Periodic Limb Movement Disorder (PLMD)

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Description

  • Periodic limb movement disorder (PLMD) is a sleep-related movement disorder characterized by periodic limb movements of sleep (PLMS) with significant sleep disturbance and/or daytime functional impairment (1).
  • PLMS are repetitive contractions of tibialis anterior muscles occurring mainly in the first hour of non–rapid eye movement (NREM) sleep (1).
  • Movements can be unilateral or bilateral, simultaneous or not, and involve rhythmic extension of the big toe and ankle dorsiflexion (1).
  • Generalized movements or arm movements occur less commonly (2).
  • Movements may be associated with cortical arousals from sleep (PLMA) (2).
  • PLMD is a diagnosis of exclusion when PLMS are not explained by other sleep disorders like obstructive sleep apnea (OSA), restless leg syndrome (RLS), or narcolepsy (1).
  • Requires significant sleep disturbance and/or daytime functional impairment (2)
  • Complaints include insomnia, nonrestorative sleep, daytime fatigue, somnolence (3).
  • No associated restlessness or dysesthesia while awake (2)
  • System(s) affected: musculoskeletal, nervous
  • Synonym(s) for PLMS: nocturnal myoclonus; sleep myoclonus

Epidemiology

Incidence

PLMD is estimated to affect 4–11% of the general adult population and 5–8% of the pediatric population (3).

Prevalence

  • PLMS increase with age: occur in 45% of patients aged >65 years and are more common in women (1)
  • PLMS occurs in >15% of patients with insomnia and 85% of patients with RLS (1).

Etiology and Pathophysiology

  • Etiology is uncertain.
  • Suprasegmental disinhibition of the descending inhibitory pathways may be a factor.
  • Evidence supports neuronal hyperexcitability with involvement of the central pattern generator for gait resulting in decreased dopamine transition.
  • Triggering and exacerbating factors:
    • Peripheral neuropathy
    • Arthritis
    • Renal failure
    • Spinal cord injury
    • Pregnancy
    • Medication side effects: antidepressants, lithium, antipsychotics, antidementia, antiemetics (antidopaminergic) and sedating antihistamines

Genetics

Possible underlying genetic component mediated via single nucleotide polymorphisms in BTBD9, TOX3/BC034767, and MEIS1 (4)

Risk Factors

  • Family history of RLS
  • Iron deficiency anemia and associated conditions
  • History of prematurity
  • Older age
  • Female gender
  • Shift work
  • Stress
  • Caffeine intake

General Prevention

  • Promote adequate sleep.
  • Avoid PLMS triggers.
  • Treat iron deficiency, frequently observed in children.

Commonly Associated Conditions

  • Narcolepsy
  • RLS (includes sensation of movement)
  • 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

  • Association with RLS more common; may precede overt RLS by years
  • Associated with and differential includes restless sleep disorder, ADHD, oppositional behaviors, mood disorders, growing pains (4)

Pregnancy Considerations

  • May be secondary to iron or 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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