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Pediatric central auditory processing disorder showing elevated threshold on pure tone audiogram
Auris Nasus Larynx 43 (2016) 570–574 Contents lists available at ScienceDirect
Auris Nasus Larynx journal homepage: www.elsevier.com/locate/anl
Pediatric central auditory processing disorder showing elevated threshold on pure tone audiogram Yukihide Maeda a,*, Atsuko Nakagawa a, Rie Nagayasu a, Akiko Sugaya a, Ryotaro Omichi a, Shin Kariya a, Kunihiro Fukushima b, Kazunori Nishizaki a a Department of Otolaryngology, Head and Neck Surgery, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8558, Japan b Shinkurashiki Ear, Nose, and Throat Clinic, 3-120-1 Shinkurashikiekimae, Kurashiki-shi, Okayama 710-0253, Japan
A R T I C L E I N F O
A B S T R A C T
Article history: Received 8 December 2015 Accepted 3 February 2016 Available online 26 February 2016
Central auditory processing disorder (CAPD) is a condition in which dysfunction in the central auditory system causes difficulty in listening to conversations, particularly under noisy conditions, despite normal peripheral auditory function. Central auditory testing is generally performed in patients with normal hearing on the pure tone audiogram (PTA). This report shows that diagnosis of CAPD is possible even in the presence of an elevated threshold on the PTA, provided that the normal function of the peripheral auditory pathway was verified by distortion product otoacoustic emission (DPOAE), auditory brainstem response (ABR), and auditory steady state response (ASSR). Three pediatric cases (9- and 10-year-old girls and an 8-year-old boy) of CAPD with elevated thresholds on PTAs are presented. The chief complaint was difficulty in listening to conversations. PTA showed elevated thresholds, but the responses and thresholds for DPOAE, ABR, and ASSR were normal, showing that peripheral auditory function was normal. Significant findings of central auditory testing such as dichotic speech tests, time compression of speech signals, and binaural interaction tests confirmed the diagnosis of CAPD. These threshold shifts in PTA may provide a new concept of a clinical symptom due to central auditory dysfunction in CAPD. ß 2016 Elsevier Ireland Ltd. All rights reserved.
Keywords: Central auditory processing disorder Pure tone audiogram Distortion-product otoacoustic emission Auditory brainstem response Auditory steady state response Functional hearing loss
1. Introduction Central auditory processing disorder (CAPD) is a condition in which dysfunction in the central auditory system causes difficulty in conversation, listening under noisy conditions, and sound localization, despite normal peripheral auditory function. Subjects with CAPD experience auditory impairment, communication impairment, or both. Dysfunction in the central auditory system is documented by central auditory testing,
* Corresponding author at: Department of Otolaryngology, Head and Neck Surgery, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8558, Japan. Tel.: +81 86 235 7307; fax: +81 86 235 7308. E-mail address: [email protected] (Y. Maeda). http://dx.doi.org/10.1016/j.anl.2016.02.005 0385-8146/ß 2016 Elsevier Ireland Ltd. All rights reserved.
including dichotic speech tests, time compression of speech signals, binaural interaction tests, and gap detection tests [1,2]. The subjective auditory symptoms and findings in central auditory testing in CAPD are diverse and heterogeneous. The etiology of CAPD ranges from neuromorphological disorders (ectopic cerebral cortex areas and polymicrogyri) and neuromaturational delay to other neurological disease or insults. Generally, subjects with normal hearing on the pure tone audiogram (PTA) are assessed by central auditory testing, in order to verify the reliability of these tests for central auditory function using stimuli delivered via the peripheral auditory system. The American Academy of Audiology (AAA) Clinical Practice Guideline for CAPD, however, does not provide definitive criteria regarding the threshold shift in PTA in patients with CAPD [2]. We present three cases of pediatric
Y. Maeda et al. / Auris Nasus Larynx 43 (2016) 570–574
CAPD associated with elevated thresholds in PTA. The relationship of the diagnoses of CAPD and functional hearing loss (FHL) is discussed, as an informative example of the current understanding and diagnosis of CAPD in children. 2. Case presentation 2.1. Case 1 A 9-year-old girl was referred to our Otolaryngology Department with complaints of difficulty with conversation in noisy surroundings and in listening to music. She had been assessed by a pediatric neuropsychiatrist because of subjective complaints of blurred vision. Ophthalmologic inspections, electroencephalography, and brain magnetic resonance imaging (MRI) detected no abnormality and she was diagnosed with high-functioning pervasive developmental disorder (HFPDD). In the preschool period, she had shown tendency to be hyperactive, but no developmental delay in language or sensorimotor ability had been noted. At the age of 9-yearold, Full-scale IQ (FSIQ), Verbal Comprehension Index (VCI), Perceptual Reasoning Index (PRI), Working Memory Index (WMI), and Processing Speed Index (PSI) were 110, 109, 109, 94, and 115 on the Wechsler Intelligence Scale for Children-IV (WISC-IV), respectively. FSIQ was within the normal range for
571
