Hearing Loss Explained: Types and Causes
According to the World Health Organization, 20% of the world’s population (1.5 billion people!) live with hearing loss, and that number is only growing. For most people, hearing loss does not seem like a difficult thing to define; almost anyone you meet knows someone that has a hearing loss, if they do not already struggle themselves. Someone is said to have hearing loss if they are not able to hear as well as someone that has normal hearing. But did you know that there are multiple types, or categories, of hearing loss? These categories are: conductive, sensorineural, and mixed.
In order for us to hear, sound waves enter the outer ear, and travel through the middle ear and inner ear to our brain. If a person has hearing loss, there is a deficiency in some part of the auditory system. The type of hearing loss is determined by where in the auditory system this deficiency lies.
Conductive Hearing Loss
When a sound wave enters the outer ear, it will travel to the eardrum, or tympanic membrane, which is what separates the outer and middle ear. The eardrum will vibrate in order to send the sound signal through a chain of tiny bones, and then on to the inner ear. A conductive hearing loss will occur if there is a blockage or damage within the outer or middle ear. Some examples of this are ear wax impaction, fluid or ear infection, an eardrum perforation (hole), eustachian tube dysfunction, or a disorder affecting the tiny bones of the middle ear such as otosclerosis or ossicular chain discontinuity. The good news is that in most cases, conductive hearing loss can be treated with medical intervention or surgery.
Sensorineural Hearing Loss
Once the sound wave passes through the middle ear, vibrations are sent on a fluid wave into the inner ear, or the cochlea. As this wave passes through the cochlea, an electrical signal is then generated and will travel up the auditory nerve to the brain. The brain then interprets this electrical signal as sound. Sensorineural hearing loss occurs when there is damage to the inner ear, causing a disruption in the electrical signal that is being sent to the brain. Some causes of this type of loss include aging, noise exposure, genetics, ototoxic medications, injury, and certain syndromes or infections. Unfortunately, sensorineural hearing loss is permanent.
Mixed Hearing Loss
Mixed hearing loss is exactly how it sounds: it is a mix between conductive and sensorineural hearing loss. This occurs when there is damage to the inner ear as well as a blockage or damage to the middle or outer ear. As there are many causes and types of hearing loss, it is important to seek audiological assessment soon after symptoms arise, so proper treatment or intervention may occur.
References:
“Deafness and Hearing Loss.” World Health Organization. Accessed October 11, 2024. https://www.who.int/health-topics/hearing-loss#tab=tab_2.
“How Do We Hear?” National Institute of Deafness and Other Communication Disorders. Accessed October 11, 2024. https://www.nidcd.nih.gov/health/how-do-we-hear.
