About Hearing Loss
There are several causes of hearing loss that can occur at almost any stage of life. From birth to old age, hearing loss can become an important factor in one’s life. In most cases, close to 90%, where no other traumatic events have occurred, hearing loss is generally caused by the accumulation of birthdays, as Arne Zabell, the original owner of my first hearing clinic was fond of saying.
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Nerve endings stop generating new cells by the time most of us are in our twenties. If damage to the nerve endings in the cochlea is sufficiently bad, then they may not regenerate at all, no matter how young we are, but in the course of a normal lifetime they start to deteriorate very slowly by the time we are between 25 and 30. For many people the deterioration never gets to a point where it manifests itself as a noticeable hearing loss, but for about 10-20% of the population, according to the most recent statistics, will realize some degree of hearing loss by the time we are in our sixties. The same statistics show that only 5% of that 10-20% will actually take steps to treat their hearing loss, which is an alarming number when you consider some of the downsides of not hearing properly.
Sensorineural hearing loss is the most common type of loss. This occurs simply when the nerve endings in the cochlea have been broken or damaged and can not properly receive the signal sent through the oval window of the inner ear. The nerve endings closest to that window are at the highest risk and are the ones which receive higher frequency sounds. On an audiogram, the graph we use to pictorially display the hearing loss, this is why they often appear as a ski hill going down from left to right; the high frequencies are pictured on the right side of the graph. We judge a hearing loss to be sensorineural when the results from the headphones match closely the results from a bone oscillator.
Conductive hearing loss is significantly different. A conductive loss occurs when the result from air conducted testing, (through headphones), shows a degree of hearing loss but the results from the bone oscillator show as normal. A good comparison is to think of a water filled balloon with a few holes in it. Water gets through, but not all of it and in needs some extra pressure to get it through.
There are several things that can cause conductive losses, but the most common is a middle ear infection which fills the middle ear cavity with fluid which in turn doesn’t allow the tympanic membrane, (the eardrum), to vibrate the way it should. Sound is not able to transfer properly to the ossicles, (the three smallest bones in the human body), and therefore it doesn’t transfer properly to the oval window. For the most part problems such as middle ear infections, and the hearing loss that accompanies them, are very cureable. They come on very quickly and resolve fairly quickly.
There are several other reasons for conductive hearing loss that are much less fixable, a severely damaged Tympanic Membrane, dissolving of the ossicles and many others, but they will often result in the same hearing loss.
A mixed hearing loss is just what you would think; some combination of both a sensorineural and conductive hearing loss. There are also many reasons that this can happen, butt the most common are Otosclerosis and Meniere’s Syndrome. Both are insidious, Meniere’s more so than Otosclerosis, but both can wreak havoc on ones ability to hear.
Otosclerosis occurs when the bone tissue around the stapes starts to overgrow and fuse the footplate to the edges of the oval window. This causes the elasticity of the oval window to be lost and reduces the vibrational energy to reduce.