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 6-17 years) and 29 adults (aged 19-83 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, 2.0-89 μg/L), and in the adults 8.5 μg/L (SD, 7.1; median, 6 μg/L; range, 2.0-32 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).