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 Table of Contents  
ORIGINAL ARTICLE
Year : 2019  |  Volume : 33  |  Issue : 1  |  Page : 8-13

Consequence of long-standing auditory neuropathy spectrum disorder on voice


1 Department of Audiology, All India Institute of Speech and Hearing, Mysore, Karnataka, India
2 Department of Clinical Services, All India Institute of Speech and Hearing, Mysore, Karnataka, India

Date of Submission31-Jul-2017
Date of Decision09-Feb-2018
Date of Acceptance06-Feb-2019
Date of Web Publication28-Jun-2019

Correspondence Address:
Sandeep Maruthy
Department of Audiology, All India Institute of Speech and Hearing, Manasagangothri, Mysore - 570 006, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jisha.JISHA_37_17

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  Abstract 


Introduction: Individuals with auditory neuropathy spectrum disorder (ANSD) are known to have temporal processing deficits and poor speech perception abilities. The distorted auditory perception, if long-standing, may influence speech production abilities. The present study was undertaken to probe into the voice characteristics of individuals with long-standing ANSD, on a perceptual scale. The study used standard groups comparison research design. Materials and Methods: The study involved 11 individuals with acquired long-standing ANSD and 20 age-matched individuals (10 males and 10 females) with normal-hearing sensitivity. The recorded reading samples of the participants were presented randomly to nine speech-language pathologists who were blindfolded to the purpose of the study. The analysis was done using the Consensus Auditory-Perceptual Evaluation of Voice which provides a 100-mm Visual Analog Scale (VAS). Descriptive statistics and Pearson's correlations were carried out. Results: The results obtained revealed that individuals with long-standing ANSD present with deviant voice characteristics in terms of rough voice, breathiness, strain, high pitch, and reduced loudness. These deviations in voice could be attributed to defective auditory feedback secondary to hearing loss. Furthermore, a significant correlation was found to exist between the duration of hearing loss and the severity of deviant voice in these individuals. Conclusions: The findings suggest that voice is deviant in individuals with long-standing ANSD. This finding necessitates early identification and rehabilitation in individuals with long-standing AD to avoid negative influence on other domains of communication such as speech production.

Keywords: Auditory dyssynchrony, ANSD, auditory feedback, voice


How to cite this article:
Maruthy S, Rallapalli V, Shukla S, Priya M B. Consequence of long-standing auditory neuropathy spectrum disorder on voice. J Indian Speech Language Hearing Assoc 2019;33:8-13

How to cite this URL:
Maruthy S, Rallapalli V, Shukla S, Priya M B. Consequence of long-standing auditory neuropathy spectrum disorder on voice. J Indian Speech Language Hearing Assoc [serial online] 2019 [cited 2019 Nov 17];33:8-13. Available from: http://www.jisha.org/text.asp?2019/33/1/8/261760




  Introduction Top


Speech perception is a complex task that involves several structures in the peripheral as well as central auditory pathway. Any breakdown in the functioning of these structures could result in deterioration in the encoding of the input, and in turn, lead to poor speech perception. Through studies in compromised auditory systems, it has been documented that damage to the cochlea and the auditory nerve results in threshold elevation, deviant loudness growth, pitch perception, and temporal processing,[1],[2],[3],[4],[5] whereas damage to the central structures is known to produce complex processing deficits in speech and sound object recognition.[6],[7],[8]

One of the auditory disorders that severely affect speech perception is auditory neuropathy spectrum disorder (ANSD). It is characterized by absent or grossly abnormal auditory brain stem responses in the presence of otoacoustic emissions and/or cochlear microphonics.[9] The individuals with ANSD typically have speech recognition deficits that are poorer than that expected from their pure-tone hearing thresholds, more so in the presence of noise.

Studies using listener judgments have reported that long-term auditory deprivation in the adventitiously deaf results in flat, unmodulated, and dysprosodic voice along with segmental speech deterioration.[10],[11] Acoustic studies on adventitiously deaf adult males also reported significant speech deterioration. The deterioration was considered to be the result of lack of auditory feedback. Specifically, speaking fundamental frequency was significantly higher,[12] intensity significantly higher,[13] and speaking rate significantly slower[13] than that of age-matched, normal-hearing individuals. Significant differences have also been reported in their articulation of speech and voice quality.[14] The speech in individuals with hearing loss is known to deteriorate slowly and is seen only in the presence of long-standing hearing loss.

