By Rachel Korson, M.D.
Recently, a 3-year-old adopted Chinese girl came into the Stanford Sleep Center complaining of difficulty falling asleep. Upon further questioning, it was clear that this difficulty was accompanied by crying, repetitive kicking, and complaints that her feet felt "itchy." Her parents would often massage her legs to help her to fall asleep. She would wake up each night around 2 a.m. with the same complaints. Initially, her parents thought she had allergies affecting her legs, and tried Benadryl and cortisone cream. Unfortunately, this provided no relief and her symptoms did not improve. She was taken to a dermatologist, but no cause of her condition could be identified. Her pediatrician thought that she was simply having growing pains.
In order to further evaluate her complaints, and because these seemed to occur more at night and out of sleep, she was referred to a sleep specialist. After hearing her story and examining her, suspicion was quickly raised that this young girl may have restless legs syndrome (RLS). To identify potential causes, a serum ferritin level was ordered. This measure of iron stores within the body came back very low, further supporting the diagnosis. The girl was placed on an iron supplement to replenish her body's stores. Later she was also started on a low dose of a medication called a dopamine agonist, which is commonly prescribed to treat RLS.[1] To the relief of her and her parents, she had a significant improvement in her symptoms and is now falling and staying asleep more easily.
What is RLS? This condition is diagnosed based on four essential features. There has to be an urge to move the legs usually accompanied or caused by an uncomfortable or unpleasant sensation in the legs. The urge to move or unpleasant sensation begins or worsens during periods of rest or inactivity, such as while lying or sitting. These sensations are partially or totally relieved by movement, such as walking or stretching, at least as long as the activity continues. The symptoms are worse in the evening or night (as compared to the day) or they only occur in the evening or night.
Many people with RLS have the condition running in their family. In this child, as she was adopted, it was impossible to determine if this contributed in her case. These symptoms may be associated with periodic limb movements of sleep (PLMS), which are identified on a standard sleep study. RLS itself is based on symptomatic complaints, so just because someone has PLMS does not mean that they have RLS. These movements may occur with other conditions such as sleep apnea.
When your doctor considers RLS as a diagnosis, it is important to consider other possible conditions. Some of these considerations include: growing pains, neuropathic pain syndromes, peripheral neuropathy, arthritis, nocturnal leg cramps, restless insomnia, positional discomfort, vascular or neurogenic claudication, drug-induced akathisia (restlessness), and habitual foot tapping.
In general, RLS is not described as a painful condition. Rather it is often referred to as a "creepy-crawly" sensation, achiness, "unscratchable itch," "unpleasant tickle," "feeling of unrest," or "ants in the pants." Nevertheless, these symptoms may lead to a great deal of discomfort and distress.
How common is RLS? It is estimated that it affects 7-10% percent of people living in North America and Europe.[2] Women are affected twice as often as men. There seem to be ethnic and geographic variations, with the condition having a clear genetic predisposition. Some of the identified genes that contribute to the condition include the BTBD9 gene on chromosome 6, MEIS1 gene on chromosome 2, MAP2K5 and transcription factor LBXCOR1 on chromosome 15q, and PTPRD gene on chromosome 9. Some of these same genes are also associated with the development of attention deficit hyperactive disorder (ADHD) and there appears to be an increased prevalence of ADHD in children with RLS.
What are the treatment options available for RLS? For unclear reasons, RLS is often associated with iron deficiency. This may occur in anemia, pregnancy, and kidney disease. Therefore, taking an iron supplement with vitamin C to improve absorption often proves beneficial in the management of RLS symptoms.[1] RLS is also associated with low levels of a chemical within the nervous system called dopamine. As observed in the child described above, it responds to medications called dopamine agonists. These include Mirapex, Requip, and the Neupro patch. It may also be treated with different medications called gabapentin or Horizant. In severe cases, very low-dose opioid medications like oxycodone or methadone may also prove very effective.
It is also helpful to avoid the triggers for RLS. Caffeine and alcohol are known triggers that worsen RLS symptoms. Cutting back on their consumption often improves symptoms. Certain medications such as anti-emetics (for nausea relief), antihistamines (for allergies), and antidepressants may also exacerbate RLS symptoms. Avoiding these drugs can also minimize the symptoms.
In conclusion, RLS is a relatively common disorder that tends to run in families and is often under-recognized in children. It may be misdiagnosed as growing pains. RLS often significantly impairs sleep quality and may lead to difficulty falling asleep and decreased quality of life. Fortunately, treatment with the right medications and the avoidance of known triggers is often very effective in improving symptoms.
Rachel Korson, M.D. is a sleep medicine fellow at the Stanford Center for Sleep Sciences and Medicine. This Center is the birthplace of sleep medicine and includes research, clinical, and educational programs that have advanced the field and improved patient care for decades. Dr. Korson is also a board-certified neurologist and plans to practice in Murray, Kentucky beginning in July 2013. To learn more, visit us at our website.
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Sources:
[1] Aurora RN, Kristo DA, Bista SR, Rowley JA, Zak RS, Casey KR, Lamm CI, Tracy SL, and Rosenberg RS. "The treatment of restless legs syndrome and periodic limb movement disorder in adults--an update for 2012: practice parameters with an evidence-based systematic review and meta-analyses." SLEEP 2012; 35(8):1039-1062.
[2] The International Classification of Sleep Disorders: Diagnostic and Coding Manual. American Academy of Sleep Medicine, Westchester, IL. 2nd edition. 2005.