Periodic Limb Movement Disorder
Periodic limb movement disorder (PLMD) is repetitive cramping or jerking of the legs during sleep. It is the only movement disorder that
occurs only during sleep, and it is sometimes called periodic leg (or limb) movements during sleep. "Periodic" refers to the fact that the
movements are repetitive and rhythmic, occurring about every 20-40 seconds. PLMD is also considered a sleep disorder, because the
movements often disrupt sleep and lead to daytime sleepiness.
PLMD may occur with other sleep disorders. It is often linked with restless legs syndrome, but they are not the same thing. Restless legs
syndrome is a condition involving strange sensations in the legs (and sometimes arms) while awake and an irresistible urge to move the
limbs to relieve the sensations. At least 80% of people with restless legs syndrome have PLMD, but the reverse is not true.
When PLMD was first described in the 1950s, it was called nocturnal myoclonus. Nocturnal means night, and myoclonus is a rapid,
rhythmic contraction of a group of muscles similar to that seen in seizures. PLMD movements are not myoclonus, however, and the
original name is not used today.
PLMD can occur at any age. Like many sleep disorders, PLMD is more common in middle-aged and older people.
Periodic Limb Movement Disorder (PLMD), previously known as Nocturnal myoclonus, is a sleep disorder where the patient moves limbs
involuntarily during sleep, and has symptoms or problems related to the movement.
If the patient moves limbs during sleep but there are no negative consequences, the condition is simply called periodic limb movements
of sleep (PLMS). Not all patients with PLMS have PLMD (in fact, most people with PLMS do not have a disorder, and do not require any
PLMD is diagnosed with the aid of a polysomnogram or PSG. PLMD is diagnosed by first finding PLMS on a PSG, then integrating that
information with a detailed history from the patient and/or bed partner. PLMS can range from a small amount of movement in the ankles
and toes, to wild flailing of all four limbs. These movements, which are more common in the legs than arms, occur for between 0.5 and 5
seconds, recurring at intervals of 5 to 90 seconds. A formal diagnosis of PLMS requires three periods during the night, lasting from a few
minutes to an hour or more, each containing at least 30 movements followed by partial arousal or awakening.
PLMD can cause insomnia and daytime sleepiness. It is estimated to occur in approximately 4% of adults (aged 15-100), but is more
common in the elderly, especially females, with up to 11% experiencing symptoms. PLMS appears to be related to restless legs
syndrome (RLS) - a study of 133 people found that 80% of those with RLS also had PLMS. However the opposite is not true: many
people who have PLMD do not also have restless leg syndrome.
Factors that increase the likelihood of PLMD in the absence of restless leg syndrome include being a shift worker, snoring, coffee
drinking, stress, and use of hypnotics. Being a woman, the presence of musculoskeletal disease, heart disease, obstructive sleep apnea,
cataplexy, doing physical activities close to bedtime and the presence of a mental disorder were significantly associated with having a
higher risk of both PLMD and restless legs syndrome.
PLMD is treated by medications aimed at reducing or eliminating the leg jerks or the arousals. Non-ergot derived dopaminergic drugs
(pramipexole and ropinirole) are preferred. Other dopaminergic agents such as co-careldopa, co-beneldopa, pergolide, or lisuride may
also be used. These drugs decrease or eliminate both the leg jerks and the arousals. These medications are also successful for the
treatment of RLS restless legs syndrome.
In one study, co-careldopa was superior to dextropropoxyphene in decreasing the number of leg kicks and the number of arousals per
hour of sleep. However, co-careldopa and, to a lesser extent, pergolide may shift the leg movements from the nighttime to the daytime.
Clonazepam, (Klonopin), in doses of 1 mg has been shown to improve objective and subjective measures of sleep.
