Cochlear Implant Receiver-Stimulator Migration Using the Subperiosteal Pocket Technique: Objective Measurements of Early and Late Positioning.

Objective: Current clinical practice for fixation of the cochlear implant receiver-stimulator (RS) may not follow recommended manufacturer's guidelines. We investigated short- and long-term RS migration using a subperiosteal pocket technique via serial objective position measurements since previous literature provided only subjective or short-term evaluation.

Study Design: Retrospective review.

Setting: Tertiary referral center.

Patients: We reviewed all patients who underwent cochlear implantation by the senior author between 2012 and 2018. At least two comparison measurements were available for 73 implants in 62 patients, 72.6% adults and 27.4% children.

Interventions: RS placement using a subperiosteal pocket technique.

Main Outcome Measure: Distance between the pinna and RS magnet in the early (<6 mo) and late (>6 mo) postoperative period.

Results: In the early postoperative period, mean RS distance was 57.0 mm (SD 9.4 mm) from the pinna compared with baseline intraoperative distance of 55.8 mm (SD 8.4 mm), p = 0.44. With some shifts closer and some farther from the pinna, there was a 3.0 mm mean absolute value migration (median 2 mm, SD 3.8 mm, range 0-15 mm). Fourteen implants (25.9%) migrated >5 mm in the early period, 35.7% closer, and 64.3% farther from pinna. In the late postoperative period, mean RS final distance was 56.6 mm (SD 10.1 mm), compared with its baseline of 59.0 mm (SD 9.2 mm), p = 0.29. Seven implants (19.4%) demonstrated shifts >5 mm, with a mean 3.6 mm shift (median 2 mm, SD 4.5 mm, range 0-17 mm).

Conclusion: A subperiosteal pocket technique demonstrated objective RS migration in 20 to 25% of adult and pediatric patients, nearly all of which were not clinically apparent unless measured. Additionally, none of these patients experienced associated symptoms or device failures.