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Assessment of auditory brainstem function in lead-exposed children using stapedius muscle reflexes
S A Counter1, Leo H Buchanan, Fernando Ortega
1Department of Neurology, Harvard Medical School/The Biological Laboratories, Cambridge, MA 02138, USA. allen_counter@harvard.edu
Journal of the Neurological Sciences
|May 7, 2011
Summary
Chronic lead exposure in children did not significantly impact auditory brainstem function, as measured by acoustic stapedius reflex (ASR) tests. Blood lead levels showed no correlation with ASR thresholds, amplitude growth, or decay in this study group.
Area of Science:
- Neuroscience
- Audiology
- Environmental Health
Background:
- Chronic lead (Pb) exposure in children is a significant public health concern, potentially affecting neurological development.
- The auditory brainstem plays a crucial role in processing sound and is susceptible to neurotoxic insults.
- Non-invasive audiological assessments are vital for evaluating the functional integrity of auditory pathways.
Purpose of the Study:
- To investigate the neurological integrity of auditory brainstem tracts and nuclei in children with chronic lead exposure.
- To assess the physiological status of afferent and efferent-neuromuscular auditory function using acoustic stapedius reflex (ASR) measurements.
- To determine the relationship between blood lead (PbB) levels and auditory brainstem responses.
Main Methods:
- Evaluated 117 Andean children (2-18 years) with chronic environmental Pb exposure from occupational Pb glazing.
- Conducted audiological examinations including acoustic stapedius reflex (ASR) testing with pure tone and broadband noise stimuli.
- Measured ASR threshold (ASRT), amplitude growth, and decay/fatigue using clinical middle ear immittance methods.
- Correlated blood lead (PbB) levels with ASR parameters using Spearman Rho analysis.
Main Results:
- Repeatable, normal ASR thresholds (ipsilateral ≤90 dB HL, contralateral ≤97 dB HL) were observed across all stimulus types.
- No significant association was found between PbB levels and ipsilateral or contralateral ASRT.
- ASR amplitude growth functions were typical, with no observed Pb-associated aberrations.
- No statistical association was found between ASR decay/adaptation (ASRD) and PbB level.
Conclusions:
- Chronic lead exposure, even at elevated PbB levels, did not demonstrate a significant relationship with the physiological integrity of auditory brainstem-mediated ASR responses in children.
- Non-invasive ASR measurements appear robust in assessing auditory brainstem function in pediatric populations with historical lead exposure.
- Further research may explore other auditory pathway components or different exposure scenarios to fully elucidate lead's neurotoxic effects on hearing.
