In a patient with restless‑legs syndrome (RLS) without periodic‑limb‑movement disorder (PLMD), what polysomnography (PSG) findings are expected and how should the condition be managed?

Polysomnography Findings in RLS Without PLMD

In a patient with restless legs syndrome (RLS) without periodic limb movement disorder (PLMD), polysomnography is typically unnecessary for diagnosis, as RLS is diagnosed clinically by history alone, and the absence of periodic limb movements does not exclude RLS. 1

Expected PSG Findings

When PLMS Are Absent

• Approximately 10% of patients with clinically confirmed RLS do not exhibit periodic limb movements during sleep (PLMS) on polysomnography. 1, 2
• The absence of PLMS does not invalidate the diagnosis of RLS, as periodic limb movements are neither necessary nor sufficient for RLS diagnosis. 1, 2
• Sleep fragmentation and increased arousal index may still be present due to the uncomfortable leg sensations preventing sleep initiation, even without measurable limb movements. 3

Clinical Characteristics of This Subgroup

• Patients with RLS lacking PLMS and dopaminergic response ("RLS-like syndrome") tend to be younger, more severely symptomatic, and have higher rates of psychiatric comorbidities compared to classical RLS patients. 4
• These patients fulfill all four essential diagnostic criteria (urge to move legs with uncomfortable sensations, worsening at rest, relief with movement, circadian pattern with evening/night predominance) but lack the supportive polysomnographic findings. 1, 5

Diagnostic Approach

Clinical Diagnosis Remains Primary

The four essential diagnostic questions must all be answered affirmatively: 1

• Is there an urge to move the legs accompanied by uncomfortable or unpleasant sensations?
• Do symptoms begin or worsen during rest or inactivity (sitting/lying)?
• Are symptoms partially or totally relieved by movement (walking, stretching) for as long as activity continues?
• Do symptoms worsen or only occur in the evening or night?

When to Consider PSG

Polysomnography should be reserved for cases where: 2, 6

• PLMD is specifically suspected based on sleep disturbance not explained by other causes
• The diagnosis remains unclear after clinical assessment
• Other sleep disorders (sleep apnea, REM behavior disorder) need exclusion

Do not order PSG for straightforward RLS diagnosis, as it adds no diagnostic value and delays treatment. 1, 6

Essential Laboratory Evaluation

• Obtain serum ferritin in all RLS patients; values <50 ng/mL indicate iron deficiency requiring supplementation. 1, 2
• Perform thorough neurological examination to exclude peripheral neuropathy or radiculopathy as secondary causes. 1, 6

Management Strategy

First-Line Pharmacologic Treatment

Current guidelines prioritize alpha-2-delta calcium channel ligands over dopaminergic agents due to augmentation risk: 2

• Gabapentin enacarbil, gabapentin, or pregabalin are recommended as first-line pharmacological treatment. 2
• These agents are particularly appropriate for RLS without PLMS, as they address sensory symptoms and sleep disruption without requiring dopaminergic mechanisms.

Dopaminergic Agents: Use With Caution

• Dopaminergic agents (ropinirole, pramipexole) may be considered for short-term use in patients who prioritize immediate symptom reduction over augmentation risk. 2
• However, patients without PLMS and without dopaminergic response represent a distinct clinical subgroup that may not benefit from these medications. 4
• Augmentation (paradoxical worsening of symptoms with dopaminergic treatment) is the main long-term complication. 5

Iron Supplementation

If ferritin <50 ng/mL, initiate iron supplementation to improve symptoms and potentially reduce augmentation risk if dopaminergic agents are used. 2, 5

Medication Review

Discontinue or substitute medications that exacerbate RLS: 1, 6

• Tricyclic antidepressants, SSRIs (except possibly bupropion), lithium
• Dopamine antagonists (antipsychotics, antiemetics)
• Antihistamines

Critical Pitfalls to Avoid

• Do not delay treatment while waiting for polysomnography in clinically obvious RLS. 1
• Do not assume RLS is excluded because PLMS are absent on PSG; 10% of RLS patients lack PLMS. 1, 2
• Do not continue escalating dopaminergic agents in patients without response; consider this a distinct RLS subtype requiring alternative approaches (gabapentinoids, opioids). 4, 7
• Do not confuse RLS with nocturnal leg cramps (painful muscle contractions relieved by stretching the specific muscle, not general movement). 6

Insomnia Management

Approximately 90% of RLS patients experience insomnia as the primary morbidity, driven by uncomfortable sensations preventing sleep initiation rather than limb movements per se. 3 Treatment targeting sensory symptoms (gabapentinoids) addresses this more directly than focusing solely on suppressing movements.