Cochlear implants in the etiopathogenesis of glioblastoma--an interesting observation or independent finding?

Occurrence of primary brain tumors in cochlear implant patients in Sweden between 1989 and 2014

PURPOSE

Cochlear implants are widely used for hearing rehabilitation of deaf children with congenital deafness or adults with acquired severe-to-profound hearing loss. The sound processor antenna creates a radio frequency-electromagnetic field transmitting the sound signal to the implant, similar to that in a mobile phone. A recent case report suggested a relationship between cochlear implants and malignant glioma, and some epidemiological studies have suggested an increased glioma and acoustic neuroma risk associated with long hours of mobile phone use. An epidemiological study is warranted to evaluate such a relationship in patients with cochlear implants.

PATIENTS AND METHODS

To examine whether this chronic radio frequency-electromagnetic field signaling is associated with an increased brain tumor risk, a population-based cohort study was performed examining all 2,748 patients receiving a cochlear implant in Sweden during the years 1989-2014. In all, 3,169 surgeries were performed in the total cohort. The expected occurrence of glioma, meningioma, and acoustic neuroma in the patient cohort was calculated using specific national incidence rates in the Swedish population.

RESULTS

Four patients were diagnosed with a brain tumor during follow-up, three of them having meningioma compared with 0.95 expected (standardized incidence ratio =3.16, 95% CI 0.65-9.24), and one had glioma compared with 1.34 expected (standardized incidence ratio =0.75, 95% CI 0.02-4.15). No case of acoustic neuroma was observed compared with 0.09 expected.

CONCLUSION

In this study, we did not find support for concerns raised in a previous case report regarding a potentially higher risk of glioma. The number of brain tumors observed was well within the numbers expected from national incidence figures. Although this was a relatively small cohort with a limited follow-up time, it is the largest epidemiological study to date to address this concern.

Deep brain stimulation and development of a high-grade glioma: incidental or causal association?

We report the case of a patient in whom 8.8 years following the implantation of a bilateral deep brain stimulation (DBS) into the Vim, a high-grade glioma was diagnosed in close proximity to the two electrode leads. A possible relationship between the permanent DBS and the development of the brain tumour is discussed.