Preoperative Imaging of Temporoparietal Scalp Thickness Predicts Off-the-Ear Sound Processor Retention in Cochlear Implants With Diametric Magnets

Abstract

Objective: To determine if temporoparietal scalp thickness assessed via preoperative imaging predicts retention events in patients who have cochlear implants with diametric magnets and various sound processor types. Study Design: Retrospective chart and radiological review. Setting: Tertiary referral center. Patients: One hundred forty-three adult patients who have cochlear implants with diametric magnets. Main Outcome Measures: Skin flap thickness, retention events, body mass index (BMI), and magnet strength. Results: Of 42 patients with the most recent generation offthe-ear sound processor (OTE2), 13 (31.0%) had retention events. Of patients with a temporoparietal scalp thickness less than 8 mm, all patients could ultimately retain the device, though one of 26 was noted to have tenuous retention. Of patients with 8 to 10 mm skin flaps, 3 of 6 (50%) could not retain the device, and with more than 10 mm skin flaps, 7 of 10 (70%) could not retain the device. In the more than 10 mm group, two additional patients could not either retain the device at initial activation or were noted to have tenuous retention. Of 124 patients with behind-the-ear (BTE) sound processors, only 2 (1.6%) could not retain the device at initial activation, and 3 (2.4%) exhibited tenuous retention after 3 months of device use. Results from the first generation off-the-ear sound processor (OTE1) are also reported. Conclusions: Temporoparietal scalp thickness measured by preoperative imaging is associated with processor retention for patients with the OTE2 sound processor and diametric magnets. All patients with less than 8 mm scalp thickness could retain the OTE2, while 50% of patients with 8 to 10 mm scalp thickness and 70% with more than 10 mm scalp thickness could not retain the device. Patients should be counseled regarding their sound processor choice and/or considered candidates for skin flap reduction or other intervention as indicated. Retention events with BTE processors are rare.

Predicting the Magnet Strength Using a Tablet-Based Tool for Patients Undergoing Cochlear Implantation

“…Yet, a strong positive correlation was observed between the skin flap thickness and the magnet strength. A similar finding was observed in Adkins et al [ 13 ] and Searle et al [ 5 ] using the Cochlear® CI devices. Nowadays, all CI manufacturers are offering the diametric magnet design in their implants, and the future study would focus on increasing the CI patient population implanted with diametric magnet design from all three major CI manufacturers.…”