Periodic limb movement disorder (PLMD) is a condition that was formerly called sleep myoclonus or nocturnal myoclonus. It is described as repetitive limb movements that occur during sleep and cause sleep disruption. The limb movements usually involve the lower extremities, consisting of an extension of the big toe and flexion of the ankle, the knee, and the hip. In some patients, the limb movements can occur in the upper extremities as well.
The limb movements occur most frequently in light non-REM sleep. The repetitive movements are separated by fairly regular intervals of 5 to 90 seconds. There can be significant night-to-night variability to the frequency of limb movements.
It is the only movement disorder that occurs during sleep and, as such, is considered to be a sleep disorder as well.
Periodic limb movement disorder (PLMD) can occur at any stage of life. It is most commonly diagnosed in middle age and older adulthood, though many people report having had symptoms since childhood.
PLMD typically involves a twitching, jerking, or flexing of the limbs during sleep, most frequently during periods of light, non-REM sleep. These movements usually occur in the lower limbs, such as the hip, knee, and ankle, but some people may experience movement in their arms.
Movements tend to be rhythmic, occurring approximately every 20 to 40 seconds. However, limb movements and their frequency can vary significantly from night to night, and from person to person.
People with PLMD are usually unaware of their condition, and it is most often their bed partners that report the limb movements. However, those with PLMD may awaken several times during the night, and experience daytime sleepiness and fatigue.
PLMD can occur in conjunction with other sleep disorders, including restless leg syndrome (RLS).True PLMD – the diagnosis of which requires periodic limb movements in sleep that disrupt sleep and are not accounted for by another primary sleep disorder including RLS – is uncommon.
PLMD has been less extensively studied than RLS. The exact prevalence is unknown. It can occur at any age; however, the prevalence does increase with increasing age. Unlike RLS, PLMD does not appear to be related to gender.
As with RLS, some medical conditions are associated with PLMD. These include uremia, diabetes, iron deficiency, OSA, and spinal cord injury.
Persistent sleep disruption and daytime sleepiness are not part of normal ageing.
The exact cause of primary PLMD is unknown. Researchers suggest that it may be linked to difficulties with nerve regulation, but studies have not led to any consistent findings.
Primary PLMD is not considered medically serious, although complications arising from the condition may cause issues.
According to the National Sleep Foundation, primary PLMD is uncommon.
Secondary PLMD is linked to underlying disorders or medication use.
This type of PLMD is more common in people with the following medical conditions:
- diabetes mellitus
- iron deficiency
- multiple system atrophy – a rare, progressive neurological disorder
- narcolepsy – a disorder causing excessive sleepiness, hallucinations, and sleep paralysis
- obstructive sleep apnea – a common disorder characterized by shallow breathing or pauses in breathing during sleep
- REM behaviour disorder – a sleep disorder where people “act out” vivid dreams, interrupting their sleep
- restless leg syndrome
- sleep-related eating disorder (SRED) – a disorder characterized by eating while sleeping
- spinal cord injury
- spinal cord tumor
- uremia – a buildup of waste products in the blood caused by problems with kidney function
Furthermore, several medications can cause the symptoms of PLMD, including some types of:
- antinausea medications
The main symptom associated with PLMD is a repetitive movement of the limbs during sleep. Most patients are actually not aware of the involuntary limb movements. The limb jerks are more often reported by bed partners. Patients experience frequent awakenings from sleep, non-restorative sleep, daytime fatigue, and/or daytime sleepiness.
Leg movements involve one or both limbs.
- Typically the knee, ankle, and big toe joints all bend as part of the movements.
- The movements vary from slight to strenuous and wild kicking and thrashing.
- The movements last about 2 seconds (and thus are much slower than the leg jerks of myoclonus).
- The movements are rhythmic and repetitive and occur every 20-40 seconds.
For the majority of people, these symptoms do not cause distress, although they may cause problems for bed partners.
