology intervention is based on a program of auditory training based on cerebral auditory plasticity.

CASE REPORT

E.A.S., 9-year old male subject, was evaluated at the Ambulatory of Otorhinolaryngology, Hospital de Clínicas, Federal University of Paraná, presenting school difficulties to learn how to read and write, being that he was taking the 1st grade for the 3rd time. There were no complaints concerning speech and/or language.

He underwent ENT assessment, which was normal, being referred to auditory assessment (pure tone audiometry, acoustic immittance measures, brainstem evoked potentials).

Pure tone audiometry showed auditory thresholds within the normal range. Acoustic immittance measures showed type A tympanometry with bilateral acoustic reflexes. Brainstem evoked potentials showed integrity of auditory pathways to stimuli on both sides.

The patient was referred to auditory processing assessment and we conducted Cognitive Evoked Potential - P300 and behavioral tests (SSW and Speech in Noise).

As to Cognitive Evoked Potential (P300), we found latency of 380ms to stimulus on the right and 385ms on the left, suggesting auditory processing disorder.

In the first stage of central auditory processing assessment, interpretation of SSW revealed severe auditory processing disorder, presenting values of TOC analysis corresponding to 86 mistakes from Total (T), 70 for Ear effect (O), and 45 for Condition effect (C) 10.

The results of the Speech in Noise test revealed over 70% errors for S/N ratio of -20/0, presented contralaterally, with marked impairment on the left.

The results were suggestive of changes to codification, organization and memory processes and significant difficulty for selective attention and auditory closure. The subject was referred to speech and hearing therapy, which was conducted once a week for 45 minutes. When the therapy began, the child did not know how to read and write yet and knew only isolated vowels. The mother attended the sessions and was continuously instructed. We also maintained close contact with the school in order to follow up the child's development, providing information about the procedures that would support the progression of the case.

The main purpose of speech and hearing therapy was to develop central auditory skills: discrimination (phonological awareness, discrimination in noise, auditory figure-ground) and recognition/identification and understanding (auditory attention, sequential auditory memory). The therapy was based on formal and informal auditory training techniques that prioritized development and training of central auditory skills 4, 12, 14.
The first step was to work with short-term memory, in which we emphasized the memory for sequences, both for verbal and non-verbal sounds. This skill was very delayed, being that he did not manage to memorize sequences of three or four elements. The work with short-term memory allowed the preparation for long-term memory practice. He could not remember events that had taken place two days before, presenting difficulty to remember what he had done the night before.

At the same time, we developed selective attention, conducting auditory figure-ground activities, and awareness of motor planning of acoustic information, through phoneme discrimination and phonemic synthesis.

The second step was to work discrimination of vocal sounds, using minimum pairs and phonemic training (through analysis and phonemic synthesis). In all those aspects, the child was very slow and had difficulty to respond.

We worked on phonological awareness, that is, the skills to explicitly reflect about the sound structure of spoken words, detected as a sequence of phonemes. It provided proficiency in the alphabetic principle of writing, relation between letters and sounds represented by them.

Written language, which was both school and family complaint, was developed by production of sentences, texts and pre-defined reading and writing activities. The child's vocabulary was also enriched (technique of Vocabulary Building)14.

After 4 months of intervention, we conducted a second battery of tests, in order to monitor the work achieved. We conducted behavioral tests, SSW and Speech in Noise.

The interpretation of SSW revealed moderate processing disorder. Competitive hearing conditions were the most impaired, in both ears. Latency of response was considered normal. Quantitative aspects were not significant for the assessed effects.

TOC analysis revealed improvement in level of responses, still at moderate level, corresponding to 27 for Total (T), 28 for Ear effect (O) and 15 for Condition effect (C).

The test of Speech in Noise presented only 4% of errors for the left ear in relation to S/N ratio of -20dB HL, with contralateral presentation of speech stimuli, which did not suggest significant difficulty for auditory closure.

The results found for P300 showed latency of 300ms of stimuli on the right and 325 ms on the left revealing, therefore, reduction of latency comparing to the first test (Table 1).

Speech and hearing therapy was maintained for 3 more months, being that after this period it was possible to observe very positive results in all aspects, leading to therapy discharge.

As to writing language, there was major progression, being that the child (who had failed twice the first grade) passed to the next grade. Reading and writing, the main complaints when we started treatment, were no longer a concern, since they were fluent. School reported significant improvement in all aspects, especially in attention.

It is important to highlight that during the therapeutic process, the patient started to demonstrate interest for reading and writing, borrowing books from the therapists to read at home and retell his friends. Long-term and short-term memory no longer had problems and the patient was capable of reporting facts that had taken place in the past without any difficulties. The support and participation of the family and the school were essential for the therapeutic process.

Table 1. Results of CAP assessment before and after auditory training.

DISCUSSION

The case presented in this study is of a subject aged 9 years with diagnosis of CAPD that presented better performance in central auditory processing after auditory training program. The improvement in response could be observed in all the tests conducted, both objective and behavioral, as well as in general behavior (attention and learning).

In the comparative analysis of results in this study with other similar studies, we could observe that the results obtained in the battery of tests was in accordance with the study by Almeida 15, who observed that competitive hearing conditions tended to be more difficult than non-competitive conditions for children who were semi-literate and literate 15.

Another study that also revealed the importance of rehabilitation for maturational process comprised two groups of children assessed by a test adapted to Portuguese by the author in 1993 12. A group comprised 40 normal children and the other had 41 children with school complaints, aged 5 to 11 years. The results revealed greater difficulty in competitive hearing conditions than in non-competitive ones, in addition to reduction of number of errors as a result of increased age, suggesting maturation of auditory central nervous system 9.

