Electric-acoustic stimulation device stabilises residual hearing: KL Krems study

August 14, 2020 0 By FM

Precision surgical implantation of electrodes for the electric-acoustic stimulation of the inner ear can stabilise the long-term residual hearing of severely hearing-impaired people and significantly improve their speech recognition, found researchers at  Karl Landsteiner University of Health Sciences in Krems (KL Krems).

The study involved carrying out 18 complex operations on patients, who received cochlear implants using a procedure that leaves the anatomy of the inner ear virtually unaltered. The treatment enabled some of the patients to retain their residual hearing, allowing for supplementary acoustic stimulation in addition to electrical stimulation.

Cochlear implants (CI) work by converting sound impulses into nerve signals. But not everyone who could benefit from a CI has total hearing loss. People with high-frequency hearing loss are not able to understand speech adequately with a hearing aid alone. The electric-acoustic stimulation (EAS), which boosts low frequencies purely by acoustic means, while relying on the more complex electrical stimulation of the hearing nerve for mid and high frequencies, demonstrated researchers at KL Krems.

“We are encouraged by the results of the study,” commented Prof Georg Mathias Sprinzl, head of St Pölten University Hospital’s Ear, Nose and Throat Department, KL Krems, in a statement.

“They show that it is possible to position cochlea implants in such a way that existing residual hearing can be preserved for years. This improves long-term hearing and significantly enhances speech recognition,” he added.

The study, published in the journal Otology & Neurotology, reported that the residual hearing of half of all the patients was still just as good two years after the operation. And for a further 30-40% residual hearing was partially preserved, where the deterioration was most likely due to age-related hearing loss. In one case, the patient maintained their residual hearing, at least partially, for almost five years.

Prof. Sprinzl’s team also measured significantly improved levels of speech recognition as a result of the hearing preservation in the low-frequency ranges. This was especially noticeable in comparison with CI patients with no residual hearing, who had, therefore, received an implant which relied purely on electrical stimulation.

In addition to the EAS implant, the surgical procedure and the skills of the operating surgeon when placing the special electrodes were also key to the success of the treatment. Inserting the implant without damaging the patient’s residual hearing requires excellent surgical abilities as well as experience, the researchers said.