DIGISONIC SP^® cochlear implants (CI) use variable time-pulse for sound coding between comfort and threshold levels. Accordingly, we previously described the impact of modulating phase duration on auditory brainstem responses at different site of the cochlea. In this study we aimed to investigate the relation between the etiology of deafness and electrically Evoked Auditory Brainstem Responses (eABR) recorded at the time of cochlear implantation.

Auditory brainstem responses evoked by a biphasic pulse train, at increasing phase duration (pulse width, T-pulse), were recorded in 188 subjects at the time of cochlear implantation. All patients were fitted with a NEURELEC CI device, initially DIGISONIC^® then DIGISONIC SP^® (2004–2006).

The mean age at implantation was 22.9 years, ranging from six months to 80 years. Clinical evaluation in that population allowed identification of a causative or precipitating pathology in 55 % (104/188). Eighty-eight patients (46.8 %) became deaf before the first year of life (Early onset deafness). In this group, the implantation age was 2.9±1.4 years. Forty-two subjects (22.3 %) were genetically predisposed; nineteen (10.1 %) GJB2-related deafness were identified (12 were homozygote carriers of the 35delG mutation). Stimulation by the CI resulted in reliable wave III and V eABR waveforms (waveV 4.28±0.42ms and 2.23±0.38ms for wave III (Mean±SD)) with latencies following an apical to basal gradient (0.32ms increase in mean eV latency and 0.12ms for eIII latency).

We report the result of eABR registered during cochlear implantation of Neurelec CIs using a single set of stimulating parameters. We describe our results with emphasis on early onset deafness and GJB2-related deafness.