Periodic Limb Movement Disorder: Symptom Management & Connection to Restless Leg Syndrome

What is periodic limb movement disorder?

Periodic limb movement disorder is an uncommon sleep disorder in which repetitive limb movements occur often just as an individual falls asleep and can cause difficulty falling asleep. Usually, the movements affect the lower limbs and occur early in sleep, in the NREM (non-rapid eye movement) phase.

Symptoms include unintentional body movements that may occur anywhere from every five to 90 seconds or more, may be repetitive or vary in severity, and may result in the harm or disturbance of your bedmate or yourself. This condition may also result in reduced sleep quality and resultant daytime fatigue and mood changes.

Treatment options include iron supplementation, behavioral changes, and possible medications that will likely have to be adjusted over time.

You should visit your primary care physician to discuss these symptoms.

Periodic limb movement disorder symptoms

Main symptoms

The main symptom of periodic limb movement disorder is the unintentional movement of different areas of the body. This movement can be described by the following details.

• Likely in the lower extremities: This may involve the extension of the big toe or flexion of the ankle, knee, or the hip.
• Timing: Movement can be separated by between five and 90 seconds and the type of movement and time between movements can vary significantly.
• May result in injury of self or others: The movement may strike your bedmate or involve more complex movements resulting in injury to yourself by striking a nearby object.
• May be repetitive and uncontrolled: Limb movement may also be repetitive and uncontrolled or involve the extension of a limb with an inability to relax the limb. These movements can be unsettling as you fall asleep.

Other symptoms

Periodic limb movement disorder usually does not come to the attention of a medical professional unless it disrupts sleep, however, the following symptoms may only be mild in some cases.

• Daytime sleepiness: While daytime fatigue is commonly associated with sleep movement disorders, there is a stronger connection between restless leg syndrome than periodic limb movement syndrome.
• Poor mood, cognition, and attention: Because periodic limb movement syndrome tends to disrupt an individual’s ability to fall asleep, over time it can lead to fatigue and poor attention, mood, and performance during the day.

Causes of periodic limb movement disorder

While the true mechanism of periodic limb movement disorder is unknown, it is possible that the mechanism involves some disturbance in the transmission of dopamine in the central nervous system.

Medications

Because periodic limb movement disorder is associated with lower than normal levels of dopamine, drugs that further reduce the amount of dopamine in the body can aggravate or even cause periodic limb movement disorder. Anti-depression and first-generation antipsychotic drugs can reduce the release or uptake of dopamine in the brain and aggravate periodic limb movement disorders. Likewise, stimulants can also increase the drive for movement in the body, and for an individual with lower levels of dopamine, they can overcome dopamine’s ability to lessen the body’s movements in preparation for sleep.

Restless leg syndrome

Restless leg syndrome (RLS) occurs in 80% of individuals with periodic limb movement syndrome. Restless leg syndrome is not a cause of periodic limb movement disorder, but the two can be caused or aggravated by similar behaviors. Restless leg syndrome responds to many of the same drugs as periodic limb movement disorder, and while restless leg syndrome is much more common, it is likely that both disorders are caused by an underlying predisposition for movement that occurs during the low point in dopamine release that most people experience in the evening.

Age

Periodic limb movement disorder occurs more commonly in middle or older age. While it occurs at 11% in the general population, that percentage rises to between 25% and 58% in the elderly population. In elderly populations, the rate has been reported as high as 85%. With age, the ability to regulate dopamine is generally reduced as the brain ages.

Obstructive sleep apnea

Periodic limb movement disorder is also associated with an increase in heart rate and blood pressure. Both increased heart rate and blood pressure are signs of increased arousal. People with obstructive sleep apnea (OSA) have trouble breathing when they are sleeping. Without waking you, the sensation of choking triggers the body to increase blood pressure and heart rate as it struggles to breathe, and this arousal may trigger involuntary movement and cause the symptoms of periodic leg movement syndrome.

