ELECTROPHYSIOLOGICAL CHANGES ON BRAINSTEM AUDITORY EVOKED POTENTIALS IN HYPOTHYROID PATIENTS

Brainstem Auditory Evoked Potential (BAEP) refers to an evoked potential generated by a brief click which is usually used to assess the integrity of both peripheral and central auditory pathway. The waveform peaks are labeled I-VII, occur within a 10-millisecond time period after a click stimulus presented at 70-90 dB. Deafness of sensory neural hearing loss is the most common otolaryngological manifestations associated with thyroid dysfunction. Brainstem auditory evoked potential (BAEP) is one of the methods used for assessing the effect of hypothyroidism on the auditory pathway in the brainstem. Studies done earlier reported that there is prolongation of both peripheral and central conduction time in hypothyroidism while few studies concluded that there was no statistically significant difference in BAEP and hypothyroid subjects suffering from hearing loss. The aim was to evaluate the auditory sensory process using BAEP (Brainstem Auditory Evoked Potential) in hypothyroidism and the effect of treatment of the same. Fifteen acquired hypothyroid patients, fifteen hypothyroid patients with treatment and fifteen controls with the age between 20-50 yrs were taken for the study. Biochemical and hematological investigations like thyroid profile (fT3, fT4, TSH) and lipid profile (HDL, LDL, VLDL, TGL and Total Cholesterol) followed by otological examination and Pure Tone Audiometry (PTA) were done. Finally they were subjected to standard and sensitive BAEP recording by placing three surface electrodes in scalp with masking wide band. The results revealed a prolongation in absolute latency of wave III and wave V of BAEP and prolongation of Inter peak latency (IPL) I-V in acquired hypothyroid patients without treatment and significant improvement in absolute latency and IPL of BAEP waves in hypothyroid patients with treatment. There was also a significant decrease in amplitude of wave I and V in hypothyroid patients without treatment and significant increase in amplitude of BAEP wave I and V in patients with treatment. The results of the present study conclude that in hypothyroid state there might be a slow conduction at the periphery and with treatment there is a better recruitment of neuronal pool of the generators of the waves of BAEP in brainstem.