What is Periodic Limb Movement Disorder?
Sleep-related movement disorders are common types of sleep illnesses that often occur. These illnesses need careful examination and treatment. Conditions in this group include restless leg syndrome (RLS), periodic limb movement disorder (PLMD), sleep-related leg cramps, and bruxism (grinding of teeth).
Periodic limb movement disorder, also known as sleep-related myoclonus syndrome or nocturnal myoclonus syndrome, involves rhythmic movements of the legs or arms while sleeping. Common movements include bending of the hip and knee, and most often, bending the foot upwards with the big toe sticking out. This condition is frequently seen in sleep studies, but just having these movements alone doesn’t mean one has PLMD, unless certain symptoms are also present.
What Causes Periodic Limb Movement Disorder?
Periodic limb movement disorder (PLMD), a condition where your limbs involuntarily move during sleep, is often linked to sleep problems. Although the cause of primary PLMD cases isn’t entirely understood, it is commonly seen with other medical conditions. For instance, 80-90% of those with restless leg syndrome (RLS), a condition where you have an irresistible urge to move your legs, also experience PLMD. Other medical conditions that often occur alongside PLMD include sleep apnea (a condition where your breathing repeatedly stops and starts while you sleep), narcolepsy (a sleep disorder characterized by excessive sleepiness, sleep paralysis, and hallucinations), REM behavioral disorder (a sleep disorder where you physically act out vivid dreams), uremia (a condition resulting from kidney disease), spinal cord tumors, and ADHD (attention-deficit/hyperactivity disorder).
Diagnosing primary PLMD involves a patient reporting sleep complaints and detecting PLMs (periodic limb movements) during their sleep study or check up. It’s important that other sleep disorders aren’t present for a PLMD diagnosis. Part of what doctors look for when diagnosing PLMD are signs of sleep disruptions, such as temporary arousal or brief moments of being awake.
There are various risk factors associated with experiencing PLM (periodic limb movements). A patient having conditions or ailments mentioned earlier increases the chances. Furthermore, inheriting RLS from family members could also increase the risk of PLMs and consequently, PLMD. Certain genes linked to RLS like MEIS1 and BTBD9, iron deficiency, and decreased ferritin (a protein that stores iron) might contribute to more instances of PLMs. Finally, certain classes of medications, such as dopamine blockers, SSRIs (selective serotonin reuptake inhibitors used for depression), and TCAs (tricyclic antidepressants) could also elevate the risk of experiencing PLMs.
Risk Factors and Frequency for Periodic Limb Movement Disorder
Periodic limb movement disorders appear to affect different populations in various ways. The percentage of adults who suffer from it is between 4% and 11%, while for children the range is 5% to 8%. However, these numbers might not completely represent the full picture, as they are based on a European study that diagnosed patients through a phone survey, not medical testing.
Furthermore, certain factors can increase a person’s risk of developing this condition. These include:
- Getting older
- Being female
- Working irregular hours
- Experiencing stress
- Consuming caffeine
Another takeaway from the study is that the prevalence of periodic limb movement disorders can vary by race. For example, fewer Black individuals were found to suffer from this condition compared to White individuals.
Last but not least, a particular measure known as PLMSI, which relates to the severity of the disorder, revealed differences according to race and the presence of insomnia. Specifically, African Americans were less likely to have a high PLMSI (>15) compared to Caucasians (with rates of 4.3% vs. 9.3%). However, individuals of any race with high PLMSI were more likely to suffer from insomnia (45%) compared to those with low PLMSI (25%).
Signs and Symptoms of Periodic Limb Movement Disorder
People with Periodic Limb Movement Disorder (PLMD) may visit their healthcare professional complaining about feeling tired during the day, having trouble sleeping, and feeling sleepy. If they have a sleeping partner, the partner might notice that the individual tends to kick their legs while sleeping. Some patients may report waking up frequently or having trouble falling asleep because of these leg movements. These movements can look a lot like the Babinski sign, where the big toe extends and the ankle, knees, and hip flex. These movements can cause an increase in heart rate and blood pressure or result in an awakening either before or after the movements occur.
Healthcare professionals should also inquire about symptoms of Restless Legs Syndrome and other sleep disorders like sleep apnea, narcolepsy, and insomnia, as these can rule out Periodic Limb Movement Disorder.
Most of the time, a physical and neurological exam will be normal for primary or idiopathic Periodic Limb Movement Disorder. However, in some cases, individuals might present signs of anemia, obesity, and possible nerve damage from conditions like diabetes. The healthcare professional should not only examine for upper airway obstruction but also check for other issues like nerve damage in the limbs, peripheral vascular disease, and varicose veins. Since these conditions, too, can cause uncomfortable limb movements and leg discomfort during sleep.
Testing for Periodic Limb Movement Disorder
The polysomnogram, which is a type of sleep study, is a crucial instrument in diagnosing Periodic Limb Movement Disorder (PLMD). This medical test can help doctors confirm PLMD.
The International Classification of Sleep Disorders (ICSD-3) lists specific criteria for diagnosing PLMD. In adults, the presence of more than 15 periodic limb movements per hour during sleep, and in children, more than five movements per hour are necessary for the diagnosis. These movements must cause sleep problems that impact daily life, and must not be attributed to any other medical, psychological, or sleep-related disorders. If a person’s sleep issues relate to other health problems, doctors then consider 5 clear events per hour of sleep as a sign of abnormal periodic limb movement during sleep.