her age, but WMI was relatively low compared with standard scores for the other indexes. Otoscopic examination showed normal results. A pure tone audiogram (PTA) showed bilateral moderate-to-severe hearing loss, predominantly in the low frequencies (Fig. 1A), but responses in distortion-product otoacoustic emissions (DPOAEs) were bilaterally intact (Fig. 1C). Thresholds in auditory steady state response (ASSR) were normal, including those in the low frequencies (Fig. 1B). As the peripheral auditory pathways were shown to be functioning normally, further central auditory testing was performed. For central auditory testing, auditory stimuli were presented via headphones at 40 dB nHL by default. Loudness was manually adjusted to the most comfortable level for the subject. For dichotic listening, forty monosyllable stimuli were presented to both ears, and laterality index was calculated as follows: (number of monosyllable stimuli with correct perception by the right ear correct perception by the left ear)/(correct perception by the right ear + correct perception by the left ear) 100. For time compression of speech signals, Japanese words with 90–10% time compression rate were presented with 10% decrement (3 stimuli for each compression rate). When 2 out of the 3 stimuli were correctly detected, the subject was considered to be able to respond correctly to speech signals with time compression. For gap detection test (gaps-innoise test), the patient’s ability to detect gaps with duration of
Fig. 1. Audiological profile of Case 1. Pure tone audiogram shows bilateral, moderate-to-severely elevated thresholds, predominantly in the low frequencies (A). Thresholds of auditory steady state response are normal (right, 30 dB; left, 30 dB) (B). Responses of distortion-product otoacoustic emissions (DPOAEs) are normal across all frequencies (C). In the figures of DPOAEs, the lower line (green line) indicates background noise level and the upper line (red or blue line) indicates DPOAE response levels. The x-axis represents F2 frequency.
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Y. Maeda et al. / Auris Nasus Larynx 43 (2016) 570–574
2–66 ms (4 ms increment and decrement) in white noise was examined. In this patient, laterality index in the dichotic speech test was 61 (normal, <5), time compression of speech signals interfered with speech perception when the compression rate was smaller than 60% (normal, 20–30%), and gap detection was possible when gaps in sounds were greater than 14 ms (during elevation of the gap time; normal, <20 ms) and 2 ms (during descent of the gap time; normal, <20 ms). As she was experiencing difficulty in following conversations and listening under noisy conditions, and impairments in the dichotic speech test and time compression test of speech signals were demonstrated, CAPD was diagnosed. Monosyllable speech discrimination score (SDS) was 85–90% in the right and left ear. The physicians recommended the use of personal frequency modulation (FM) systems in order to improve the ability to follow conversations in the classroom, but she has not revisited our otolaryngology clinic since we confirmed the diagnosis of CAPD. 2.2. Case 2 A 10-year-old girl was referred to our Otolaryngology Department after bilateral hearing loss was detected on screening audiometry at her primary school. In the preschool period, she had shown developmental delay both in language and motor ability without hearing loss. The patient’s mother experienced a fever at 26 weeks pregnant. Ventricles of the
patient’s brain were enlarged as shown by fetal ultrasound at 30 weeks pregnant and neonatal anti-cytomegarovirus IgM was positive immediately after the birth. At the age of 10 years, she also experienced subjective difficulty in listening to conversations. Otoscopic examination yielded normal results. PTA resulted in bilateral, flat, moderate (right) or severe (left) sensorineural hearing loss (Fig. 2A), although behavioral observation showed that she was able to communicate without assistance such as hearing aids. DPOAE was bilaterally intact across all frequencies (Fig. 2C). Thresholds of auditory brainstem response (ABR) were normal (right, 30 dB nHL; left, 40 dB nHL; Fig. 2B), showing that the peripheral auditory pathways were intact. Central auditory processing was examined by audiological testing. Laterality index in dichotic speech tests was 17. Time compression of speech signals interfered with speech perception when the compression rate was less than 30%. The binaural interaction test (cognition of Japanese sentences alternatingly presented to the right and left ears) showed impairment (4 correct detections out of 5 stimuli; normal range, 5 correct detections out of 5 stimuli). Gap detection was possible when the gaps in the sounds were greater than 6 ms (elevation) and 2 ms (descent). Based on the complaint of difficulty in conversation, and positive results in dichotic speech tests and binaural interaction tests, CAPD was diagnosed. Speech audiometry resulted in SDS of 65% in the right and 100% in the left ear. Be´ke´sy audiometry resulted
Fig. 2. Audiological profile of Case 2. Pure tone audiogram shows severe (right) and moderate (left) threshold shifts (A). Thresholds of auditory brainstem responses are normal (right, 30 dB; left, 40 dB) (B). Responses of distortion-product otoacoustic emissions (DPOAEs) are bilaterally normal (C). In the figures of DPOAEs, the lower line (green line) indicates background noise level and the upper line (red or blue line) indicates DPOAE response level.
