Types of Hearing Loss
There are many different kinds of hearing loss. However, no hearing loss is considered a “normal” part of health and should be taken very seriously. People can have different types of hearing losses in each ear or each ear can be working the same. If someone suspects their ears are working differently, it is very important to follow up with their ear, nose, and throat physician. Please read on to find out more about the different types of hearing loss. The type of hearing loss you have usually is related to the problem area in the anatomy of the ear (inner, middle, or outer ear), as well as by its severity.
1. Sensorineural Hearing Loss
Sensorineural hearing loss: This is a hearing loss which originates in the inner ear. This can either be within the organ of hearing, the cochlea, or with the nerve fibers that run from the inner ear up to the brain. The cochlea is a small snail shaped organ which houses three chambers of fluid which are unique to the ear along with little cells called hair cells. When someone has a sensorineural hearing loss, often it is due to damage to any of these structures within the cochlea or between the synapse of the hair cells and the auditory nerve.
a. Sudden Idiopathic Sensorineural Hearing Loss (SISNHL): THIS IS AN EMERGENCY.
A sudden idiopathic sensorineural hearing loss is when someone experiences a sudden drop in hearing that does not return within a few minutes with no obvious reason why. Time is of the essence when this happens. There is a very short period of time, typically no more than 3 days, in which this type of hearing loss has a possibility of being reversed. The sooner an ear, nose, and throat specialists can provide treatment, the better prognosis a patient has to recover this lost hearing.
b. Noise induced sensorineural hearing loss (NISNHL): Just as the name implies, this is a hearing loss due to noise exposure. This noise exposure does not have to be a recent event to result in this type of hearing loss. All it takes is one blast, or an extended time of being exposed to a loud noise to result in a noise-induced hearing loss. This is the one type of hearing loss which can be prevented so it is extremely important to wear hearing protection while around loud sounds. When someone has a noise-induced hearing loss the little hair cells within that person’s cochlea have been damaged to the point that they cannot recover. The stereocilia (or little hairs) have become all tangled or are quite literally blown away in the areas on the cochlea of hearing loss.
c. Temporary thresholds shift (TTS): Have you ever gone to a concert and then come home and felt like you had cotton in your ears to wake up the next morning to normal hearing again? This is a temporary threshold shift. During the time that you were exposed to a lot of noise, like a concert, the little hairs in the cochlea became overwhelmed and experienced some damage. In the time that these cells are resetting people can experience a temporary hearing loss. However, just because this is a temporary hearing loss doesn’t mean people should ignore it. When this happens, we have done a significant amount of damage to our ears which will come back a haunt us in our future!
2. Conductive Hearing Loss
Conductive hearing loss: When someone has a conductive loss, the inner ear and nerve are working how they should work but the person is still experiencing a decrease of hearing. This is because there is something, either in the outer ear or middle ear which is preventing the eardrum and bones in the ear from vibrating like they should. Some examples of what may cause a conductive hearing loss include: earwax completely blocking the ear canal or resting on the ear drum, ear infections, perforated eardrums, trauma, fluid within the middle ear, or any disease of the outer and middle ear. If someone has a conductive loss, it is very important to see their ear, nose, and throat physician to discuss medical treatment for this hearing loss. Sometimes this type of hearing loss can be reversed!
3. Mixed Hearing loss
Mixed hearing loss: Simply put, this is when there is a conductive hearing loss (affecting the outer/middle ear) in addition to a sensorineural hearing loss (affecting the inner ear/nerve). Just like with a conductive loss, it is very important to follow up with a physician when a mixed hearing loss is found. Often, this is a sign of another pathology which needs to be addressed.
4. Auditory Neuropathy Spectrum Disorder (ANSD)
Auditory Neuropathy Spectrum Disorder (ANSD): This is a very rare type of hearing loss and is often diagnosed as a child. ANSD is a disorder in which all the parts of the ear appear to be working but a child is still having a hard time and cannot understand what is being said to them. This requires more in-depth testing. A child will do well on their traditional hearing test and may even do well on the speech portion of this test. In addition, the child will have present OAEs. However, when running something called an auditory brainstem response (ABR), the child will have an abnormal test result. What does this tell us? It tells us that the ear and all the parts of the ear are working how they should be, however, the auditory nerve is not firing the signals it is receiving in a synchronous manner. For a baby, child, or adult to have a normal ABR, all of the nerve fibers within the auditory nerve must have synchrony. When it doesn’t, we get an abnormal result and the child will have a difficult time understanding the world around them. This difficulty is exacerbated when the child has to try to hear in the presence of background noise, making situations like school extremely hard and discouraging.
5. (Central) Auditory Processing Disorder - (C)APD
(Central) Auditory Processing Disorder – (C)APD: Just like ANSD, this is an extremely rare disorder which is often seen in children. Sometimes people will refer to this type of hearing loss as hidden hearing loss because when typical formal testing is completed, nothing can be found that indicates any type of pathology. This is very similar to ANSD. These children also have problems understanding speech which gets harder when background noise is introduced. However, these are not the same disorder. In CAPD, when an ABR is completed, the child has a normally functioning nerve in addition to a normal hearing test and present OAEs. This tells us that the issue is not with the ear or the nerve transmitting the information. Instead, we can conclude the issue is a processing problem in the brain. There are different types of (C)APD depending on where in the brain this processing breakdown is. A special battery of tests are used to determine what the specific issues a child is having in comparison to their neurotypical peers. This information is used to not only diagnose but also determine the best path of treatment for a child.