Sleep disorders are becoming ever more prevalent in modern society with reasons such as stress, noise, anxiety and lifestyle all cited as possible causes. Two common sleep problems are restless legs syndrome and the lesser known periodic limb movement disorder. Often people mistake one for the other and although they do share some similarities, there are noticeable differences.


What is PLMD and RLS

Periodic limb movement disorder (PLMD) is classed as a sleep disorder whereas restless legs syndrome (RLS) is a neurological disorder. These conditions can run in families but can affect anyone at any age. Up to 10% of people suffer from restless legs syndrome at some stage  and unfortunately, incidence only seem to increase with age. Both conditions cause considerable disruption to sleep quality, leaving the sufferer feeling excessively tired and exhausted.  While up to 80% of restless legs sufferers also have PLMD, most people with PLMD don't have RLS.

Sufferers of PLMD may be completely unaware of their problem since they are asleep when the symptoms occur. But even so, their sleep patterns can still be severely disrupted. Often the only sign that anything is wrong is their excessive tiredness after a poor night's sleep. And in many cases the condition is only brought to their attention by their bed partner who is frequently disturbed by their movements.

RLS sufferers differ in that they are fully awake during their symptoms. Indeed it is their symptoms that are preventing them from going to sleep, leading to sleep loss and tiredness the next day. Though it can affect anyone, it’s quite common in children and is sometimes called ‘growing pains’.

Symptoms

Periodic limb movement disorder is characterized by rapid, involuntary and jerky movements of the lower limbs, usually the knee, ankle and big toe and occur roughly every 20-40 seconds, hence the name ‘periodic’. The symptoms most often begin soon after falling asleep and the intensity of the movements varies from person to person, from small twitching motions to strenuous kicking.

Restless legs syndrome on the other hand, is more of an annoying or unpleasant feeling in the legs and occasionally the arms. It’s often described as a burning or tingling sensation, where the sufferer feels an overwhelming urge to move their limbs which can make it impossible to fall asleep. The symptoms nearly always appear towards the evening while at rest or in bed and often the only way relief can be found is by getting up again and stretching or walking around.

Possible Causes and Treatments

In many cases the causes of both conditions are unknown. Periodic limb movement disorder and restless legs syndrome can be primary (where the cause is unknown) or secondary (the result of an underlying medical condition). The primary cause of PLMD is thought to be due to abnormalities of the nerve functions between the brain and lower limb, whereas the primary cause of RLS may be due to an imbalance of the chemical dopamine in the brain.

Secondary causes of both PLMD and RLS can be the result of an underlying medical condition, for example an iron deficiency, which is quite common among women and children. Other possible causes for both sleep conditions include poor kidney function, diabetes, caffeine or withdrawal from certain medications.

If symptoms of either disorder are particularly troublesome and are causing excessive sleep disruption, it may be possible to provide some relief by altering the diet or in more severe cases, through medication. Treatments which are used for both PLMD and RLS include benzodiazepines, narcotics or drugs used for Parkinson's disease. In some cases the symptoms may clear up completely.

While restless legs syndrome and periodic limb movement disorder have quite different symptoms, both have the potential to cause significant sleep disruption. And though the exact cause may never be known, those suffering from either problem may be able to find some relief through lifestyle changes or medication and finally achieve a restful night's sleep.