What Is Periodic Limb Movement Disorder (PLMD)?

Periodic limb movement disorder (PLMD), also known as sleep-related myoclonus syndrome or nocturnal myoclonus syndrome, is a type of sleep-related movement disorder.

If you have periodic limb movement disorder, you’re not alone. It is estimated that 5% to 8% of children and 4% to 11% of adults live with this condition. Fortunately, the condition is not considered medically serious, and the symptoms can be treated with medication and lifestyle changes.

This article discusses the symptoms, causes, diagnosis, and treatment of periodic limb movement disorder. We also explore how this condition can affect your mental health and suggest strategies to help you cope.

Symptoms of Periodic Limb Movement Disorder

While the condition typically affects the lower limbs and causes movement in the toes, ankles, knees, or hips, it may also affect some people’s upper limbs and cause them to move their arms involuntarily.

These limb movements are not the same as the movements you make while stretching, changing sleep positions, or experiencing a muscle cramp.

The movement episodes can last from a few minutes to an hour, with movements lasting between 0.5 and 10 seconds and recurring at 5 to 90 seconds intervals. They can affect one limb or both.

When Does Periodic Limb Movement Disorder Occur?

The limb movements can occur:

• During sleep: The movement episodes are most common and can disrupt your sleep several times during the night. They typically occur during non-rapid eye movement (NREM) sleep during the first half of the night, the degree of severity can vary. You may first become aware of the symptoms when someone you share a bed with tells you that you’ve been moving in your sleep.
• During wakefulness: Limb movements are less common and generally occur in more severe periodic limb movement disorder cases.

The symptoms often start after age 40 and become more severe with age.

How Periodic Limb Movement Disorder Affects Mental Health

Periodic limb movement disorder can affect your ability to sleep and get a good night’s rest. Sleep deprivation can take a toll on your mental health and cause you to experience symptoms such as:

• Fatigue
• Irritability
• Anxiety
• Mood swings 
• Inability to concentrate
• Difficulty learning
• Slow reaction times
• Poor judgment
• Functional impairment
• Loss of productivity
  

Causes of Periodic Limb Movement Disorder

The exact causes of periodic limb movement disorder are unknown, but these are some of the risk factors that can make you more likely to develop it:

• Sleep disorders: Having a sleep disorder such as restless leg syndrome, sleep apnea, narcolepsy, or rapid eye movement behavior disorder can increase your chances of developing periodic limb movement disorder. It is estimated that 80% of people with restless leg syndrome also have periodic limb movement disorder.
• Mineral deficiencies: Deficiencies of minerals such as iron and magnesium may cause periodic limb movement disorder.
• Neurological factors: A spinal cord tumor, injury, or a neurological disorder such as multiple system atrophy can lead to periodic limb movement disorder. 
• Medications: Certain medications such as antidepressants, antihistamines (anti-allergy medications), lithium, and dopamine-receptor antagonists (including some anti-nausea medications) can cause or exacerbate periodic limb movement disorder.
• Health conditions: Other health conditions, such as Parkinson’s disease, post-traumatic stress disorder (PTSD), attention deficit hyperactivity disorder (ADHD), multiple sclerosis, kidney disease, and pregnancy have also been linked to the development of periodic limb movement disorder.

Diagnosing Periodic Limb Movement Disorder

Diagnosing periodic limb movement disorder may involve the following steps:

• Medical history: Your healthcare provider will need a complete personal and family history. They will need to know what medications you are currently on or have taken in the past. They will also need to know whether you have any health conditions and which ones run in your family.
• Clinical interview: Your healthcare provider will inquire about the severity and frequency of your symptoms. They will also need to understand your lifestyle and how your symptoms affect your quality of life. 
• Health check-up: Your healthcare provider may perform a physical or neurological exam to rule out other causes of your symptoms. They may also prescribe other health tests, such as a blood test, to check your iron levels.
• Sleep diary: Your healthcare provider may ask you to maintain a sleep diary, wherein you note down factors like sleep time, wake time, sleep quality, sleep disruptions, and other symptoms. Someone who shares a bed with you can help record the timings and frequency of your limb movements at night.
• Sleep study: Your healthcare provider may recommend doing a sleep study, which will monitor factors such as your limb movements, eye movements, brain waves, heart rate, blood pressure, and breathing while sleeping.

Periodic Limb Movement Disorder vs. Other Sleep Disorders

We take a quick look at how periodic limb disorder differs from other sleep disorders.

Periodic Limb Movement Disorder vs. Restless Legs Syndrome

Periodic limb movement disorder and restless legs syndrome (RLS) are two distinct sleep disorders; however, they often go hand in hand. Many people with restless legs syndrome also develop periodic limb movement disorder; however, most people with periodic limb movement disorder don't develop restless legs syndrome.

While both conditions are characterized by involuntary limb movements, people with restless legs syndrome tend to experience unpleasant sensations in their legs, which are then relieved when they move their legs. These sensations are often described as itching, pulling, tingling, or crawling sensations deep within their legs. These symptoms usually start in the late afternoon or evening hours and become more intense at night, making it hard for them to get restful sleep.

Treatment for both conditions often involve similar medications.

Periodic Limb Movement Disorder vs. REM Sleep Behavior Disorder

REM sleep behavior disorder (RBD) is another distinct sleep disorder. It is characterized by acting out one's dreams or nightmares, both physically and vocally, during the REM stage of sleep.

The symptoms of REM sleep behavior disorder include:

• Talking, shouting, screaming, or cursing while sleeping
• Punching or grabbing the air or one's bed partner in their sleep
• Twitching, jerking, or twitching limbs one's limbs at night
• Jumping or falling out of bed, which can result in injuries

Periodic limb movement disorder, restless legs syndrome, and REM sleep behavior disorder are all classified as parasomnias, which are a category of sleep disorders characterized by unwanted movements, events, or experiences that disrupt sleep.

While all three disorders may involve leg movements during sleep, REM sleep disorder is accompanied by other disruptive symptoms as well.

Periodic Limb Movement Disorder vs. Periodic Limb Movements in Sleep

Periodic limb movements in sleep (PLMS) are the primary symptom of periodic limb movement disorder. They are quite common, and many people experience them occasionally, but they are often not frequent enough to significantly disrupt sleep.

Periodic Limb Movement Disorder Treatment

Treatment options for periodic limb movement disorder may involve:

• Medications, such as dopamine agonists, anti-seizure medications, narcotic painkillers, or benzodiazepines
• Sleeping tablets to help you sleep better
• Iron supplementation, in case you have an iron deficiency
• Lifestyle changes, such as avoiding alcohol and caffeine to improve sleep quality

Coping With Periodic Limb Movement Disorder

If periodic limb movement disorder is affecting your well-being, these are some steps that can help you cope:

• Learn about the condition: Educating yourself about the condition and its causes, symptoms, and treatment options can help you better understand what you’re experiencing.
• Seek professional support: If you’re having difficulty coping with the condition or its impact on your life, seeking support from a mental healthcare provider may be helpful. 
• Consider couples therapy: If the condition is affecting you and/or your partner’s ability to sleep and harming your relationship as a result, it could be helpful for the two of you to go to couples therapy together.
• Join a support group: You can also join a support group for people with periodic limb movement disorder or other sleep disorders. Support groups can be valuable sources of information, advice, inspiration, and resources.