The deterioration in the speech of individuals with adventitious hearing loss is reported to be the result of compromised auditory feedback.[15] The auditory feedback is used to check the accuracy of the speech output and, in turn, adjust the speech motor behaviors accordingly. Zimmerman and Rettaliata[16] reported that the deterioration of speech in adventitiously deaf individuals is due to overlearned motor patterns, and errors made without the knowledge of errors occurring. They reported that it takes many instances of exceeding the normal range of variability to change the production.

Although abnormalities in speech in individuals with adventitious hearing loss depend on the degree of hearing loss, the actual influencing factor is likely to be the extent of disruption in perception caused by damage in the auditory structures. This is particularly true in hearing loss of neural origin. Individuals with auditory nerve disorders are reported to have more serious perceptual deficits compared to those of cochlear origin, and it may not be proportional to the degree of hearing loss. Poor speech perception abilities in these patients are attributed to abnormal temporal coding and asynchrony.[17],[18]

The pathophysiology of cochlear hearing loss differs from neural hearing loss. This, in turn, will result in differences in perceptual deficits between the two types of hearing loss. In addition to distortion of the spectral information that is seen in cochlear hearing-impaired individuals,[19],[20] individuals with ANSD experience distortion in temporal information.[17],[18],[20] Hence, input signal in the auditory system is a lot more distorted in individuals with ANSD compared to those with cochlear pathologies. This is supported by the findings of studies on speech perception in individuals with ANSD.[21],[22],[23]

Given the fact that perceptual deficits are different in cochlear and auditory nerve disorders, speech production characteristics may be hypothesized to deteriorate differently in each of these disorders. According to a study done by Higgins et al.,[24] despite having highly intelligible speech, most of the individuals with cochlear hearing loss had perceptibly abnormal voices which included strained or breathy quality, high pitch, and cul-de-sac resonance.

As a preliminary study, Pooja and Sandeep[25] studied individuals with ANSD and reported abnormalities in all the parameters of speech on both perceptual as well as acoustical measures. However, the study reports of abnormalities in speech from a broad perspective, while there is a need to characterize each parameter of speech in detail in individuals with ANSD. Hence, the present study was undertaken to specifically probe into the voice characteristics of individuals with long-standing ANSD in detail on a perceptual scale.

The primary objective of this study was to compare the voice characteristics of individuals with acquired long-standing ANSD with that of normal-hearing individuals. If found deviant, the secondary objective was to correlate the voice characteristics of individuals with ANSD with the duration of hearing loss, speech identification scores (SIS), and degree of hearing loss.


  Methods Top


Subjects

A total of 31 individuals participated in the study. They were divided into two groups; clinical group consisting of individuals with ANSD and a control group that included age-matched normal-hearing individuals.

Clinical group

Convenient sampling was used to recruit individuals into this group. The clinical group included 11 individuals (seven females and four males) in the age range of 17–30 years who had long-term ANSD. Long-term ANSD was operationally defined as ANSD for more than 5 years. The duration of ANSD was determined based on the reports from detailed case history of the individuals. They had reported to All India Institute of Speech and Hearing, Mysore, with a complaint of reduced hearing sensitivity. The diagnosis of ANSD was based on the results of auditory brainstem responses (ABRs) (absent or very poor responses) and otoacoustic emissions (OAEs) (robust or normal responses). They had no evidence of space occupying lesion on neurological examination. Hearing loss in these individuals was of sensorineural type and the degree ranged between minimal to severe hearing loss. [Table 1] gives the audiological details of individuals in the clinical group.
Table 1: Audiological details of subjects in the clinical group

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Control group

Control group had 20 age-matched individuals with normal-hearing sensitivity. All of them had normal OAEs as well as normal ABRs. SIS were normal in quiet as well as at 0 dB signal-to-noise ratio. They did not have any past/present history of neurologic and/or otologic disorders.

Individuals in both the groups were native speakers of Kannada and belonged to the same geographical location (Mysore city or places within Mysore district). As reported by the caregivers and also as observed in the informal testing, all the individuals in the present study had normal speech and language development. Oral mechanism examination was done to rule out the presence of any structural abnormality. The presence of any throat infections on the day of collecting speech samples was ruled out through ENT examination. A written consent about willingness to participate in the study was obtained from all the individuals. The approval for the research from the Institutional Review Board was obtained before the commencement of the study.