Sleep stages Rapid eye movement sleep · Non-rapid eye movement sleep · Slow-wave sleep
Brain waves Alpha wave · Beta wave · Gamma wave · Delta wave · Theta rhythm · K-complex
Sleep disorders Advanced sleep phase syndrome · Automatic behavior · Circadian rhythm sleep disorder · Delayed
sleep phase syndrome · Dyssomnia · Hypersomnia · Insomnia · Narcolepsy · Night eating syndrome ·
Night terror · Nocturia · Nocturnal myoclonus · Non-24-hour sleep-wake syndrome · Obesity
hypoventilation syndrome · Ondine's curse · Parasomnia · Sleep apnea · Sleep deprivation · Sleeping
sickness · Sleepwalking · Somniloquy
Benign phenomena Dream · Exploding head syndrome · False awakening · Hypnagogia · Hypnic jerk · Lucid dream ·
Nightmare · Nocturnal emission · Sleep paralysis · Somnolence
Related topics Bed (Bunk bed, Four poster bed, Futon, Hammock, Mattress) · Bed bug · Bedding · Bedroom · Bedtime
· Bedtime toy · Bedtime story · Caffeine nap · Chronotype · Dream journal · Jet lag · Lullaby · Methods
of falling asleep · Nap · Nightwear · Polyphasic sleep · Polysomnography · Power nap · Siesta · Sleep
and creativity · Sleep and learning · Sleep debt · Sleep diary · Sleep inertia · Sleep medicine · Sleeping
while on duty · Sleepover · Snoring · Excessive daytime sleepiness
Periodic limb movement disorder (PLMD) and restless legs syndrome (RLS) are distinct disorders, but they often occur simultaneously.
PLMD and RLS are types of parasomnia (i.e., conditions that occur during sleep and create a disruptive event). They also are called
(nocturnal) myoclonus, which describes frequent or involuntary muscle spasms.
Periodic limb movement was formally described first in the 1950s, and, by the 1970s, it was listed as a potential cause of insomnia. In
addition to producing similar symptoms, PLMD and RLS are treated similarly.
Periodic Limb Movement Disorder (PLMD)
Periodic limb movement disorder affects people only during sleep. The condition is characterized by behavior ranging from shallow,
continual movement of the ankle or toes, to wild and strenuous kicking and flailing of the legs and arms. Furthermore, abdominal, oral,
and nasal movement sometimes accompanies PLMD. Movement of the legs is more typical than movement of the arms in cases of
PLMD. Movements typically occur for 0.5 to 10 seconds, in intervals separated by five to 90 seconds.
In 1979, the Association of Sleep Disorder Centers (ASDC) set the parameters for determining the presence of PLMD:
A formal diagnosis of nocturnal myoclonus requires three periods during the night, lasting from a few minutes to an hour or more, each
containing at least 30 movements followed by partial arousal or awakening. (ASDC 1979)
Today, these parameters are a bit more relaxed, and PLMD usually includes any repetitive, involuntary movement during the night.
These limb movements usually occur in deep stage two sleep, but often cause arousal. Thus, PLMD can cause poor sleep, which may
lead to sleep maintenance insomnia and/or excessive daytime sleepiness.
The incidence of PLMD increases with age. It is estimated to occur in 5% of people age 30 to 50 and in 44% of people over the age of
65. As many as 12.2% of patients suffering from insomnia and 3.5% of patients suffering from excessive daytime sleepiness may
Restless Legs Syndrome (RLS)
Restless legs syndrome was described as early as the 16th century but was not studied until the 1940s. People with RLS complain of an
irresistible urge to move their legs while at rest. A person with RLS will experience a vague, uncomfortable feeling while at rest that is
only relieved by moving the legs.
Symptoms of RLS may be present all day long, making it difficult for an individual to sit motionless. Or they may be present only in the
late evening. Late evening symptoms can lead to sleep onset insomnia, which tends to compound the effects of RLS. Pregnancy, uremia,
and post-surgery conditions have also been known to increase the incidence of RLS. And, surprisingly, fever seems to decrease it.
Although one study found RLS to be most prevalent in middle-aged females, its incidence increases with age.
Restless legs syndrome is estimated to affect 5% of the population. Approximately 80% of people with RLS have PLMD, though most
people with PLMD do not experience RLS.
American Sleep and Epilepsy Centers