The complications that arise from the disorder, however, can be problematic for people with PLMD. These include:
- daytime sleepiness
- poor sleep
PLMD is diagnosed primarily based on an overnight polysomnogram (PSG), a type of test carried out in a sleep laboratory. However, before a PSG, a doctor may carry out a physical examination to rule out other conditions.
Gender – It affects both sexes, but women are more susceptible. Pregnancy increases the risk, but some women who have restless leg syndrome during pregnancy may experience a complete cure or long-term remission soon after delivery.
Age – restless leg syndrome is more prevalent in people older than 40 years, but in many of these cases, people would have had occasional symptoms in their 20s. Even very young children can have restless leg syndrome.
Lifestyle – Nicotine may precipitate restless leg syndrome symptoms or worsen them, probably because it inhibits sleep. Habitual alcohol use also has a similar effect. A sedentary lifestyle also is a risk factor.
Food/drugs – Foods containing caffeine and medications used for treating a number of psychological and physical disorders can cause restless leg syndrome or worsen the symptoms. The list includes sedatives, antidepressants, antihistamines taken for allergies, and opioids used for pain relief.
Other medical conditions – People who have diabetes, obesity, anaemia, Parkinson’s disease, or peripheral neuropathy are more likely to have restless leg syndrome.
Genetics – The majority of people with restless leg syndrome have a genetic history. Several genes are found to carry this risk, and people with restless leg syndrome often have other family members or relatives suffering from it.
A doctor will carry out a thorough physical examination to check whether there is an underlying cause of the sleep problem. The doctor will also take a full medical history and ask about medications, family medical history, and lifestyle factors.
The doctor may request blood tests to detect anaemia, other deficiencies, and infections related to PLMD. These tests may also identify any problems with thyroid function and magnesium levels. A urine sample can detect traces of drugs that contribute to sleep problems.
People experiencing symptoms of PLMD may want to complete a sleep diary for 14 days before the physical examination. This diary should detail sleeping patterns, associated symptoms, such as fatigue and daytime sleepiness, and their effects on daily life.
A PSG records sleep, breathing, movement, and other bioelectrical signals, including brain waves and heartbeat, during sleep. This test helps to rule out the presence of other conditions that may be causing disrupted sleep and excessive limb movements.
After a PSG, a neurologist may be asked to check for other neurological issues or to confirm the diagnosis of PLMD.
In some cases, doctors may recommend additional tests in a sleep laboratory.
This test records:
- brain waves
- heart rate
- oxygen levels in your blood
- eye movements
- other nerve and muscle functions during sleep
- blood pressure
It’s usually done at a sleep disorders unit in a hospital or at a designated sleep centre. A sleep technologist places sensors on your scalp, temples, chest, and legs using medical glue or tape. The sensors are then connected to a computer with long wires, and measurements are taken all through the night while you’re asleep.
Your doctor may also get your complete medical history and give you a physical exam to look for other underlying issues that may be disrupting your sleep. Urine and blood samples are often taken to look for signs of iron deficiency anaemia and any metabolic disorders. Low iron and metabolic disorders such as diabetes have been linked to PLMD.
Treatment for PLMD will depend on the results of the sleep study and other diagnostic tests as well as the severity of your disorder. It may also depend on whether you have another sleep disorder, such as RLS.
Avoiding caffeine and reducing stress
You might not need treatment at all if your PLMD is moderate and doesn’t disturb you or your partner too much. In this case, cutting down on caffeine, alcohol, and smoking can help. Caffeine isn’t just found in coffee. It’s also in sodas, teas, chocolates, energy drinks, and some medications, such as Excedrin.
Yoga, meditation, and other relaxation exercises may also help reduce symptoms. As well, massages or a hot bath prior to sleep can help tame symptoms at night.
Treating the underlying condition
If you’re diagnosed with iron deficiency or another medical condition, treatment is aimed at the underlying condition. Your doctor may want to monitor your iron levels over time and prescribe an iron supplement or recommend a diet high in iron-rich foods.
For severe cases of PLMD, medications that regulate muscle movements may be prescribed as a last resort.
There are several medications available to treat PLMD. They work by reducing or eliminating the limb movements or by enabling the person to sleep through the movements.
