Acoustic stapedius muscle reflex in mercury-exposed Andean children and adults

Conclusion: The results suggested mercury (Hg)-induced anomalies in the brainstem-mediated acoustic stapedius muscle reflex in children. Objectives: Hg exposure has been associated with hearing impairment and brainstem anomalies. Acoustic stapedius reflex (ASR) thresholds, growth functions, decay/adaptation times, and behavioral auditory thresholds were used to screen Andean children and adults for Hg-induced auditory brainstem and facial nerve impairment. Methods: Fifty-one participants, which included 22 children (aged 617 years) and 29 adults (aged 1983 years) living in gold mining areas of Ecuador where Hg is widely used in amalgamation, were screened using ASR immittance procedures. Results: Mean blood mercury (HgB) level in the children was 15.6 μg/L (SD, 21.3; median, 7 μg/L; range, 2.089 μg/L), and in the adults 8.5 μg/L (SD, 7.1; median, 6 μg/L; range, 2.032 μg/L). Mean contralateral ASR thresholds (ASRT) for the screening frequency of 2000 Hz in the children (39 ears) was 92.9 dB HL (SD, 6.1; range, 80-105 dB HL), and in the adults (53 ears) 90.0 dB HL (SD, 6.4; range, 65-105 dB HL). The ASRT in the children increased significantly with HgB level (rho = 0.433; p = 0.008).