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Periodic Limb Movements – Overview & Facts


Periodic limb movements are when you have episodes of simple, repetitive muscle movements. You are unable to control them. They usually do not keep you from falling asleep. Instead, they severely disrupt your sleep during the night. This can cause you to be very tired during the day. They do not involve a change in body position, stretching a muscle, or a cramp. Instead, the movements tend to involve the tightening or flexing of a muscle. They occur most often in the lower legs. They can occur at two different times:
  • Periodic limb movements while you sleep (PLMS)
  • Periodic limb movements while you are awake (PLMW)
PLMS are much more common. When they occur often through the night, they can disrupt your sleep many times. Normally, you are unaware of the movements or of waking up. A typical movement is for the big toe to extend. Often the ankle, knee or hip will also bend slightly. Though it is less common, this can also happen in your upper arms. The degree to which these movements occur can change from night to night. They usually happen during non-Rapid Eye Movement (NREM) sleep in the first half of the night. When these movements are very severe, then they may also happen while you are awake (PLMW).

An episode will normally last from a few minutes to an hour. Within that time, movements tend to occur every 20 to 40 seconds. They may affect only one of the legs. More often, they will affect both legs. PLMS are quite common. For most people, the movements do not disturb their sleep in a severe way. This means that it is not a sleep disorder. The sleep of the bed partner tends to be affected more often than that of the patient. The movements reach the level of a disorder, periodic limb movement disorder (PLMD), when they disrupt the patient’s sleep and daily life.

This disorder may be a factor in causing you to have any of the following:
  • Depression
  • Bad memory
  • Short attention span
  • Fatigue
continue to Symptoms & Risk Factors »