Can periodic limb movements (PLMs) be scored while a person is awake overnight?

Periodic Limb Movements During Wakefulness: Scoring Guidelines and Clinical Implications

Periodic limb movements (PLMs) should not be scored during wakefulness as they are specifically defined as a sleep phenomenon according to American Academy of Sleep Medicine (AASM) guidelines. 1

Definition and Diagnostic Criteria

• Periodic limb movements during sleep (PLMS) are specifically defined as brief (0.5-10 seconds), recurrent movements of the lower extremities that occur approximately every 15-30 seconds during sleep, particularly during the first 4 hours of the sleep period 1
• The diagnosis of Periodic Limb Movement Disorder (PLMD) requires:
  • Frequent PLMS (>15 events/hour in adults, >5 events/hour in children)
  • Clinically significant sleep disturbance not better explained by another disorder
  • Absence of other sleep disorders associated with high rates of PLMS (RLS, untreated OSA, REM behavior disorder, narcolepsy) 1

Why PLMs Are Not Scored During Wakefulness

• The AASM scoring manual specifically addresses PLMs as a sleep phenomenon, with no established criteria for scoring during wakefulness 1
• Electromyography (EMG) during polysomnography (PSG) is the gold standard for diagnosing PLMD, and the periodic limb movements of sleep index (PLMSI) is specifically calculated during sleep periods 1
• Without evaluation of simultaneous EEG (which confirms sleep state), the evaluation of arousals from sleep is not possible, which is a key component in assessing the clinical significance of PLMs 1

Related Phenomenon: Periodic Limb Movements During Wakefulness (PLMW)

• While similar movements can occur during wakefulness (termed PLMW), they have different characteristics and clinical significance than PLMS 2
• PLMW show different time structure compared to PLMS:
  • Intermovement intervals during wakefulness typically show one peak at approximately 4 seconds, gradually decreasing with increasing interval 2
  • PLMW have limited correlation with PLMS and cannot reliably predict PLMS severity 2

Clinical Implications

• PLMW have been described as a wearing-off phenomenon in Parkinson's Disease, but this represents a different clinical entity than PLMS 3
• The circadian rhythm of PLMs peaks at the circadian phases when usual sleep onset occurs, preceding the evening rise in melatonin secretion 4
• The PLMS index alone does not correlate well with symptom severity or treatment response; the rhythm of contractions and percentage of PLMs causing arousals may be more clinically relevant 5

Diagnostic Recommendations

• For proper diagnosis of PLMD, clinicians should:
  • Use EMG during PSG to measure PLMs during confirmed sleep periods only 1
  • Not substitute actigraphy for EMG in diagnosing PLMD, as actigraphy produces unreliable estimates of periodic limb movements 1
  • Consider that the PLMSI varies significantly night-to-night in both adults and children 1

In conclusion, while similar limb movements can occur during wakefulness, the formal scoring of periodic limb movements is specifically defined as a sleep phenomenon in current AASM guidelines, and there are no established criteria for scoring PLMs during wakefulness.