Audiological Evaluation using Brainstem Evoked Response Audiometry in Hypothyroid Females Attending a Tertiary Care Hospital – A Control Study

Abstract

Background: Hypothyroidism is a multi organ endocrine disorder also results in retro cochlear sensor neural hearing loss. Neuromuscular symptoms present in 30-80% of patients with hypothyroidism. BRAINSTEM EVOKED RESPONSE AUDIOMETRY (BERA) has expanded the possibility of objective testing of conduction in auditory pathway and hearing functions. Aim: To evaluate the audiological conduction i.e. electrical potential differences in auditory pathway recorded from the scalp in response to auditory stimuli as clicks. Objective: To use BERA as a tool to assess the hearing impairment of hypothyroid females. Materials and Methods: Study design was a cross sectional study. BERA recording was done in neurophysiology laboratory of Research wing, Department of Physiology, Stanley Medical College, using Polyrite Medicaid- Neuroperfect Plus. 30 hypothyroid females diagnosed from endocrine OPD and 30 normal healthy females were selected from Master Health Check Up. The left and right ears were tested separately in all subjects. Absolute Wave latencies I, II, III, IV and V, interpeak latency I-III, III-V and I-V and amplitudes of waves were measured. Statistical analysis was done by Student unpaired t test using SPSS software 11 version. There was significant prolongation of the inter peak latency of I-V in the study group compared to the control group and there was significant prolongation in the absolute latencies of the waveforms III and V which indicates thyroid hormone effects myelination of nerves. Hence hypothyroidism has leaded to demyelination caused by mitochondrial oxidative defects, decreased degradation of proteins. Conclusion: To conclude electrophysiological studies can be useful in the diagnosis of asymptomatic polyneuropathy in hypothyroid subjects. BERA can be a tool used to detect the neurological involvement earlier even before the subjects present clinically with complications of hypothyroidism. The other laboratory methods are highly improbable in diagnosing earlier involvement of nerves and muscles.