Comparative Study of Two Different Perimodiolar Electrode Array Cochlear Implants. Surgical and Audiological Outcomes

Objective: To compare the surgical technique and audiological outcomes of two different perimodiolar electrode array cochlear implants: Nucleus Contour Advance® (CA) and Nucleus 532® (N532).

Design: A total of 79 patients with a history of congenital or acquired hearing loss received a Nucleus cochlear implant, 39 of which received a Contour Advance (CA) electrode and 40 a N532 electrode. Audiological studies were registered before and 3, 6 and 12 months after the surgery. We also documented mean impedances and mean T and C levels.

Results: The type of cochleostomy with the N532 was through a round window (67.5%), while with CA a promontory cochleostomy (92.3%). PTA values before and 12 months after surgery were 90 dB (SD:10.7) and 119 (7.9) respectively for CA group and 98.2 (7.6) and 89.7 (5.6) for N532 group, with a significant statistical difference between groups (p = 0.040). On mean disyllabic words recognition, there were not statistical differences (p = 0.849) between both groups after 12 months follow-up [70.31% (4.36) for CA group and 69% (5.2) for N532 group]. Mean impedances decreased from 10.38 (0.33) to 6.66 (0.31) for CA group and from 14.01 (0.14) to 8.33 (0.53) for N532 group throughout the 12 months; difference between groups was statistically significant (p = 0.006). TC level range during the study period was from 22.29 (2.1) to 30.38 (2.07) for CA group and from 31.20 (1.80) to 38.12 (2.3) for N532 group, significantly lower difference was found between groups during all the study period (p = 0.012).

Conclusion: CI model influenced the surgical procedure (cochleostomy). Significant better hearing preservation levels, faster disyllabic words improvement, higher impedances and lower T and C levels are observed with N532 compared to CI CA.