Cochlear Implants in Auditory Neuropathy Spectrum Disorder: Role of Electrically Evoked Auditory Brainstem Responses and Serial Neural Response Telemetry

Objective To evaluate the utility of neural response telemetry (NRT) and electrically evoked auditory brainstem response (EABR) in patients with auditory neuropathy spectrum disorder (ANSD)

Methods Four patients with ANSD who underwent cochlear implantation and usage for more than 1 year were studied. All the four patients underwent preoperative transtympanic EABR (TT-EABR), intraoperative neural response telemetry (NRT), postoperative NRT at 3 months, 6 months, and 1-year intervals after switch-on and outpatient CI (cochlear implant) EABR testing at 1-year post switch-on.

Results and Discussion The authors propose a new practical classification of understanding the neural responses in relation to TT-EABR wave-form morphology and latencies. NRT and/or EABR measurements showed improvements in all the four patients. Three out of the four patients had NRTs on three or more electrodes and all the four patients had EABRs at 1 year of implant use. In addition, it was apparent that the children with better wave-form morphology on TTEABR preoperatively had better category of auditory performance (CAP) and speech intelligibility ratings (SIRs) scores at 1 year of implant use.

Conclusions Improvements in EABR and NRT over time with CI use indicates that electrical stimulation is a favorable scheme of auditory stimulation in ANSD patients. This also provides an objective way to monitor changes/progress in the auditory pathways after cochlear implantation.