Tinnitus, Targeting "Central" (Brain) or Peripheral (Cochlear) Treatments

[mock turtle]

in the last several years there appears to be "shift" in thinking; that tinnitus is more a problem of the central brain and brain stem processing, than previously thought...but i am none the less struck by one simple fact

research has established that a number of drugs administered to the cochlea decrease tinnitus

i accept that the brain is plastic and hearing trauma and damage cause a change in the way the brain reprocesses sound.... including a failure of higher brain executive functions to filter out tinnitus and as well, even a limbic system over response to tinnitus

but doesnt this line of investigation cause us to shift focus too much from the immediate cause and possible remedy, to an approach that may likely be ameliorative at best?

let me be clear i think its great that approaches like neuromonics, tinnitus retraining therapy and notched music are helping sufferers to "deal" with tinnitus...but

but....researchers have established that down-regulating the potassium ion channel in the cochlear stereocilia cells markedly decreases the tinnitus signal in animal models...and as a further example we know that direct administration of lidocaine to the cochlea (all-be-it temporarily) turns tinnitus off too!

its great that researchers are retraining the brain to decrease the perception of tinnitus ....but i for one wish we could see more emphasis and progress in treating the root cause of tinnitus. which, with few exceptions is predominately the result of damage to the cochlea.

is it not true that ,the reorganization of sound perception by the damaged dorsal cochlear nucleus , higher auditory brain functions and even the limbic systems over response is a RESULT of otoxicity and loud noise and other sources of cochlear damage and thus tinnitus, not the other way around ?

dr silvi's recent work with animal studies, indicates that down-regulation of cochlear potassium ion channels may end tinnitus. it is disheartening that web searches indicate few if any research projects aimed at progressing along the lines of these findings towards human trials .

where are the ongoing tinnitus studies of maxipost (bms 204352) ?

 

[Markku]

Surgical treatment of tinnitus includes destructive procedures, neurectomies, stapedectomies and tympanosympathectomies. Translabyrinthine procedures for the removal of acoustic neuromas and sectioning of the eighth nerve to eliminate vertigo are analogous to cutting the eighth nerve as a surgical intervention for tinnitus. After surgical removal of acoustic tumours with excision of the auditory nerve in 414 patients, only 40% reported improvement in their tinnitus. Of 68 patients undergoing translabyrinthine eighth nerve section, 60 (80%) had tinnitus preoperatively. Improvement occurred in 45%, while 55% reported the condition to be the same or worse. In patients undergoing middle cranial fossa section of the vestibular nerve for vertigo or dizziness, most reported the tinnitus to be the same but a significant number felt that it was worse. Stapedectomy improves hearing in most patients but improves the symptom of tinnitus in only about half of the patients. Cochlear implant patients report an improvement in their tinnitus with use of the stimulator and implant. Implant procedures might therefore be used in patients who suffer from severe tinnitus. Surgical management of tinnitus, although successful in some cases, does not provide a valid and reliable mode of treatment for subjective tinnitus.

(http://www.ncbi.nlm.nih.gov/pubmed/6915835)

That is the question. After surgically cutting the auditory nerve, not even 50% reported improvement in their tinnitus. If the pathway between the cochlea and brain is cut and yet tinnitus remains, how could we expect treatments of the cochlea help us?

It's very much possible central nervous system related treatments will be needed for many patients.

I'm not quite sure, but don't researchers and scientists currently think that tinnitus might be treatable soon after onset via treatments that affect the cochlea? Like the drug AM-101 that is going through the trials right now. It's thought that AM-101 may only help acute tinnitus cases, ie. cases started within 3 months.

However, once tinnitus "settles in" after a while and becomes chronic, it becomes more brain-related. Yes, wrong signals are likely still being sent to the brain, but at the chronic stage it doesn't matter anymore that much; if the auditory nerve is cut, the brain is still very much sensing tinnitus.

