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Some sleep disorders are a little harder to spot than others. You may only experience occasional daytime sleepiness and mild fatigue, and it may seem that nothing is wrong with your sleep. However, if these symptoms persist for a more extended period, your sleep quality may suffer more dramatically, and you can develop insomnia. Lack of proper rest increases the risk of developing numerous medical conditions; it also decreases your cognitive functioning, performance, and overall quality of life. Because of that, it is essential that you consult with your physician if you notice any abnormal behavior with your or your partner’s sleep.
Periodic limb movement disorder (PLMD) is one of those sleep disorders that you might not notice at first. It is characterized by repetitive limb movements during sleep. PLMD usually involves the movement of hip, knees, ankles, and toes, but in some rare cases, arm movements can be present. While PLMD doesn’t have any dramatic consequences, it can lead to daytime sleepiness and fatigue, fragmented sleep, and insomnia if symptoms get worse. It might do more harm to your partner’s rest since the person affected often doesn’t realize that they are making these repetitive movements during sleep. The diagnosis requires an overnight sleep study, and the treatment might include the use of medications and lifestyle adjustments.
When PLMD was first discovered in the 1950s, it was named nocturnal myoclonus. We now use term nocturnal myoclonus for a wider variety of muscle jerking and twitching during the night, and PLDM is now characterized by repetitive movements of limbs during sleep. Periodic refers to rhythmic movements that occur every 20-40 seconds, and these events can last up to an hour. It usually involves big toe, ankles, or knees, but it can affect arms as well.
PLDM is the only sleep-related moving disorder that occurs exclusively during sleep. Hypnic jerks or sleep starts are other types of involuntary movements, but they mostly happen during the transition between wakefulness and sleep. You know that feeling, when you suddenly twitch your body, wake up, and it seems like you were dreaming of falling or tripping over. They are entirely normal and occur frequently, but they are not the same as PLDM. Restless legs syndrome (RLS) is another sleep-related disorder that affects limbs, but unlike PLDM, it only affects legs. RLS is described by the extremely unpleasant feeling and pain in lower extremities, and the sufferer feels like they should move to ease the pain. We should make the distinction between those two disorders, even though some researchers are suggesting that they are a part of the same condition. Individuals who have RLS also have PLDM in 80% of the cases, but the reverse can not be said. Unfortunately, the cause for both of these disorders is yet to be found, so there is still plenty of research to be done ahead of us.
Periodic limb movements happen during the non-REM sleep, mostly during light stages of sleep. The people experiencing them often don’t have a clue what’s happening until their partner points it out. Their partners can be awakened multiple times each night, as these movements can vary from mild to kicking, and can make sleeping impossible. Also, people with PLMD might experience one of the following consequences:
- Daytime sleepiness
- Fragmented sleep
- Poor memory
- Shorter attention span
When more intense movements occur, the people experiencing them is most likely to wake up, and that can lead to sleep fragmentation. Falling back asleep after a few of these events might be hard for some people, and it can further lead to sleep deprivation and insomnia. Memory, learning, and other cognitive abilities such as problem-solving all suffer when you are not getting enough sleep. Your brain and body don’t have enough time to repair and restore, and your daytime functioning becomes worse and worse with every night of insufficient sleep. That is why it is important to talk to a medical professional if you notice that something is impairing your regular rest.
Causes and Risk Factors
PLDM can be primary or secondary. The cause for primary PLDM is still unknown, while secondary PLDM is caused by some underlying medical problem or medication abuse. Some abnormalities in nerves regulating limbs have been observed in the individuals with primary PLDM, but the nature of these abnormalities is still unknown, and it should be a subject of further research. Secondary PLDM has many different causes including:
- Diabetes mellitus
- Iron deficiency
- Spinal cord injury
- Spinal cord tumors
- Anemia – low levels of hemoglobin, a molecule that carries oxygen and carbon dioxide through the bloodstream
- Sleep apnea – breathing difficulties during sleep that causes oxygen deficiency and carbon dioxide build up
- Narcolepsy – a sleep disorder characterized by excessive daytime sleepiness and an overwhelming urge to fall asleep during waking hours
- Uremia – a build-up of waste products in blood due to the poor kidney functioning
- Multiple system atrophy – a rare neurological disorder
- REM behavior disorder – muscles are typically paralyzed during REM sleep, but with this disorder, they are not, so people act out during their vivid dreams
- Restless legs syndrome
- Sleep-related eating disorder – a condition characterized by people eating in their sleep
- Medication use such as antidepressants, antipsychotics, anti-nausea medication, and antihistamines.