Low iron levels

Researchers have linked a lack of available iron in the body to a reduction in available dopamine in the brain. For this reason, conditions that cause a decrease in iron in the body over a long time can predispose individuals to periodic leg movement disorder or restless leg syndrome. This includes conditions like pregnancy in which available blood or resources to create blood may be diverted to maintain the pregnancy.

Obstructive sleep apnea (OSA) and low iron levels are two conditions that can be closely associated with periodic limb movement disorder (PLMD). OSA, characterized by repeated episodes of upper airway obstruction during sleep, can trigger involuntary limb movements as the body struggles to breathe. This arousal may manifest as symptoms of PLMD. Studies have shown that treating OSA with continuous positive airway pressure (CPAP) can sometimes reduce the frequency of periodic limb movements, highlighting the interconnected nature of these sleep disorders.

Low iron levels, particularly iron deficiency anemia, have also been linked to an increased risk of PLMD. Iron plays a crucial role in the production of dopamine, a neurotransmitter involved in regulating movement. When iron levels are low, dopamine function may be impaired, potentially leading to involuntary limb movements during sleep. Addressing iron deficiency through supplementation or dietary changes may help alleviate symptoms of PLMD in some cases.

It's important to note that the relationship between OSA, iron levels, and PLMD is complex and not fully understood. Some individuals may experience improvements in their PLMD symptoms by treating underlying OSA or correcting iron deficiency, while others may require additional interventions. A comprehensive evaluation by a sleep specialist can help determine the most appropriate treatment approach for those experiencing symptoms of PLMD in conjunction with OSA or low iron levels.

Liver or kidney failure

Failure of the kidney and liver causes an accumulation of one of the main components in urine called urea. When urea accumulates in the body, and particularly when it begins to concentrate in the brain, it can cause involuntary movements by disrupting the ability of certain neurons in the brain that impede movement to work correctly. This leads to uncontrolled movements.

Treatment options and prevention

Iron replacement

If you have been found to have a low iron level by a blood test, your physician may first attempt to treat your periodic limb movement disorder by treating you with oral iron replacement. Iron is not harmful and has been shown to provide a benefit in the symptoms of people with iron deficiency or end-stage kidney disease. It is usually given orally as a tablet with vitamin C (and should be taken with water sitting upright). Benefits from iron therapy may take up to 12 weeks to take full effect and usually your physician will repeat your blood test to ensure that your iron levels have returned to normal.

Behavioral treatment

Before treating with drugs that may alter the biochemistry of the brain, it is important to assess whether periodic limb movement disorder can be treated by behavioral strategies. Possible beneficial behaviors include:

• Performing mentally stimulating activities: Such as writing or performing crossword puzzles during times of rest or boredom
• Engaging in exercises that use the affected limbs
• Reducing caffeine intake
• Adjusting other medication usages: If antihistamines, antipsychotics, or antidepressants are taken, altering the dosage or using an alternate medication may improve symptoms.

Medications

If you do not respond to iron treatment or behavioral change mentioned above, then it may be appropriate to trial pharmacologic treatment. Appropriate drugs include dopamine agonists — or drugs that increase the amount dopamine present in the brain — and another sort of drug that acts on a channel for calcium. Drug choice will depend on whether or not you have other health conditions, what they are, and what drugs you are already taking. If you deal with pain, anxiety, or addiction, you may be prescribed a calcium channel drug while people with depression or obesity may be prescribed a dopamine agonist. Ultimately, you may end up trialing a series of different medications over weeks before finding one that best suits and alleviates your symptoms. The lengthy time period is required to safely increase the dosage of each trial medication and find the correct and safest medication or combination.

When to seek further consultation

Periodic limb movement disorder is not a life- or limb-threatening condition, but it may worsen with age or with increasing dosages of offending medications. If your symptoms are causing you to lose sleep, are interrupting your daily function, or your ability to interact with loved ones, it is important to seek evaluation. It is common to seek care for significant sleep disruption and a loss of sleep that affects either work or mood as it is likely you cannot resolve it on your own.