Objective: To establish the objective, noninvasive recording of the electrically evoked amplitude modulation following response (EAMFR) for the assessment of auditory nerve function in cochlear implant candidates.
Study design: Prospective clinical study from 2007 to 2010.
Setting: Cochlear Implant Programme at the Charité-Universitätsmedizin Berlin (Germany).
Patients: Thirty-eight patients with severe-to-total bilateral sensorineural hearing impairment.
Intervention: Diagnostic.
Main outcome measures: The EAMFR thresholds were correlated with the mean thresholds of the intraoperative electrically evoked compound action potential (ECAP) derived by auditory nerve response telemetry and with the subjective electrical stimulation test. The intraindividual left-right similarity of the EAMFR and ECAP thresholds was investigated in 9 bilaterally implanted patients. Additionally, the correlation between auditory performance and EAMFR thresholds was investigated.
Results: The EAMFR auditory nerve function test produced clear responses in all patients. The EAMFR thresholds correlated significantly with the mean ECAP thresholds (r = 0.58, p < 0.01) and the subjective electrical stimulation test (r = 0.32, p < 0.05). In the bilaterally implanted patients, there was either no side difference, or the ear with the lower preoperative EAMFR threshold also was the one with the lower intraoperative mean ECAP threshold. No correlation was found between EAMFR thresholds and postoperative speech recognition scores.
Conclusion: These novel results support the notion that the EAMFR auditory nerve function test is a useful objective and noninvasive tool to provide information about the responsiveness of the auditory nerve to electrical stimulation in cochlear implant candidates.