The difference between “recruitment” and tinnitus

I just want to be very clear on the difference between these two phenomena.

They’re both auditory sensory related, but have some significant differences.

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What happened with the “recruitment”?

I got this question from a reader (Candy):

Kim’s post send me here, and I really like your post.  What gets me amazed is that I do have that problem some of the time and I never knew there was a word for it!  😉
Do you have implants now? and, if so, does it helps get rid of recruitment?  If it does, then it would be a good reason for me to get it and stop procrastinating!  😉

Instead of answering Candy directly, I think everybody who has read my original post about the phenomenon called “recruitment”, also deserves to see my response:

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Vestibular disorder symptoms I have experienced

I came across an interesting website for an organization called VEDA (VEstibular Disorder Association).  I found this list of possible symptoms that is very interesting.

Image copied from “vestibular system.” Online Art. Encyclopædia Britannica Online. 23 Jan. 2008
Here is an explanation of the Vestibular system.

I did not initially place all these symptoms into the same category (i.e. having to do with my hearing), but maybe I should have??? I exctracted the whole list and will excempt (a strikethrough line) those not experienced by me. If commented, the comment has been marked like this.

This list was a revelation to me… It all fits, kind of… Seems it connects to the wiring of the vestibulo-cochlear nerve: the nerve that carries information from the inner ear to the brain. Also called the eighth cranial nerve, auditory nerve, or acoustic nerve. If the “recruitment”-theory in my previous article holds water, the information about these symptoms could also have some bearing on the subject of my condition.

Vision

  • Trouble focusing or tracking objects with the eyes; objects or words on a page seem to jump, bounce, float, or blur or may appear doubled
  • Discomfort from busy visual environments such as traffic, crowds, stores, and patterns.
  • Sensitivity to light, glare, and moving or flickering lights; fluorescent lights may be especially troublesome Very much so!
  • Tendency to focus on nearby objects; increased discomfort when focusing at a distance
  • Increased night blindness; difficulty walking in the dark Yes, have to find walls or points of support in order to be able to move, get a complete feeling of immediate disorientation
  • Poor depth perception

Hearing

  • Hearing loss; distorted or fluctuating hearing Well, that’s not exactly news…
  • Tinnitus (ringing, roaring, buzzing, whooshing, or other noises in the ear) Very much so!
  • Sensitivity to loud noises or environments Especially high pitch like childrens voices
  • Sudden loud sounds may increase symptoms of vertigo, dizziness, or imbalance Yes!

 

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Explaining the analogy: "Recruitment" of hair cells in cochlea

During my research into my own declining hearing- and health condition, I came across information about a phenomenon regarding hair cells in cochlea called “recruitment”. I strongly suspect “recruitment” is what happens to me. It certainly would explain a lot of the things that happen(ed) to me and my hearing and the fatigue…

(Most of the text that follows is copied from this page at hearinglosshelp.com and edited by myself for the sake of this blog and my readers.)

What is “Recruitment”?

Very simply, “recruitment” is when we perceive sounds as getting too loud too fast. How is it possible to hear too loud when the hearing in fact is vanishing, you may ask… Well, be patient with me and read on…

“Recruitment” is always a by-product of a sensorineural hearing loss. If you do not have a sensorineural hearing loss, you cannot have “recruitment”. In simple layterm this means that this condition only affects those who have a significant loss of hearing caused by haircell-damage in cochlea (mainly).

As a sidenote; there are two other phenomena that often get confused with “recruitment”. These are hyperacusis (super-sensitivity to normal sounds) and phonophobia (fear of normal sounds resulting in super-sensitivity to them). Both hyperacusis and phonophobia can occur whether you have normal hearing or are hard of hearing.

An analogy for understanding how “Recruitment” got its name

Perhaps the easiest way to understand “recruitment” is to make an analogy between the keys on a piano and the hair cells in a cochlea.

