Long-term evolution of the electrical stimulation for cochlear implant adult patients. The role of a progressive adaptation method.

Background: In clinical experience patients who do not frequently check the cochlear implant (CI) maps have poor auditory performance and poor acceptance of map variations over time.Aims: The aim of the present study was to evaluate the effect of CI map optimization on both speech perception and subjective hearing in a group of CI patients with a long-standing map.Material and methods: 14 patients (6 females and 8 males; age range 16-77, mean age 45.86 ± 23.85 years) fitted with a unilateral CI (Cochlear Ltd, Sydney, Australia) and a map unchanged for at least 12 months were evaluated. All CIs were remapped using mapping method with progressive adaptation. The speech discrimination in noise and subjective hearing perception (SSQ questionnaire) were evaluated with old and new map.Results: The differences in electrode level with old and new map were significantly different both for T and C- Levels (p < .001). Speech discrimination in noise was significantly better (22.9%; p < .0001) after map optimization. The SSQ questionnaire showed no statistically significant difference in the overall scores, except the listening effort sub-scale.Conclusions: Longstanding MAPs are associated with poor speech discrimination. Degradation of electrical stimulation is associated with increased mental effort.

Evaluation of different cochlear implants in unilateral hearing patients during word listening tasks: A brain connectivity study.

Advanced methodologies used for the biomedical signal interpretation allow using cerebral signals to assess important cognitive functions in humans. In the present study, as parameter of cerebral effort, has been employed the isolated effective coherence, in order to estimate the effective connectivity and network organization. The hypothesis was that the lower the number of inter-connections engaged, the lower the cerebral effort induced by the experimental condition. In the present research this index has been applied to test the reaction to the use of different cochlear implant processors (Freedom, CP810 and CP910 - Cochlear Ltd), with the aim to identify the most performing device during a word in noise recognition task. Results support the capability of identifying the device eliciting less brain area connections. In particular, the CP910 was the processor inducing the lower number of inter-connections among the tested ones. This investigation appeared to be worthy, since representing a tool to identify devices that would make available user's cognitive resources for additional tasks, a matter susceptible of generalization to various fields of application. The employment of the cerebral signals therefore open the way to the evaluation of the impact of different sensors and prosthetic devices, also using connectivity measures.