The American Academy of Sleep Medicine (AASM) has specific guidelines for diagnosing PLMD. They look at limb movements via an electromyogram (a test that measures muscle activity) of the anterior tibialis muscle (located near the shin). They consider a limb movement countable if it shows an increase of more than 8 microvolts above resting muscle activity and lasts between 0.5 to 10 seconds. If there are more than 4 such movements that occur 5 to 90 seconds apart, they can be formally classified as a series of periodic limb movements.
It is crucial to understand that PLMD is commonly diagnosed only if no other conditions can explain the symptoms.
In recent findings, some sleep-related breathing disorders, like mild obstructive sleep apnea or upper airway resistance syndrome were identified as potential causes of periodic limb movements during sleep. Treating these conditions with a continuous positive airway pressure (CPAP) mask showed improvement in symptoms. However, it’s worth noting that severe obstructive sleep apnea can sometimes mask underlying periodic limb movements, which can actually worsen during treatment. Additionally, the CPAP mask itself can potentially cause periodic limb movements.
Treatment Options for Periodic Limb Movement Disorder
Periodic limb movement disorder, or PLMD, often goes hand in hand with restless legs syndrome (RLS). As a result, medications that enhance the activity of a brain chemical called dopamine, could also help decrease leg movements in PLMD patients. These medications include pramipexole, ropinirole, and rotigotine, as well as other drugs such as gabapentin and pregabalin. However, keep in mind that currently, there’s no scientific research to fully support this treatment method for PLMD.
Science has looked into other medications to help people with PLMD. While these treatments are based only on a little scientific evidence, they have still shown some potential. These include clonazapam, which might improve sleep quality and decrease leg movements during REM (Rapid Eye Movement) sleep, and melatonin, which might decrease leg movements and the arousals they cause, if taken 30 minutes before bedtime. Valproate may also improve sleep quality and decrease leg movements, though the evidence isn’t strong. Selegiline is another medication that could be considered in some cases.
It’s important to note that doctors need to use their clinical judgement when deciding the best therapy for a patient, given the lack of clear-cut evidence for these treatments.
Just a tip: some antidepressants may increase leg movements, so it’s best to avoid these. These include mirtazapine, venlafaxine, sertraline, fluoxetine, and amitriptyline. However, an antidepressant called bupropion is a preferred choice for treating people who have both depression and PLMD. Other antidepressants that don’t seem to worsen leg movements include trazodone, nefazodone, and doxepin.
For younger patients, iron deficiency is often found alongside RLS and PLMD. In this case, the main goal is to treat the iron deficiency anemia first. Unfortunately, there isn’t a lot of information yet on the use of dopamine-boosting medicines in children with RLS and PLMD.
What else can Periodic Limb Movement Disorder be?
When a patient shows symptoms of Periodic Limb Movement Syndrome (PLMS), other conditions with similar symptoms need to be considered. They include:
- Restless leg syndrome
- Peripheral neuropathy
- REM behavioral disorder
- Uremia
Less common sleep-related movement disorders should also not be overlooked, such as:
- Excessive fragmentary myoclonus (EFM)
- Sleep-related leg cramps, bruxism
- Rhythmic feet movements (RFM)
- Hypnagogic foot tremors (HFT)
- Alternating leg muscle activation (ALMA)
When a patient demonstrates sleep-related limb movements, it is important to first ask about symptoms of restless leg syndrome. Then, physicians should consider other sleep-related issues that could be linked with PLMS such as narcolepsy, sleep apnea (OSA), REM behavioral disorder, and uremia. If any of these conditions are found, then the patient cannot be diagnosed with PLMD (Periodic Limb Movement Disorder).
What to expect with Periodic Limb Movement Disorder
If your Periodic Limb Movements (PLM), which are repetitive movements that typically occur in your legs during sleep, are caused by conditions like Restless Legs Syndrome (RLS), treating these underlying conditions can help. RLS is a condition characterized by an intense urge to move your legs when resting. By receiving treatment, such as dopamine agonists (drugs that help with movement) and other medications, many people report better sleep quality, efficiency, and improved sleep stages.
While the improvements are noticeable, there might be no significant change in the number of occurrences of PLM during sleep, as measured in sleep studies. But remember that the aim is overall better sleep and managing the symptoms.
Possible Complications When Diagnosed with Periodic Limb Movement Disorder
Research indicates that people with sleep-related movement disorders can experience unusual changes in blood pressure and high blood pressure due to an imbalance in their nervous system. This imbalance, favoring more activity in the part of the nervous system that controls the body’s fight or flight response, places individuals with Restless Legs Syndrome (RLS) and Periodic Limb Movement Disorder (PLMD) at increased risk for high blood pressure, stroke, and heart disease.
Key Points:
- Abnormal blood pressure changes often occur in those with sleep-related movement disorders.
- These disorders can cause a nervous system imbalance, enhancing the body’s fight or flight response.
- As a result, individuals with Restless Legs Syndrome (RLS) and Periodic Limb Movement Disorder (PLMD) have a higher risk of developing high blood pressure, stroke, and heart disease.
Preventing Periodic Limb Movement Disorder
It can really be helpful for patients to understand and discuss the possible reasons behind their periodic limb movement disorder – a condition where a person’s limbs move involuntarily during sleep. Because it’s rare for this condition to occur on its own, doctors generally look for other underlying causes. Treating any underlying conditions, such as Restless Legs Syndrome (a neurological disorder characterized by an irresistible urge to move one’s body to stop uncomfortable sensations) and sleep apnea (a condition where breathing repeatedly stops and starts during sleep), can be great for your long-term health.
By improving the quality of your sleep through treatment, it could also help in reducing your risk factors for other serious health problems, such as stroke, heart disease, and high blood pressure. This means that getting good, uninterrupted sleep might not only help control your limb movements but could also have additional health benefits.
