|Year : 2014 | Volume
| Issue : 4 | Page : 169-172
Pre-post therapy comparison of electrophysiological auditory findings in stutterers
Noorain Alam1, Vikas Sinha2, Deepanshu Gurnani2, Sachin Jindal2, Pawan Sharma2, Ambuj Pandey2
1 Department of Audiology and Speech Therapy, C U Shah Medical College and Hospital, Surendranagar, India
2 Department of Otolaryngology and Head and Neck Surgery, MP Shah Government Medical College, Jamnagar, Gujarat, India
|Date of Web Publication||13-Dec-2014|
Department of Audiology and Speech Therapy, CU Shah Medical College and Hospital, Surendranagar 363 001, Gujarat
Source of Support: None, Conflict of Interest: None
Introduction: Stuttering is a speech disorder in which the flow of speech is disrupted by involuntary repetitions and prolongations of sounds, syllables, words or phrases, and involuntary silent pauses or blocks in which the stutterer is unable to produce sounds. Aim: The aim of the study was to verify whether there is alteration of auditory-evoked potentials (AEPs) as a result of speech therapy; and to find out which parameters of AEPs alters, which can be attributed to the effect of speech therapy. Materials and Methods: The research sample was composed by 14 adult males with moderate stuttering. This group was assessed twice through brainstem auditory evoked response (BAER), middle latency response (MLR) and late latency response (LLR); assessments were carried out with a 3-month interval time. Both pre and post therapy measurements were compared. Results: Comparison between pre and post speech-language therapy results indicate an alteration of at least one parameter of each category. The observed results showed that in auditory brain stem response (ABR) test there was predominance decrease in 8 subjects (64.28%) was observed in wave I latency, while in MLR, there was predominance of increase of Pa wave (57.14%) in 8 subjects. Conclusion: Altered electrophysiological findings were observed in persons with stuttering as a result of speech therapy. ABR and LLR measurements were mostly altered showing the change in neural response to auditory stimuli.
Keywords: Auditory evoked potentials, AEP, Stuttering
|How to cite this article:|
Alam N, Sinha V, Gurnani D, Jindal S, Sharma P, Pandey A. Pre-post therapy comparison of electrophysiological auditory findings in stutterers. Indian J Otol 2014;20:169-72
|How to cite this URL:|
Alam N, Sinha V, Gurnani D, Jindal S, Sharma P, Pandey A. Pre-post therapy comparison of electrophysiological auditory findings in stutterers. Indian J Otol [serial online] 2014 [cited 2020 Jan 19];20:169-72. Available from: http://www.indianjotol.org/text.asp?2014/20/4/169/146932
| Introduction|| |
Stuttering is a speech disorder in which the flow of speech is disrupted by involuntary repetitions and prolongations of sounds, syllables, words or phrases, and involuntary silent pauses or blocks in which the stutterer is unable to produce sounds (WHO, 2007). 
Stuttering may be related with problems with auditory processing. This includes problems with retaining auditory images, making figure ground distinction, or selecting meaningful from non- meaningful auditory signals. Stuttering is less prevalent in deaf and hard-of-hearing individuals (Ward and David, 2006)  and stuttering may be improved when auditory feedback is altered, such as masking, delayed auditory feedback (DAF), or frequency altered feedback (Gordon, 2002).  Auditory evoked potentials are valid and useful measures to study auditory processing in persons with stuttering as they reflect changes in auditory system as stimuli is processed.
Auditory processing in normal and stuttered speech production
Behavioral studies of auditory processing in adults and children who stutter have yielded evidence of central auditory processing differences in these populations relative to fluent age-matched peers. Rousey, Goetzinger and Dirks (1959)  reported that 20 stuttering children showed below normal performance on sound localization. Lack of sound localization skills may be indicative of temporal lobe disorders (Jerger et al., 1969).  Various studies have employed batteries of audiometric tests to evaluate behavioral central auditory processing in adults children who stutter. Rousey, Goetzinger and Dirks, 1959  reported that 20 stuttering children showed below normal performance on sound localization. Hall and Jerger, 1978  reported that adults who stutter performed poorly relative to fluent adults on a subset of such tests. They concluded that the results suggested the presence of a subtle central auditory processing deficit in adults who stutter. Anderson, Hood and Sellers, 1988  conducted a similar study and found that adolescents who stuttered performed poorly on only one subtest as compared with a group of age-matched control participants. They similarly concluded that if a deficit exists, it is subtle.
