Prognostic Value of Auditory Brainstem Evoked Response in Patients with Idiopathic Sudden Sensorineural hearing loss.

hormone serum level were assessed after admission. Result: Hearing recovery was observed in 21 patients (70%). The absolute latencies of waves I, III, and V latencies were statistically significantly delayed in the affected ears compared with the unaffected ears. There was a statistically significant correlation between hearing outcome and wave I latency. Wave V latency was statistically significantly negatively correlated with free T4. Conclusion: Auditory brainstem response is an important prognostic factor in ISSNHL but caution should be considered when adopting ABR testing without assessing thyroid hormone levels.

https://ejmr.journals.ekb.eg/hormone serum level were assessed after admission.Result: Hearing recovery was observed in 21 patients (70%).The absolute latencies of waves I, III, and V latencies were statistically significantly delayed in the affected ears compared with the unaffected ears.There was a statistically significant correlation between hearing outcome and wave I latency.Wave V latency was statistically significantly negatively correlated with free T4.Conclusion: Auditory brainstem response is an important prognostic factor in ISSNHL but caution should be considered when adopting ABR testing without assessing thyroid hormone levels.
It refers to sudden sensorineural hearing loss that occur in72 hours, affecting at least two adjacent frequencies with hearing loss more than 20 dBHL. [2]In spite there was any clear pathogensis of ISSNHL but theories may suspect viral infection,circulatory causes ,autoimmune disorders , and neoplasm as causes. [3]Many studies have described prognosting factors for ISSNHL to be considered in the following of these cases like the timing of initial therapy, hearing loss duration, pure tone audiometry configurations and accompanied symptoms. [1]Auditory brainstem response (ABR )is an electrophysiological test used in detecting the integrity of the auditory pathway and explore the retrocochlear lesions.Previous researches have stated that ABR may act as a prognostic tool in these patients with ISSNHL. [3]e thyroid gland is considered as one of the most important organ of the human body.thresholds and otoacoustic emission results. [4]out 25 % of patients demonstrated different types and degrees of hearing loss ,associated with congenital thyroid abnormalities. [3]ong the patients with ISSHL, the prognostic value of ABR and the association between its results and the thyroid hormone https://ejmr.journals.ekb.eg/serum levels (TSH, T3, and free T4) were assessed.

Aim of The Work:
To investigate the the prognostic value of ABR and the association between its results and the thyroid hormone serum levels in ISSNHL patients.with 30 dB hearing loss at three consecutive frequencies. [5]tients who have any infectious ear disorders (acute and chronic otitis media), eardrum The latencies of waves I, III, and V will be studied with BAEPs.

Patients And Methods:
Pure-tone audiometry, speech audiometry and ABR testing were performed on the day of admission then performed again on the third day after admission and 1 month after the onset of ISSHL.Evaluations of audiological https://ejmr.journals.ekb.eg/improvement were performed using pure-tone average (PTA) thresholds at four frequencies (0.5, 1.0, 2.0, and 4.0 kHz).Their outcomes were classified as follows: (1) complete recovery, (2) partial recovery, and (3) no recovery.
-Laboratory investigations including TSH, serum free T3 & serum free T4.The normal reference range is as follows: serum free T3=

Results:
A The comparison of ABR metrics between the affected and unaffected ears in all patients shows that the absolute latencies of wave I, wave III, and wave V were significantly prolonged in the affected ears compared with the unaffected ears.The amplitude of wave I, was significantly lower in the affected ears compared with the unaffected ears.The inter-peak latencies of wave I, wave III, and wave V were not significant in the affected ears compared with the unaffected ears.Table (2)

Table (2):
Comparison of Initial PTA average, SDS%, and ABR metrics between the affected and unaffected ears in all patients with ISSNHL before treatment.
A comparison of ABR metrics between the affected ears in all patients before and after treatment shows that the absolute latencies of wave I and wave III were not significant, only wave V was significantly prolonged in the affected ears before treatment compared with after treatment Table (3) .
There was significant correlation between absolute latency wave I and hearing outcomes in all patients with ISSNHL Table (5)   According to Person's rank correlation coefficient analysis, initial PTA average at 500Hz was statistically significantly positively correlated with free T3, and at 1 kHz, 2 kHz, 4 kHz, and 8 kHz was statistically significantly positively correlated with free T3 and free T4.Wave V latency was statistically significantly negatively correlated with free T4.Table (6).

