I'm sure you've heard of a cochlear implant, which are some of the most advanced hearing devices available today. They are typically useful for people with severe or profound hearing loss. But can a cochlear implant cure tinnitus? Read on to find out more.
Tinnitus is defined as a ringing, hissing or buzzing sound without the presence of any external noise source. It is incredibly common, affecting 1 in 8 people. Although we have a good understanding of what causes tinnitus, many of the potential treatments are still in the exploratory phases.
Hearing loss and tinnitus
It is well known that tinnitus and hearing loss are closely linked, with around 80% of people with hearing loss having tinnitus. So it is unsurprising that many people have tinnitus by the time their hearing is bad enough to require a cochlear implant.
What are cochlear implants?
A cochlear implant is an electronic device that is surgically implanted to allow some hearing in patients with significant hearing problems.
It can be thought of as having several parts, broadly divided into:
- internal parts - buried under the skin and/or in bone
- external parts - worn outside the skin and attach via magnets
How do cochlear implants work?
The way the sound impulse travels is different to the way that sound is naturally transmitted through the hearing system.
- A sound wave is directed towards the ear canal by the pinna (the soft external part of the ear)
- This bounces down the ear canal and vibrates the ear drum
- The vibration passes through the three tiny bones of hearing (the malleus, incus and stapes; or hammer, anvil and stirrup as they are sometimes called)
- The third bone compresses the fluid within the cochlea, allowing the transmission of sound into the inner ear.
- Within the cochlea, this vibration is converted to electrical impulses that are transmitted up to the brain.
With a Cochlear Implant
- The external parts consist of microphones and a sound processor, which filters and processes sounds received
- A transmitter then sends the signal to the internal parts
- The internal parts are a receiver/stimulator that converts the signal from the sound processor into electric impulses
- These impulses are then transmitted via an electrode array into the inner ear (cochlea)
- The the auditory nerve is directly stimulated and the signal is passed to the brain.
The results of direct electrical stimulation from a cochlear implant are not as good as a well-functioning biological ear, but may improve people's hearing significantly, for example allowing patients to use a telephone, or to hear their children call from upstairs.
Can a cochlear implant cure tinnitus?
The short answer is no, a cochlear implant is not a 'cure' for tinnitus. However, since the 1970s research studies have shown that cochlear implantation can reduce tinnitus significantly in some with hearing loss, though not in everyone.
A recent study showed that the improvement in quality of life for patients receiving cochlear implants was greater for those with severe tinnitus than those without. It isn’t clear whether this is because of the extra listening effort for people with tinnitus to concentrate on what other people are saying, or because of the reduction in tinnitus severity following implantation, or a combination of factors.
Improvement of around 20 points on the EuroQol 5D (EQ-5D) shows a huge improvement in quality of life and an improvement of 51.4 points on the Nijmegen Cochlear Implant Questionnaire (NCIQ) for tinnitus.
But can cochlear implants help tinnitus?
A recent systematic review screened more than 4,000 research papers to find 7 studies describing cochlear implantation for tinnitus. A systematic review is a detailed and reproducible way to find scientific studies. These studies reported on more than 100 patients, and whilst the studies were not perfectly designed or carried out, the overall results suggest that cochlear implantation has a positive effect on tinnitus distress, with statistically significant differences shown in every study.
This study reported results of 53 adult cochlear implant recipients and showed that whilst the implant was on tinnitus was completely suppressed in 23 patients (43% of the total) and improved in 20 patients (38%), suggesting that in total more than 80% of patients with tinnitus reported some or total suppression of their tinnitus.
Why aren't cochlear implants more widely used?
We know that only around one in ten people that would benefit from a cochlear implant are currently referred for one.
This may be because patients think that nothing can be done for them and don’t come forward, or because their suitability for cochlear implantation is not recognised by their Audiologist or ENT surgeon, or there are significant financial constraints. There are also people that have some useful hearing and they do not want to risk losing it by having an implant, as it can cause the loss of some residual hearing.
There are ongoing efforts to improve implantation for these groups, including using “soft surgery” techniques, medicines, such as steroids to reduce inflammation within the ear and devices that offer electroacoustic stimulation (EAS). This is a combination of direct electrical stimulation as with a standard cochlear implant and some acoustic stimulation in a similar way to a conventional hearing aid.
What does the future hold?
Scientific and clinical interest in cochlear implants remains high with otologists (ENT surgeons that specialist in disorders and surgery of the ear) often reporting that cochlear implantation is one of the most rewarding operations they perform.
Scientific studies have been designed with electrodes that slowly discharge medication, known as drug eluting electrodes, into the cochlea and these mechanisms may allow a route for some of the many novel treatments currently in development to get into the inner ear.
However, as with all things tinnitus, the complex interrelationship between the ear and the brain means that we’ll just have to wait and see what the extent of the effect will be on tinnitus.
You can keep up to date with the latest tinnitus research in our articles section.