Restless Legs Syndrome - RLS and Pain (27)

Not named in the criteria, yet often felt as pain.

"This is not tingling - it hurts." The diagnostic criteria for restless legs syndrome speak of an urge to move usually accompanied by unpleasant sensations. Pain is not explicitly named in any of today's criteria. Anyone who describes their symptoms as pain is often left with a painkiller and a shrug. Yet in one clinical study, 23.8% of 160 people with idiopathic restless legs syndrome described their symptoms as painful. This group had lower ferritin levels, more severe symptoms and poorer quality of life.

Studies have measured changes in pain processing. In one study, 40 previously untreated people with RLS showed three- to fourfold greater sensitivity to pinprick stimuli than healthy controls, at the hand as well as at the foot. In another study, the body's own pain inhibition was weaker: 69% of the brain response remained, compared with 52.5% in healthy controls. Each of these findings comes from a single study.

The second part looks from the other direction. In people with a pain condition, restless legs syndrome is often not diagnosed because another diagnosis has already been made. In a meta-analysis, restless legs syndrome was reported in 21.5% of people with polyneuropathy, and in one study of people with chronic low back pain, 35.3% had it. The four questions about restless legs take a minute. A positive answer raises the possibility of the condition, which then needs a full assessment.

In trial analyses, leg pain improved with the same drugs as the urge to move. In two large trials of pramipexole, the median change in leg pain was -33.5 and -31.0 millimetres on a 100-millimetre scale, compared with -11.0 under placebo. The participants had not been selected for pain. The effectiveness of common painkillers for RLS-related symptoms, by contrast, has not been established in reliable studies. Iron status is assessed first. The series uses a ferritin at or below 100 µg/l as the threshold for discussing iron treatment, with transferrin saturation always measured.

Common non-opioid analgesics should be distinguished from drug classes that are also used to treat RLS, such as alpha-2-delta ligands and, in selected cases, opioids. Opioids are used in severe RLS that has not responded to other treatments, usually at doses well below those used in pain medicine. The Cochrane review included one eligible controlled study and names missing safety data as the main shortcoming. In a registry of 448 people followed for two years, 58.9% kept the same dose or reduced it.

WHAT IS IN THE BOOK
- Is what I feel in my legs actually pain?
- The missing words, and why the figures vary between studies
- What distinguishes people with painful restless legs syndrome
- Calf cramps, narrowed arteries and other causes of nocturnal leg pain
- The pinprick: the hypersensitivity that can be measured
- The pain brake that works less well, and the body's own opioid system
- When damage to the small nerve fibres is involved after all
- Iron, dopamine, lack of sleep and the pain threshold
- When pain at an unusual site may be a form of RLS
- Polyneuropathy, back pain, rheumatic diseases, migraine and fibromyalgia
- Growing pains in children, and the features that distinguish them
- What helps with pain in RLS, and the special case of opioids

WHO THIS BOOK IS FOR
For people whose symptoms hurt and who therefore have not received a diagnosis, for people with chronic pain and restless nights, and for health professionals working between pain medicine and sleep medicine.

ABOUT THE SERIES
Volume 27 of 52 in the book series on restless legs syndrome, part "RLS with Other Conditions". Every volume can be read on its own. The statements in this volume rest on 240 professional sources, each one listed individually in the reference section.