Radiologic Evidence of Cochlear Implant Bone Bed Formation Following the Subperiosteal Temporal Pocket Technique.

Objective: To compare the thicknesses of bone beneath the internal receiver stimulator (IRS) with the symmetric contralateral unimplanted side in postoperative temporal high-resolution computed tomography (CT) and/or cranial CT of the patients for whom cochlear implants were secured by the subperiosteal temporal pocket technique.

Study Design: Case series with chart review.

Setting: Tertiary care hospital, cochlear implant referral center.

Subjects: Cochlear-implanted pediatric patients with postoperative temporal high-resolution CT and/or cranial CT were reviewed. The study group included 10 patients with Clarion devices (Advanced Bionics, Valencia, California).

Methods: Thicknesses of bone were recorded independently by 2 radiologists in the standardized coordinates of proximal, middle, and distal segments of both the IRS bed and the contralateral unimplanted side in each patient. Bone thickness differences in the proximal, middle, and distal segments of IRS were investigated. Any correlation between bone thickness differences and patient age at implantation or duration of implantation was also investigated.

Results: Mean values of bone thicknesses obtained from the IRS side and contralateral unimplanted side were, respectively, as follows: 2.40 ± 0.80 mm and 4.17 ± 1.10 mm in the proximal segment (P = .0001); 1.48 ± 0.33 mm and 3.02 ± 0.85 mm in the middle segment (P = .0001); and 2.13 ± 0.41 mm and 3.40 ± 0.61 mm in the distal segment (P = .006). Significant positive correlation was found between patient age at implantation and decrement values in the distal segments (r = 0.681, P = .03).

Conclusion: The subperiosteally secured IRS eventually creates its own well on the skull vault. This new radiologic evidence shows that device migration risk decreases over time, and it supports the findings of other clinical series showing device stability using the subperiosteal pocket technique.