Cochlear Implants Associated With New Bone Formation, Residual Hearing Loss

By Linda Carroll

December 09, 2021

NEW YORK (Reuters Health) - Scans using ultra-high-spatial-resolution CT within a year of cochlear implantation show new bone formation in many patients, according to a new study.

Among 123 patients, 68% had new bone formation near one or more electrode contacts and 17% had new bone formation around all contacts. The new tissue was associated with a negative effect on long-term residual hearing loss (22.9 dB vs. 8.6 dB in those with no new bone formation, P=0.04), researchers report in Radiology.

"The investigation of new tissue formation around cochlear implants was until now reserved to postmortem studies," said Dr. Floris Heutink of Radboud University Medical Center in Nijmegen, the Netherlands. "We identified new bone formation during life with medical-imaging techniques. In our study this finding was related to loss of long-term residual hearing."

The new findings should not worry patients, Dr. Heutink told Reuters Health by email.

"Cochlear implantation tremendously improves speech perception in most implantees, despite the potential presence of new bone formation," Dr. Heutink said. "The findings in this study should be seen as a possible new opportunity to further improve clinical care of (cochlear implants). More research is needed to understand the clinical influence of (new bone formation) and whether preventing (it) could form a next step to further improve the hearing results with (cochlear implants) for the patient."

To take a closer look at whether cochlear implants might spark new bone formation, Dr. Heutink and his colleagues conducted a single center cross-sectional study between 2016 and 2018 and recruited 129 patients who had postlingual onset of hearing loss, defined as onset of severe-to-profound hearing loss after age 5, and cochlear implantation between 2010 and 2016.

The researchers excluded patients with a prelingual onset of hearing loss, cognitive dysfunction, anomalies of the cochleovestibular system at preoperative imaging or less than 12 months of experience with their cochlear implant. Six participants were dropped from the study because the image quality was too poor.

The analysis was based on data from 123 participants (mean age, 63) who received unilateral cochlear implants at the Radboudumc Cochlear Implant Center in Nijmegen.

To look at whether the new bone formation might have had an impact on clinical parameters, the researchers divided the patients into two groups: 83 in the group that showed new bone formation and 40 in the group with no new bone formation.

Patients with a pure-tone average over three frequencies (PTA3) higher than 90 dB at first fitting were excluded from the analysis of residual hearing loss as the researchers did not consider them to have functional residual hearing, which left 24 in that group. The PTA3 difference in the cochlear-implant ear was significantly larger in the group with new bone formation than the group without new bone formation.

The novelty of the new study is that it documents new bone growth, said Dr. Maura Cosetti, director of the Ear Institute of New York Eye and Ear Infirmary of Mount Sinai and the Cochlear Implant Program at the Mount Sinai Health System. "I think we all thought there was some," Dr. Cosetti said.

"The study suggests this is more common in individuals who do not have preserved hearing," Dr. Cosetti said.

And that highlights one of the limitations of the study, she added. "The number of people with preserved hearing is small," she added. "We're always trying to do research on how to preserve hearing in that ear. It's not clear what the significance is of the bone growth. It's possible that it somehow has an effect on preserved hearing. But I don't think the study is powered enough to prove that."

"The study does document something we all believe in a scientifically sound way and a very clearly written way," Dr. Cossetti said. "It doesn't suggest that we are going to start doing CT scans after a cochlear implantation."

SOURCE: Radiology, online December 7, 2021.