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| ORIGINAL ARTICLE |
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| Ahead of print publication |
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Normative data for brainstem auditory evoked potential responses in North Indian menopausal females
Shallu Mittal1, Supriya Arora2, Sharat Gupta1, Sonika Loona3, Kamal Dev Singh4, Kashish Mehra3
1 Department of Physiology, Kalpana Chawla Government Medical College, Karnal, Haryana, India
2 Department of Physiology, Gian Sagar Medical College, Banur, Punjab, India
3 Kedlec Primary Care Clinic, Pasco, USA
4 Department of Physiology, Government Medical College, Patiala, Punjab, India
| Date of Submission | 07-Aug-2021 |
| Date of Decision | 22-Aug-2021 |
| Date of Acceptance | 26-Aug-2021 |
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Correspondence Address:
Sharat Gupta,
Department of Physiology, Kalpana Chawla Government Medical College, Karnal, Haryana
India
 Source of Support: None, Conflict of Interest: None DOI: 10.4103/mjdrdypu.mjdrdypu_650_21
Background: Ovarian hormones are known to influence central neuronal functioning. Many studies have established the brainstem auditory evoked potential (BAEP) pattern vis-à -vis the cyclical fluctuations of these hormones in young females; however, there is a paucity of research involving BAEP patterns among menopausal females. Aim: This study was conducted to provide normative values for various BAEP parameters in menopausal females from North India. Materials and Methods: A cross-sectional study was done on 100 females aged 46–70 years. BAEP recording was done using a standardized protocol. The data were analyzed using SPSS software. It consisted of mean wave latencies I, II, III, IV, and V and interpeak latencies (IPL) I-V, I-III, and III-V. Student's unpaired t-test was used for statistical analysis. Results: The average value of means of wave latencies and IPL from both the ears was obtained. The latencies of waves I, II, III, IV, and V were 1.82 ± 0.27 ms, 2.81 ± 0.27 ms, 4.09 ± 0.35 ms, 4.87 ± 0.33 ms, and 6.19 ± 0.31 ms, respectively. The mean values of IPL I-V, I-III, and III-V were 4.37 ± 0.38 ms, 2.26 ± 0.33 ms, and 2.1 ± 0.32 ms, respectively. Conclusion: The study findings compared favorably with already existing data from similar studies conducted elsewhere. The data from the present study would prove useful to the clinicians to detect subtle neurodegenerative changes at an early stage within the central auditory pathways, even in the absence of any perceptible hearing loss, in this subset of population.
Keywords: Auditory brainstem response, auditory evoked potentials, estrogen, hearing loss, interpeak latency, menopause, neuro-otology
How to cite this URL:
Mittal S, Arora S, Gupta S, Loona S, Singh KD, Mehra K. Normative data for brainstem auditory evoked potential responses in North Indian menopausal females. Med J DY Patil Vidyapeeth [Epub ahead of print] [cited 2023 Mar 20]. Available from: https://www.mjdrdypv.org/preprintarticle.asp?id=339185 |
| Introduction | |  |
Sex hormones undergo continuous quantitative changes during menarche, menstrual cycle, pregnancy, and menopause. Besides affecting the females both physically and emotionally, these changes have also been found to have a significant impact on the central neuronal electrophysiology.[1] Estrogen receptors have recently been identified within the inner ear sensory cell nuclei, thus suggesting a physiological role of gonadal steroids in auditory perception.[2] Furthermore, there is ample literary evidence that indicates the neuromodulatory role of 17β-estradiol within the central auditory pathway.[3],[4],[5]
Menopause is defined as a condition characterized by cessation of menstrual flow due to age-related decline in ovarian function. The biological marker of menopause is one full year from the date of the last menstrual period.[6] During menopause, there is a marked fall in the secretion of ovarian hormones, followed by a constantly low secretion of plasma estradiol. This increases the risk of osteoporosis and coronary artery disease in menopausal females and also affects various aspects of their central nervous system function (e.g., mood, memory, and cognition).[7]
Brainstem auditory evoked potential (BAEP) recording is a specialized electrophysiological technique that has recently gained popularity as a useful clinical tool for the assessment of sensory and cognitive aspects of central neuronal function.[8] BAEP waveforms comprise five distinct waves that represent small electrical voltage potentials that are generated at various locations within the auditory pathway within 10 ms of applying an acoustic stimulus. These potentials are recorded via surface electrodes placed on the scalp. Wave I is generated from the segment of auditory nerve closest to cochlea, wave II from cochlear nucleus, wave III from lateral lemniscus, and wave V from inferior colliculus (in midbrain).[9]
The clinical utility of BAEP has already been established in auditory screening and assessment of hearing in infants and uncooperative patients, estimation of auditory threshold, determining type of hearing loss, etc.[10] Various authors have already documented the variation in BAEP response during different phases of menstrual cycle, indicating that there is a significant influence of female hormones on these waves.[11],[12],[13],[14] To the best of our knowledge, there is a severe paucity of such data among menopausal women. The present study was, therefore, designed to investigate the pattern of BAEP waveform in menopausal females to establish the normative data for the benefit of the clinicians by enabling them to effectively screen these females for early impairments within the central auditory pathway. The results of the present study have also been compared with those from other similar studies conducted elsewhere.
| Materials and Methods | | |
The present study was carried out over a period of 2 years in the physiology department of a Premier Government Medical College of North India. The procedures followed were in accordance with the ethical standards of the institutional committee on human experimentation and with the Helsinki Declaration.
