New Discovery On Cause Of Tremor

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.

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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.”

Source: Medical News Today.Jun 2. 2010

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