Y. Maeda et al. / Auris Nasus Larynx 43 (2016) 570–574
in type 1 pattern in the both ears. She was fitted with a personal FM system to improve listening in the classroom and reported a favorable result with the device in conversation. To fit the hearing aid for using FM system, we assumed that her ‘‘actual’’ hearing level was 35 dB nHL with flat audiogram pattern and verified the response from the subject with the device. To track the development of her condition, further assessment of language development was performed. Vocabulary was normal according to the Picture Vocabulary TestRevised and Standardized Comprehension Test of Abstract Words. Auditory comprehension was delayed, as shown by the Syntax Test for Aphasia (equivalent to a developmental level of 7 years and 10 months). FSIQ was 81 by the WISC-IV. Brain MRI suggested enlargement of the inferior horn of the lateral ventricle (atrophy of the temporal lobes) (Fig. 3, arrows). Electroencephalography demonstrated no focal abnormalities or spike activity. 2.3. Case 3 An 8-year-old boy was referred to our Otolaryngology Department with a chief complaint of difficulty listening to conversations in noisy surroundings. He had been diagnosed with HFPDD by pediatricians. They had detected no organic abnormality in his brain. In the preschool period, no
573
Fig. 3. Brain MRI of Case 2. Enlargement of the inferior horn of the lateral ventricle (atrophy of the temporal lobes) was suspected (arrows).
developmental delay in language or sensorimotor ability had been noted. Otoscopic examination showed no abnormality. PTA resulted in bilateral, mild-to-moderate sensorineural hearing loss (Fig. 4A), but responses and thresholds of DPOAEs (Fig. 4C) and ASSR (right, 30 dB nHL; left, 30– 40 dB nHL) (Fig. 4B) were bilaterally normal. Laterality index in dichotic speech tests was 5. Time compression of speech signals interfered with speech perception when the compression rate was less than 50%. Binaural interaction test was poor
Fig. 4. Audiological profile of Case 3. Pure tone audiogram shows bilateral, mild-to-moderately elevated thresholds (A). Thresholds of auditory steady state response are bilaterally normal (right, 30 dB; left, 30–40 dB) (B). Responses of distortion-product otoacoustic emission (DPOAE) are also bilaterally normal (C). In the figures of DPOAEs, the lower line (green line) indicates background noise level and the upper line (red or blue line) indicates DPOAE response level.
