New treatments for a common neurological disorder that blights the lives of 6.5 million Brits could be on the horizon after a breakthrough by scientists.
Known as Restless Legs Syndrome (RLS), it triggers the irresistible urge to move around.
Until now it was believed to be caused by genetic, metabolic and central nervous system mechanisms.
But an international team has shown for the first time nerve cells targeting the muscles themselves are also responsible.
It could lead to the development of drugs that target the ion channels that are essential for them to communicate with each other.
Study corresponding author Dr Dirk Czesnik said: “Patients who suffer from Restless Legs Syndrome complain of painful symptoms in the legs leading to sleep disturbances.
“The mechanisms for RLS are still not completely understood.
“We have shown that also the nerve cells supplying muscles in the leg are responsible and hereby additional drug treatments may be ahead targeting these nerve cells.”
The findings, published in the Journal of Physiology, show that the involuntary leg movements in RLS are caused by increased excitability of the nerve cells that supply the muscles in the leg.
Researchers explained that it results in an increased number of signals being sent between nerve cells.
Dr Czesnik, of Gottingen University in Germany, and colleagues said RLS is a common condition of the nervous system that causes an overwhelming irresistible urge to move the legs.
Patients complain of unpleasant symptoms such as tingling, burning and painful cramping sensations in the leg.
More than eight in 10 people with RLS experience their legs jerking or twitching uncontrollably, usually at night.
Dr Czesnik said: “Targeting the way messages are sent between nerve cells to reduce the number of messages to normal levels may help prevent the symptoms of RLS occurring
“This could be achieved by new drugs that block the ion channels that are essential for the communication between nerve cells.”
Working with colleagues in the US and Australia, Dr Czesnik measured the nerve excitability of motor nerve cells of patients suffering with RLS and healthy subjects.
Dr Czesnik added: “The next step is to investigate the effect of different medications in patients and the effect on RLS.”
The condition causes sufferers to toss and turn all night because the can’t keep their legs still. Their legs tingle as though there’s an electrical current in them that won’t switch off.
It is estimated to affect about ten percent of people in Britain alone. Symptoms tend to be most severe when sufferers are at rest, in the evening and at night, and especially when they lie down.
Restless Legs Syndrome also affects many people over 65, especially those with a secondary condition, such as renal disease or anaemia.
The syndrome ranks as the fourth-leading cause of insomnia, according to the British National Sleep Foundation.
Most people with RLS have lived with it for years, even decades, before finding a doctor who can put a label on their problem.
By that time, many are so sleep deprived and so miserable that they feel they’re losing their minds.
Opioids and dopamine have been used to ease symptoms. But these can come with troublesome side effects, including dizziness, nausea, vomiting and the risk of addiction.
With the new research, it is hoped that more sophisticated drugs can be developed to treat the problem.
RLS affects twice as many women as men. Many sufferers first develop symptoms in their early forties, but people of all age groups can suffer from the condition.