- Withdrawal from sedative medications
The prevalence of PLMD is not known, but it is estimated to be about four percent in the adult population. Unlike RLS that is twice as likely to affect women than men, sex doesn’t play a significant factor when it comes to PLDM. It can also affect people of all ages, but it is much more common as you get older. Prevalence is at around 30% for people who are over 60 years old. Listed conditions and disorders increase the chances of developing PLDM, while scientists also argue that we could look for a cause among genetic factors and disrupted dopamine regulation.
Poor sleep, daytime sleepiness, and fatigue are the most bothersome symptoms for most people affected by PLMD. However, it never occurs to them that their sleep problems are related to nocturnal limb movements since these symptoms are shared with most sleep disorders. Your health care provider might ask you a series of questions to determine the cause of your sleep disturbances. They are likely to ask you about your other medical problems both current and the past ones, your family medical history, your medication use, your travel and work history, as well as your general habits and lifestyle. They might ask you to keep a sleep diary for a week or two prior to your physical exams, with the information about your sleep patterns, associated symptoms, and the way they affected your daily life.
A detailed physical examination takes place to uncover if there is any underlying medical condition causing nocturnal limb movements. Blood tests are carried to determine hemoglobin levels and whether the patient is suffering from anemia, but also to show magnesium and iron levels, basic organ functioning, thyroid hormone levels, and any possible infection that could be causing the disease. A urine sample tells doctors if there is any drug use that could be the cause of the problem. Besides, these tests can show them whether there is some other deficiency and if your body is working properly. Unfortunately, no test can show a positive result and say that you have PLMD, so doctors need to consider various options and also do an overnight sleep study called polysomnography.
Polysomnography is done in a sleep facility where you are closely observed by sleep technicians. They monitor your breathing, heart rate, movements, brain activity, snoring, and other factors to determine the cause of your sleep problems. This helps them gather all the information they need, rule out other sleep disorders, and make sure that PLMD is the right diagnosis.
Unfortunately, there is no cure for this disorder, but there are some things that can improve the symptoms. For mild PLMD, doctors often suggest only lifestyle adjustments, while individuals with more severe symptoms are prescribed some medications to help ease them.
Most of the medications used are similar to ones used to treat RLS, and they include:
- Benzodiazepines – drugs that suppress muscle contraction. They are also sedatives, so they will help you sleep through the limb movements. Clonazepam has been shown to produce the best results as it drastically reduces total limb movements per hour. It is the most widely used drug to treat PLMD.
- Dopamine agonists – drugs that increase the levels of dopamine, an important neurotransmitter involved in regulating muscle movement. While these are effective in some people, that is not the case with all PLMD patients.
- Anticonvulsant agents – medications that reduce muscle contraction.
- GABA agonists – these agents inhibit the release of some neurotransmitters that play a role in muscle contraction. The result is less contraction and relaxation of muscles.
Lifestyle adjustments can help patients with mild symptoms, but people with more severe ones are also recommended to make them besides taking the appropriate medications. Following a regular sleep schedule can improve sleep quality. Creating a relaxing bedtime routine is important, and people with PLMD can try taking a warm bath, a light walk, or a leg massage before sleep to help with the symptoms. Doctors recommend avoiding alcohol and caffeine, especially at a later hour. Be aware that caffeine is also found in chocolate, tea, sodas, and not only coffee and energy drinks.
Proper treatment might lead to cessation of symptoms, but keep in mind that there is no cure for PLMD, and that relapses can occur at any point. Follow good sleep hygiene to minimize the chances of that happening, and regularly check with your medical provider to get a better insight about your condition.
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Dusan is a biologist, a science enthusiast and a huge nature lover. He loves to keep up to date with all the new research and write accurate science-based articles. When he’s not writing or reading, you can find him in the kitchen, trying out new delicious recipes; out in the wild, enjoying the nature or sleeping in his bed.