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(2 correct detections out of 5 stimuli). Gap detection test (elevation) was unable to be performed, as the subject could not concentrate on the task. Based on the chief complaint of difficulty listening to conversations and poor performance in the time compression test of speech signals and binaural interaction test, CAPD was diagnosed. SDS was 75% in the right and left ear. 3. Discussion In these three cases, thresholds in PTA were elevated, but responses and thresholds of DPOAEs, ABR, and ASSR were normal. As the peripheral auditory pathways were shown to be functioning normally, the results of central auditory testing such as dichotic speech tests, time compression of speech signals, binaural interaction tests, and gap detection tests offered reliable detection of dysfunction in the central auditory pathway. The chief complaint of these patients was difficulty in listening to conversations, particularly in noisy surroundings. As dysfunction in central information processing was demonstrated by central auditory testing, CAPD was diagnosed. These cases represent CAPD associated with elevated thresholds in PTA. Audiological professionals can recommend the use of personal FM systems in the classroom for these school-aged children with CAPD. Auditory training is one option to enhance listening, communication, social, and learning outcomes in children with CAPD. For example, auditory exercise (dichotic listening training) can be performed in CAPD patients with large laterality index, in order to promote interhemispheric transfer of sound information in the brain [1]. In case that peripheral hearing loss is present in CAPD patients, AAA and American Speech-Language-Hearing Association (ASHA) diagnostic criteria for CAPD require audiological professionals to verify the reliability of central auditory testing [2–4]. ASHA technical report for diagnosis of CAPD emphasizes that basic evaluation of peripheral auditory system should be conducted prior to central testing [3]. British Society of Audiology (BSA) practice guidance for CAPD defines ‘‘developmental CAPD’’ as cases presenting in childhood with normal hearing. BSA guidance categorizes ‘‘secondary CAPD’’ as cases where CAPD occurs in the presence, or as a result, of peripheral hearing impairment [5]. In the diagnosis of CAPD, it is essential to demonstrate that auditory dysfunction has its origins in impaired neural function. The most interesting point is that the pathological origin of the threshold shift in PTA in the CAPD patients in this report may be dysfunction of the central auditory system, as central auditory testing detected impairment of central auditory processing in all patients. Although central auditory testing in the diagnosis of CAPD does not directly reflect the ‘‘threshold shift’’ in PTA, it is plausible to speculate that these threshold shifts in PTA represent clinical symptoms involved in the spectrum of CAPD.
From another perspective, the elevated thresholds in PTA of these patients may be categorized as nonorganic FHL. In Cases 1 and 3, HFPDD was detected as a co-morbid condition of APD. Dysfunction in the central nervous system in CAPD contributes significantly to CAPD appearing as a co-morbidity of other disorders such as attention deficit hyperactivity disorder and learning disabilities [6]. CAPD is reported to affect 2–5% of school-aged children, and around 50% of children with learning disorders manifest CAPD [1]. These neuropsychological traits are often significant background conditions for FHL in children [7]. In Case 2, auditory language comprehension was delayed as compared to her actual age. Although her FSIQ (81) did not meet the definition of mental retardation (below 70), the FSIQ was at the lower limit of the normal range and brain MRI suggested the possibility of organic abnormality (atrophy of the temporal lobes) in the central nervous system. A relatively low IQ observed in children is reportedly significantly linked to the incidence of FHL [8]. As depicted in these 3 cases, CAPD can be diagnosed even in the presence of elevated thresholds in PTA, provided that the normal function of the peripheral auditory pathway can be verified by DPOAEs, ABR, and ASSR. These threshold shifts in PTA may represent a new concept for clinical symptoms due to central auditory dysfunction in CAPD. Further attention is needed regarding the viewpoint that the diagnoses of CAPD, as an organic dysfunction of the central auditory system, and nonorganic FHL often represent overlapping conceptualizations in such pediatric patients depicted in Cases 1, 2, and 3. Conflict of interest None. References [1] Bellis TJ, Bellis JD. Central auditory processing disorders in children and adults. Handb Clin Neurol 2015;129:537–56. [2] Diagnosis, Treatment and Management of Children and Adults with Central Auditory Processing Disorder. American Academy of Audiology Clinical Practice Guidelines; 2010. [3] (Central) auditory processing disorders [Technical Report]. American Speech-Language-Hearing Association; 2005. [4] (Central) auditory processing disorders – The role of audiologist [Position statement]. American Speech-Language-Hearing Association; 2005. [5] An overview of current management of auditory processing disorder (APD)-practice guidance. British Society of Audiology; 2011. [6] Bamiou DE, Musiek FE, Luxon LM. Aetiology and clinical presentations of auditory processing disorders – a review. Arch Dis Child 2001;85:361–5. [7] Ashitani M, Ueno C, Doi T, Kinoshita T, Tomoda K. Clinical features of functional hearing loss with inattention problem in Japanese children. Int J Pediatr Otorhinolaryngol 2011;75:1431–5. [8] Aplin DY, Rowson VJ. Psychological characteristics of children with functional hearing loss. Br J Audiol 1990;24:77–87.
