Tinnitus in the Brain? Not Always...

Here is an interesting data point about people with an acoustic neuroma. This paper compares outcomes of Micro surgery and Gamma Knife. The former process cuts the auditory nerve (leading to deafness), while the latter to preserve it (as well as it can).

The results will be surprising to some:

In the TLM group (n=27), vestibulocochlear nerves were definitely cut. There was a higher rate of tinnitus improvement in TLM group (52%) than GKS group (16%, p=0.016). The GKS group had a significantly higher rate of tinnitus worsening (74%) than TLM group (11%, p<0.001). Mean scores of THI and VAS scores significantly decreased in the TLM group in contrast to significant increases in the GKS group. Tumor volume and preoperative hearing did not affect the changes in THI or VAS.​

So cutting the nerve resulted in a much higher improvement in tinnitus than those who had their nerve preserved.

We often hear/read that cutting the nerve will make your tinnitus worse, but things seem more complicated than that, as this study shows. It probably depends on where the genesis of the sound is in the "hearing pipeline", and clearly - as this study shows - it's not always in the brain.

Ref: https://www.ncbi.nlm.nih.gov/pubmed/24339282

 

Don't like this. It indicates to me that there are damaged structures in the ear sending out a bad signal. If that's the case then just growing new hair cells with Frequency therapeutics won't stop the tinnitus. You would have to somehow clear away the damaged structures making the tinnitus signal first.

 

Well, it speaks of acoustic neuroma, which is a tumor.

 

is there anyway to freeze the nerve to simulate it being cut?

 

this hypothesis of tinnitus attemps to explain why cutting the auditory nerve will sometimes releive tinnitus, but I am open to the possibility of peripheral versions of tinnitus possibly existing outside of otoacoustic emissions

Dr. Robert Aaron Levine's Tinnitus...

 

Good thing then that they aren't "just growing new hair cells".

"it's about getting a non-regenerative SYSTEM to behave in a regenerative way"
-Will McLean @15:02 from the below presentation.

Lecture: Toward a True Cure for Hearing...

 

I loved the video but I see an inconsistency. If the auditory nerve input is the only input that contributes to the (+) positive excitation of the fusiform cells, then if it is cut, the only remaining input would be the suppressive somatosensory signal. Thus by cutting the auditory nerve, the only remaining input should be one that suppresses Tinnitus and therefore cutting the nerve should always cure it. And it doesn't.

 

it may also depend on where the nerve is cut, on the axon, the body, etc.

 

Here is another thought... If the only positive excitation of the fusiform cells depends on input from Inner Hair Cells and negative excitation depends (partially) on input from Outer Hair Cells then Tinnitus and hearing loss at a certain frequency almost certainly means that your OHC are damaged/dead but your IHC are mostly intact. Seems to me that if you were to blast your ears with noise at that same frequency and you killed off your IHC at that frequency too then you would be deaf at that frequency but there would no longer be any positive excitation of the fusiform cells and your Tinnitus would stop. Not that I am desperate enough to do that but it beats having your Auditory Nerve cut, which kills all frequencies, even ones for which both your IHC and OHC have healthy responses.

 

Lidocaine but it's short acting and chronic use causes health problems so no doctor will prescribe it.

 

Is ther any correlation with Lidocaine helping and Nerve being cut helping?

 

Has that actually been done to make someone temporary deaf to see it T goes away?

 

I see what your doing here @GregCA !

Could it be instead a situation where it is much easier for the brain to plastically adapt to no input (cutting)? Where as the gamma knife causes a more difficult situation from the plasticity perspective?

I still feel like in these scenarios it IS being generated in the brain, how else could it exist when the nerve is cut? It takes A) faulty brain or B) faulty nerve + faulty brain. But a C) faulty nerve alone doesn't seem to lead to tinnitus. I think

 

It could be indeed! However, we do have mixed reports on outcomes of nerve cutting (not from this study): both outcomes (T and no-T) are fairly well represented in such cases, so having a much easier way for the brain to adapt to no input is an interesting hypothesis but not really supported by the data we currently have.

Why does it have to be an either/or?
We know that there are T conditions where the sound genesis goes back to the pre-cochlea stage in the hearing pipeline (otitis media, ear drum perforations/damage, otosclerosis, ear canal growths, etc), so clearly there are cases where "it's not in the brain". Then we do have the cases where sectioning the nerve either induces or does not stop existing T, which supports "it's in the brain", along with other theories (central gain, bimodal research).

I don't see much of a point in focusing on "the one single truth" about T: when we get too close to that tree, we forget the forest around it, and that tunnel vision prevents us from seeing very useful data that can help us make progress. I know I'm preaching to the choir.