Brainstem auditory evoked responses in children living at high altitude in the andes mountains.

Objectives: This neurophysiological study compared brainstem auditory evoked responses (BAER) in children living at high elevations (2800 to 3000 meters) in the Andes Mountains of Ecuador with a reference group of children living at sea level in the U.S.

Methods: BAER absolute latencies of waves I through V; interpeak latencies I-III, III-V, and I-V; amplitudes of waves I and V; and the V/I amplitude ratio were measured by scalp electrodes at acoustic click stimulus rates of 10 and 50 pulses per second (pps).

Results: Statistical analysis showed that the high-altitude group had significantly longer absolute and interpeak BAER latencies than the sea-level reference group at both the 10 and 50 pps stimulus rates for most wave peaks. The amplitudes of waves I and V were significantly reduced for the high-altitude group at 10 and 50 pps, suggesting blood O2 saturation effects.

Conclusions: The BAER of children in the high-altitude group suggested physiological anomalies in auditory neural conduction and summation compared with the sea-level group. The results further suggest that small physiological effects of altitude on BAER, especially at elevations near 3000 meters and higher, should be taken into consideration in the evaluation of brainstem auditory function.