Auris Nasus Larynx journal homepage: www.elsevier.com/locate/anl
Pediatric central auditory processing disorder showing elevated threshold on pure tone audiogram Yukihide Maeda a,*, Atsuko Nakagawa a, Rie Nagayasu a, Akiko Sugaya a, Ryotaro Omichi a, Shin Kariya a, Kunihiro Fukushima b, Kazunori Nishizaki a a Department of Otolaryngology, Head and Neck Surgery, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8558, Japan b Shinkurashiki Ear, Nose, and Throat Clinic, 3-120-1 Shinkurashikiekimae, Kurashiki-shi, Okayama 710-0253, Japan
A R T I C L E I N F O
A B S T R A C T
Article history: Received 8 December 2015 Accepted 3 February 2016 Available online 26 February 2016
Central auditory processing disorder (CAPD) is a condition in which dysfunction in the central auditory system causes difficulty in listening to conversations, particularly under noisy conditions, despite normal peripheral auditory function. Central auditory testing is generally performed in patients with normal hearing on the pure tone audiogram (PTA). This report shows that diagnosis of CAPD is possible even in the presence of an elevated threshold on the PTA, provided that the normal function of the peripheral auditory pathway was verified by distortion product otoacoustic emission (DPOAE), auditory brainstem response (ABR), and auditory steady state response (ASSR). Three pediatric cases (9- and 10-year-old girls and an 8-year-old boy) of CAPD with elevated thresholds on PTAs are presented. The chief complaint was difficulty in listening to conversations. PTA showed elevated thresholds, but the responses and thresholds for DPOAE, ABR, and ASSR were normal, showing that peripheral auditory function was normal. Significant findings of central auditory testing such as dichotic speech tests, time compression of speech signals, and binaural interaction tests confirmed the diagnosis of CAPD. These threshold shifts in PTA may provide a new concept of a clinical symptom due to central auditory dysfunction in CAPD. ß 2016 Elsevier Ireland Ltd. All rights reserved.
Keywords: Central auditory processing disorder Pure tone audiogram Distortion-product otoacoustic emission Auditory brainstem response Auditory steady state response Functional hearing loss
1. Introduction Central auditory processing disorder (CAPD) is a condition in which dysfunction in the central auditory system causes difficulty in conversation, listening under noisy conditions, and sound localization, despite normal peripheral auditory function. Subjects with CAPD experience auditory impairment, communication impairment, or both. Dysfunction in the central auditory system is documented by central auditory testing,
* Corresponding author at: Department of Otolaryngology, Head and Neck Surgery, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8558, Japan. Tel.: +81 86 235 7307; fax: +81 86 235 7308. E-mail address: [email protected] (Y. Maeda). http://dx.doi.org/10.1016/j.anl.2016.02.005 0385-8146/ß 2016 Elsevier Ireland Ltd. All rights reserved.
including dichotic speech tests, time compression of speech signals, binaural interaction tests, and gap detection tests [1,2]. The subjective auditory symptoms and findings in central auditory testing in CAPD are diverse and heterogeneous. The etiology of CAPD ranges from neuromorphological disorders (ectopic cerebral cortex areas and polymicrogyri) and neuromaturational delay to other neurological disease or insults. Generally, subjects with normal hearing on the pure tone audiogram (PTA) are assessed by central auditory testing, in order to verify the reliability of these tests for central auditory function using stimuli delivered via the peripheral auditory system. The American Academy of Audiology (AAA) Clinical Practice Guideline for CAPD, however, does not provide definitive criteria regarding the threshold shift in PTA in patients with CAPD [2]. We present three cases of pediatric
Y. Maeda et al. / Auris Nasus Larynx 43 (2016) 570–574
CAPD associated with elevated thresholds in PTA. The relationship of the diagnoses of CAPD and functional hearing loss (FHL) is discussed, as an informative example of the current understanding and diagnosis of CAPD in children. 2. Case presentation 2.1. Case 1 A 9-year-old girl was referred to our Otolaryngology Department with complaints of difficulty with conversation in noisy surroundings and in listening to music. She had been assessed by a pediatric neuropsychiatrist because of subjective complaints of blurred vision. Ophthalmologic inspections, electroencephalography, and brain magnetic resonance imaging (MRI) detected no abnormality and she was diagnosed with high-functioning pervasive developmental disorder (HFPDD). In the preschool period, she had shown tendency to be hyperactive, but no developmental delay in language or sensorimotor ability had been noted. At the age of 9-yearold, Full-scale IQ (FSIQ), Verbal Comprehension Index (VCI), Perceptual Reasoning Index (PRI), Working Memory Index (WMI), and Processing Speed Index (PSI) were 110, 109, 109, 94, and 115 on the Wechsler Intelligence Scale for Children-IV (WISC-IV), respectively. FSIQ was within the normal range for
571