Discussion:
This study was aiming to study the effect of idiopathic sudden sensorineural hearing loss on auditory brainstem response latencies and to assess the relationship between thyroid hormone levels and the quantitative data of ABR tests in ISSNHL individuals.The amplitude or latency of wave I or the lack of wave V were examined in the earlier research [3,4] as potential related factors with hearing outcomes in individuals with ISSNHL.We looked at the absolute and inter-peak latencies as potential determinants of variation among treatment outcome groups.
In our study we found that the mean latencies of the wave I increased with initial severity of hearing loss.The mean SDS and threshold in dBHL also increased with initial severity of hearing loss.That was in agreement with Heo et al. in 2019, who stated that the mean latencies of the wave V and waves I-V intervals increased with initial severity of hearing loss [4] The absolute latencies of wave I, wave III, and wave V were significantly prolonged in the affected ears compared with the unaffected ears.
The inter-peak latencies were not significant in the affected ears compared with the unaffected ears.
In accordance with our results, the study of Bang et al. in 2019, as they reported that the mean latency of ABR wave I was significantly longer in the affected ear than in the unaffected ear [6].
In our study we found statistically significant difference in wave I amplitude between affected and unaffected ears.These results came in accordance with Seo and his colleagues, 2022.They suggested that the decrease in amplitude of the ABR wave I in ears that have completely recovered from SSNHL suggests that cochlear synaptopathy may be involved in the pathogenesis of SSNHL. [7]In contrast Bang et al. in 2019, reported that the mean amplitudes of wave and wave V did not differ between the groups. [6] regard the absolute latencies of wave I and wave III were not significant, only wave V was significantly prolonged in the affected ears before treatment compared with after treatment.These findings demonstrated that better hearing outcomes were associated with shorter wave I latency in the affected ear. [8] the study of Zarandy and his colleagues in 2017, they stated that the chance of responsiveness in patients with profound hearing loss who responded to medical therapy and had at least wave V ABR was correlated with the presence of ABR . [9]rthermore, Heo in 2019 revealed that the comparison of the ABR outcomes between the one-month successful recovery and poor recovery groups were showed whereas The mean latencies of all ABR metrics were not significantly different between the two groups. [3]e present study showed that among cases, one patient (3.3%) had preexisting hypothyroidism, and 4 patients (13.33 %) had preexisting hyperthyroidism while 25 patients had normal thyroid functions.Our results showed that initial PTA average at 500Hz was statistically significantly positively correlated with free T3, and at 1kHz, 2kHz, 4kHz, and 8kHz was statistically significantly positively correlated with both free T3 and free T4.Wave V latency was statistically significantly negatively correlated with free T4.
Our results were supported by study of Heo et al. in 2019 as they revealed that wave V latency was negatively associated with serum T3 levels.The waves III-V intervals and the waves I-V intervals were negatively associated with serum T3 levels. [3]andrasekhar in 2011, reported delay of absolute latency of wave III and wave V in hypothyroid patients compared to wave III and wave V of control group. [10]Whereas Anjana in 2006, showed that the latency of wave III was prolonged from in control to in hypothyroidism patients. [11]gardless of the outcome of the hearing test, our findings showed that T4 levels were inversely correlated with wave V latency in ABR testing.This outcome contrasts with other research that suggested the ABR might serve as a prognostic indication in ISSNHL patients. [9]This difference in the study's findings Thus, it is conceivable that the cochlea, central auditory pathway, and retrocochlear area could be impacted by decreased thyroid hormone levels. [12]is research has several restrictions.First off, patients with hearing thresholds above 90 dBnHL cannot undergo the ABR exam.
Second, the study's sample size was too small to conclusively identify a connection between thyroid hormone levels and the results of the ABR.
In conclusion, this study is the studied ABR in patients with ISSNHL and the role of thyroid hormones in adopting it as a prognostic factor.
The findings show that clinical caution should be exercised when adopting ABR testing without assessing thyroid hormone levels.
Further evaluation is needed to confirm the relationship between initial ABR results in patients with ISSNHL and levels of thyroid hormones before we adopt the ABR results as a prognostic factor in ISSNHL patients.

Conclusion:
Auditory brainstem response is an important prognostic factor in ISSNHL but caution should be considered when adopting ABR testing without assessing thyroid hormone levels.

3. 3 .
Statistical analysisThe data collected were tabulated and analyzed by SPSS (statistical package for social science) version 25 (Armonk, NY: IBM Corp).The data was tested for normality using Kolmogorov-Smirnov test, Shapiro-Wilk tests then two types of statistics were done: Descriptive statistics: According to the type of data qualitative ,data was represented as frequency and percentage, quantitative data was represented by mean ± SD.Analytical statistics:Independent sample t-test was used for comparison between two groups ANOVA (f) test: is a test of significance used for comparison between three or more groups having quantitative variables.Person's rank correlation coefficient: used to study correlation between two variables having normally distributed data.P-value of < 0.05 was considered statistically significant & <0.001 for high significant results for two tailed tests.
suggests that using ABR testing without first determining thyroid hormone levels should be done with caution.It is still unclear exactly how thyroid hormone levels affect pathophysiology.Segmental demyelination of Schwann cells is thought to be influenced by hormone imbalance, according to one pathophysiological theory for the dysfunction of the nerves in hypothyroidism.Additionally, according to other researchers, low thyroid hormone levels impair microcirculation, which in turn affects the metabolism and oxygenation of cells as well as the creation of energy in cells.The central auditory pathway is known to be regulated by https://ejmr.journals.ekb.eg/thyroid hormones in terms of protein synthesis and myelin formation.T4 also functions in the central nervous system as a neurotransmitter.
Comparison of Initial PTA average, SDS%, and ABR metrics of the affected ears in all patients with ISSNHL before and after treatment * https://ejmr.journals.ekb.eg/Table (3): Comparison between ABR parameters as regards hearing recovery outcomes in ISSNHL patients after treatment.