Periodic Limb Movement Disorder (PLMD)



Sleep-related movement disorder characterized by periodic limb movements of sleep (PLMS) with significant sleep disturbance and/or daytime functional impairment:

  • PLMS demonstrated during polysomnography
  • PLMS are repetitive contractions of tibialis anterior muscles occurring mainly in non–rapid eye movement (NREM) sleep.
  • Movements consist of unilateral or bilateral, simultaneous or not, rhythmical extension of the big toe and ankle dorsiflexion.
  • Sometimes, knee and hip flexion are noted.
  • Arm movements or more generalized movements occur less commonly.
  • Movements might be associated with cortical arousals from sleep unbeknownst to the patient (PLMs with arousals—PLMA).
  • A clinical history of significant sleep disturbance and/or functional impairment is necessary for diagnosis.
  • Complaints include insomnia, nonrestorative sleep, daytime fatigue, and somnolence.
  • Bed partner may complain of patient’s movements.
  • Other sleep disorders such as obstructive sleep apnea (OSA), narcolepsy, and restless legs syndrome (RLS) do not explain the PLMS.
  • No associated restlessness or dysesthesia while awake
    • If there is an associated sensory perception or restlessness, the diagnosis is not PLMD but possibly RLS.
  • System(s) affected: musculoskeletal, nervous
  • Synonym(s) referring to the PLMS: nocturnal myoclonus; sleep myoclonus



  • PLMD is rare, affecting children and adults (1).
  • PLMS occurs in > 15% of insomnia patients.
  • PLMS are frequent in narcolepsy, RBD, OSA, and during initiation of CPAP.


  • PLMS increases with age: 45% of patients aged >65 years exhibit PLMS >5/hr but not PLMD.
  • PLMD is much less common: <5% of adults but also underdiagnosed (1)
  • 85% of RLS patients have PLMS (2).

Etiology and Pathophysiology

  • Understudied; most data reports on PLMS as it pertains to RLS:
    • CNS dopamine dysregulation supported by increased incidence of PLMS in untreated Parkinson disease (PD) and decreased incidence of PLMS in schizophrenia
  • Triggering and exacerbating factors:
    • Peripheral neuropathy
    • Arthritis
    • Renal failure
    • Spinal cord injury
    • Pregnancy
  • Medication side effects:
    • Most antidepressants (except bupropion or desipramine) and lithium
    • Some antipsychotic and antidementia medications
    • Antiemetics (antidopaminergic)
    • Sedating antihistamines

BTBD9 on chromosome 6p associated with PLMS in patients with or without RLS but not in RLS patients without PLMS

Risk Factors

  • Family history of RLS
  • Iron deficiency and associated conditions
  • History of prematurity

General Prevention

  • Promoting adequate sleep
  • Avoid PLMS triggers such as iron deficiency, frequently observed in children (3).

Commonly Associated Conditions

  • Narcolepsy
  • End-stage renal disease; cardiovascular disease; stroke
  • Gastric surgery
  • Pregnancy
  • Arthritis
  • Lumbar spine disease; spinal cord injury
  • Peripheral neuropathy
  • Insomnia, insufficient sleep, parasomnias
  • ADHD, anxiety, oppositional behaviors

Pediatric Considerations

  • PLMD may precede overt RLS by years (3).
  • Association with RLS is more common.
  • Association and differential diagnosis with restless sleep disorder, ADHD, oppositional behaviors, mood disorders, growing pains (3)

Pregnancy Considerations

  • May be secondary to iron, folate deficiency
  • Most severe in the 3rd trimester
  • Usually resolves after delivery

Geriatric Considerations

  • May cause or exacerbate circadian disruption and “sundowning”
  • PLMS may increase risk of atrial fibrillation in elderly.

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