General: In many cases, there is no known cause of restless legs syndrome. Researchers believe that the disorder may be the result of an imbalance of a brain chemical called dopamine. This chemical sends messages to control muscle movement.

Genetics: About 50% of RLS cases appear to run in families. Scientists have identified specific locations on chromosomes where RLS genes may be present.

Other medical conditions: Most cases of RLS are not caused by underlying medical problems. However, RLS sometimes occurs in patients who have peripheral neuropathy, which damages the nerves in the hands and feet.

RLS may also occur in patients who have low levels of iron in their blood. RLS is common among patients who are undergoing dialysis. This is because patients who have kidney failure may also have iron deficiency, which may cause or worsen RLS.

In addition, many patients with Parkinson's disease also have RLS. However, it is important to note that having Parkinson's disease does not appear to increase the risk of developing RLS. Also, having RLS also does not appear to increase the risk of developing Parkinson's disease later in life.

Pregnancy: Some women experience RLS for the first time during pregnancy, especially during the last trimester. However, this condition is temporary for most pregnant women, and symptoms usually go away about one month after delivery.

Factors that may worsen symptoms: Stress has been shown to worsen symptoms of RLS. Pregnancy, hormonal changes, or iron deficiency may temporarily worsen symptoms. In addition, alcohol and tobacco may trigger or worsen symptoms of RLS. Certain medications, such as H2-histamine blockers (e.g. Zantac® or Tagamet®), some antidepressants (e.g. Elavil®), anti-nausea drugs, and calcium channel blockers, may also worsen symptoms.

During a physical examination, a healthcare provider will first rule out other medical conditions, such as muscle diseases, joint conditions, nerve problems, and circulation problems, that may be causing symptoms.

The International Restless Legs Syndrome Study Group has developed four diagnostic criteria for RLS. However, RLS is still a difficult condition to diagnose because healthcare providers primarily depend on the patients' descriptions of their symptoms. The diagnostic criteria include: 1) the patient has a desire to move the limbs, often associated with abnormal sensations (called paresthesias) or unpleasant abnormal sensations (called dysesthesias); 2) symptoms that are worse or only present during rest are partially or temporarily improved with physical activity; 3) the patient experiences motor restlessness; and 4) symptoms are the worst during sleep.

Although most patients with RLS have period limb movements of sleep (PLMS), it is not necessary for a diagnosis. If PLMS is suspected, the patient may be asked to spend the night at a sleep center. When the patient is asleep, researchers monitor the electrical activity of the brain and heart, the movement of the muscles, the movements of the eyes, and breathing patterns.

General: Restless legs syndrome can develop at any age. Symptoms vary in severity and duration among patients. They generally begin when the patient is sitting or lying down for extended periods of time and lessen when the patient moves the affected legs. In some patients, the condition may worsen with age. Some patients may experience short periods of remission that may last for days, weeks, or months.

Symptoms during inactivity: Symptoms develop when the individual sits or lies down for an extended period of time, especially during sleep.

Symptoms typically include unpleasant sensations, such as burning, tingling, aching, jittery, or crawling sensations, in the legs. These sensations typically occur deep inside the leg, between the knee and ankle. In rare cases, the sensations may also occur in the feet, thighs, arms, or hands. Both sides of the body are usually affected, although it is possible for symptoms to occur on just one side. These feelings cause an uncontrollable urge to move.

Symptoms go away with movement: Once the patient stands up, walks, or moves the legs around, the symptoms start to go away. Patients may frequently stand up, pace, jiggle their legs, or toss and turn during sleep.

Periodic limb movement of sleep: More than 80% of patients with RLS experience a condition called period limb movement of sleep (PLMS). Although many patients with RLS also develop PLMS, most people with PLMS do not experience RLS. This condition causes the patient to involuntarily twitch or jerk the legs during sleep. Oftentimes, the patient is unaware of these symptoms. Patients who have severe RLS may have more serious symptoms of PMLS that cause significant leg jerking that can occur while the individual is awake. PMLS is more common among adults older than middle age.

Insomnia and daytime fatigue: Restless legs syndrome (RLS) may make it difficult to fall asleep at night. This is because symptoms are generally worse when the individual is lying down for extended periods of time. Period limb movement of sleep (PLMS), which often occurs in RLS patients, may also disrupt sleep in some patients. Sometimes limb movement may also wake up the patient's bedmate.

When individuals do not get enough sleep, they may experience excessive daytime drowsiness. During the day, patients may feel tired, inattentive, or unable to concentrate.

Quality of life: Symptoms of RLS may interfere with an individual's quality of life. Patients who experience symptoms are encouraged to visit their doctors because lifestyle changes and medications can help reduce symptoms of the disorder.