Restless Leg Syndrome & Periodic Limb Movement Disorder

A Brief Overview

Restless Leg Syndrome (RLS) — also known as Willis-Ekbom disease — is a sensorimotor disorder characterised by an irresistible urge to move the legs, usually accompanied by uncomfortable creeping, crawling, or aching sensations deep within the limbs. The symptoms are worst when at rest, particularly in the evening or at bedtime, and are relieved by movement. RLS commonly disturbs sleep onset and can be extremely distressing.

Periodic Limb Movement Disorder (PLMD) — characterised by repetitive limb movements (most often of the legs) during sleep, typically every 20–40 seconds. Many people with PLMD are unaware of the movements themselves; partners notice them, or they are detected on sleep studies. PLMD can fragment sleep and cause daytime tiredness even when the patient is unaware of what is happening overnight.

RLS and PLMD often coexist. Both share many of the same triggers and respond to many of the same treatments. The first step in both is reviewing medications and iron status.

Medication Review — A First Step

A number of commonly prescribed drugs are known to trigger or worsen RLS and PLMD. If you have these symptoms and are taking any of the following, ask your GP or pharmacist to review whether they are still needed:

• Antihistamines — particularly the older sedating ones such as chlorphenamine (Piriton) and diphenhydramine (Benadryl, Nytol).
• Anti-sickness tablets — metoclopramide, prochlorperazine.
• Antipsychotic medications — particularly the older typical antipsychotics, but also some newer atypicals.
• Antidepressants — SSRIs (citalopram, sertraline, fluoxetine, etc.) and tricyclics (amitriptyline, nortriptyline). Mirtazapine is also strongly associated with worsening RLS.
• Lithium.

Do not stop these drugs without medical advice — some are essential, and stopping abruptly can cause withdrawal effects. The point is to review the list with your GP or specialist.

Iron Status — The Central Investigation

Low iron in the body — even when not severe enough to cause anaemia — is one of the most well-established contributors to RLS and PLMD. Iron is required for dopamine synthesis in the brain, and brain iron status appears to be especially relevant to these conditions.

The tests to ask for

• Ferritin — reflects how much iron your body has in storage. A normal ferritin can falsely reassure if you have RLS.
• Transferrin saturation — shows how efficiently iron is being carried around the body.

What the results mean for RLS

Standard "normal" ferritin ranges for the general population are too low for patients with RLS. The current evidence supports the following thresholds:

• Ferritin below 75 micrograms per litre, or transferrin saturation below 20% — iron replacement is recommended.
• Ferritin between 75 and 100 micrograms per litre — may still be low enough to contribute to symptoms; iron replacement is often worth trying.
• Ferritin above 100 micrograms per litre — iron deficiency is unlikely to be the driver of symptoms.

How to replace iron

• Oral iron tablets — typically ferrous sulphate 200 mg daily, taken with a source of vitamin C (which improves absorption). Common side effects are constipation, dark stools and nausea. Some patients tolerate ferrous fumarate or ferrous bisglycinate better than ferrous sulphate.
• Intravenous iron infusion — if oral tablets do not raise ferritin above 100 micrograms per litre, or if oral iron is not tolerated, an IV infusion is highly effective. The infusion with the strongest evidence in RLS is ferric carboxymaltose, which is now considered a very effective first-line treatment for RLS patients with low iron stores.

Associated Conditions to Consider

Several conditions are associated with RLS and PLMD and may be exacerbating symptoms. Ensure these have been considered and are appropriately managed:

• Kidney disease — particularly chronic kidney disease and dialysis.
• Diabetes mellitus, particularly with diabetic neuropathy.
• Pregnancy — RLS commonly emerges or worsens in pregnancy, particularly the third trimester, and often resolves after delivery.
• Depression and anxiety — tricky because many antidepressants worsen RLS. If treatment of mood disorder is essential, advice from a psychiatrist or sleep physician about which agents are least likely to worsen RLS is valuable.

Medical Treatment

For patients in whom symptoms remain troublesome despite iron repletion and lifestyle measures, a sleep physician may consider:

• Gabapentin or pregabalin — current guidelines support these as the preferred first-line pharmacological options for moderate-to-severe RLS. Side effects include drowsiness, dizziness, weight gain, and (rarely) mood changes.
• Dopamine agonists — pramipexole, ropinirole, rotigotine patches. Historically the standard treatment but now used more cautiously because of the long-term risk of augmentation (paradoxical worsening of symptoms on these drugs over time).
• Opioids — low-dose opioid medications are sometimes used in severe refractory cases under specialist supervision.

Lifestyle Measures

• Sleep regularity — go to bed and wake at consistent times; avoid sleep deprivation, which makes symptoms worse.
• Caffeine — limit caffeine, particularly later in the day. Coffee, tea, energy drinks, and chocolate can all aggravate symptoms.
• Alcohol and nicotine — both can worsen RLS.
• Exercise — moderate regular exercise often helps; very strenuous or unaccustomed exercise can paradoxically trigger episodes.
• Stretching and massage at bedtime help some patients.
• Avoid prolonged immobility — long-haul flights and theatre seats are common triggers.

When to See a Specialist

See your GP for initial assessment, including medication review and iron studies. Ask for referral to a sleep physician or neurologist if symptoms are significantly affecting sleep or daytime functioning despite first-line measures. If you have a known sleep disorder such as obstructive sleep apnoea and PLMD has been detected on a sleep study, treating the OSA first often improves limb movements significantly.

For booking advice, the secretarial team can guide you on appropriate referral pathways for RLS/PLMD.