The Difference between Hearing Aids and Cochlear Implants

I’ve seen many references on various blogs/comments that say that hearing aids are non-invasive, so they are a better choice than the cochlear implant. The implication is that the cochlear implant works the same as hearing aids. That is like comparing camels and horses. You can ride both of them. But horses work better on solid ground, and camels work better on sandy ground. They each have different strengths and weaknesses.

Hearing aids work by amplifying sound. The idea is that the few working hair cells in the cochlea will then work harder, and send more sound signals to the auditory nerve. Hearing aids work best if the hair cells in the cochlea are evenly distributed. Newer digital hearing aids work better, because they can separate out different frequencies, and add more or less amplification at a given pitch range, depending on what the audiogram shows. The problem occurs when there are simply not enough hair cells in the cochlea in a given frequency for the amplified sound to work. If there are no hair cells, there is no sound sent to the auditory nerve, no matter how much amplification occurs.

This is where the cochlear implant comes in. Hearing aid trials are required before the implant can even be considered as an option. If you receive adequate amplification across the frequency range then you are not a candidate for the implant. You are only a candidate for implantation if hearing aids do not support reasonable hearing across the speech “banana” on an audiogram. The implant works by turning sound into digital signals, transferring them via radio type signals to the internal implant, which in turn transmits them directly to the auditory nerve via a transmitter electrode array implanted into the cochlea. This allows for the full spectrum of frequencies to reach the auditory nerve. As long as the entire electrode array is inserted into the cochlea, and the auditory nerve is healthy, sound IS getting to the brain. The key is how the brain handles the signals. If the brain is able to fully integrate the sound signals to understandable information, then the implant is considered a “success”. If the brain is unable to interpret the signals then the implant is considered a “failure”. But the truth is much more complicated than that. Partly it depends on what the implanted person expects to get from the implant. Part of it depends on how hard the person is willing to work to make their brain learn how to understand the implant. Part of it depends on how much sound the person was exposed to prior to implantation, and how well their brain understood that sound. And part of it depends on how old you are at the time of implantation.

The people who seem to do best at making sense of the implant signals are those who had the most hearing prior to becoming deaf, and those who have had the shortest period of deafness prior to getting implanted. Among that group are babies and toddlers. Even though they may not have had any hearing prior to implantation, their brains are so flexible (plastic) that they have no problem interpreting the signals. The older they get, the harder they have to work to make sense of sound.

If you have a mild to moderate loss, hearing aids are the answer. If you have a severe to profound loss, and hearing aids are not enough, then that is where implants can be considered.

K.L.