Prevalence and clinical characteristics of patients with restless legs syndrome with painful symptoms

Sensory aspects of restless legs syndrome: Clinical, neurophysiological and neuroimaging prospectives

Restless Legs Syndrome (RLS) is a complex sensorimotor disorder, classified among the sleep-related movement disorders. Although sensory symptoms appear as key features of the disorder, they are still poorly characterized from a clinical perspective and conceptualized from a pathophysiological point of view. In this review, we aim to describe the clinical and functional substrates of RLS, focusing mainly on its sensory symptoms and on their neurophysiological and anatomical correlates. Knowledge of both subjective sensory symptoms and objective sensory signs are still controversial. Current data also indicate that the sensory component of RLS seems to be subserved by anomalies of sensorimotor integration and by mechanism of central sensitization. Overall, electrophysiological findings highlight the involvement of multiple generators in the pathogenesis of RLS, eventually resulting in an increased nervous system excitability and/or alterations in inhibition within the somatosensory and nociceptive pathways. Structural and functional neuroimaging data show the involvement of several crucial areas and circuits, among which the thalamus appears to play a pivotal role. A holistic approach looking at brain connectivity, structural or functional abnormalities, and their interplay with molecular vulnerability and neurotransmitter alterations is warranted to disentangle the complex framework of RLS.

Efficacy and Safety of Acupuncture for Restless Legs Syndrome in Patients with End-Stage Renal Disease: A Randomized-Controlled Trial at Hospital-Based Hemodialysis Center

Background: Restless legs syndrome (RLS) is frequent in patients with hemodialysis (HD) and occurs predominantly in its most severe forms. The study was conducted to evaluate the efficacy and safety of acupuncture for RLS in patients with end-stage renal disease (ESRD) at hospital-based HD center. Methods: This single-blind, randomized controlled trial was performed on patients with HD and RLS who were randomly assigned to the experimental group and control group. Data were collected using the International Restless Legs Syndrome Rating Scale (IRLSRS), Insomnia Severity Index (ISI), and heart rate variability (HRV) records at baseline, after the therapeutic course (12 times/4 weeks), and 1-week follow-up. Result: A total of 47 patients were evaluated with IRLSRS score from 11 to 30 in this study. There were 41 patients enrolled in the study based on inclusion/exclusion criteria and allocated randomly into two groups. A total of 35 participants completed the trial, including 18 subjects in the experimental group and 17 subjects in the control group. The comparison of IRLSRS and ISI showed a significant reduction between two groups after acupuncture treatment (p = 0.002, p = 0.003). The ISI after 1-week follow-up also revealed significant decrease (p = 0.003). This HRV results showed that high frequency (HF%) increased significantly (p = 0.021) and low frequency (LF%) decreased significantly in the acupuncture group (p = 0.021). The generalized estimating equation showed that the IRLSRS improved by 2.902 points (p < 0.001) in the acupuncture group compared with the control group and by 1.340 points (p = 0.003) after 1-week follow-up. There were no adverse effects observed during HD in this study. Discussion: The authors conclude that acupuncture could effectively improve the symptoms of RLS significantly. The results from this study provide clinical evidence on the efficacy and safety of acupuncture to treat the patients with RLS at the HD center.

The Melanocortin and Endorphin Neuropeptides in Patients with Restless Legs Syndrome

OBJECTIVE

Based upon similarities between the urge to move and sensory discomfort of restless legs syndrome (RLS) and properties of melanocortin hormones, including their incitement of movement and hyperalgesia, we assessed plasma and cerebrospinal fluid (CSF) α-melanocyte-stimulating hormone (α-MSH) and β-endorphin in RLS patients and controls.

METHODS

Forty-two untreated moderate-to-severe RLS patients and 44 matched controls underwent venipuncture at 19:00, 20:30, and 22:00; 37 RLS and 36 controls had lumbar puncture at 21:30. CSF and plasma were analyzed for pro-opiomelanocortin (POMC), adrenocorticotropin hormone (ACTH), α-MSH, β-MSH, and β-endorphin by immunoassay. RLS severity was assessed by International RLS Study Group Severity Scale.