Test materials

The speech sample was collected through a reading task using a Standardized passage in Kannada on “Bengaluru.” The passage has two paragraphs comprising of 12 sentences. The reading sample was preferred over phonation or spontaneous speech in view of maintaining uniformity in the sample across individuals. Each individual was instructed to read the passage clearly. The samples were recorded using a Samsung digital voice recorder-Voice Yepp*TM VY-H350 with an inbuilt unidirectional dynamic microphone that was kept at 6 inches from the speaker's mouth. The VU meter in the recorder was monitored at optimum levels during the recording. The recorded samples were given an identification code and were transferred into a personal laptop computer (Acer Aspire 4820T).

Analysis

Each sample was perceptually analyzed by nine speech-language pathologists, who were trained in perceptual analysis. The samples were played to the listeners through HDA 200 headphones connected to the Acer Aspire 4820T. The listeners were blindfolded to the purpose of the study as well as to the samples. The samples of control individuals and individuals with ANSD were randomly presented to the listeners. They were instructed to listen to each sample carefully and rate the voice in the reading samples based on the Consensus Auditory Perceptual Evaluation of Voice (CAPE-V). The rating was taken immediately after listening to each sample. The attributes rated under CAPE-V were as follows:

  1. Overall Severity
  2. Roughness
  3. Breathiness
  4. Strain
  5. Pitch
  6. Loudness.


Each attribute was accompanied by a 100-mm line forming a Visual Analog Scale (VAS). The speech-language pathologist indicated the degree of perceived deviance from normal for each parameter on this scale, using a tick mark. For each dimension, scalar extremes are unlabeled.

Judgments were assisted by referring to general regions indicated below each scale on the CAPE-V where:

  • “MI” refers to “mildly deviant”
  • “MO” refers to “moderately deviant”
  • “SE” refers to “severely deviant.”


Scoring for each attribute was done by physically measuring the distance in mm from the left end of the scale. Such a score was obtained for each of the six attributes mentioned earlier, in each individual. The individual data obtained from CAPE-V were tabulated to derive the descriptive statistics (mean and standard deviation). The mean represents the average of the ratings given by the nine speech-language pathologists for the sample of a particular individual. The data of CAPE-V were correlated with that of degree of hearing loss, duration of hearing loss, and SIS using Pearson's correlations.


  Results Top


The interrater reliability was determined by combining the ratings of all the parameters, and the resultant reliability was 0.84. Voice in the speech samples of all the 20 normal-hearing individuals was rated “Zero” on the VAS. This was true for all the attributes of CAPE-V. However, the voice in speech samples of individuals with ANSD was always designated some severity rating on VAS. For example, the mean overall severity rating (average of rating given by nine speech-language pathologists) ranged from 12.22 to 56.00 across the 11 individuals, while the mean rating for breathiness ranged between 3.56 and 47.56. The pitch of the samples was rated less deviant (4.79 - 32.78) than the other attributes. The means and standard deviations of the rated severity for different attributes of CAPE-V for individuals with ANSD are given in [Table 2].
Table 2: The means and standard deviations (in parentheses) of severity ratings for different attributes of CAPE-V in the clinical group

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The secondary purpose of the present study was to determine whether the severity of the deviations in voice could be related to characteristics of hearing loss such as degree of hearing loss, duration of condition, and SIS. The correlation was tested on Karl Pearson's Correlation Coefficient test. The results of the test showed that there was no significant correlation (P > 0.05) of the severity of voice deviance with degree of hearing loss and SIS. However, there was a significant positive correlation with the duration of condition. Results are as given in [Table 3] and depicted in [Figure 1]a,[Figure 1]b,[Figure 1]c,[Figure 1]d,[Figure 1]e,[Figure 1]f.
Table 3: Results of correlation analysis between vocal attributes and duration of hearing loss in the clinical group

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Figure 1: Scatter plot depicting the relationship between vocal attributes (as in CAPE-V) and duration of hearing loss in individuals with auditory dyssynchrony ([a] relationship between overall severity and duration, [b] relationship between roughness and duration, [c] relationship between breathiness and duration, [d] relationship between strain and duration, [e] relationship between pitch and duration, [f] relationship between loudness and duration)