My thinking is that in the future recent cases of tinnitus could be helped with cochlea treatments, like AM-101 or other such treatments, but chronic cases would need approaches that also take the brain into consideration. Chronic cases might need both; a combination of cochlea and brain related treatments.

The potassium ion channel research done on rats was interesting I admit. Thanks for posting that.

 

[Karl]

in the last several years there appears to be "shift" in thinking; ....but i for one wish we could see more emphasis and progress in treating the root cause of tinnitus. which, with few exceptions is predominately the result of damage to the cochlea.
?

I've also been thinking along the same lines. We're talking about, what is the basic cause of ototoxic caused tinnitus? Can researchers get that one right?

It seems like a de facto assumption that we assume the cochlea "has been damaged". But has it really, and how? Are hairs twisted, or did they fall out? Have researchers seen damaged cochlea? Can it been observed in MRI's?

Forgive my ignorance, but I'm just beginning to catch up with you guys in my reading list. I just read of a different line of thought: Rather than "damage", one researcher has proposed protein build-up on the cochlea outer hairs. (I'm not shy when I have a purpose. I've tried contacting this researcher, with no luck. It seems that I would have a better chance meeting President Obama! )

I agree with mock turtle. The ATA and other tinnitus professional organizations should focus on the fundamental root causes of tinnitus. There may already be a scientist who already understands the root cause. It is important that these professional organizations pounce on the correct theory, in lieu of perpetuating endless theories meant for Phd disertations.

 

[mock turtle]

Markku

thanx for the reply...you make so many good points that i cant, and would not argue with

the issues you raised regarding the surgical treatment of tinnitus are fascinating...many successes and many failures

the mixed results are so puzzling

and as you point out further below in your message, treatment especially for those who have had tinnitus for some time may require that problems with the brain AND the cochlea be addressed for a more complete and effective treatment

when you posed this question you really got me to thinking
"...After surgically cutting the auditory nerve, not even 50% reported improvement in their tinnitus. If the pathway between the cochlea and brain is cut and yet tinnitus remains, how could we expect treatments of the cochlea help us?

a great question which i dont have an answer for, but i have kind of an idea...a guess

so here it is

i dont know if im correct on this but if i understand what i have read correctly,,,
the inner hair cells (IHCs) and outer hair cells (OHCs) of the cochlea perform quite different tasks

OHCs are connected to "efferent" nerves and that means they send signals from the brain to the cochlea !! (isnt this amazing ! the OHCs "make noise"

where as IHCs are "afferent" , and that means these cells sense sound and send signals back to the brain

maybe whether the efferent or the afferent nerves are cut matters for different patients and even for different frequencies of hearing depending upon whether IHCs or OHCs have been damaged at that frequency

im just thinking that if the IHCs (afferent) are badly damaged or wiped out such that a person cant hear a certain frequency ( but the outer hair cells for that frequency are not totally destroyed), does that prompt the brain to boost signals from the brain to the OHCs in the cochlea trying desperately to make contact and get a signal back from the damaged IHCs...the "hearing" part of the system?

if this was the case, the brain would be generating this huge signal, getting nothing back and thus maybe causing central tinnitus (tinnitus originating in the brain)?

the opposite of this idea is that if the Outer hair cells (the sound senders) are severely damaged or wiped out for a certain frequency but but some or most of the IHCs (sound receivers) survive for that frequency then the brain turns up the receiver volume like we would do for a weak radio station signal, and just like that radio, we would hear a lot of fuzz buzz and static but not much from the weak radio station.

obviously im no doctor and im no scientist or anything, but just being an average guy struggling with trying to build a picture in my mind as to how these inconsistent results to meds (like klonopin) and surgeries could possibly be explained

im probably wasting eveybodys time with this kind of idea but with all this crazy ringing in my ears i just cant stop wondering what it could all be

sorry for the long message

hoping for less noise
mock turtle

 

[mock turtle]

