Abstract
Background: Widespread metabolic derangements in overt hypothyroidism have also been suggested to involve adult human brain with the involvement of cochlea and other inner ear structures. More interestingly, abnormal electrophysiological alterations in patients with normal hearing have also been documented.

Aims and Objectives: This study is an attempt to detect auditory pathway dysfunctions by brainstem auditory evoked potential (BAEP) tests in overt hypothyroidism patients without clinical evidence of hearing defects.

Materials and Methods: BAEP was performed in 25 female patients with overt hypothyroidism in the age-group of 30-50 years and 25 age-matched healthy females. BAEP absolute latencies I, II, III, IV and V, interpeak latencies (IPLs) I-III, III-V and I-V and BAEP amplitudes of wave I, wave V and amplitude ratios were compared and analyzed in the two groups by unpaired t-test. Statistical significance was considered at P < 0.05.

Results: BAEP responses revealed statistically significant prolongation of mean absolute latencies (I, III and V) as compared to controls (P < 0.05) (both the ears) by unpaired t-test. IPLs prolonged too with statistical significance for I-V IPL prolongation (P < 0.05). Furthermore, wave V amplitude was found to be reduced in overt hypothyroidism with statistical significance (P < 0.05).

Conclusion: BAEP documents abnormal alterations in patients with overt hypothyroidism with normal hearing with central as well as peripheral auditory pathway impairment. BAEP can be a useful objective tool to assess the patients for central nervous system involvement in overt hypothyroidism.

Key words: Brainstem Auditory Evoked Potentials; Absolute Latency; Interpeak Latency; Overt Hypothyroidism