The results of CAP tests are consistent with other observations conducted in this case: school performance, writing and reading skills, attention and memory.

The selection of auditory training procedures used during therapy, as well as the adaptation of the program during treatment were directed by the CAP tests performed.

Other deficit areas were also developed, such as attention, memory, vocabulary and writing language. The subject was motivated by the work and school and family had active participation in the process.

A systematic therapeutic process is fundamental, since many different studies about auditory plasticity demonstrated that intense stimulation is essential.

Success in auditory training and cerebral plasticity are closely linked since the benefit of understanding better is connected with neural plasticity, which is demonstrated when the auditory system is trained and improves its performance 2.

The purpose of auditory training is to improve functioning of auditory system concerning treatment of acoustic signs 5 and recent increase of interest for this type of training is the fact that there is substantial literature demonstrating plasticity of the auditory system and the value of auditory training, especially in subjects with language problems and CAPD. However, only isolated auditory training will not provide all benefits, since a global approach directed to all deficit areas, such as language and learning, will produce positive results. Compensation strategies employed by the family and the school will also be substantial.

Therefore, it is essential that professionals that work in this area get to know effective ways of acting and also of assessing the effectiveness of this type of intervention.

CLOSING REMARKS

It is important to determine the presence of impairment of auditory skills in children with learning disorders, since this information can guide treatment strategies and indicate educational goals.

As a result of the conduction of objective and behavioral tests, it was possible to define a goal for training directed to the affected skills of the case reported here. After analysis of the results of the central auditory processing tests, it was possible to define a comprehensive plan of strategies, both specific and individualized, directed to a qualified professional, family guidance and teachers, providing to the subject the right therapy to his affected auditory skills.

As a result of directed therapeutic training, we found improvement in results of the monitored tests, school performance and family relationship.

The assessment of central and peripheral auditory function is essential since it provides information for therapeutic definition, being that the harm caused by central auditory processing impairment affects both acquisition and development of educational, social, psychological and/or vocational factors. We observed that as a result of auditory function assessment and monitoring it was possible to diagnose the changes to CAP, directing goals for treatment and mapping treatment evolution.

REFERENCES

1. ASHA. Central Auditory Processing - current strategies and implications of clinical practice. American Journal of Audiology 1996; 5 (2): 41-54.
2. Chermak GD, Musiek FE. Auditory training: principles and approaches for remediation and managing auditory processing disorders. Seminars in Hearing 2002; 23: 297-308.
3. Gillet P. Auditory Processes. Novato, CA: Academic Therapy Publications; 1993.
4. Bellis TJ. Assessment and Management of Central Auditory Processing Disorders in the Educational Setting: From Science to Practice. Delmar Learning, 2003.
5. Ivey RG. The P300 response in children. London: The Hearing Journal Oct. 1992; 45(10): 27-32.
6. Diniz Junior J. Contribuição ao estudo do potencial evocado auditivo de longa latência em crianças. São Paulo, 1996 (Tese de Mestrado - Escola Paulista de Medicina, Universidade Federal de São Paulo).
7. Keith R. A central auditory evaluation protocol: a guide for training and diagnosis of lesions of the central system. Ear Hear 1983; 4: 229-30.
8. Borges ACL. Adaptação de teste SSW para a língua portuguesa. Nota preliminar. Acta AWHO 1986; 5, (supl. 1): p. 38-40.
9. Machado SF. O Teste SSW: avaliação e aplicação de um instrumento no estudo da avaliação da percepção da fala. São Paulo, 1993 (Tese de doutorado - Pontifícia Universidade Católica de São Paulo).
10. Pereira LD, Schochat E. Processamento Auditivo Central: manual de avaliação. São Paulo: Ed. Lovise; 1997.
11. Kozlowski L, Wimens GMR, Magni C. The auditory training & auditory processing disorders: a case study. Brain and Language (in press).
12. Musiek F. Habilitation and Management of Auditory Processing Disorders: Overview of Selected Procedures. Journal of the American Academy of Audiology 1999; 10:329-42.
13. Musiek F, Shinn J, Hare C. Plasticity, auditory training, and auditory processing disorders. Seminars in Hearing 2002; 23(4):263-75.
14. Katz J. Central auditory processing disorders: mostly management. Williams & Wilkins; 1998.
15. Almeida CC. Semi-alfabetizados versus alfabetizados: avaliação auditiva através dos testes SSW, discriminação e consciência fonológica. São Paulo, 1997 (Monografia apresentada à Universidade Federal de São Paulo).

1 PhD, Universidade Tuiuti do Paraná.
2 Master degree, Federal University of Paraná.
3 Master degree, Universidade do Vale do Itajaí.
4 Specialist, Clinical Speech and Hearing Therapist.
Affiliation: Universidade Tuiuti do Paraná.
Address correspondence to: Lorena Kozlowski - Rua Tapajós, 582 Curitiba PR 80510-330
Tel/fax (55 41) 338-0438 - E-mail:ldc.kozlowski@umontreal.ca
Study presented at 18° Encontro Internacional de Audiologia, 11 - 13/4/2003, Curitiba PR, Annual Meeting of Theoretical & Experimental Neuropsychology, 19 - 21/6/2003, Montreal, Canada, VIII and Congrès Biennal de la SLAN - Société Latinoaméricaine de Neuropsychologie, 8 - 11/10/2003, Montreal, Canada.

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