Sensori-neural hearing loss

Depending on where you are experiencing problems in your ear will determine what type of hearing loss you have and what help you can get to improve your particular situation. If you have not already done so, you might find it helpful to read my previous posts. If you think a picture of the auditory or hearing system would be helpful while you read this post, simply, type, “anatomy/images of the ear” into your favourite browser and you will see many links to pictures of the ear.

Today’s post will focus post on sensori-neural hearing loss. When you get your hearing tested, you undergo a series of tests which help the clinician ascertain which type of hearing loss you have. The results of the tests also help the clinician recommend how you can best be helped depending on your type of hearing loss.

The ear per se is divided into three sections: the outer ear, the middle ear and the inner ear. Generally speaking, sounds are “conducted” from the environment around us down our ear canals, causing our ear drums to vibrate. The movement of the ear drums cause the bones in the middle ear to vibrate against the oval windows which sit at the entrance of the inner ear. The inner ear hair cells change the vibrations from the middle ear into electrical impulses which are sent along the auditory nerve to the brain which makes sense of the things we hear around us.

Because the outer and middle ears are responsible for “conducting” sounds to the inner ears, anything that can go wrong with the outer and/or middle ears results in “conductive” hearing loss. For more information about conductive hearing loss, please go to my previous post (April 2013).

Sensori-neural hearing loss, typically referred to as “nerve deafness”, occurs when damage most often occurs in the “inner” ear but can also occur along the hearing nerve.
Approximately 90% of people who have hearing impairment have sensori-neural hearing loss, making it the most common type of hearing impairment. Generally speaking, sensori-neural hearing loss is permanent and irreversible.

Most common causes of sensori-neural hearing loss include; but are not limited to:
• Aging
• Exposure to loud noise
• Viral infections
• Ototoxic drugs
• Head injury
• Genetic or hereditary predisposition

Generally speaking, because the problems associated with sensori-neural hearing loss result from damage to many of the hundreds of thousands of inner ear hair cells or the auditory nerve, the signals (messages) transmitted to the brain are not complete and, therefore, distorted and incomprehensible. Those who suffer from this condition may complain that people seem to mumble or that they hear, but do not understand, what is being said; they HEAR sounds but not always clear enough to DISCERN OR UNDERSTAND what is being said.

For a moment, liken the inner ear to a pedal (concert) harp which is a large, modern harp. Typically, it has 46 or 47 strings with a range of six and one-half octaves. If you were to listen to a song played on a harp that is in perfect working order, you would be able to hear the music from the harp AND discern or understand the song that is being played. However, if you remove half of the strings and listen to the same song being played, you would hear that “something” is being played on the harp but, most likely, you would not be able to discern or understand what song is being played!

Imagine the following sentence to be what it would be like to hear through an intact or healthy auditory system:

THE QUICK BROWN FOX JUMPED OVER THE LAZY DOGS.

When a person experiences a severe sensori-neural hearing loss, the same sentence would look something like the following sentence:

–E wI– b-OW- -og –Um- – – O-er –e la-y gOg-.

This sentence attempts to illustrate that sounds are getting through to the inner ear but, because so many hair cells in the inner ear are damaged, the signals (messages) transmitted to the brain are distorted and incomprehensible.

The brain receives a message and hears sound but the message is distorted so the brain has trouble deciphering what the message means!

In the vast majority of cases, sensori-neural hearing loss is not medically or surgically treatable. However, most people with sensori-neural loss notice a great deal of benefit from wearing some form of amplification devices (hearing aids, bone-anchored hearing aid (BAHA), cochlear implants, etc.).

Treating any hearing loss depends on prompt diagnosis and treatment. All hearing losses should be evaluated by an audiologist and physician to explore all potential treatment options.
Glen Sutherland, MCISc

Audiologist

Disclaimer
Please note that the information in this blog is presented for the purpose of providing information and should not be used for medical diagnosis or treatment nor should it be used in place of medical advice from your doctor or hearing health care professional.

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One response to “Sensori-neural hearing loss

  1. Wow.. the written distortion of The Quick Brown Fox is a powerful image to help me understand a little bit more about hearing loss… thanks!

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