Hearing loss is described in types and degrees of loss. The type of hearing loss is determined by the location of the dysfunction. The degree of loss is determined by how much power is needed to hear sound. The ear is divided into the outer ear, middle ear and inner ear. This article is an introduction to the anatomy and function of the inner ear organ and the hearing loss that may originate in this area.
Inner Ear Anatomy
The inner ear is made up of the cochlea and the vestibular (balance) system. Here, we will focus on the hearing organ or cochlea. The cochlea is responsible for receiving a mechanical sound and changing it into an electrical signal. This electrical signal is what the brain will use to hear and understand. The cochlea is a fluid-filled organ that looks like a snail shell. Inside the snail shell are layers of tissue, which support flexible nerve cells that move in response to sound. As the nerve cell is moved, it creates the electrical signal that is sent into the brain.
Inner Ear Hearing Function
The cochlea is designed to change a sound wave (mechanical energy) into an electrical impulse. As sound enters the cochlea, it travels around the “snail shell” in a very specific manner. The vibration activates (or moves) the nerve cells along the membrane according to its frequency. The lower frequencies are registered nearer the center of the organ and the higher frequencies are activated near the entrance from the middle ear. As the sound travels around the circle, it vibrates the nerve cells causing the proper response to send on to the brain. This vibration is key to the function of the cochlea.
Inner Ear Hearing Loss
The most common hearing loss is nerve deafness. For years, people were told that when they have nerve deafness and that nothing could be done to help. Actually, the vast majority of people who wear hearing aids have this type of hearing loss. Sensorineural hearing loss, or nerve deafness, is usually evident only in portions of the cochlea. There will be varying degrees of damage throughout the nerve cells, depending on how much trauma the cochlea suffered and what frequencies were involved. The excessive sound can rupture the tips of the cells; fuse sensory cells together, damage the area through which the cells transmit signal, and even change the vascular pathways inside the organ. The vulnerability of the inner ear is dependent upon several factors, such as smoking, hypertension, lipid levels, age, gender and other genetic factors.
Trauma is just one of the causes for sensorineural hearing loss. Other causes are ototoxic medication, autoimmune disease, history of hearing loss in the family, heart disease, diabetes and many other medical conditions. Many people feel that just because they are getting older they will have hearing loss. If your gene pool is strong for the hearing organ, then you may not acquire hearing loss. If you did not expose your ears to loud noise, then you may not suffer hearing loss.
Treatment for Sensorineural Hearing Loss
For the majority of people with sensorineural hearing loss, treatment involves making sound louder. The trick is to increase only the sounds you need with the least amount of distortion. How do you focus the increase in sound to the specific areas in the cochlea but continue to allow the cochlea to use its natural ability to hear? The answer is open fit hearing aids! The computer in the hearing aid will focus the energy to specific frequencies and set the maximum energy it will produce in each area to keep the sound comfortable. Because of the open fit, natural sound also goes into the ear canal, complementing the hearing aid generated sound.
If trauma has occurred either by excessive noise, medical history or even medications an individual takes, then we know the pathways into the area of the brain that makes sense of all the nerve signals may also have suffered damage. The current “treatment” for the nerve areas of the brain is stimulation. Keep the brain stimulated and you will have the best outcome. Properly fitting hearing aids, with the necessary ongoing adjustments as you get used to the sound, is the ideal treatment for sensorineural hearing loss. The newer technology gives more people the opportunity to join the hearing world with the least amount of distortion. This means the quality of the sound is better and people are more likely to wear the aids all day long! QCBN
By Karon Lynn, Au.D.