Sleep-Related Movement Disorders

Sleep-related movement disorders are conditions that involve abnormal sensations or movements either before or during sleep. While it’s common to change positions, twitch, or jerk occasionally while sleeping, a doctor may diagnose a sleep-related movement disorder when these movements are persistent, interfere with sleep, and affect daily life.

We cover the key details about these sleep disorders and offer suggestions about when you should consider discussing sleep-related movements with a medical professional.

People with restless legs syndrome (RLS) have unpleasant sensations in their limbs that make them feel the need to move around. The symptoms of RLS may include tingling, pain, or itchiness in the legs. These symptoms tend to arise at night and during periods of rest, and can usually be relieved temporarily by moving the legs. 

RLS can vary in severity, and symptoms can change over time. RLS can lead to sleep difficulties while also affecting mood, concentration, and memory. Although as many as 15% of people in the United States have RLS, less than 3% have severe symptoms. RLS also occurs in around 20% of pregnancies.

The exact cause of RLS is unclear, though many researchers believe that the condition is related to both a person’s genes and environment. Medical conditions that can increase the risk of RLS include iron deficiency anemia, diabetes, kidney disease, and Parkinson’s disease. Symptoms may also be exacerbated by substances like alcohol, caffeine, and nicotine.

Treatment for restless legs syndrome focuses on reducing symptoms, as there is currently no cure for RLS. If their symptoms are mild to moderate, many people can manage them through lifestyle changes, treating underlying health conditions, and medications.

Periodic limb movement disorder (PLMD) involves recurring movements of the arms or legs that interfere with sleep. Although it’s common for people to occasionally move or jerk in their sleep, adults with PLMD average more than 15 of these movements every hour, leading to regular sleep disruptions.

These kinds of periodic limb movements often affect people with restless legs syndrome, and they can also be caused by other health conditions. Doctors only diagnose PLMD when a person’s sleep-related limb movements are not the result of RLS or another health problem.

Around 4% to 11% of adults have PLMD, which may also affect up to 8% of children. Symptoms include movements of the toes, ankles, knees, or hips that usually happen every 20 to 40 seconds. In PLMD, nighttime symptoms can disturb sleep, aggravate bed partners, and lead to tiredness and other daytime consequences of sleep loss.

Researchers are still learning about the complex causes of PLMD, which occurs more often in older adults. While current treatment approaches for PLMD are similar to those for RLS, including lifestyle changes and medications, only a few studies have evaluated the effectiveness of different treatments for PLMD. 

Sleep-related leg cramps involve a sudden spasm and tightening of the thigh, calf, or foot while a person is asleep or lying in bed. This type of painful cramp, also called a charley horse, can last from seconds to minutes and cause serious sleep disruptions. 

Periodic leg cramps are common in adults and are usually nothing to worry about. However, longer and more disruptive sleep-related leg cramps become more frequent with age, affecting as many as 33% of people over 60 years old and 50% of people over 80. 

Leg cramps may be caused by another health condition or occur without a clear cause. Factors that increase the likelihood of nighttime leg cramps include:

• Dehydration 
• Recent exercise 
• Electrolyte imbalance 
• Prolonged sitting or standing 
• Pregnancy
• Certain medications
• Medical conditions such as diabetes and metabolic disorders

Doctors may suggest several approaches to preventing and alleviating leg cramps. During a cramp, it can help to stretch the leg, massage the muscles, or apply a heating pad. To prevent leg cramps, it’s important to stay hydrated and stretch regularly. 

If leg cramps don’t get better with these approaches, a doctor may look for underlying causes that can be corrected or treated.

Bruxism is the medical term for clenching or grinding the teeth. When people clench or grind their teeth while sleeping, their doctors may diagnose sleep-related bruxism. Repeated clenching can lead to worn or damaged teeth, tooth sensitivity, jaw pain, headaches, and, in severe cases, trouble falling and staying asleep. 

