There are only three types of hearing loss, and the most common one is sensorineural hearing loss (often abbreviated SNHL). What happens when you have sensorineural hearing loss, and what do you do about it?
How We Hear
First, to understanding sensorineural hearing loss, let’s take a look at how we hear. The hearing system can be broken down into three distinct sections: the outer ear, the middle ear, and the inner ear.
The outer ear consists of your auricle, your ear canal, and your eardrum. The middle ear consists the eardrum, the ossicles (the bones of hearing), the Eustachian tube, and the middle ear space. The inner ear encompasses the cochlea (also known as your hearing organ).
Sensorineural hearing loss occurs when there is damage to the cochlea or the structures inside the cochlea, or the auditory nerve that goes from the cochlea up to your brain. A typical hearing test can identify if you have sensorineural hearing loss, as opposed to conductive hearing loss or mixed hearing loss.
Causes of Sensorineural Hearing Loss
The following are possible causes of sensorineural hearing loss:
- Head trauma
- Ototoxic chemical exposure
- Tumor on the auditory nerve
- Other genetic factors that you might have
- Noise exposure
- Age-related hearing loss
The most common causes of sensorineural hearing loss are noise exposure and age. Noise-exposed hearing loss or age-related hearing loss typically occur due to the death of the outer hair cells in the high frequency range.
This causes a lack of perceived clarity when people are talking to you, as high frequency encompasses clarity in speech (on the other hand, low frequency encompasses volume in speech). It is common for someone who has an age-related hearing loss or a noise-exposure related hearing loss to say, “I feel like I can hear fine, but people are just mumbling” or “I just can’t understand what they’re saying.”
Another common complaint I hear when someone has a noise-exposure related or an age-related hearing loss is that noise overshadows everything when they’re in a noisy background. If you have good low frequency hearing still, you’ll experience a phenomenon called “the upward spread of masking”: you hear the background noise well, but it drowns out all of the high frequency components and takes away all of your clarity, so you cannot understand speech in those situations.
Treating Sensorineural Hearing Loss
Treatment for sensorineural hearing loss depends on where the damage occurs, either in the cochlea or along the auditory nerve.
The outer hair cells are your ears’ natural amplifiers. When sound comes in through your ear, those outer hair cells make the basilar membrane vibrate more, which sends a more powerful signal up to your brain. If you have outer hair cell death inside the cochlea, your ear cannot naturally amplify sound and thus requires the use of a hearing aid. It is important to understand that a hearing aid only works in this situation when the hearing aid is fit and programmed properly, using real ear verification.
If you have excessive inner hair cell death, a hearing aid will not provide you a massive amount of benefit. Hearing aids are only useful when it comes to outer hair cells. When inner hair cells die beyond the rate of which a hearing aid can help, then you are a candidate for a cochlear implant. Cochlear implants bypass the cochlea entirely and stimulate the auditory nerve electrically.
If you have an acoustic neuroma (a tumor growing on your auditory nerve), you could potentially benefit from hearing aids if that tumor is small and not growing. If the tumor has to be removed, you’ll be left with no hearing on the side that you had the tumor. If this is the case, then you are a candidate for a CROS device. A CROS device sends and reroutes sound from your bad ear (the ear that no longer hears) to your better ear, so that your better ear can use sound from the other side of your head. Another option is a bone-anchored device, which is implanted on the back of your skull and vibrates your skull to help your ear on the opposite side hear.
In some extreme cases where both auditory nerves have tumors that need to be removed, you could potentially be a candidate for an auditory brainstem implant, which as the name suggests, is an implant on your brainstem that will trigger your brain to hear.
Visit an Audiologist to Determine if You Have SNHL
Over 90% of hearing losses are sensorineural in nature, and a large portion of those require hearing aids as the main treatment option. That being said, it is impossible to know exactly which treatment option is right for you unless you have your hearing evaluated properly by an audiologist. If you feel like you’re experiencing hearing loss, your best option is to schedule an appointment with an audiologist, so they can determine exactly what type of hearing loss you have.