Do limb movements during wakefulness after sleep onset correlate with Restless Leg Syndrome (RLS) rather than Periodic Limb Movements during sleep (PLMS)?

Limb Movements During Wakefulness After Sleep Onset and Their Correlation with Restless Leg Syndrome

Limb movements during wakefulness after sleep onset are more strongly associated with Restless Legs Syndrome (RLS) than Periodic Limb Movements during Sleep (PLMS). 1, 2

Understanding RLS and PLMS

RLS is a sleep-related movement disorder characterized by:

• An urge to move the legs (and sometimes arms) when immobile, often associated with uncomfortable sensations 1
• Symptoms that worsen during periods of rest or inactivity 1
• Relief of symptoms with movement 1
• Symptoms that worsen or only occur in the evening or night 1

PLMS are characterized by:

• Brief (0.5-10 seconds), recurrent movements of the lower extremities 1
• Movements occurring approximately every 15-30 seconds 1
• High night-to-night variability in both adults and children 1
• Association with electroencephalogram arousal and elevations in heart rate and blood pressure 1

Relationship Between Limb Movements During Wakefulness and RLS

Research indicates that limb movements during wakefulness after sleep onset have a stronger correlation with RLS than with PLMS for several reasons:

• Approximately one-third of RLS patients show periodic leg movements during relaxed wakefulness (PLMW) 2
• While PLMW and PLMS indices are correlated in RLS patients, the correlation is not strong enough to suggest PLMW can reliably predict PLMS 2
• Limb movements during wakefulness in RLS patients have distinct characteristics compared to controls:
  • Higher limb movement activity during wakefulness than controls 2
  • Intermovement intervals during wakefulness show a peak at approximately 4 seconds in RLS patients 2

Clinical Significance

The distinction between limb movements during wakefulness and PLMS is important for several reasons:

• RLS diagnosis is based on clinical criteria, not on the presence of PLMS 3
• PLMS are nonspecific and can occur in other sleep disorders and even in normal individuals 3
• Short-interval limb movement activity during wakefulness might be linked to the severity of sleep disruption in RLS patients 2
• The differences between limb movement features during wakefulness versus sleep may be relevant for diagnosing sleep disturbances in RLS 2

Diagnostic Implications

When evaluating patients with limb movements:

• RLS is diagnosed through clinical criteria, not through polysomnography findings 1, 3
• A careful clinical history is imperative as there is no objective test to aid in making an RLS diagnosis 1
• PLMD requires both the presence of PLMS on polysomnography and an associated sleep complaint not better explained by other disorders 3
• The diagnostic criteria for PLMD include:
  • Frequent PLMS (>15 events/h in adults, >5 events/h in children) 1
  • Coexisting clinically significant sleep disturbance not better explained by another disorder 1
  • Absence of other sleep disorders associated with high rates of PLMS (including RLS) 1

Treatment Considerations

Treatment approaches differ based on whether the patient has RLS or PLMD:

• For RLS, first-line treatments include:

  • Gabapentin enacarbil, gabapentin, or pregabalin (strong recommendations) 1
  • Iron supplementation for patients with appropriate iron status 1
  • Dopaminergic agents (with caution due to augmentation risk) 4, 1

• For PLMD, treatment may include:

  • Similar medications as RLS but with greater reliance on levodopa compounds and sedative-hypnotics 3
  • Avoidance of medications that may worsen symptoms, such as valproic acid and triazolam 1

Clinical Pitfalls to Avoid

• Do not rely solely on the presence of PLMS to diagnose RLS 3
• Recognize that limb movements during wakefulness after sleep onset may be more indicative of RLS than PLMS alone 2
• Be aware that medications such as tricyclic antidepressants, SSRIs, lithium, and dopamine antagonists can exacerbate RLS symptoms 1
• Consider that the correlation between PLMW and PLMS decreases with increasing limb movement activity, making PLMW less predictive of PLMS in severe cases 2