The piano keyboard contains a number of white keys while our inner ears contain thousands of “hair cells.” Think of each hair cell as being analogous to a white key on the piano.

The piano keyboard is divided into several octaves. Each octave contains 8 white keys. Similarly, the hair cells in our inner ears are thought to be divided into a number of “critical bands” with each critical band having a given number of hair cells. Each critical band is thus analogous to an octave on the piano.

Just as every key on the piano belongs to one octave or another, so also, each hair cell belongs to a critical band.

The requirements for “Recruitment” 

When you play a chord on the piano—you press two or more keys together but they send one sound signal to your brain. Similarly, when any hair cell in a given critical band is stimulated, that entire critical band sends a signal to our brains which we “hear” as one unit of sound at the frequency that critical band is sensitive to. This is the situation when a person has normal hearing.

However, when we have a sensorineural hearing loss, some of the hair cells die or cease to function. When this happens, each “critical band” no longer has a full complement of hair cells. This would be analogous to a piano with some of the white keys yanked out. The result would be that some octaves wouldn’t have 8 keys any more.

Our brains don’t like this condition at all. They require each critical band to have a full complement of hair cells. Therefore, just as any government agency, when it runs short of personnel, puts on a recruitment drive, so too, our brains do the same thing. But since all the hair cells are already in service, there are no spares to recruit.

Getting to the point – what “Recruitment” means

What our brains do is rather ingenious. They simply recruit some hair cells from adjacent critical bands. (Here is that word: recruit or recruitment.) These hair cells now have to do double duty or worse. They are still members of their original critical band and now are also members of one or more additional critical bands.

With only a relatively few hair cells dead, then adjacent hair cells may just do double duty. However, if many hair cells die any given hair cell may be recruited into several different critical bands, in order to have a full complement of hair cells in each critical band.

 

 

The results of the phenomenon known as “Recruitment” – the conclusion

The results of this “recruitment” gives us two basic problems. (notice the underlined parts!)

  1. The sounds reaching our brains appear to be much louder that normal. This is because the recruited hair cells still function in their original critical bands and also in the adjacent one(s) they have been “recruited” into.

    Remember that when any hair cell in a critical band is stimulated, the whole critical band sends a signal to our brains. So the original critical band sends one unit of sound to our brain, and at the same time, since the same hair cell is now “recruited” to an adjacent critical band, it stimulates that critical band also. Thus, another unit of sound is sent to our brains. Hence, we perceive the sound as twice as loud as normal.

    If our hearing loss is severe, a given hair cell may be “recruited” into several critical bands at the same time. Thus our ears could be sending, for example, eight units of sound to our brains and we now perceive that sound as eight times louder than normal. You can readily see how sounds can get painfully loud very fast! This is when we complain of our “recruitment”.

    In fact, if you have severe “recruitment”, when a sound becomes loud enough for you to hear, it is already too loud for you to stand.

  2. The second result of “recruitment” is “fuzzy” hearing. Since each critical band sends one signal at the frequency of that spesific critical band, when hair cells get recruited into adjacent bands, they stimulate each critical band they are a member of to send their signals also. Consequently, instead of hearing just one frequency for a given syllable of sound, for example, perhaps our brains now receive eight signals at the same time—each one at a different frequency.

    The result is that we now often cannot distinguish similar sounding words from each other. They all sound about the same to us. We are not sure if the person said the word “run” or was it “dumb,” or “thumb,” or “done,” or “sun,” or? In other words, we have problems with discrimination as well as with volume. If our “recruitment” is bad, our discrimination scores likely will go way down.

    When this happens, basically all we hear is either silence, often mixed with tinnitus or loud noise with little intelligence in it. Speech, when it is loud enough for us to even hear it, becomes just so much meaningless noise.

    This is why many people with severe recruitment cannot successfully wear hearing aids. Their hearing aids make all sounds too loud—so that they hurt. Also, hearing aids cannot correct the results of our poor discrimination. We still “hear” meaningless gibberish.

