Trans-impedance measurement is a novel methodology for assessing the positioning of a cochlear implant (CI). This study proposes an innovative use of trans-impedance measurements to characterize specific hearing pathologies by means of the trans-impedance matrix (TIM) quantitative analysis. Three indices are used: Shannon Entropy, the Exponential Decay constant and Spatial Correlation. These indices were computed on the TIMs of two groups of patients, clustered in terms of hearing pathology: (i) congenital hearing loss (CONG) and (ii) otosclerosis (OTO). The study aimed to demonstrate the sensitivity of the above synthetic indices in relation to the considered hearing pathologies. Furthermore, the first two indices were employed to explore the influence of the positioning of the electrode, either over (i) the basal or (ii) the apical regions, on the TIMs patterns. The results suggest that the indices were statistically different for the patient groups and the positioning impacted solely on OTO patients. In particular: (i) CONG patients displayed significantly higher Shannon Entropy (p = 0.0002) and (ii) a lower Exponential Decay constant than OTO patients (p = 0.001); (iii) the OTO patients exhibited a lower Shannon Entropy and a higher Exponential Decay constant over the basal regions than the apical regions (p < 0.008); (iv) Spatial Correlation demonstrated that TIMs had specific patterns according to the hearing pathology (p < 0.008).
Keywords: Apical and basal electrodes; Cochlear implant; Exponential Decay constant; Shannon Entropy; Spatial correlation; Trans-impedance matrix (TIM).
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