Brainstem auditory evoked potential in clinical hypothyroidism

Is auditory brainstem response a prognostic factor in patients with sudden sensorineural hearing loss?

Background: Serum thyroid hormone levels are closely related to the normal functioning of the cochlea. However, the relationship between initial auditory brainstem response (ABR) results and levels of thyroid hormone remained unclear until we adopted ABR as a prognostic factor in Idiopathic sudden sensorineural hearing loss (ISSNHL) patients. Objective: This investigation aimed to elucidate the association between ABR and outcomes in patients with ISSNHL. Material and methods: Thirty-three patients presenting with unilateral ISSNHL underwent blood sampling and ABR tests on the day of admission. The mean latencies of the ABR results were compared among the groups which were classified by ISSNHL outcome, based on Siegel's criteria. The association between the ABR results and the thyroid hormone serum levels (TSH, T3, and free T4) were assessed. Results: The overall successful recovery rate was 60.6% (n = 20). The mean latencies of all the ABR parameters were not significantly different between the different treatment outcome groups (Mann-Whitney U test). Wave V latency, III-V interval and I-V interval were negatively associated with T3 serum levels. Conclusion: The results indicate that clinical caution should be exercised when conducting ABR tests without assessing thyroid hormone levels.

Evaluation of the Female Patients with Subclinical Hypothyroidism by Brainstem Auditory Evoked Potentials: Case-Control Study

INTRODUCTION

Hypothyroidism, a common endocrinological disorder is quite prevalent in its subclinical state in the adult population. Nervous system involvement is frequent in hypothyroidism with documentation of peripheral and central conduction delays as abnormal latency prolongations in Brainstem Auditory Evoked Potential (BAEP) records. Subclinical hypothyroidism however, has been less extensively studied for investigating the involvement of the auditory functions.

AIM

To assess the auditory functions and Central Nervous System (CNS) involvement in the patients with subclinical hypothyroidism by recording BAEP.

MATERIALS AND METHODS

The study comprised of 50 females (25 females with subclinical hypothyroidism and 25 age-matched healthy females) in the age-group of 30-50 years. BAEP absolute and Interpeak Latencies (IPLs) (I, III and V, I-III, III-V and I-V) were compared between the two groups by unpaired t-test. The p<0.05 was considered as statistically significant.

RESULTS

Mean BAEP absolute latencies (III and V) increased in the subjects with subclinical hypothyroidism as compared to controls (p<0.001) (both the ears) and wave I absolute latency also increased with p<0.001 (both the ears) by unpaired t-test. Among IPLs (interpeak latencies), III-V and I-V IPLs exhibited increase (p<0.01), while I-III IPL did not vary with statistical significance (both the ears) in the two groups.

CONCLUSION

Patients with subclinical hypothyroidism were found to demonstrate central as well as peripheral auditory pathway affections. BAEPs can prove valuable and sensitive tests to detect involvement of the CNS and auditory dysfunctions earlier in hypothyroidism.