The use of hearing aids or cochlear implants is suggested as a treatment option for people affected by varying degrees of hearing impairment. The following HealthHearty write-up provides information on how these work, and how to decide between a cochlear implant and a hearing aid.
According to the National Institute on Deafness and Other Communication Disorders (NIDCD), three out of every 1,000 children in the United States are born deaf or hard-of-hearing, and 47% of adults aged 75 and above are affected by hearing impairment.
Hearing aids are usually the first-line treatment for mild to moderate hearing impairment. It must be noted that the treatment option could vary, depending on the degree of hearing loss. Hearing loss could be partial or total. It could affect one or both ears. At times, the affected person may hear faint or muffled sounds, and may have difficulty understanding what others are saying. This occurs in case of conductive hearing loss wherein the outer or middle ear is affected.
Sensorineural hearing loss occurs due to damage to the inner ear or the nerve pathways from the inner ear to the brain. Though the quality of life of people affected by mild or moderate hearing loss could be improved with the help of hearing aids, cochlear implants might be recommended when the benefit from a hearing aid has been minimal. This HealthHearty article provides information on how these devices work.
Cochlear Implant Vs. Hearing Aid
To be able to decide between a cochlear implant and a hearing aid, and why one of these devices emerges a better option in certain cases, one needs to understand how these work. It must be noted that none of these devices have the ability to cure hearing loss.
Working of Cochlear Implants and Hearing Aids
The components of a hearing aid include a microphone, amplifier, and speaker.
➞ The microphone picks up the sound, converting the sound waves to electrical or digital signals.
➞ The signals are then sent to the amplifier.
➞ The sounds are then amplified and sent through the speaker to the ear.
Based on their placement, hearing aids are categorized into the in-the-ear (ITE), in-the-canal (ITC), behind-the-ear (BTE), and completely-in-canal (CIC) hearing aids. The technology for processing or amplifying sound is different in case of analog and digital hearing aids.
Digital hearing aids, which are becoming increasingly popular, convert sound waves into digital signals and make adjustments as per the user’s needs. The signals are then converted into sound, and sent to the ear through the speaker. The digital hearing aids are known to reduce the background noise.
A cochlear implant is a small electronic device that can be surgically implanted to facilitate hearing in people affected by severe to profound hearing loss. The external part of this device consists of a microphone, sound/speech processor, and a transmitter.
➞ The microphone picks up the sound signals from the environment, and sends them to the sound processor.
➞ The sound processor puts the sound signals into digital form, and sends them to the transmitter, which in turn sends the signals to the receiver/stimulator.
➞ The receiver converts the signals into electric impulses, sending the impulses to the group of electrodes placed in the inner ear, providing direct electrical stimulation to the auditory nerve, which sends a signal to the brain.
➞ The brain recognizes these signals as sound.
Degree of Hearing Loss
Though hearing loss could be present at birth, it could be acquired due to trauma, noise exposure, presbycusis (age-related hearing loss), Meniere’s disease, meningitis, the use of ototoxic drugs, etc. Hearing loss is measured in decibels (dBs). The following table gives the hearing loss range for varying degree of hearing loss.
|Hearing Loss Range
|Normal||10 – 15|
|Slight||16 – 25|
|Mild||26 – 40|
|Moderate||41 – 55|
|Moderately Severe||56 – 70|
|Severe||71 – 90|
|Profound||91 and above|
Deciding Between a Cochlear Implant and a Hearing Aid
Most speech sounds might be audible to people affected by normal hearing loss when it’s quiet, but people affected by mild hearing loss may miss words when background noise is present.
Hearing aids are often required for people affected by moderate hearing loss. People affected by mild or moderate hearing loss have difficulty in hearing soft sounds due to the damage to the outer hair cells in the cochlea. Hearing aids can amplify these sounds, and may prove useful. Here are the pros of using hearing aids.
➞ With the advancements in technology, it’s possible to sort out different frequencies, and provide amplification at a given pitch range, as per the degree of hearing loss.
➞ Hearing aids don’t have to be surgically implanted.
➞ They are easy to maintain, and the cost of repairs is less.
➞ The user also has the option of checking out different devices to find the one that works best.
➞ The device can be changed as and when newer and better technology is introduced.
However, hearing aids may not really work for people with severe to profound sensorineural hearing loss, wherein the hair cells in the cochlea are very less in number, damaged, or not evenly distributed. After all, the task of sending the signals to the auditory nerves is still performed by the working hair cells in the cochlea. The common problems associated with them include the acoustic feedback or buzzing sounds, issues with the ear-mold, and difficulty in hearing sounds in the high-frequency range.
Cochlear implants are recommended for people affected by severe to profound sensorineural hearing loss, but they are considered only after hearing aid trials have been performed. Sensorineural hearing loss is characterized by damage to the outer and inner hair cells in the cochlea. The inner hair cells sort and transmit various frequencies of sound, whereas the transmission of soft sounds is done by outer hair cells.
When these hair cells get damaged, differentiating sounds of different frequencies or pitch becomes difficult. The affected people may derive limited benefit from hearing aids because these devices will just amplify the sound, and the user might not be able to understand what the other person is saying due to distortion. Cochlear implants are looked upon as a better alternative as these bypass the damaged hair cells in the cochlea, directly stimulating the auditory nerve.
How helpful an implant will prove to be will vary, depending on certain factors.
➞ The duration and severity of hearing loss can certainly affect the outcome.
➞ It may take the user some time to adjust to hearing sounds. Mapping or adjustment of the speech processor also needs to be performed by trained audiologists.
➞ It’s been observed that younger patients do better than the aged people who have been affected by hearing loss for a long time.
➞ It may help the affected children hear conversations and other environmental sounds, thereby helping them learn the spoken language.
➞ It might even make telephonic conversations possible.
➞ The earlier the implant is used after the onset of hearing loss, the better it would be.
➞ The health of the cochlea, the user’s ability to learn and communicate, the duration of the use of implant, the depth at which the implant is inserted in the cochlea, the type of implanted electrode and signal processing method, etc., are some of the factors that affect the outcome.
Besides the risks associated with surgery, disadvantages include the loss of residual hearing, problems in the event of damage to the implant, the need to avoid contact with static-generating materials or electronic environment, the need to avoid activities that can cause impact near the ear, programming issues, etc.
On a concluding note, the viability of hearing aids or cochlear implants as treatment options would depend on the degree of hearing loss. Both of these come with a set of advantages and disadvantages. Though cochlear implants facilitate hearing at high frequencies, the ability to hear lower frequencies is determined by the insertion depth of the electrode array.
When it comes to the ability to hear at lower frequencies that are below 250 Hz, hearing aids are likely to work better than these implants. However, people affected by severe to profound hearing loss are more likely to benefit from the use of implants. Due to this reason, people affected by profound hearing loss in both ears are encouraged to use an implant in one ear, and a hearing aid in the other.
The information provided in this article is solely for educating the reader. It is not intended to be a substitute for the advice of a medical expert.