New Discovery On Cause Of Tremor

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New Discovery On Cause Of Tremor

http://www.medicalnewstoday.com/articles/190665.php

In a new discovery, UK scientists have found a mechanism in the spine that

counteracts the brain waves that produce tremor: they suggest the discovery

could help around 1 million people in the UK who suffer from shakes and tremors.

A paper on the research that led to the discovery, which was funded by the

Wellcome Trust, and conducted by scientists at the Institute of Neuroscience at

Newcastle University, Newcastle upon Tyne, was published online ahead of print

in the 1 June issue of the Proceedings of the National Academy of Sciences.

Most healthy individuals have experienced mild tremor, it is not uncommon when

we feel tired, hungry or nervous, but more severe forms can be a symptom of

neurological disease, including Parkinson's, Multiple Sclerosis and also

Essential Tremor which is usually a disease of old age but it can also affect

young people and it often leaves patients unable to walk unaided.

Dr Stuart Baker, professor of movement neuroscience at Newcastle, told the media

that:

" We don't fully understand the brain systems causing these tremors but they can

really have a massive impact on someone's quality of life. They lose their

independence and can't do something as simple as make a cup of tea. "

Baker explained the approach they took in their research: instead of looking at

why people have tremors, they decided to investigate why most people don't have

them.

He said that the part of the brain that controls movement produces brain waves

the work at 10 cycles per second, so in theory everyone should have tremors that

have that frequency.

In fact we do, said Baker, but the tremor is so smal that we don't notice it. So

he and his team wondered if there was another process at work, one that

countered the effect of the 10 cycles per second.

For their study, Baker and colleagues used macaque monkeys: they taught them how

to move their index finger backwards and forwards very slowly, which exacerbated

the natural minor tremor that we humans and our primate relatives have in

common.

They then recorded nerve cell activity in the brain and spinal cord as the

animals performed their slow finger movements.

The results showed that not only was the rhythm of nerve cell activity in the

brain and spinal cord oscillating at around the same frequency as the tremor,

but that the spinal cord was exactly out of phase with the brain, effectively

cancelling out its oscillations and thus reducing the size of the tremor.

The researchers wrote that:

Convergence of antiphase oscillations from the SC [spinal cord] with cortical

and subcortical descending inputs will lead to cancellation of approximately 10

Hz oscillations at the motoneuronal level. "

They concluded that:

" This could appreciably limit drive to muscle at this frequency, thereby

reducing tremor and improving movement precision. "

Baker said there are many types of disease associated with tremor, and perhaps

in some of these the controller in the spine malfunctions and that is what

actually leads to tremor.

In other diseases, he said, we already know the cause of tremor is a problem in

brain regions that produce abnormally high oscillations.

" But even then, the spinal system we have discovered will reduce tremors, making

the symptoms much less severe than they would otherwise be, " he added.

The researchers suggested that the more we understand about how the spinal

controller works, the better chance we have of developing treatments that adjust

it to work better and thereby reduce the levels of tremor that patients

experience and improve their quality of life.

" Spinal interneuron circuits reduce approximately 10-Hz movement discontinuities

by phase cancellation. "

R , Demetris S Soteropoulos, and Stuart N Baker.

PNAS, published ahead of print June 1, 2010.

DOI:10.1073/pnas.0913373107