Periodic Limb Movements in Sleep

Periodic limb movements in sleep (PLMS) is a condition during sleep in which the limbs twitch or jerk every 20 to 40 seconds.

Each movement lasts between half a second to five seconds and can involve the big toe, ankle, knee, and sometimes the hip.

PLMS was previously called as nocturnal myoclonus.

Some of the people who are suffering from PLMS also experience jerking of the arms.

Most jerking movements cause a brief awakening; as if every time you fell asleep, someone shook you just enough to wake you again.

PLMS is not to be confused with hypnic jerks, which only occur at sleep onset and are considered normal.

Causes of PLMS

The cause of periodic limb movements in sleep is unknown. Some doctors have suggested that the movements are caused by reactions in the brain, whereas others suggest it might originate in the spinal cord or may be associated with circulatory problems.

It is not unusual to also find PLMS in patients who have sleep disordered breathing or narcolepsy. Periodic limb movements in sleep has also been linked diseases such as

• Diabetes
• Renal disease
• Anemia
• Uremia
• Chronic lung disease
• Leukemia
• Arthritis

Certain medications can make PLMS worse, such as certain tricyclic antidepressants.

Symptoms of Periodic Limb Movements in Sleep

PLMS patients frequently complain of sleep onset insomnia because as soon as they relax enough to fall asleep, their legs begin to jerk, thus waking them again.

Patients who wake up numerous times during the night might also experience excessive daytime sleepiness. Many patients are unaware that they kick but are aware of difficulty falling asleep.

Some PLMS patients also complain of feeling restless at night, whereas some complain of having extremely cold feet. PLMS patients are reported to sleep about an hour less per night than people without periodic limb movements in sleep.

Restless Legs Syndrome

A related disturbance to PLMS, restless legs syndrome (RLS) is related with uncomfortable, creepy, crawling sensations in the lower legs, feet, or thighs that result in an irresistible urge to move the limbs.

These sensations are sometimes described as “pins and needles” in the leg. These sensations are called dysesthesias or paresthesias. These sensations usually occur when you are relaxed or resting and often interfere with falling asleep.

Some patients when they wake up at night experience the same sensations, and find themselves walking or rubbing their legs to try to relieve the uncomfortable feelings.

Restless legs syndrome is frequently seen in patients with kidney failure, uremia, rheumatoid arthritis, or in pregnant women.

The symptoms of restless legs syndrome get worsen by drinking large amounts of caffeine, as may being overly tired and exposure to a very cold or very warm environment. Typically, RLS begins in the third decade of life, but commonly gets worse with age. Often RLS is hereditary.

Almost all patients with RLS have periodic limb movements in sleep, but not all patients with periodic limb movements in sleep have restless legs syndrome. Patients with RLS may also complain of insomnia or of excessive daytime sleepiness.

Periodic Limb Movement Movements in Sleep Diagnosis

Leg movements are recorded during sleep as part of the normal clinical workup. Sensors are placed over the tibialis muscle on the calf of each leg. The number of times you kick your legs during each hour of sleep is counted. This is called the myoclonus index.

If you kick your legs at least 5 times for every hour of sleep, with each kick causing an awakening, then the diagnosis of PLMS is made.

In general, the kicks occur in the lighter stages of sleep, i.e. in stage 1 or stage 2 of sleep.

Thus people who kick often have difficulty falling asleep, as their leg movements wake them up each time they begin to enter stage 1 or stage 2 of sleep. It is less common to see kicks during REM sleep or during the deeper stages of sleep.

The number of kicks varies from night to night, so sometimes two lights of recording are essential. The kicks can occur in one leg at a time, in both legs together, or alternate from one leg to the other.

Can PLMS Be Treated?

Several medications can be used to treated Periodic limb movements in sleep. Unfortunately, it is sometimes difficult to know how best to treat it as we do not know what causes the leg movements.

As all medications work for all people, you and your doctor may need to try different treatments before you find the one that works best for you. The different medications recommended include:

• Certain sleeping pills
• Certain types of pain killers
• Some of the drugs used in Parkinson’s disease

Drugs with opiates are the pain killers used to treat PLMS. These drugs reduce the number of leg kicks, but do not always reduce all the awakenings.

In other words, you may stop kicking, but you may still wake up periodically. These drugs also are potentially addictive and only should be used at the lowest possible dose and only if prescribed by your physician.

Benzodiazepines such as clonazepam (Klonopin) or temazepam (Restoril) are the most common sleeping pills used to treat PLMS.

These drugs reduce the number of awakenings at night, but have little effect on the number of leg jerks. Thus the symptom of insomnia disappears but the symptoms of leg movements do not.