her age, but WMI was relatively low compared with standard scores for the other indexes. Otoscopic examination showed normal results. A pure tone audiogram (PTA) showed bilateral moderate-to-severe hearing loss, predominantly in the low frequencies (Fig. 1A), but responses in distortion-product otoacoustic emissions (DPOAEs) were bilaterally intact (Fig. 1C). Thresholds in auditory steady state response (ASSR) were normal, including those in the low frequencies (Fig. 1B). As the peripheral auditory pathways were shown to be functioning normally, further central auditory testing was performed. For central auditory testing, auditory stimuli were presented via headphones at 40 dB nHL by default. Loudness was manually adjusted to the most comfortable level for the subject. For dichotic listening, forty monosyllable stimuli were presented to both ears, and laterality index was calculated as follows: (number of monosyllable stimuli with correct perception by the right ear correct perception by the left ear)/(correct perception by the right ear + correct perception by the left ear) 100. For time compression of speech signals, Japanese words with 90–10% time compression rate were presented with 10% decrement (3 stimuli for each compression rate). When 2 out of the 3 stimuli were correctly detected, the subject was considered to be able to respond correctly to speech signals with time compression. For gap detection test (gaps-innoise test), the patient’s ability to detect gaps with duration of
Fig. 1. Audiological profile of Case 1. Pure tone audiogram shows bilateral, moderate-to-severely elevated thresholds, predominantly in the low frequencies (A). Thresholds of auditory steady state response are normal (right, 30 dB; left, 30 dB) (B). Responses of distortion-product otoacoustic emissions (DPOAEs) are normal across all frequencies (C). In the figures of DPOAEs, the lower line (green line) indicates background noise level and the upper line (red or blue line) indicates DPOAE response levels. The x-axis represents F2 frequency.
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Y. Maeda et al. / Auris Nasus Larynx 43 (2016) 570–574
2–66 ms (4 ms increment and decrement) in white noise was examined. In this patient, laterality index in the dichotic speech test was 61 (normal, <5), time compression of speech signals interfered with speech perception when the compression rate was smaller than 60% (normal, 20–30%), and gap detection was possible when gaps in sounds were greater than 14 ms (during elevation of the gap time; normal, <20 ms) and 2 ms (during descent of the gap time; normal, <20 ms). As she was experiencing difficulty in following conversations and listening under noisy conditions, and impairments in the dichotic speech test and time compression test of speech signals were demonstrated, CAPD was diagnosed. Monosyllable speech discrimination score (SDS) was 85–90% in the right and left ear. The physicians recommended the use of personal frequency modulation (FM) systems in order to improve the ability to follow conversations in the classroom, but she has not revisited our otolaryngology clinic since we confirmed the diagnosis of CAPD. 2.2. Case 2 A 10-year-old girl was referred to our Otolaryngology Department after bilateral hearing loss was detected on screening audiometry at her primary school. In the preschool period, she had shown developmental delay both in language and motor ability without hearing loss. The patient’s mother experienced a fever at 26 weeks pregnant. Ventricles of the
patient’s brain were enlarged as shown by fetal ultrasound at 30 weeks pregnant and neonatal anti-cytomegarovirus IgM was positive immediately after the birth. At the age of 10 years, she also experienced subjective difficulty in listening to conversations. Otoscopic examination yielded normal results. PTA resulted in bilateral, flat, moderate (right) or severe (left) sensorineural hearing loss (Fig. 2A), although behavioral observation showed that she was able to communicate without assistance such as hearing aids. DPOAE was bilaterally intact across all frequencies (Fig. 2C). Thresholds of auditory brainstem response (ABR) were normal (right, 30 dB nHL; left, 40 dB nHL; Fig. 2B), showing that the peripheral auditory pathways were intact. Central auditory processing was examined by audiological testing. Laterality index in dichotic speech tests was 17. Time compression of speech signals interfered with speech perception when the compression rate was less than 30%. The binaural interaction test (cognition of Japanese sentences alternatingly presented to the right and left ears) showed impairment (4 correct detections out of 5 stimuli; normal range, 5 correct detections out of 5 stimuli). Gap detection was possible when the gaps in the sounds were greater than 6 ms (elevation) and 2 ms (descent). Based on the complaint of difficulty in conversation, and positive results in dichotic speech tests and binaural interaction tests, CAPD was diagnosed. Speech audiometry resulted in SDS of 65% in the right and 100% in the left ear. Be´ke´sy audiometry resulted
Fig. 2. Audiological profile of Case 2. Pure tone audiogram shows severe (right) and moderate (left) threshold shifts (A). Thresholds of auditory brainstem responses are normal (right, 30 dB; left, 40 dB) (B). Responses of distortion-product otoacoustic emissions (DPOAEs) are bilaterally normal (C). In the figures of DPOAEs, the lower line (green line) indicates background noise level and the upper line (red or blue line) indicates DPOAE response level.