RESULTS

RLS participants were 52.7 ± 12.0 years old, 61.9% were women, 21.4% had painful RLS, and RLS severity was 24.8 ± 9.0. Controls had similar age and sex. Plasma ACTH, α-MSH, and β-endorphin were similar between groups. Plasma POMC was significantly greater in RLS than controls (17.0 ± 11.5 vs 12.7 ± 6.1fmol/ml, p = 0.048). CSF ACTH was similar between groups. CSF β-MSH was significantly higher in painful than nonpainful RLS or controls (48.2 ± 24.8 vs 32.1 ± 14.8 vs 32.6 ± 15.2pg/ml, analysis of variance [ANOVA] p = 0.03). CSF α-MSH was higher in RLS than controls (34.2 ± 40.9 vs 20.3 ± 11.0pg/ml, p = 0.062). CSF β-EDP was lowest in painful RLS, intermediate in nonpainful RLS, and highest in controls (8.0 ± 3.4 vs 10.8 ± 3.1 vs 12.3 ± 5.0pg/ml, ANOVA p = 0.049). The ratio of the sum of CSF α- and β-MSH to CSF β-endorphin was highest, intermediate, and lowest in painful RLS, nonpainful RLS, and controls (p = 0.007).

INTERPRETATION

CSF β-MSH is increased and CSF β-endorphin decreased in RLS patients with painful symptoms. ANN NEUROL 2024;95:688-699.

Quality of life among patients with restless legs syndrome: A systematic review and meta-analysis

OBJECTIVE

The primary aim was to estimate the pooled mean score of quality of life (QoL) (total, mental and physical health components) among patients with Restless Legs Syndrome (RLS). Secondary aims were to assess: (I) QoL differences for RLS vs. control groups, (II) heterogeneity and possible sources; and (III) moderating variables.

METHODS

Studies identified in PubMed, Scopus, Web of Science, and ProQuest between January 2000 and December 2022 were included. Methodological quality was assessed with Newcastle Ottawa Scale. The protocol was pre-registered (PROSPERO, CRD42023387318).

RESULTS

Twenty-seven studies (20121 participants, 12 countries) were included. The corrected pooled estimated mean score of QoL was 47.92 (27 studies, CI 95 %: 43.11 to 52.72, range 0-100, i.e., low-high QoL) and was marginally affected by publication year (increased 0.89 by each year, p = 0.12). The corrected pooled estimated mean score of the mental health component was 47.32 (17 studies, 95 % CI: 43.12 to 51.51, range 0-100) and influenced by RLS instrument (decreased with recent versions, p = 0.05). The corrected pooled estimated mean score of the physical health component was 39.08 (17 studies, 95 % CI: 33.05 to 45.10, range 0-100), with no statistically significant moderator. The pooled estimated QoL scores were statistically significantly lower in RLS patients compared to control groups with standardized mean difference (SMD) of -0.78, -0.57 and -0.50 respectively for overall QoL (24 studies), physical and mental health components (14 studies). Total QoL SMD was affected by proportion of women.

CONCLUSION

Low QoL was revealed among RLS patients, which was statistically significantly reduced compared to control groups.

Chronic testicular pain cured by low-dose pramipexole: is there an association with restless legs syndrome?

Restless legs syndrome (RLS) is characterized by an urge to move the legs, predominantly at night. About one quarter of the patients with RLS report painful symptoms in the legs. In this case report, the patient presented at the sleep clinic with a chief complaint of insomnia and the classical symptoms of RLS. He also mentioned a chronic testicular pain (CTP). For over a year, the patient had undergone urologic investigation and empiric treatments, with only mild improvement of the testicular pain. After 3 months of therapy with pramipexole, the RLS symptoms and the CTP were no longer present. Finding an etiology for CTP can be challenging and many cases are diagnosed as idiopathic. RLS may be a forgotten and unidentified etiology for CTP in typical urological care. Considering the high prevalence of RLS and CTP, it is relevant to clarify the possible association.

CITATION

Tedesco Silva LM, Lenz MCS, Martinez D. Chronic testicular pain cured by low-dose pramipexole: Is there an association with restless legs syndrome? J Clin Sleep Med. 2022;18(5):1467-1469.

Periodic limb movements during sleep: a narrative review

Objective

Using narrative review techniques, this paper evaluates the evidence for separable underlying patho-mechanisms of periodic limb movements (PLMs) to separable PLM motor patterns and phenotypes, in order to elucidate potential new treatment modalities.

Background

Periodic limb movement disorder (PLMD) is estimated to occur in 5–8% of the paediatric population and 4–11% of the general adult population. Due to significant sleep fragmentation, PLMD can lead to functional impairment, including hyperactivity and delayed language development in children, and poor concentration and work performance in adults. Longitudinal data demonstrate that those with PLMD are at greater risk of depression and anxiety, and a 4-fold greater risk of developing dementia. PLMD has been extensively studied over the past two decades, and several key insights into the genetic, pathophysiological, and neural correlates have been proposed. Amongst these proposals is the concept of separable PLM phenotypes, proposed on the basis of nocturnal features such as the ratio of limb movements and distribution throughout the night. PLM phenotype and presentation, however, varies significantly depending on the scoring utilized and the nocturnal features examined, across age, and co-morbid clinical conditions. Furthermore, associations between these phenotypes with major neurologic and psychiatric disorders remain controversial.