Evidence of a subtle central auditory processing deficit has also been demonstrated in children who stutter. For example, children who stutter have been found to have higher thresholds on backward masking tasks than children who do not stutter (Howell et al., 2000).  Howell et al., also found a positive correlation between backward masking thresholds and stuttering severity in children who stutter. In a follow-up study by Howell and Williams, 2004,  investigated children who stutter on a battery of audiometric tests including backward masking tasks. Based on the profile of performance on the audiometric battery of tests, Howell and Williams, 2004,  reached the conclusion that children who stutter had a different developmental pattern of central auditory processing abilities relative to their fluently speaking age-matched peers but they did not specify the nature of that difference.
More recently, central auditory functioning was evaluated behaviorally and with electroencephalography in adults who stutter (Hampton and Weber-Fox, 2008).  Behaviorally, adults who stutter performed less accurately and demonstrated longer reaction times in response to the prompt tone in a standard oddball paradigm. However, a small subgroup of adults who stutter was found to be driving the results. The same subgroup of poor performing adults who stutter also demonstrated abnormal evoked auditory waveforms. Hampton and Weber-Fox, 2008,  concluded that this subgroup demonstrated deficient non-linguistic auditory processing.
Auditory-evoked potentials (AEPs) and auditory processing
Evoked potentials (EPs) are bioelectric potentials recorded using electrodes placed on body. In AEPs, the potentials are elicited by giving external auditory stimuli through earphones. Objective tests like AEPs are valid and useful measures to study auditory processing in persons with stuttering as they reflect changes in auditory system as stimuli is processed. The therapeutic process progress can be monitored through changes in latency and amplitude of such potentials given the plasticity of Central Auditory Nervous System (Hayes et al., 2003).  In fact, systems that are responsible for learning have to maintain some ability to modify the neural "trigger" throughout life, otherwise no novel learning would happen (Kraus, 2001). 
Several studies have used the AEP to assess and monitor the auditory pathway in Persons with stuttering, however, varied results have been reported which include predominance of altered responses in persons with stuttering, statistically significant increase on absolute latency of waves I, III and V and interpeaks I-III and I-V on the ABR of Persons with stuttering. (Andrade et al., 2007).  Thus, it is important to characterize the hearing of this population through AEP in order to clarify possible correlations between auditory aspects and fluency.
Aim of the study
The purposes of this study was to find out if there any change occurring in AEPs as a result of speech therapy.
| Materials and Methods|| |
Present study was carried out in Audiology and Speech therapy department at C U Shah Medical College, Surendranagar.
The study group (SG) consisted of 14 males with stuttering between age range 18 and 30 years. They were diagnosed in the speech therapy department. All the subjects were classified as moderate stuttering on stuttering severity instrument. All subjects were having normal hearing that is their hearing threshold was up to 25 dB across frequency range of 250 Hz to 8 KHz. None had any other hearing, neurological or psychological complaints.
Initially, Otoscopic examination was carried out which was followed by Pure tone audiometry for which GSI 61 model from Grason-Stadler, was used.
For AEP measurement IHS system was used. The acoustic stimulus used on ABR was the click of rarefied polarity. It was presented monaurally by insert earphone at 80 dBnHL and with speed of presentation of 21.1 clicks per second. A total of 2000 stimuli were presented. The window used for recording was of 10 ms. The electrodes were placed on the forehead (Fpz) and on left and right mastoids (A1, A2). The absolute latencies of waves I, III, V and interpeaks I-III, III-V, I-V were analyzed.
For MLR measurement, the stimuli were presented monaurally using insert earphone at speed of 7.1 clicks per second and at intensity of 80 dBnHL. Sweeps of 1024 clicks were presented and the recording window used was 100 ms. The electrodes were arranged at mastoids (A1, A2), vertex (Cz) and forehead (Fpz - ground or common). Latencies of Na and Pa waves, and amplitude Na-Pa were analyzed.