Y. Maeda et al. / Auris Nasus Larynx 43 (2016) 570–574
in type 1 pattern in the both ears. She was fitted with a personal FM system to improve listening in the classroom and reported a favorable result with the device in conversation. To fit the hearing aid for using FM system, we assumed that her ‘‘actual’’ hearing level was 35 dB nHL with flat audiogram pattern and verified the response from the subject with the device. To track the development of her condition, further assessment of language development was performed. Vocabulary was normal according to the Picture Vocabulary TestRevised and Standardized Comprehension Test of Abstract Words. Auditory comprehension was delayed, as shown by the Syntax Test for Aphasia (equivalent to a developmental level of 7 years and 10 months). FSIQ was 81 by the WISC-IV. Brain MRI suggested enlargement of the inferior horn of the lateral ventricle (atrophy of the temporal lobes) (Fig. 3, arrows). Electroencephalography demonstrated no focal abnormalities or spike activity. 2.3. Case 3 An 8-year-old boy was referred to our Otolaryngology Department with a chief complaint of difficulty listening to conversations in noisy surroundings. He had been diagnosed with HFPDD by pediatricians. They had detected no organic abnormality in his brain. In the preschool period, no
573
Fig. 3. Brain MRI of Case 2. Enlargement of the inferior horn of the lateral ventricle (atrophy of the temporal lobes) was suspected (arrows).
developmental delay in language or sensorimotor ability had been noted. Otoscopic examination showed no abnormality. PTA resulted in bilateral, mild-to-moderate sensorineural hearing loss (Fig. 4A), but responses and thresholds of DPOAEs (Fig. 4C) and ASSR (right, 30 dB nHL; left, 30– 40 dB nHL) (Fig. 4B) were bilaterally normal. Laterality index in dichotic speech tests was 5. Time compression of speech signals interfered with speech perception when the compression rate was less than 50%. Binaural interaction test was poor
Fig. 4. Audiological profile of Case 3. Pure tone audiogram shows bilateral, mild-to-moderately elevated thresholds (A). Thresholds of auditory steady state response are bilaterally normal (right, 30 dB; left, 30–40 dB) (B). Responses of distortion-product otoacoustic emission (DPOAE) are also bilaterally normal (C). In the figures of DPOAEs, the lower line (green line) indicates background noise level and the upper line (red or blue line) indicates DPOAE response level.
