|Year : 2022 | Volume
| Issue : 2 | Page : 167-170
The presence of atypical auditory brainstem response waveforms in a child with normal hearing
Mohd Fadzil Nor Rashid, Mohd Normani Zakaria, Maziah Romli, Wan Najibah Mohamad, Mahamad Almyzan Awang
Department of Audiology, School of Health Sciences, Universiti Sains Malaysia, Kubang Kerian, Kelantan, Malaysia
|Date of Submission||15-Apr-2021|
|Date of Decision||16-Jun-2021|
|Date of Acceptance||28-Jul-2021|
|Date of Web Publication||21-Sep-2022|
Dr. Mohd Normani Zakaria
Department of Audiology and Speech Pathology, School of Health Sciences, Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan
Source of Support: None, Conflict of Interest: None
Auditory brainstem response (ABR) is an objective test typically carried out to estimate behavioral hearing thresholds among difficult-to-test children. The latencies of ABR waveforms are commonly used for hearing diagnosis. The available ABR normative data are utilized as guidelines by clinicians to identify the prominent peaks of ABR. In this paper, atypical ABR waveforms of a normal child were reported. Several useful points were highlighted from the present case report to guide clinicians to appropriately interpret the ABR results.
Keywords: Audiometry brainstem response, hearing threshold, latency, waveform
|How to cite this article:|
Rashid MF, Zakaria MN, Romli M, Mohamad WN, Awang MA. The presence of atypical auditory brainstem response waveforms in a child with normal hearing. Indian J Otol 2022;28:167-70
|How to cite this URL:|
Rashid MF, Zakaria MN, Romli M, Mohamad WN, Awang MA. The presence of atypical auditory brainstem response waveforms in a child with normal hearing. Indian J Otol [serial online] 2022 [cited 2022 Sep 25];28:167-70. Available from: https://www.indianjotol.org/text.asp?2022/28/2/167/356456
| Introduction|| |
Getting reliable hearing test results can be challenging when dealing with difficult-to-test children. Depending on the age and other factors, some children are not cooperative during behavioral hearing assessments. As such, objective hearing tests such as auditory brainstem response (ABR) and auditory steady-state response can be conducted to estimate the behavioral hearing thresholds.,,,
Even though ABR consists of seven peaks, the first five prominent peaks (i.e., Wave I, Wave II, Wave III, Wave IV, and Wave V) receive more attention in clinical settings. Waves VI and VII of ABR are less commonly reported as they are thought to be less robust if compared to the Wave V of ABR., For clinical applications, the normative data of ABR are available for different age groups. In this regard, when estimating behavioral thresholds and type of hearing loss of a particular patient, the resultant ABR waveforms are compared with the corresponding normative values. Since the latencies of ABR peaks are more stable than the amplitudes, the ABR latencies are typically used in the results interpretation. Due to its robustness, the Wave V serves as the main indicator in the ABR testing., As such, if the absolute latency of Wave V latency is prolonged at specific supra-threshold levels (compared to the normative data), hearing loss is suspected. In this case report, we present atypical waveforms of ABR in a child with normal hearing, in which a further consideration was needed to properly interpret the ABR results.
| Case Report|| |
This is a case of a 2-year-old Malay boy who was referred from a district clinic due to speech delay. At the moment, he was able to pronounce/mama/, identify certain alphabets correctly, and sing along the songs without articulation errors. He started to babble at 1 year of age and produce the first word not long after that. According to his mother, he was not so responsive when his name was called, refused to speak, and frequently used gestures to express his needs. Due to this, his mother suspected that his son to have some hearing problems. Nevertheless, while watching YouTube videos via a handphone, an average volume level was used. For the antenatal history, the mother had diabetes mellitus during pregnancy and was under a controlled diet. The child was born full-term through spontaneous vaginal delivery with a birth weight of 3.04 kg. The neonatal history was uneventful. In terms of physical development, he could sit at age of 9 months and started to walk around 1 year of age. He was hospitalized for a left reducible inguinal hernia and underwent surgery as the treatment. No family history of hearing loss reported, and he is the first child of two siblings.
The boy visited the Audiology Clinic, University Hospital for hearing assessments twice, and he was healthy in both appointments. On the first visit, the otoscopic examination revealed the presence of earwax in both ears. The tympanometry showed a Type A tympanogram bilaterally, suggestive of normal middle ear function. The distortion product otoacoustic emission (DPOAE) test revealed “pass” results at all frequencies tested (2 kHz to 5 kHz) bilaterally, indicating robust emissions of outer hair cells. The visual reinforcement audiometry was conducted using insert earphones, but the results were incomplete (due to his inattentiveness). That is, some hearing information could only be obtained for his left ear, in which his hearing was found to be not worse than a moderate loss at high frequencies (2 kHz and 4 kHz). The test reliability was rated fair to good. The boy was then referred for an ear toilet and ABR testing was scheduled within 3 weeks.
On the second visit, his mother reported that the boy showed a slight improvement in hearing after the ear toilet at a private clinic. However, his mother reported that she had to call him for several times and use gestures to get his attention. No otalgia and otorrhea were reported. The otoscopic examination revealed minimal dry earwax and intact tympanic membrane bilaterally. The tympanometry revealed a Type A tympanogram bilaterally.
