Restless Leg Syndrome
Someone told me the other day that they thought “restless leg syndrome” (RLS) was a condition cooked up by pharmaceutical companies to sell medications. You may have seen commercials for Requip and Mirapex, both drugs used to treat this condition.
People have described symptoms suggestive of restless legs since the 17th Century. The Swedish neurologist Erik Ekborn initially coined the term in the 1940s. It is estimated that between ten to fifteen percent of Americans suffer from the condition. The incidence in women is about twice that of men. About 40 percent of people develop symptoms prior to age twenty. Since symptoms tend to be mild initially and worsen with age, most sufferers are not diagnosed for 10 to 20 years after they start having problems.
The symptoms of RLS are highly variable, but most people describe a bothersome, irresistible urge to move their legs. This feeling is worsened during periods of inactivity and often interferes with sleep with about 85 percent of sufferers having trouble falling asleep. Stress and fatigue can also exacerbate the symptoms.
Restless Legs Syndrome is a movement disorder that primarily affects the legs but the arms can also be involved. The exact cause of RLS is not known, but there are many hypotheses. The most widely accepted proposed mechanism involves a genetic defect that impairs the ability of certain nerves in the brain to use 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 buildup of waste products is the underlying 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, likely making it a multifactorial condition.
The diagnosis of RLS is based on the medical history. The International RLS Study Group described the four necessary elements for the diagnosis in 1995: (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 appear 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.
Leg cramps that occur at night are often mistaken for RLS. These usually differ from RLS by being in one leg, being painful, having a sudden onset, and having one or more hard muscles. 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 often confused with RLS and is actually present in 85 percent of RLS sufferers. PLMS, also known as nocturnal myoclonus, causes jerking of the limbs or brief, intermittent muscle contractions 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, vitamin deficiencies, and other conditions that can affect nerve function should also be evaluated. Tests of nerve function and possibly a sleep study can be also be helpful.
Treatment of RLS involves avoiding caffeine, alcohol, and tobacco as well as correcting vitamin & mineral deficiencies and treating other underlying problems. Medications that mimic the neurotransmitter dopamine are frequently prescribed 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.
Dr. John Roberts is a retired member of the Franciscan Physician Network specializing in Family Medicine.