    However, people with lesser recruitment problems will find much help from properly adjusted hearing aids. Most modern hearing aids have some sort of “compression” circuits in them. When the compression is adjusted properly for our ears, these hearing aids can do a remarkable job of compensating for our recruitment problems.

Battling tinnitus, headaches and fatigue

While living my life, with the absence of the working life strains, I still have to deal with stuff that is quite heavy.

First out is the tinnitus. Coming on strong in the evening and especially before sleep, I can feel the phase-shift as I have taken out my BTE HA (behind-the-ear hearing-aid) and the sound-world has disappeared.
After only a few minutes the concert starts with mid-level frequency sounds (where I have never ever had a sound chart reading above 110 Db) trying to find the right tune, just like violinist warming up before a show. The level of sound varies a little, and I have different sounds in the right ear from left ear. In short: a cacophony just as a whole orchestra is warming up before a concert…
Sometimes I get a spike of sound. A sound very distinct almost like the ping sound a submarine uses in it’s sonar just lasting a little longer. And that sound startles me every time, since it’s very loud. And it pops up in both left and right ear totally randomly.

Then there’s headaches. I get headaches almost daily for what feels like very different reasons. Sometimes it’s the overload of sounds either in loudness or in durability. Other times it’s strain headaches from stress from various situations, or just plain stiff neck. And the wintertime low sunshine on clear days can also induce headaches. Seems like I have a low tolerance for headaches. Just checked my brain with MR and x-rays and all results came back negative, which is good news. One less thing to worry about.
I have taken some actions to fight the headaches, and I think I’m on the right path. I have started doing exercises for my neck. And I’m doing it very slow and careful now in the beginning, as I get headaches from doing these simple exercises.
Most HOH and near-deaf people have one thing in common: we move our head forward as to signal to anyone that we need to hear better. I think it is also an instinct in order to make the distance between us and the source of sound as short as possible.
My neck is  very agile going forward, but back and to the sides, it’s as stiff as a stick…. So these exercises, bending my head back and forth, from side to side, and rolling my head slowly around are having an impact… I can feel the cracking of neck-bones and the headaches come bad right away, which I think is the rush of blood extending the blood vessels in my head. And my head isn’t used to those extending blood vessels, thus giving me headaches… I hope it’s temporarily, because if it is, I know I’m on track of doing something that will improve my day to day shape.

Then we’re on to the fatigue… Tinnitus and headaches clearly attributes to the fatigue, no doubt. I have also recently heard about a phenomenon called “recruitment” that could explain the sensations I get from my ears and the following feeling of fatigue and exhaustion. Will read more about that later, and research it too. See link to the article I found under the heading: “Special Subjects”.
Depression is also a common factor resulting in fatigue… Am I depressed??? I really am not sure… Sometimes, yes I would say I’m depressed, other times I’m as happy as a lark in the sky singing away… So, you tell me…

Pre-sleep-phenomenon

Oh yes, I have for a long time wanted to describe a re-occurring  phenomenon that takes place just before I fall asleep. Obviously I have taken out my hearing aids some 10 to 20 minutes before…

It is like a switch is being flicked inside my ears and head. Difficult to describe, but I will try…

Imagine you are on a voyage in a plane or a boat which makes a constant high-pitched engine-noise. This voyage takes all day long, and the noise is there all the time. And just before you fall asleep, someone turns that noise off like magic. It’s like landing on soft cotton-clouds after being tossed and heaved around all day… I can feel a “wave” of electric current sweeping from the front of my head to the back, very quick. It’s like the shock of icy-cold water thrown on your head while lying down, only that this sensation is rather pleasant…. Does this makes sense?

This sensation occurs every night just before I fall asleep. When it happens, I know that I’m seconds away from sleeping…. Very pleasant and soothing.

If anyone has experienced similar, I would like to know. If someone has an idea something might explain this phenomenon, I want to know….  🙂