Objective: To evaluate the electrophysiological characteristics of electrically evoked auditory brainstem responses (EABR) and its application in cochlear implantation, especially in evaluating acoustic nerve survival.
Method: An auditory evoked potential instrument was used to record responses and Cochlear Nucleus 24CA implants were used to generate electrical stimulation. We measured EABR in 23 patients with cochlear implants and compared EABR with behavioral measures and neural response telemetry (NRT).
Result: EABR III-V waveforms were recognized in all of the 23 patients. The characteristics and origins of EABR waveforms were similar to those of ABR. The average EABR threshold was (172.61 +/- 14.61) CL. At 20 CL above threshold, the average latencies of Wave III, V were (2.93 +/- 0.18)ms, (4.80 +/- 0.28)ms which were 1-2 ms shorter than ABR latencies. But III-V intervals remained at (1.86 +/- 0.18)ms. EABR thresholds were strongly correlated with behavioral performance and NRT thresholds, while EABR input-output function is correlated with behavioral dynamic range (DR).
Conclusion: EABR is such an effective method to objectively evaluate the function of auditory pathway which can estimate residual spiral ganglion cell count. This is consistent with the foreign study leading to the conclusion that DR reflects spiral ganglion cell survival.