Thursday, September 15, 2011

Hope for Ringing in the Ears?

Me, and a few million other people in the US suffer from a persistent ringing in the ears, known as tinnitus.  I don't have a bad case, but it some people near to madness, and even suicide.  There has been no effective treatment.  It looks like there may be new treatment on the horizon that offers hope for reducing it and even eliminating it:
Bao's experiments in rats with induced hearing loss explain why the neurons in the auditory cortex generate these phantom perceptions. They showed that neurons that have lost sensory input from the ear become more excitable and fire spontaneously, primarily because these nerves have "homeostatic" mechanisms to keep their overall firing rate constant no matter what.

"With the loss of hearing, you have phantom sounds," said Bao, who himself has tinnitus. In this respect, tinnitus resembles phantom limb pain experienced by many amputees,

One treatment strategy, then, is to retrain patients so that these brain cells get new input, which should reduce spontaneous firing. This can be done by enhancing the response to frequencies near the lost frequencies. Experiments over the past 30 years, including important research by Merzenich, have shown that the brain is plastic enough to reorganize in this way when it loses sensory input. When a finger is amputated, for example, the region of the brain receiving input from that finger may start handling input from neighboring fingers.
So, no surgery?  Just retrain the brain to use those neurons on something else?  I can imagine software, probably aided by biofeedback, that would retrain those neurons.  I'd try it.  But there may also be some advances in drugs that will help, too.
Another treatment strategy, Bao said, is to find or develop drugs that inhibit the spontaneous firing of the idle neurons in the auditory cortex. Hearing loss causes changes at junctions between nerve cells, the so-called synapses, that both excite and inhibit firing. His experiments showed that tinnitus is correlated with lower levels of the inhibitory neurotransmitter GABA (gamma-aminobutyric acid), but not with changes in the excitatory neurotransmitters.

He demonstrated that two drugs that increase the level of GABA eliminated tinnitus in rats. Unfortunately, these drugs have serious side effects and cannot be used in humans. He has applied for several grants to start screening drugs for their ability to enhance GABA receptor function, increase the synthesis of GABA, slow the re-uptake of GABA around nerve cells, or slow its enzymatic degradation.
How did I get it?  Take your pick, childhood ear infections (a particularly bad case when I was in college - after which I had detectable hearing loss in the high frequencies), careless chainsaw use, firing high powered rifles without ear protection, any of these, and probably all of them may have contributed.  Faster please!

1 comment:

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