While he was asleep (after being sedated), the ABR testing was conducted using the standard clinical protocol. The stimuli (clicks and tone bursts) were delivered through insert phones at a rate of 11.1/s. The resultant click-evoked ABR waveforms are shown in [Figure 1]. [Table 1] shows the absolute latency values of Waves I, III, and V at 80 dBnHL for each ear. As revealed in [Figure 1], at a high-intensity level (80 dBnHL), the morphology of waveforms was good, and the prominent Waves (I, III, and V) were repeatable for both ears. Nevertheless, while the absolute latency of Wave V was within the normal range for the right ear (5.78 ms), the absolute latency of Wave V was abnormally prolonged for the left ear (6.65 ms) [Table 1]. Lower intensity levels were then tested, and a repeatable Wave V was still noted down to 20 dBnHL for both ears (suggestive of hearing within the normal limit bilaterally at high frequencies) [Figure 1].
|Figure 1: Click-evoked auditory brainstem response waveforms for the right ear (left panel) and the left ear (right panel)|
Click here to view
Using tone bursts (250 Hz), a repeatable Wave V was observed down to 20 dBnHL for both ears (suggestive of normal low-frequency hearing bilaterally). [Figure 2] illustrates the ABR waveforms (evoked by the tone bursts) at 80 dBnHL and 20 dBnHL for the left ear. As shown, the absolute latency of Wave V was 9.0 ms at 80 dBnHL. In addition, the acoustic reflex screening test was also carried out and revealed “pass” results at all frequencies tested (500 Hz, 1000 Hz, and 2000 Hz) for the left ear. However, the right ear could not be tested as the boy started to wake up.
|Figure 2: Auditory brainstem response waveforms evoked by 250 Hz tone burst for the left ear|
Click here to view
| Discussion|| |
In the ABR testing, 80 dBnHL is the common initial intensity level employed by many clinicians. At this high-intensity level, the prominent peaks are identified and plotted accordingly. At this level, the absolute latency of Wave V of ABR is expected to be <6 ms among normal-hearing individuals., If the absolute latency is delayed, there is a suspicion of hearing loss. The ABR waveforms at lower intensity levels are then determined until ABR thresholds are obtained. It is worth noting that around 2 years of age, the ABR waveforms would reach adult-like waveforms.,
In this case report, even though the Wave V of click-evoked ABR was identifiable down to 20 dBnHL for both ears (suggestive of normal high-frequency hearing bilaterally), the prolongation of absolute latency of Wave V for the left ear was not expected (i.e., 6.65 ms at 80 dBnHL). As reported elsewhere, the delayed Wave V latency could be due to conductive hearing loss, severe level of sensory loss, or neural problems., Nevertheless, the findings of acoustic reflex and DPOAE tests were all unremarkable (excluding the possibility of having these disorders). In fact, when the absolute latency of Wave V was compared between the click-evoked ABR (i.e., 6.65 ms) and the tone-evoked ABR (i.e., 9.0 ms) at a similar intensity level (80 dBnHL), the difference was 2.35 ms. This value was also insensible as the traveling wave delay between 250 Hz and 4000 Hz was around 4 ms.,
After a thorough discussion among the clinicians, it seemed possible that for the left ear, the identification of ABR peaks was incorrect. The peaks were then replotted, and the “corrected” peaks are shown in [Figure 3]. The “corrected” absolute latency of ABR peaks is revealed in [Table 1]. As indicated, the “corrected” absolute latency of Wave I was 1.08 ms (compared to 2.11 ms for the “uncorrected” Wave I). On the other hand, the “corrected” absolute latency of Wave V was 4.86 ms (compared to 6.65 ms for the “uncorrected” Wave V). In this regard, the “confusion” arose because of poorer morphology of Wave I, as well as a robust Wave VI was seen (that was mistakenly thought as Wave V) for the left ear [Figure 3]. Even though these “corrected” latencies were shorter than the published normative data, they are more consistent with “normal-hearing” diagnosis (rather than hearing disorders). In fact, at 20 dBnHL, the “corrected” Wave V looked more robust compared to the “uncorrected” Wave V [Figure 1] and [Figure 3]. Furthermore, when the traveling wave delay was calculated (between the “corrected” absolute latency of Wave V and the respective latency of tone-evoked ABR), the value was 4.14 ms, which is consistent with those of previous studies., Collectively, the “corrected” ABR latencies appear more sensible and the overall ABR results are now in line with the results of other tests (i.e., suggestive of normal hearing bilaterally).
|Figure 3: Corrected peaks of auditory brainstem response waveforms for the left ear|
Click here to view
Several useful points could be gathered from this case report. Firstly, it seems insensible to have normal ABR thresholds with the presence of abnormally prolonged Wave V latency at supra-threshold levels. If this situation occurs, a further attention is required to “revise” the ABR results. As such, knowledge and experience in the ABR testing (including the use of appropriate normative data) are essential to properly interpret the ABR results. Secondly, due to the high variability of ABR amplitudes, it is possible to have a small-amplitude Wave I at supra-threshold levels. Thirdly, recording ABR with both click and tone burst stimuli is recommended to verify the ABR results. Finally, it is always beneficial to compare the ABR results with other test results to have better ideas for case diagnosis. In terms of case management, the boy was scheduled for the behavioral testing in 3 months and will be seeing a speech-language pathologist for improving his speech and language skills.
| Conclusions|| |
In this case report, it is imperative to appropriately interpret ABR results to achieve an accurate hearing diagnosis. As such, a further consideration is warranted if the ABR latencies are prolonged, but the ABR thresholds are normal. The information gathered from this case report would be useful to guide clinicians to avoid misdiagnosis in clinical practice.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published, and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]