Karl

never apologize for asking a question, especially, because you are asking the same questions we all have asked or will ask some time soon

im no expert and just learned some of this so i hope im not saying this wrong

i think there are two answers to your question... one is that the hairs (stereocilia) can be damaged as a result of sound, loudness, impacts etc but not necessarily destroyed..the damage if minor is caused by something called "reactive oxygen species" and i have to confess i just read about that and dont understand yet what it means...but evidently if somebody takes n-acetyl -cysteine or other anti oxidants right away they maybe can save the damaged hairs and cells

but if the damage is more severe or happens over and over, the poor little hearing hair cells are wiped out like blades of grass cut short to the ground

i think scientists can slice up damaged animal cochleas and actually "see" the damage with very powerful microscopes
and
i read that even a brain mri can show cochlear damage but the image is gross and undefined

as to your concern that scientists get on with understanding the cause and the complete picture of what tinnitus is about...i think some (many?) are trying really hard to do this

heres one example thats very interesting...U of washington, in seattle, bloedell hearing research center

http://depts.washington.edu/hearing/

best wishes
mock turtle

 

[Markku]

im just thinking that if the IHCs (afferent) are badly damaged or wiped out such that a person cant hear a certain frequency ( but the outer hair cells for that frequency are not totally destroyed), does that prompt the brain to boost signals from the brain to the OHCs in the cochlea trying desperately to make contact and get a signal back from the damaged IHCs...the "hearing" part of the system?

if this was the case, the brain would be generating this huge signal, getting nothing back and thus maybe causing central tinnitus (tinnitus originating in the brain)?

the opposite of this idea is that if the Outer hair cells (the sound senders) are severely damaged or wiped out for a certain frequency but but some or most of the IHCs (sound receivers) survive for that frequency then the brain turns up the receiver volume like we would do for a weak radio station signal, and just like that radio, we would hear a lot of fuzz buzz and static but not much from the weak radio station.

This makes sense and isn't this basically why many times tinnitus is noticed in the first place? Hair cells being damaged/destroyed -> missing/misfiring signals -> brain senses/amplifies that frequency? It seems you have done a lot of researching on your own, I mean you know a lot more than I do, so I really, really appreciate you are sharing your thoughts & findings. They are very fascinating even to a layman such as myself.

I would love to know what's the situation with my hair cells. And what would happen right now if all of them were back to being healthy (pre-tinnitus state). Would parts of my brain already be "changed" (plasticity and all?) in a way that I would still hear ringing...

On the whole I more than agree with you that more studies and research should be done on the cochlea... It's possible researchers are being too focused on the after effects of tinnitus, ie. how brain responds to cochlea damage.

Wouldn't it be possible that if the cochlea damage could be treated, the brain then could adapt to that somehow and tinnitus would go away. But if the auditory nerve is completely cut, auditory parts of brain might go into a loop of sorts and the tinnitus remains or becomes even worse. Comparing these two (fixing cochlea damage vs. cutting auditory nerve) might not be fruitful.

--
Markku
PS. Have a great weekend everyone!

 

[joe]

wouldnt it be nice if all us T people had a T free weekend, If I had one wish I would wish for us all to be cured and enjoy our weekends like before

 

[Karl]

Karl

..the damage if minor is caused by something called "reactive oxygen species" and i have to confess i just read about that and dont understand yet what it means...but evidently if somebody takes n-acetyl -cysteine or other anti oxidants right away they maybe can save the damaged hairs and cells

I will begin reading up. I'm impressed by your knowledge.

I may be wrong, but I sense that tinnitus researchers may not have a consensus about even the basic mechanisms of tinnitus. For exampe, can they define "damage" related to tinnitus? What is it in terms of either a chemical process or physical trauma to a particular anatomical part?

You have made some very interesting assesments of what damage is; but I've also heard a whole smorgasbord of opinions. Last month, I was using a a vibrating toothbrush against my temple, "to shake of the crust off my cochlea hairs", based on one guy's idea of what causes tinnitus!

Let's hope that tinnitus researchers are still not in the "alchemy stage", waiting for their own version of Neils Bohr to come along. I recently joined the ATA, which is now celebrating 40 years. I will insist that they make some progress.