Study participants
The present cross-sectional study was conducted among elderly female relatives and attendants of patients visiting the various outpatient departments of the institute. The sample size was calculated using Cochran's formula for continuous data, and the participants were selected using simple random sampling.[15] Written consent was obtained from all participants after explaining them all the necessary details about the study in their native language. Out of the initial 129 participants, 29 were subsequently excluded either due to voluntary withdrawal or as per exclusion criteria; the remaining 100 females were made to undergo BAEP procedure. Confidentiality of all the participants was maintained throughout the study.
Inclusion criteria
The study group included 46–70-year-old healthy females, with apparently normal hearing and who had attained natural menopause (without panhysterectomy) for at least 1 year before the start of the study.
Exclusion criteria
Those females were excluded who had a personal/family history of menstrual disturbances, systemic disorders (e.g., diabetes mellitus and hypertension), ear trauma/surgery, hearing impairment, and intake of medications that could potentially alter the study findings (e.g., antidepressants, hormone replacement therapy, oral contraceptive pills, and ototoxic drugs like aminoglycosides) during the preceding 6 months. The subjects who refused to give consent and who chose to withdraw in between were also excluded from the study.
Medical and biochemical examination
Before conducting the BAEP recording, all the participants were asked to fill out self-administered questionnaires to know about medical/family/drug history and lifestyle. After this, they were subjected to a general physical examination by a physician, an ENT assessment (otoscopic examination and tuning fork tests), and general biochemical tests (e.g., fasting plasma glucose and serum creatinine)
Brainstem auditory evoked potential study
For the study, the guidelines of the American Clinical Neurophysiological Society were followed.[16] BAEPs were recorded in a semidark room with quiet surroundings on RMS EMG EP Marc-II Channel machine (Recorders and Medicare Systems Pvt. Ltd., Chandigarh, India). Before the test, we calculated the age (rounded off to the nearest completed year), height (in standing posture, without shoes, in cm), and body weight (with minimum clothes, in kgs). The subjects sat on a chair such that their back was turned toward the machine. They were instructed not to move unnecessarily and any metallic jewelry/ornaments worn by them were also removed.
BAEP recording was performed monoaurally. The acoustic stimulus consisted of “broadband clicks” that were delivered via earphones at a frequency of 11.1 Hertz. Masking was done in contralateral ear simultaneously. Filter setting was kept at 100 and 3000 Hertz; in this way, two thousand clicks were delivered on an average to each ear at an intensity >60 dB above the subject's hearing threshold level, which was determined by ascending and descending limit method. Silver-based surface electrodes were used for recording BAEPs. Active electrodes were placed over both mastoid process, reference electrode was positioned over vertex, and the midline frontal position on the forehead was chosen for ground electrode placement. We ensured that the impedance remained below 5 KOhms. We recorded at least two responses for both the ears, to ensure replicability. The data consisted of wave latencies I-V and interpeak latencies (IPL) I-III, III-V, and I-V.
Statistical analysis
The data were analyzed statistically using Statistical Package for the Social Sciences software version 27.0 (SPSS Inc. Chicago, US). Student's unpaired t-test was used for the analysis. All the values were expressed as mean and standard deviation. P value was calculated to note the statistical significance. P < 0.05 was considered statistically significant. The normal reference range of IPL was kept at 95% confidence level. The results of this study were compared with similar studies done previously elsewhere.
| Results | | |
The study was conducted among 100 audiometrically normal menopausal females aged 46–70 years who had no overt clinical signs and symptoms of auditory impairment.
[Table 1] summarizes the demographic characteristics of the study subjects. The duration of menopause in our subjects ranged from 1 to 22 years, the mean value being 11.25 ± 5.67 years. A comparison between the mean values of wave latencies and IPL was done for both the ears [Table 2]. It was seen that all the corresponding BAEP latencies were comparable between the left and right ears (P > 0.05). This indicates that the left–right latency asymmetry is within normal limits in our study population, thus ruling out any unilateral hearing impairment. | Table 2: Comparison of brainstem auditory evoked potential parameters between left and right ears of subjects
Click here to view |
A comparison between our study findings and those obtained by other researchers is presented in [Table 3]. We took the average of the mean value of latencies of both the ears for this comparative analysis since the latencies of both the ears were comparable in our study subjects as already noted above.
| Discussion | | |
The present study establishes the baseline normative data for various BAEP parameters in audiometrically normal menopausal females. To the best of our knowledge, only three similar studies have been conducted till date.[17],[18],[19] Furthermore, all these studies are almost two–three decades old and involve fewer participants.
Our mean latency values of wave I are similar to Lenzi et al.,[19] higher than Tandon et al.[17] and lower than Wharton et al.[18] Latency of wave V in our subjects was higher than Tandon et al.[17] but lower than others.[18],[19] Furthermore, our value of interpeak latency I-V was higher than others;[17],[18] however, the mean values of IPL I-III were similar to those obtained by Wharton et al.[18] and lower than those of Tandon et al.[17] The values of IPL III-V in our study were highest among all.[17],[18] The normative data for latencies of waves II and IV could not be compared due to nonavailability of similar data from previous studies.
The probable reasons for the above variations in results can be attributed to the differences in the age, demographic profile of participants, and also the lower sample size in other studies.
Study limitations
Nonestimation of serum estradiol levels was a major limitation, due to financial constraints. We feel that their inclusion would have made the observations much more meaningful and elaborate. Another limitation is that the sample size of the present study may not be representative of the general population.
| Conclusion | | |
The study has provided normative data for BAEP waveforms in elderly menopausal North Indian females. The findings of this study assume clinical importance due to the fact that knowledge about the baseline characteristics will enable the clinicians in screening and early detection of central acoustic neuropathy in this population subset, despite the absence of clinically apparent hearing loss.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]
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