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Hearing implants could actually damage hearing

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(Graphic via SWNS)

By Tom Campbell via SWNS

People who get cochlear implants are at risk of actually damaging their hearing, warns a new study.

In some cases new bone formation around the device undermines its ability to restore part of the patient's hearing, according to a new study.

Hearing, or cochlear implantation, is a well-established and increasingly popular way of treating severe hearing loss. It's estimated that around 6.6 million Americans have severe to profound hearing loss.

While the implants do not fully restore hearing, patients are able to recognize words and better understand speech, provided there are no complications.

Post-mortem examinations have found cochlear implants can cause inflammation, fibrosis and new bone formation.

But what impact the formation of new bones has on patients while they are still alive has remained a mystery, until now.

A new bone, usually at the base of the cochlea, began growing in 68 percent of patients within four years of them getting the implant. (SWNS)

Co-author Dr. Floris Heutink at the Radboud University Medical Center in the Netherlands said: "Such subtle changes are challenging to visualize in vivo, in particular in the vicinity of a metallic implant causing artifacts on computed tomography images.

"However, through the new availability of an ultra-high-resolution CT scanner, we were encouraged to investigate this.”

Cochlear implants have two parts, an external element that sits behind the ear and another which is surgically implanted under the skin.

This stimulates nerves in the cochlea, part of the inner ear responsible for transmitting sounds to the brain.

Ultra-high spatial resolution CT (UHRCT) scans were used to identify new bone formation in 123 patients with cochlear implants.

A new bone, usually at the base of the cochlea, began growing in 68 percent of patients within four years of them getting the implant.

Those with an extra bone experienced significantly more hearing loss in the long term, the researchers found.

New bone formation may also complicate re-implantation surgery (SWNS)

Co-author Dr. Berit Verbist said: "As indicated by our study, there is a correlation between new bone formation and long-term residual hearing loss."

The new bone had a negative impact on the device and structures surrounding it, the researchers also found.

It sometimes affected the spread of electrical current, making it harder for the implant to be fitted and for the patients to hear properly.

It could also complicate future medical procedures such as gene therapy to restore cochlear function.

Verbist said: "Last but not least, new bone formation may complicate re-implantation surgery."

Improvements in design and surgical techniques have made cochlear implantation increasingly popular for those with severe to profound hearing loss.

This increase in patients makes a method for detecting and monitoring new bone growth all the more urgent, the researchers say.

Heutink said: "Still, many remaining questions have to be answered before the detection of new bone formation in an individual patient would have therapeutic consequences.

"This technique will be a valuable tool to gain insight into occurrence, time course and the pathophysiology of this process and might be used to evaluate still-to-be-developed treatments against new bone formation."

The findings were published in the journal Radiology.

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