What makes legs restless?
Monday, January 13, 2014 9:00 PM
Someone told me the other day that they thought "restless leg syndrome" was a condition made up by pharmaceutical companies to sell more medications. I'm sure everyone has seen the commercials for Requip® and Mirapex®, both drugs used to treat this malady.
People have described symptoms suggestive of restless legs since the 17th Century. The Swedish neurologist Erik Ekborn, initially coined the term "restless legs syndrome" in the 1940's. It is estimated that between 10-15 percent of Americans suffer from RLS to some degree. The incidence in women is about twice that of men. About 40 percent of people develop symptoms prior to age 20. Since symptoms tend to be mild initially and worsen with age, most sufferers are not diagnosed for 10 to 20 years.
The symptoms of RLS are highly variable, but most people describe a bothersome, irresistible urge to move their legs (and sometimes the arms). This urge to move the legs is worse during periods of inactivity and often interferes with sleep. About 85 percent of sufferers have difficulty falling asleep. Stress and fatigue can also exacerbate the symptoms.
Although RLS is a movement disorder that primarily affects the legs, the arms can be involved as well. The exact cause of RLS is not known, but there are many hypotheses. The most widely accepted proposed mechanism involves a genetic problem that reduces the ability of certain nerves in the brain to utilize the neurotransmitter dopamine to communicate. Another hypothesis has to do with impaired iron metabolism.
Most feel it is a nerve cell disorder, while others think a build up of waste products is a factor. The neurotransmitter link is supported by a reduction in RLS symptoms in those who take medications that increase the levels of dopamine in the brain. The condition seems to involve all of these factors to varying degrees in different people.
The diagnosis of RLS is based on the medical history. The International RLS Study Group in 1995 described the four necessary elements for the diagnosis: (1) a compelling urge to move the limbs, usually with tingling or abnormal sensation, (2) motor restlessness (floor pacing, tossing/turning in bed, rubbing the legs), (3) symptoms present at rest or worse with rest with variable relief on activity and (4) symptoms that are worse in the evening or night and typically better by 5 a.m.
Most cases of RLS are "idiopathic," meaning there is no clear cause. Again, there appears to be some genetic predisposition. There are also other conditions that seem to be associated with RLS. These include iron deficiency, peripheral neuropathy, vitamin & mineral deficiencies (folate, magnesium, B12), diabetes, rheumatoid arthritis and pinched spinal nerves, among others.
There are conditions that people often mistake as RLS. Probably the most common is leg cramps that occur at night. These usually differ from RLS by being in one leg, causing pain, having a sudden onset and having a hard muscle. Certain psychiatric medications can cause abnormal movements. These movements are usually generalized (not just the legs) and don't happen only at night or at rest, unlike RLS.
Periodic leg movements of sleep (PLMS) is another condition that is often confused with RLS and is actually present in 85 percent of those who have RLS. PLMS, also known as "nocturnal myoclonus," is a condition where the limbs jerk or contract for a few seconds in a repetitive fashion every 20-40 seconds. This can be very disruptive to normal sleep.
An evaluation for RLS should include blood work to look for iron deficiency (particularly a ferritin level), and perhaps vitamin or mineral deficiencies. Thyroid problems, diabetes and other conditions that can affect nerve function should also be looked into. Other investigations may include tests of nerve function and a sleep study.
Treatment of RLS involves avoiding caffeine, alcohol and tobacco, correcting vitamin & mineral deficiencies and treating other underlying problems. Medications that mimic the neurotransmitter dopamine are usually recommended if RLS symptoms are present three or more nights a week. Examples include levodopa, Mirapex®, Requip® and the Neupro patch. Blood pressure medications like clonidine and occasionally medications to promote sleep such as clonazepam are used as well.
Dr. John Roberts is a Crawfordsville physician and one of the owners of The Paper. In addition to his weekly column, he writes a daily health tip that can be found on page A1.