Sleep-related bruxism affects as many as 40% of children and 10% of adults. This condition may be due to a person’s genetics, level of stress, and emotional state. Additionally, the risk of sleep-related bruxism can be affected by other sleep disorders, neurological and mental health conditions, and substances like alcohol, caffeine, tobacco, and certain medications.

Treatment may not be necessary for mild bruxism. But when the teeth are worn or damaged, doctors may recommend lifestyle changes to promote healthy sleep habits and reduce stress, in order to decrease teeth grinding. They may also suggest custom-fitted nighttime mouthguards to protect the teeth.

Sleep-related rhythmic movement disorder (RMD) involves repetitive and patterned movements that begin when a person, usually a child, is tired or sleeping. Children may exhibit a variety of movements during RMD episodes, including rocking, banging, or rolling of the head, limbs, torso, or the entire body. 

Many children make these types of movements occasionally. But health professionals only consider them disorders if they cause injury or sleep disturbances on a regular basis. 

Rhythmic movements are most common in infants and young children, affecting around 59% of children during infancy, 33% at 18 months, but only about 5% by age 5. Some experts believe that rhythmic movements may be an element of healthy development, a form of self-soothing, or a way of responding to stress or anxiety. 

Treatment for RMD often focuses on preventing injury until a child grows out of the condition. Doctors may recommend designing a sleep area with padding or having the child wear protective headgear in bed.

Myoclonus describes a sudden and uncontrollable movement, shake, or spasm of one or more muscles. Typical and harmless types of myoclonus include hiccups and sleep starts. Other forms of myoclonus may be signs of an underlying health condition or side effects of certain medications. 

Experts classify two rare forms of myoclonus as sleep disorders.

• Benign Sleep Myoclonus of Infancy (BSMI): This disorder, believed to be harmless, affects fewer than 0.1% of infants. BSMI is frequently mistaken for epilepsy because infants with this condition can have jerks in several muscles simultaneously while they sleep. 
• Propriospinal Myoclonus at Sleep Onset (PSM): PSM typically occurs when an adult is lying down and relaxing, such as when falling asleep. This condition involves a sudden movement that usually begins in the torso and spreads to the arms, legs, and neck. PSM can make it hard to fall asleep and can cause anxiety around bedtime.

Infants with benign sleep myoclonus of infancy do not require treatment since the condition is not dangerous and does not negatively affect development. In adults with propriospinal myoclonus at sleep onset, doctors often look for and treat any underlying cause or recommend medications to reduce symptoms.

Several other sleep-related movements are either normal experiences or isolated events. Experts do not consider these sleep disorders, because they don’t interfere with sleep on a regular basis.

• Hypnic Jerks: Also called sleep starts, hypnic jerks are quick muscle contractions that happen right as a person is falling asleep. As many as 70% of people experience occasional hypnic jerks, which often happen at the same moment as a change in perception, such as tingling, a feeling of falling, or another visual or auditory sensation.
• Excessive Fragmentary Myoclonus: Excessive fragmentary myoclonus (EFM) describes unconscious minor twitches in the face, torso, or limbs. Unlike in periodic limb movement disorder, movements in EFM happen very quickly, in rapid succession, and to such a small degree that they’re barely visible.
• Hypnagogic Foot Tremors: Some people find themselves unknowingly moving their toes or feet as they fall asleep. Hypnagogic foot tremors are common and typically last from a few seconds to several minutes.
• Alternating Leg Muscle Activation: Alternating leg muscle activation involves engaging a large muscle near the shinbone called the anterior tibialis. During an episode, a person may activate this muscle in one leg, then the other, then back again in succession. 

While it’s normal to move occasionally while you’re sleeping, you should talk to a doctor if you are concerned about nighttime movements or if you have a symptom such as:

• Trouble falling or staying asleep
• Uncomfortable feelings in the limbs
• Jaw pain, tooth damage, or difficulty opening your mouth
• Muscle cramps that are intense, long-lasting, or frequent
• Significant daytime sleepiness