Neuroscientists reveal the brain malady responsible for tinnitus, chronic pain

Neuroscientists at Georgetown University Medical Center and Germany's Technische Universität München say they've uncovered the brain malady responsible for tinnitus and for chronic pain — the uncomfortable, sometimes agonizing sensations that persist long after an initial injury.

In the October issue of Trends in Cognitive Sciences, researchers say identifying the problem is the first step to developing effective therapies for these disorders, which afflict millions of people. None now exist.

The scientists describe how the neural mechanisms that normally "gate" or control noise and pain signals can become dysfunctional, leading to a chronic perception of these sensations. They traced the flow of these signals through the brain and showed where "circuit breakers" should be working — but aren't.

In both disorders, the brain has been reorganized in response to an injury in its sensory apparatus, says Josef Rauschecker, PhD, DSc, director of the Laboratory for Integrative Neuroscience and Cognition at GUMC. Tinnitus can occur after the ears are damaged by loud noise, but even after the brain reorganizes itself, it continues to "hear" a constant hum or drum. Chronic pain can occur from an injury that often is healed on the outside but persists inside the brain.

"Some people call these phantom sensations, but they are real, produced by a brain that continues to 'feel' the initial injury because it cannot down-regulate the sensations enough," he says. "Both conditions are extraordinarily common, yet no treatment gets to the root of these disorders."

Areas of the brain responsible for these errant sensations are the nucleus accumbens, the reward and learning center, and several areas that serve "executive" or administrative roles —the ventromedial prefrontal cortex (VNPFC) and the anterior cingulate cortex.

All of these areas are also important for evaluating and modulating emotional experiences, Rauschecker says. "These areas act as a central gatekeeping system for perceptual sensations, which evaluate the affective meaning of sensory stimuli — whether produced externally or internally — and modulates information flow in the brain. Tinnitus and chronic pain occur when this system is compromised."

Other issues often arise in "lockstep" with tinnitus and/or chronic pain, such as depression and anxiety, which are also modulated by the nucleus accumbens, he says. Uncontrollable or long-term stress is another important factor.

Ironically, the brain plasticity that produces some of these changes provides hope that this gatekeeping role can be restored, Rauschecker says. Because these systems rely on transmission of dopamine and serotonin between neurons, drugs that modulate dopamine may help restore sensory gating, he says.

"Better understanding could also lead to standardized assessment of individuals' risk to develop chronic tinnitus and chronic pain, which in turn might allow for earlier and more targeted treatment," adds Markus Ploner, MD, PhD, a consultant neurologist and Heisenberg Professor of Human Pain Research at the Technische Universität München (TUM).

Source:

Georgetown University Medical Center

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Comments

  1. mike teri mike teri United States says:

    Can the injury be 4,5 or even 6 decades old?  Does the injury have to have been treatable? Is the onset of tinnitus, chronic pain immediate? Or could it start decades after the injury?

  2. Steve Brown Steve Brown United States says:

    I read your article with great interest. I lost my right eye due to illness 3 years ago and have since suffered hearing loss in my right ear and tinnitus in my right ear. I would like to learn more about this subject and if the research is suggesting any treatment methods. I look forward to hearing more

  3. Mark Headley Mark Headley United States says:

    >"THE brain malady" --  How harmfully ludicrous.  So a vet's persisting agony after losing her legs, etc. in combat suffers only because of her supposed "brain" defect?  

    >"Chronic pain CAN occur from an injury that OFTEN is healed on the outside but persists inside the brain."

    AH.  Some sensible caveats.

    Still, drs, researchers, have no business wrongly insisting they can rule out infections, other persisting tissue injury to nerves, other organs, outside the brain.  'Absence of evidence is not [conclusive] evidence of absence' -- as researchers elsewhere have underscored.  Actually, intense chronic pain IS evidence of persisting damage -- albeit not necessarily establishing persisting damage OUTSIDE the brain.  As quoted here, however "often [injuries APPEAR] healed on the outside," in many cases persisting injury CAN be documented.  Increasingly so as medical science, practice has advanced, advances further.

    Similarly, roundtable discussion at the Novartis Foundation Symposium on Anaphylaxis underscored drs., researchers can never entirely rule out "allergy".  At most, they can tell us they have detected no allergy and hence classify sever reaction as "Anaphylactoid," or (presumptively) "Nonallergic Anaphylaxis" -- in WHO parlance.

    >"Tinnitus and chronic pain occur when this system is compromised."

    Whoops!  Who zapped caveats, nuance necessary to keep this sweeping assertion from being so harmfully, wildly inaccurate?

    Should read something more like:

    ""Tinnitus, chronic pain, or both CAN occur when [WHAT WE ENVISION, WHAT WE DESCRIBE DESCRIBE AS] this system is IMPAIRED.""  

    Most people I know suffering persisting agony DO have persisting afflictions/damage outside the brain, yet no tinnitis.  Same as me.  Consistent w/ the top excerpt, even if injuries "often" APPEAR to be "healed on the outside," often they do NOT.  And we can never know for sure that the failure to detect is not a failure of current medical methodology, of current scientific understanding.

    Took researchers years, with much debate, much funding, to identify AIDSyndrome as an infectious disease, with HIV the culprit.

    Debate still rages w/ many nominally "POST-"infectious afflictions, including many autoimmune disorders, whether the pathogen merely triggered the continuing disease, or whether the pathogen persists as an irritant driving the continuing disease, autoimmunity, etc.

    Hence, for example, a researcher's PCR analysis of fluid from my prostate documented a reportedly chronic pathogen that standard clinical methodology does not.  See also, e.g.,

    Improvement of postherpetic neuralgia after treatment with intravenous acyclovir followed by oral valacyclovir, Quan D, Hammack BN, Kittelson J, Gilden DH., Arch Neurol. 2006 Jul;63(7):940-2.

    >"pain signals can become dysfunctional, leading to a chronic perception of these sensations"

    Gibberish.  Sensations perceived?  What, then, are UNperceived sensations?  Pain is an experience.  "Pain perception" makes no more sense than would gibberish about "nausea perception."  Because nausea, too, does not exist beyond our experience.  Stimuli can induce pain, but there is no "pain" for us to "perceive."  Such gibberish gets bandied, IMO, to confuse us and push patently ludicrous, harmful agendas that all chronic pain stems from brain defects.

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News-Medical.Net.
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