Although the term nocturnal myoclonus sometimes is used to describe these movements, they usually are not sudden lightning-like movements. Rather, they typically last for about 1 second and consist of extension of the great toe with variable degrees of ankle extension, knee extension, and hip extension or flexion.

PLMS (previously called nocturnal myoclonus) is a disorder in which repetitive, brief, and stereotyped limb movements occur during sleep, usually about every 20 to 40 seconds. Dorsiflexions of the big toe, ankle, knee, and sometimes the hip are involved. Periodic movements occur during sleep but the unpleasant evening and nighttime sensations are absent.

Arousals associated with the PLMs may lead to complaints of insomnia or daytime sleepiness, or the disorder may be asymptomatic (Without Symptoms). The sleep study (polysomnography) is only way to confirm the presence of periodic legs mouvements.

Symptoms Of The Restless Leg Syndrome

1. Leg kicks every 20-40 s.
2. Duration of 0.5-5 s.
3. Complaints of insomnia.
4. Excessive sleepiness.
5. Restless legs.
6. Cold or hot feet.
7. Uncomfortable sensations in legs.

Questioning of the patient or bed partner often yields reports of restlessness, kicking, cold feet, disrupted and torn bedclothes, un-refreshing sleep, insomnia, or excessive daytime sleepiness. Patients may be unaware of these pathological leg movements or arousals, although their bed partners may be all too aware of the kicking, frequent movements, and restlessness.

Patients with RLS complain of a gradual buildup of a subcutaneous crawling, pulling, itching, aching, or pins-and-needles sensation that affects the muscles or bones of the calves and thighs. As the sensation builds, the associated urge to move gradually becomes irresistible and movement provides temporary relief.

Most patients have insomnia with difficulty getting to sleep and frequent awakenings during which they may flex and extend the legs, repeatedly turn over in bed, or get out of bed and walk. About 80 to 90 percent of patients with RLS have PLMs, usually during light NREM sleep, that contribute to awakenings and arousals.

During the day and especially during attempts to remain still, many patients fidget, swing their legs, or have movements that are similar to the extensor movements during sleep. Apart from the movements, neurological examination is usually normal.

In PLM disorder, the condition is associated with arousals that lead to sleep disruption and complaints of insomnia or daytime sleepiness, but the sensory symptoms and waking dyskinesias that accompany RLS do not occur. Although severely affected patients may produce movements throughout sleep, PLMs may also be entirely asymptomatic, causing no disruption of sleep patterns, and are sometimes brought to medical attention either as an incidental finding on a polysomnogram or because the spouse is unable to sleep owing to the leg jerks and kicks.

Causes Of Restless Leg Syndrome

Unknown; hereditary factors are involved in some patients.

Who Gets RLS and PLMS?

The prevalence of RLS is about 2 to 5 percent for the adult population and increases with age, but many patients report having had the same sensations as adolescents and even as children. Men and women are affected equally, and symptoms begin after age 40 in most patients.

About one third to one half of patients report that other family members are affected, and in some families, the syndrome occurs in a pattern consistent with an autosomal dominant inheritance. Periodic limb movements without waking symptoms of RLS occur in about 5 percent of persons between ages 30 and 50 years and in 30 to 45 percent or more of persons older than 65 years of age.

Whereas almost all patients with restless legs syndrome have PLMS, not all patients with PLMS have restless legs syndrome. Restless legs syndrome may be frequent in patients with uremia and rheumatoid arthritis or in pregnant women.

In sleep disorders clinic populations, about 11% of those complaining of insomnia are diagnosed with PLMS.

The prevalence of PLMS in older populations has been estimated to be 44%. This disorder, therefore, may account for many of the complaints reported by elderly people about difficulty in falling asleep. In the elderly, however, this condition is extremely common; more than 40% have at least five leg kicks per hour of sleep.

Risk Factors

Peripheral neuropathy may be a factor in some cases, although peripheral nerve function is clinically normal in most affected patients. Symptoms occur in 10 to 20 percent of pregnant women and usually resolve postpartum. Other disorders that may be associated with PLMs or RLS include venous disease, degenerative CNS disorders, and vitamin deficiency.

RLS and PLMs may be induced or aggravated by a variety of conditions. The list below summarizes these conditions:

1. Chemical agents.
2. Caffeine.
3. Antidepressants (Trazadone & Nefazadone are exceptions).
4. Dopamine Antagonists.
5. Metoclopramide.
6. Calcium Channel Blockers.
7. Theophylline.
8. Adrenergics.
9. Withdrawal from Sedatives/Narcotics can augment symptoms. 

Treatment

Because the pathogenesis of PLMS is usually unknown, treatment is often symptomatic. Walking about, rubbing or moving the limbs briefly relieves the symptoms. Other interventions for RLS and PLMS include eliminating aggravating factors:

1. Removal of caffeine containing foods, beverages, and OTC drugs can often result in improvement.
2. Avoidance of most antidepressants (Serzone and Trazodone excepted).
3. Avoidance of dopamine blocker antipsychotics, metoclopramide (Reglan), and calcium channel blockers.
4. Supplement essential minerals: K, Ca, Mg, if indicated - being careful not to overtreat (especially in presence of K-sparing diuretics).
5. Ferrous sulfate in individuals with a ferritin level of 50 mcg/ml or less.
6. Regular sleep habit with adequate 7 1/2-8 hrs sleep time.
7. Mild to moderate regular exercise is particularly helpful to RLS/PLMS patients.

Medications Include:

1. Levodopa - Sinemet (Beginning 30 minutes before bedtime).
2. Opiates (Tylenol with codeine).
3. Gabapentin.
4. Carbamazepine.
5. Clonidine.
6. Benzodiazepines are commonly given, not because they eliminate the abnormal movements but because they enable the patient to sleep through the movements without awakening.
7. Clonazepam may be useful.
8. Myrapex.

Each type of treatment has its advantages and disadvantages, and the benefit-to-risk ratio of long-term treatment is unresolved.

For patients with PLMs without RLS, it may be difficult to determine the extent to which PLMs contribute to daytime symptoms. The decision to treat PLMs depends on the frequency of movements and associated arousals and on the clinical assessment of the degree to which other sleep disorders contribute to symptoms.

Prognosis and Future Perspectives.

RLS has a variable course. Some patients have long periods of relative stability, whereas others worsen with age. Permanent remissions are rare.