Active inhibition of the first over the second ear implanted sequentially

To identify the influence of the first implanted ear on the performance of the delayed sequentially implanted ear in pediatric patients.

Retrospective case series review.

Outpatient Cochlear Implant (CI) center.

Congenitally deaf children who underwent unilateral implant at various ages followed by sequential implant of the contralateral ear with various delays were enrolled in the study. Children were divided into two groups based on the retention of the first implant or its removal, creating a sequential unilateral user group (USG) and a sequential bilateral user group (BSG). Both groups reflect differing durations of auditory deprivation in each ear, being relatively longer for the USG group for each ear than for the BSG group.

Rehabilitative.

All patients underwent periodic speech recognition testing for two years after the second surgery. The results for each implanted ear in both groups were evaluated and an index score representing the Difference Between the Ears, (DBE), was calculated.

A statistically significant difference results was obtained between the groups. Both groups reached interaural equivalence (i.e. DBE=0%), after two years post-sequential implant. The USG patients achieved interaural equivalence at a faster rate than the BSG patients with 85% USG subjects demonstrating it at 6months compared to the majority of BSG patients demonstrating equivalence at one-year post-sequential implant.

The performance of the sequentially implanted ear depends to an extent on a negative influence, which could be considered as a type of inhibition, of the first implanted ear over the second ear. It appears that the role of the unilateral auditory deprivation is not the primary influencing factor. These findings have driven us clinically to redefine some important considerations for rehabilitation management of the deaf children in the cases of delayed sequential implant.