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Y. Maeda et al. / Auris Nasus Larynx 43 (2016) 570–574
(2 correct detections out of 5 stimuli). Gap detection test (elevation) was unable to be performed, as the subject could not concentrate on the task. Based on the chief complaint of difficulty listening to conversations and poor performance in the time compression test of speech signals and binaural interaction test, CAPD was diagnosed. SDS was 75% in the right and left ear. 3. Discussion In these three cases, thresholds in PTA were elevated, but responses and thresholds of DPOAEs, ABR, and ASSR were normal. As the peripheral auditory pathways were shown to be functioning normally, the results of central auditory testing such as dichotic speech tests, time compression of speech signals, binaural interaction tests, and gap detection tests offered reliable detection of dysfunction in the central auditory pathway. The chief complaint of these patients was difficulty in listening to conversations, particularly in noisy surroundings. As dysfunction in central information processing was demonstrated by central auditory testing, CAPD was diagnosed. These cases represent CAPD associated with elevated thresholds in PTA. Audiological professionals can recommend the use of personal FM systems in the classroom for these school-aged children with CAPD. Auditory training is one option to enhance listening, communication, social, and learning outcomes in children with CAPD. For example, auditory exercise (dichotic listening training) can be performed in CAPD patients with large laterality index, in order to promote interhemispheric transfer of sound information in the brain [1]. In case that peripheral hearing loss is present in CAPD patients, AAA and American Speech-Language-Hearing Association (ASHA) diagnostic criteria for CAPD require audiological professionals to verify the reliability of central auditory testing [2–4]. ASHA technical report for diagnosis of CAPD emphasizes that basic evaluation of peripheral auditory system should be conducted prior to central testing [3]. British Society of Audiology (BSA) practice guidance for CAPD defines ‘‘developmental CAPD’’ as cases presenting in childhood with normal hearing. BSA guidance categorizes ‘‘secondary CAPD’’ as cases where CAPD occurs in the presence, or as a result, of peripheral hearing impairment [5]. In the diagnosis of CAPD, it is essential to demonstrate that auditory dysfunction has its origins in impaired neural function. The most interesting point is that the pathological origin of the threshold shift in PTA in the CAPD patients in this report may be dysfunction of the central auditory system, as central auditory testing detected impairment of central auditory processing in all patients. Although central auditory testing in the diagnosis of CAPD does not directly reflect the ‘‘threshold shift’’ in PTA, it is plausible to speculate that these threshold shifts in PTA represent clinical symptoms involved in the spectrum of CAPD.
From another perspective, the elevated thresholds in PTA of these patients may be categorized as nonorganic FHL. In Cases 1 and 3, HFPDD was detected as a co-morbid condition of APD. Dysfunction in the central nervous system in CAPD contributes significantly to CAPD appearing as a co-morbidity of other disorders such as attention deficit hyperactivity disorder and learning disabilities [6]. CAPD is reported to affect 2–5% of school-aged children, and around 50% of children with learning disorders manifest CAPD [1]. These neuropsychological traits are often significant background conditions for FHL in children [7]. In Case 2, auditory language comprehension was delayed as compared to her actual age. Although her FSIQ (81) did not meet the definition of mental retardation (below 70), the FSIQ was at the lower limit of the normal range and brain MRI suggested the possibility of organic abnormality (atrophy of the temporal lobes) in the central nervous system. A relatively low IQ observed in children is reportedly significantly linked to the incidence of FHL [8]. As depicted in these 3 cases, CAPD can be diagnosed even in the presence of elevated thresholds in PTA, provided that the normal function of the peripheral auditory pathway can be verified by DPOAEs, ABR, and ASSR. These threshold shifts in PTA may represent a new concept for clinical symptoms due to central auditory dysfunction in CAPD. Further attention is needed regarding the viewpoint that the diagnoses of CAPD, as an organic dysfunction of the central auditory system, and nonorganic FHL often represent overlapping conceptualizations in such pediatric patients depicted in Cases 1, 2, and 3. Conflict of interest None. References [1] Bellis TJ, Bellis JD. Central auditory processing disorders in children and adults. Handb Clin Neurol 2015;129:537–56. [2] Diagnosis, Treatment and Management of Children and Adults with Central Auditory Processing Disorder. American Academy of Audiology Clinical Practice Guidelines; 2010. [3] (Central) auditory processing disorders [Technical Report]. American Speech-Language-Hearing Association; 2005. [4] (Central) auditory processing disorders – The role of audiologist [Position statement]. American Speech-Language-Hearing Association; 2005. [5] An overview of current management of auditory processing disorder (APD)-practice guidance. British Society of Audiology; 2011. [6] Bamiou DE, Musiek FE, Luxon LM. Aetiology and clinical presentations of auditory processing disorders – a review. Arch Dis Child 2001;85:361–5. [7] Ashitani M, Ueno C, Doi T, Kinoshita T, Tomoda K. Clinical features of functional hearing loss with inattention problem in Japanese children. Int J Pediatr Otorhinolaryngol 2011;75:1431–5. [8] Aplin DY, Rowson VJ. Psychological characteristics of children with functional hearing loss. Br J Audiol 1990;24:77–87.