Restless leg syndrome (RLS), also known as Willis-Ekbom disease, is a common condition that causes an irresistible urge to move the legs. This urge to move is often accompanied by uncomfortable sensations in the legs. RLS symptoms typically occur when sitting or lying down and are relieved by movement. They are most bothersome in the evening and at night.
What are the symptoms of RLS?
The main symptom of RLS is an overwhelming urge to move the legs when they are at rest. This urge is often accompanied by uncomfortable sensations in the legs described as creeping, crawling, tingling, pulling, itching, burning, aching, or like insects crawling inside the legs. The unpleasant feelings prompt an uncontrollable need to move the legs.
RLS sensations range from mild to intolerable. Symptoms come and go but are generally worse in the evening and during the night. The sensations are difficult to describe to someone who has not experienced them, but people use words like aching, boring, crawling, creeping, electric, itchy, pins and needles, pulling, throbbing, tingling, and wormy.
RLS symptoms get worse when lying down or sitting for prolonged periods. Symptoms are usually temporarily relieved by movement such as walking or stretching. However, relief continues only as long as the movement. RLS symptoms may improve or even disappear for days, weeks, or months, but they usually return.
What causes the urge to move the legs?
The cause of RLS is unknown, but most evidence suggests that RLS has a genetic component. People are more likely to have RLS if they have a family member with RLS. Studies show that genes in chromosomes 12 and 14 are associated with RLS.
RLS has also been related to low iron levels in the brain. This may explain why RLS symptoms often improve with iron treatment. Other factors that can worsen symptoms or trigger RLS include:
- Pregnancy
- Chronic diseases such as kidney failure, diabetes, and peripheral neuropathy
- Certain medications including antidepressants, antihistamines, and antinausea drugs
- Caffeine, tobacco, and alcohol use
- Sleep deprivation or sleep disorders
- Anemia and iron deficiency
Who develops restless leg syndrome?
RLS can affect people of any age but symptoms are more common and more severe among older individuals. RLS occurs in both genders but is more prevalent in women than men.
RLS affects up to 10 percent of U.S. adults to some degree. It is estimated that 2 to 3 percent of adults have RLS that is moderate to severe with symptoms occurring 2 or more times per week.
What are the diagnostic criteria for RLS?
There are no medical tests such as blood tests or imaging scans that can diagnose RLS. The condition is diagnosed based on clinical features. The following criteria are used to make a diagnosis of RLS:
- An urge to move the legs due to uncomfortable sensations in the legs
- Symptoms begin or worsen with rest
- Symptoms are partially or totally relieved by movement
- Symptoms are worse in the evening or at night
These features must not be solely accounted for by another medical or behavioral condition such as leg cramps, positional discomfort, nerve issues, arthritis, anxiety, or habitual foot tapping.
Clinical interview
To determine if someone meets the diagnostic criteria for RLS, a doctor will begin with a clinical interview. They will ask about:
- Symptoms in the patient’s own words
- Location, nature, frequency, timing, duration, and severity of symptoms
- What makes symptoms start or become worse
- What provides relief
- Impact on sleep and daytime functioning
- Family history of RLS
- Medical history and current conditions and medications
- Use of stimulants like caffeine, tobacco, and alcohol
Information obtained during the interview can help distinguish RLS from other conditions like leg cramps, akathisia, positional leg discomfort, arthritis, and peripheral neuropathy.
Physical examination
A physical exam will also be performed as part of the diagnostic process. This includes an examination of the nervous system to check muscle tone, muscle strength, reflexes, and sensory function.
The exam looks for signs of:
- Numbness or tingling sensations
- Pain
- Swelling
- Skin discoloration
- Varicose veins
- Weakness
- Muscle tenderness
- Joint pain or inflammation
- Changes in reflexes
The physical exam along with the patient history helps identify or exclude medical conditions that could be causing or contributing to symptoms.
Sleep study
A sleep study, also called polysomnography, records brain waves, heart rate, breathing, and limb movements during sleep. This test may be recommended to rule out other sleep disorders like periodic limb movement disorder (PLMD).
Individuals with RLS almost always have periodic limb movements in sleep, which are involuntary jerking movements of the legs that occur every 20-40 seconds. However, most people with PLMD do not have RLS symptoms when awake.
A sleep study can demonstrate the extent of sleep disruption due to RLS versus PLMD. It can also show that symptoms are worse at night, which is a key diagnostic criterion for RLS.
Blood tests
There are no blood tests to diagnose RLS, but blood work may be ordered to check for conditions that can trigger or worsen RLS, including:
- Anemia
- Kidney disease
- Diabetes
- Thyroid problems
- Iron deficiency
Iron deficiency, even without anemia, can exacerbate RLS symptoms. A blood test checking ferritin levels, which indicate iron stores in the body, may be recommended.
How is RLS distinguished from other conditions?
RLS symptoms can be similar to other medical conditions, so part of the diagnostic process involves excluding other potential causes. Conditions that may resemble RLS include:
Leg cramps
Leg cramps cause tight, painful leg muscles. They typically happen at night and are relieved by stretching. Leg cramps are not accompanied by an urge to move the legs.
Positional leg discomfort
Discomfort caused by pressure on nerves or reduced blood flow can disturb sleep. Position changes relieve the discomfort. Positional problems improve once standing, unlike RLS.
Akathisia
Akathisia is an unpleasant feeling of inner restlessness and inability to stay still that may arise from medications. Akathisia occurs during wakefulness and persists throughout the day, while RLS mainly occurs at rest and at night.
Peripheral neuropathy
Numbness, tingling, burning, or pain in the feet and legs can be due to nerve damage from diabetes, alcoholism, or vitamin deficiencies. However, these sensations are constant and not associated with an urge to move.
Arthritis
The aching discomfort of arthritis may worsen at night but does not display other RLS characteristics of relief with movement or worsening at rest.
Anxiety
Anxiety can cause restlessness and agitation but does not have the circadian pattern of RLS symptoms that are worse at nighttime.
Conclusion
RLS is diagnosed based on a thorough clinical evaluation. The doctor elicits a detailed history of symptoms, performs a physical exam to rule out other conditions, and may order tests like blood work or a sleep study. The diagnosis is made if the patient satisfies all four diagnostic criteria for RLS.
Distinguishing RLS from other potential causes of leg discomfort is an important part of the diagnostic process. Once RLS is accurately diagnosed, appropriate treatment can be initiated to provide symptom relief.