Many of the medications used to treat PLMD are also used for RLS. They include:
- Dopamine agonists: These agents are usually the first line drug treatment for PLMD. They increase the levels of dopamine, a brain chemical which helps to regulate the movement of muscles.
- Benzodiazepines: These drugs may be used for PLMD, though some people avoid using them because of concerns about addiction. They act as sedatives, which enable an individual to sleep through the limb movements, and they help to suppress muscle contractions.
- Anticonvulsant agents: These are used to reduce muscle contractions.
- GABA agonists: These medications inhibit the release of some brain chemicals, helping to reduce muscle contractions.
As we have seen, rest or sedentary pose, especially sitting down or lying on the bed for a long time, triggers restless leg syndrome. Not surprisingly, exercise seems to act as an antidote. Being active daily for 30 minutes to one hour is one of the most practical solutions for preventing restless leg syndrome as well as reducing its symptoms
Stretching exercises are particularly helpful. Most restless leg syndrome patients report a significant reduction in symptoms, better sleep, and improvement in daytime function with as little as 30 minutes of daily exercise. Mild forms of exercise such as walking at a comfortable pace and light jogging are more effective than vigorous workouts. Also, it is better to avoid workouts in the evening.
Chronic stress seems to increase the risk of restless leg syndrome as well as worsen the symptoms. That could be because of stress hormones keep the muscles in a constant state of tension. Meditation, deep breathing, and other relaxation techniques can reduce stress and improve restless leg syndrome.
3. Leg massages
Massaging the lower legs and other parts that have restless leg syndrome symptoms help the respective muscles relax. Self-massage works, but massage by another person is even more effective in reducing symptoms. Extra blood circulation to the muscles also might be contributing to this effect.
4. Hot and cold compression
A hot bath before bed can help anyone with insomnia, but for those who have restless leg syndrome, it has the additional benefit of relaxing the muscles and reducing the symptoms. Warm compresses also have a similar effect, but alternating heat and cold compresses are found to be even more helpful in reducing pain and discomfort. Try different methods and choose what works best for you.
5. Healthy diet
What you eat has a role in how you feel, and that’s true in the case of restless leg syndrome. A diet that provides sufficient amounts of protein, essential fats, vitamins, and minerals may remedy the nutritional deficiencies that cause restless leg syndrome.
Include green leafy vegetables, meat, beans, seeds, and fruits that contain quality protein, iron, calcium, magnesium and B-complex vitamins in the diet. Eat more of spinach, chard, pumpkin seeds, almonds, black beans, dark chocolate, avocado, bananas, and figs. Bone broth is excellent too. Flavour the food with unrefined sea salt and Himalayan pink salt.
Taking some probiotic foods like live-culture yoghurt and kefir may help increase the population of beneficial gut bacteria. They help with the absorption of many nutrients from the food, besides fighting off any undesirable microbes. People with celiac disease have an increased risk of restless leg syndrome, so anyone with gluten intolerance or other food allergies should avoid the respective foods.
7. Vitamin and mineral supplements
Deficiency in certain minerals and vitamins is known to increase the risk of restless leg syndrome. If you cannot close the gap with dietary modifications, consider taking supplements, but get a doctor to prescribe them.
The link between anaemia and restless leg syndrome had been observed by Dr Karl-Axel Ekbom after whom the condition was originally called Willis-Ekbom disease. It is now known that dopamine deficiency in the substantia nigra of the brain, which controls neuromuscular movements, is a risk factor for restless leg syndrome as it is for Parkinson’s disease. Since Iron is essential for dopamine synthesis, it explains why people with anaemia are prone to restless leg syndrome.
However, Iron supplementation should be done at a doctor’s recommendation and only after conducting a ferritin test.
Magnesium deficiency causes muscle twitches and tightening that can trigger or worsen restless leg syndrome. The right balance between this mineral and calcium is necessary because it is required to remove excess calcium from soft tissues and help them relax. Deficiency of magnesium can result in calcification of smooth muscles too.