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  Discussion Top


The results of the present study suggest that individuals with ANSD certainly have deviations in their voice. The speech samples were presented randomly to the listeners and also the listeners were blindfolded to the purpose of the study. In spite of this, none of the individuals with normal-hearing sensitivity were assigned any severity rating. This validates the rating assigned by the nine listeners. Furthermore, none of the speech samples of ANSD were given “Zero” rating. From this finding, it can be inferred that irrespective of the degree of hearing loss and SIS, voice is deviant in individuals with long-standing ANSD. In general, voice of individuals with ANSD was reported to be sounding rough, strained, and more breathy. Findings show that the pitch of the voice was higher while the loudness was lesser in these individuals. These changes in voice could be a compensatory strategy used by individuals with ANSD to get better feedback of their voice.

These deviations in voice can be attributed to the defective auditory feedback secondary to hearing loss[10],[11],[12],[26],[27],[28],[29] and ANSD. In individuals with adventitious sensorineural hearing loss, voice was reported to have strained or breathy quality, high pitch, more loudness, and cul-de-sac resonance.[24] In contradiction to these findings, in the present study, individuals with ANSD had soft voice. The exact reason for this is difficult to derive from the results of the present study. Since the individuals with ANSD in our study had significant hearing loss, it is difficult to give physiological explanation in terms of hearing loss, for the reduced loudness of voice. One possible reason could be the psychological factor. Since most of these individuals suffer from low confidence secondary to their severe perceptual deficits, they may be using a softer voice.

The results revealed a positive correlation between the duration of the condition and the perceptual rating of voice quality in these individuals. The vocal attributes of roughness and strain showed a high positive correlation with the duration of condition, while the remaining attributes, that is, breathiness, pitch, and loudness showed a moderate positive correlation with the duration of loss. However, there seemed to be no correlation between the overall severity of voice quality and the duration of the condition. This could be explained on the basis of the fact that the perceptual rating of overall severity of voice quality was influenced by other aspects such as fluency, articulation, and speech intelligibility being seemingly normal to the listener's ear.

The absence of a significant correlation between the degree of hearing loss and the deviance in voice means that, in individuals with ANSD, even with less degree of hearing loss, there could be more deviance in voice and vice versa. This suggests that in individuals with ANSD, the deviations in voice is attributable to the extent of dyssynchrony rather than the amount of hearing loss. However, this needs to be scientifically explored.

Although the present findings confirm the presence of deviations in voice in individuals with ANSD, one cannot be sure of dyssynchronous neural firing being the primary cause for voice deviations from these preliminary findings. One could conjecture the above findings in various combinations: one, the auditory disruption causes limitations in the available feedback for monitoring of speech/voice output (beyond what would be expected from the peripheral component); second, a similar underlying mechanism disrupts both auditory processing and voice production; and finally, auditory processing deficits cause social problems which lead to voice patterns that differ from normal.

There was also no correlation observed between SIS and the deviance in voice attributes in individuals with ANSD. This implies that it might not be possible to predict the severity of voice deviance on the basis of either degree of hearing loss or SIS.

Duration of hearing loss showed a significant correlation with voice deviance, that is, longer the duration of ANSD, greater was the deterioration in voice quality. This supports the need for early identification and rehabilitation of ANSD. If ANSD could be rehabilitated early, further deterioration of voice can be avoided.


  Conclusions Top


The present study revealed voice parameters to be deviant in individuals with long-standing ANSD. The deviations were found in breathiness, roughness, pitch, strain, and loudness of voice. Severity of the deviations correlated with the duration of hearing loss, calling for the need to identify, and rehabilitate ANSD before it could negatively influence the other domains such as speech.

However, one is cautioned while interpreting the results about the cross-sectional approach used in the study. Such findings need to be further validated by undertaking longitudinal studies. The future studies could be taken up to acoustically analyze the changes in voice in these individuals. The present study highlights the importance of the fact that referrals for voice evaluation must be made for individuals with long-standing ANSD.

Acknowledgment

The authors would like to thank the Director, All India Institute of Speech and Hearing, Mysore, for the permission to conduct research and for all the logistic support.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Tables

  [Table 1], [Table 2], [Table 3]



 

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