ICSD Criteria for PLMD and Coexistence with RLS
PLMD cannot coexist with RLS—the presence of RLS explicitly excludes a diagnosis of PLMD. 1
Diagnostic Criteria for PLMD
According to the 2025 AASM guidelines, PLMD requires all three of the following criteria 1:
1. Frequent Periodic Limb Movements During Sleep (PLMS)
- Adults: >15 events per hour
- Children: >5 events per hour
- PLMS are brief (0.5–10 seconds), recurrent movements of the lower extremities
- Occur roughly every 15–30 seconds
- Particularly prominent during the first 4 hours of sleep
- Associated with EEG arousals and invariably with elevations in heart rate and blood pressure
2. Clinically Significant Sleep Disturbance and/or Daytime Dysfunction
- Must cause meaningful nighttime symptoms or daytime impairment
- Cannot be better explained by another concurrent sleep, medical, neurological, or mental disorder
- The implication is that PLMS directly cause the symptoms, and reducing PLMS will result in symptomatic improvement
3. Absence of Exclusionary Sleep Disorders
PLMD is a diagnosis of exclusion. The following conditions must be absent 1:
- Restless Legs Syndrome (RLS)
- Untreated obstructive sleep apnea
- REM sleep behavior disorder
- Narcolepsy
Why PLMD and RLS Cannot Coexist
The diagnostic framework is hierarchical and mutually exclusive. People with RLS often exhibit PLMS (approximately 90% of RLS patients have PLMS on polysomnography), but these movements are considered a feature of RLS, not a separate disorder 1.
The logic is straightforward:
- If a patient has RLS symptoms (urge to move legs when immobile, relieved by movement, worse in evening/night), any PLMS present are attributed to the RLS
- PLMD can only be diagnosed when PLMS occur in the absence of RLS and other exclusionary conditions
- This prevents double-counting the same pathophysiology
Clinical Pitfalls
The most common diagnostic error is misclassifying patients with RLS as having PLMD simply because PLMS are seen on polysomnography 2. A 2026 systematic review found that more than half (55.6%) of published PLMD samples were incompatible with a PLMD diagnosis under contemporary standards, most often due to exclusionary comorbidities like RLS 2.
Always obtain a careful clinical history before diagnosing PLMD, as there is no objective test for RLS—it is a clinical diagnosis based on symptoms 1. Ask specifically about:
- Urge to move legs when sitting or lying down
- Uncomfortable sensations in the legs (dysesthesias)
- Relief with movement
- Worsening in the evening or at night
If any of these RLS features are present, the diagnosis is RLS (with associated PLMS), not PLMD.