Evaluation of cochlear implant users' performance using middle and late latency responses.

Aim of the study was to investigate whether postoperative middle and late latency responses (MLR and LLR) give some clues of postoperative performance of cochlear implant (CI) users. The study was performed in ten prelingual and six postlingual-CI patients with the age ranging from 6 to 48 years (mean 19.7 +/- 15.7 years). The following criteria were sought for inclusion: (1) to have active 15 electrodes for a Nucleus implant and six electrodes for a Medel implant at least and (2) to be cooperative for the tests. Ten healthy subjects with no hearing and balance problem were also included into the study as a control group. All implanted patients had auditory perception and linguistic development tests pre- and postoperatively, MLR and LLR testing postoperatively. Latencies and amplitudes of MLR and LLR were measured. Patients were divided into groups based on the onset of hearing loss (pre- and postlingual), auditory performance (good and moderate), and also duration of postimplantation period. Latency and amplitude of potentials were compared among the pre- and postlingual-CI patients and the control group. The same parameters were compared among the patients with good and moderate auditory performance scores and the control group. Finally, the parameters were analyzed in patients implanted within last 12 months and those implanted earlier. Latency of MLR and LLR was found to be shorter in postlingually deaf implantees compared to prelingually deaf implantees. Amplitudes of MLR and LLR tended to be higher in postlingually deaf implantees compared to prelingually deaf implantees. The better postoperative performance was associated with shorter latency and higher amplitude of MLR and LLR. MLR and LLR latencies were very close to each other in patients implanted within last 12 months and those implanted earlier. MLR and LLR amplitudes were higher in patients implanted earlier than 13 months. However, mentioned comparisons failed to yield statistical strength. Based on these results, it would be reasonable to conclude that postoperative MLR and LLR might give some clues about postoperative performance of CI users.