Hearing Preservation After Complete Cochlear Coverage in Cochlear Implantation With the Free-Fitting FLEXSOFT Electrode Carrier

Abstract

To demonstrate the possibility of atraumatic insertion with the free-fitting FLEX electrode by evaluating the degree of hearing preservation postoperatively. Retrospective study. Academic tertiary care center. Twenty-two severely to profoundly hearing impaired subjects with measurable residual hearing preoperatively. Atraumatic implantation with the 31.5-mm-long, free-fitting, and highly flexible FLEX electrode using either the round window approach or a cochleostomy technique. Subjects were tested preoperatively in unaided condition and at varying intervals postoperatively. Preoperative and postoperative low-frequency pure-tone average (PTA) and PTA shifts were calculated. Speech perception was measured preoperatively and postoperatively using the Freiburger monosyllabic word test in quiet. Preoperative low-frequency hearing could be preserved to a certain degree in 77.3% of subjects (17/22) after insertion of the FLEX electrode up to the point of first resistance. Complete loss of residual hearing was observed in 22.7% of subjects (5/22). In 18.2% of the subjects (4/22), the preoperative PTA was preserved within 10 dB. Pure-tone average results between preoperative and most recent testing showed statistically significant differences (p < 0.001 to p = 0.031) for almost all loudness levels ranging from 125 Hz to 1.5 kHz. The maximum threshold shift was 40 dB at 250 Hz for the lower frequencies up to 1 kHz. Monosyllable testing in quiet demonstrated significant improvement over time (p < 0.001). This study showed that preservation of residual hearing is possible in a high number of subjects when a flexible electrode and atraumatic surgical techniques are used.