For LLR measurement electrodes were positioned on left and right mastoids (A1, A2), vertex (Cz) and forehead (Fpz). The acoustic stimulus used was the clicks at 80dB HL at the rate of 1.1 click per second. The recording window was 500 ms. Presence and absence of such potential were verified, and latencies for N1, P1, N2 and P2 waves and amplitude N1P2 were analyzed.
A comprehensive speech therapy program was administered. There were three fluency skill goals of the speech therapy.
- Air flow management
- Gentle phonatory onset and
- Rate reduction
- Specific techniques used were
- Hand tapping
- Shadow reading
- Abdominal Breathing exercise.
The therapy was scheduled twice a week. Total duration was of three months. Post therapy of all the above-mentioned AEP measurements was re-administered.
In the comparative analysis of results obtained in the assessments before and after therapy, obtained potentials were classified as decrease, increase or maintenance of latency and amplitude values of SG. It is important to highlight that values that suggest improvement in neural transmission of auditory stimuli are the ones of decrease of latency values (in ms) and increase of amplitude values (in μv).
The comparative result analysis of assessments before and after therapy was performed. Statistical analysis was performed using the t-tests. The significance level was of 5%. [Table 1], [Table 2] and [Table 3] and [Figure 1], [Figure 2] and [Figure 3].
|Table 1: ABR changes in pre and post speech therapy in absolute latencies as well as inter- peak latencies|
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|Table 2: MLR changes in pre and post speech therapy in Na, Pa latencies and Na/Pa amplitude|
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|Table 3: LLR changes in pre and post speech therapy in N1, P1, N2 & P2 latencies and Na/Pa amplitude |
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| Results|| |
The AEP analysis was done on the evaluations before and after Speech-Language therapy for SG. The results observed have been discussed below.
As seen in [Table 1], on the result comparison between before and after Speech-Language therapy on BAER, there was a predominance of wave I latency decrease in SG (64.28%). However, such difference was not statistically significant (P = 0.165). For wave III, there was a predominance of latency maintenance in SG (42.85%) with no statistical significance (P = 0.169). There was predominance on increase of interpeaks I-III, III-V and I-V; however, such increase was not statistically significant (P = 0.257, P = 0.371 and P = 0.569, respectively).
Results of the qualitative data obtained on MLR before and after speech therapy in both groups, are shown in [Table 2]. Regarding the Na wave latency, an decrease predominance (49.98%) was observed in SG, although not statistically significant (P = 0.673). A predominance of increase in latency of Pa wave (57.14%) in SG was observed - statistically significant (P = 0.031). No statistically significant alterations were observed regarding amplitude Na/Pa (P = 0.578).
Results of the qualitative analysis of latency and amplitude of LLR wave in SG are described in comparative analysis of latency values of N1 and P1 wave showed a non-statistically significant predominance (P = 0.564) of decrease in the group (64.28%). While for N2 and P2 there was increase (49.98%) and (71.42%), respectively, which were statistically not significant (P = 0.239) and (P = 0.641), respectively. Regarding amplitude values, no statistically significant difference was observed (P = 0.621).
| Discussion|| |
The observed results showed in ABR test there was predominance decrease in 8 subjects (64.28%) that was observed in wave I latency, whereas in MLR there was predominance of increase of Pa wave (57.14%) in 8 subjects. Regarding the LLR, 10 subjects from SG presented decrease in latency of P2 (71.42%). Therefore, when pre and post therapy findings of AEP measurements in persons were compared, there was predominant change in at least one of the measurements in all categories of AEPs but this difference was not statistically significant.
Regarding the comparative study of AEP between assessments (before and after Speech-Language Therapy), the present study showed that there was a predominant decrease in latencies of wave I of BAER and of LLR in the SG. These results indicate that as a result of speech therapy functional, neroplasticity has occurred in person with stuttering resulting into a changed neuronal response to the auditory stimuli.
As the sample size was small in the study, further investigation is warranted in this direction.
| Conclusion|| |
An altered electrophysiological finding was observed in persons with stuttering as a result of speech therapy. ABR and LLR measurements were mostly altered showing the change in neural response to auditory stimuli.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3]