Methods

In order to elucidate potential divergent biological pathways that may help clarify important new treatment modalities, this paper utilizes narrative review and evaluates the evidence linking PLM motor patterns and phenotypes with hypothesised underlying patho-mechanisms. Distinctive, underlying patho-mechanisms include: a pure motor mechanism originating in the spinal cord, iron deficiency, dopamine system dysfunction, thalamic glutamatergic hyperactivity, and a more cortical-subcortical interplay. In support of the latter hypothesis, PLM rhythmicity appears tightly linked to the microarchitecture of sleep, not dissimilarly to the apnoeic/hypopneic events seen in obstructive sleep apnea (OSA).

Conclusions

This review closes with a proposal for greater investigation into the identification of potential, divergent biological pathways. To do so would require prospective, multimodal imaging clinical studies which may delineate differential responses to treatment in restless legs syndrome (RLS) without PLMS and PLMS without RLS. This could pave the way toward important new treatment modalities.

[Restless legs syndrome]

Restless legs syndrome (RLS) is seen widely in clinical practice. RLS commonly occurs at night time and presents with unpleasant or uncomfortable sensations in the legs that causes an urge to move them. This article describes the epidemiology, risk factors and pathophysiology of RLS. There is a detailed description of clinical presentations, diagnostic criteria and also management of RLS.

(Neuro)Inflammatory Component May Be a Common Factor in Chronic Widespread Pain and Restless Legs Syndrome

Purpose of Review

Recent studies have linked fibromyalgia (nociplastic pain) and depression to neuroinflammation. Restless legs syndrome (RLS) is highly prevalent in CWP (chronic widespread pain) and FMS (fibromyalgia syndrome) as well as in depression. This review focuses on evidence in the relationship between CWP and RLS and possible common pathophysiological mechanisms.

Recent Findings

CWP is chronic pain spread over various locations of the body and is a cardinal sign of fibromyalgia. Poor sleep quality is a common symptom in fibromyalgia as well as high levels of fatigue, poor cognition, and other associated features which include depression, headache, and abdominal pain. Evidence for a bilateral relationship between pain and sleep deficit is robust. The latest research focus is not only on insomnia symptoms in chronic pain but also on other types of sleep disorders such as RLS which is characterized by complaints of an “urge to move” frequently associated with dysesthesias. These sensations can also have painful characteristics. Thus, there is a possible overlap between these two entities. The high prevalence of RLS (33–54%) in CWP has been shown in several studies. The pathophysiological mechanisms behind CWP and RLS are still not completely known, but there is a rising amount of evidence on proinflammatory and neuroinflammatory processes in CWP. In RLS, there are links to dopaminergic dysfunction and more generally to monoaminergic dysfunctional circuits, BID (brain iron deficiency), altered glutamatergic neurotransmission, and genetic traits. Depression is a common comorbidity as well in CWP as RLS, and proinflammatory mechanisms have also been demonstrated in this condition.

Summary

The association between CWP and RLS is shown to be high and the pathogenesis of both conditions is still not completely understood. Recent research is focusing on proinflammatory and neuroinflammatory processes, not uniquely emerging in fibromyalgia/CWP, but inflammatory features have been found in depression as well as in sleep deficit. Proinflammatory/neuroinflammatory processes may be an underlying, common factor in both CWP and RLS that future research should investigate further.

Spinal Cord Stimulation in Patients With Chronic Pain and Restless Legs Syndrome: A Case Report

Restless legs syndrome can be a debilitating condition that affects a patient's ability to function and their quality of life. Neuromodulation may represent a potential option for nonpharmacological management of restless legs syndrome. We present 3 patients who have a chronic pain diagnosis and medically refractory restless legs syndrome that warranted neuromodulation. After neuromodulation, all 3 patients had improvement in their restless legs syndrome symptoms and were taking less pain medication, and 2 out of 3 had significantly improved functionality at short-term follow-up. This case series suggests that spinal cord stimulation may be a viable nonpharmacological treatment option for medically refractory restless legs syndrome.

Characterization of painful Restless Legs Syndrome sensations in an English-speaking South African population

Background and aims Restless Legs Syndrome (RLS) is characterised by unusual sensations in the legs which can be described as painful in up to 60% of RLS patients. The purpose of this study was to characterise and examine whether the presence of pain influenced the words used to describe the sensations of RLS in an English speaking population. Methods RLS participants (n=55) were divided according to whether or not painful RLS sensations were reported upon questioning. They completed the McGill Pain Questionnaire (MPQ), the International Restless Legs Syndrome Severity Scale (IRLS) and selected descriptors from a list of previously published RLS terms. Results Thirty-five percent of the RLS patients had painful sensations. The participants with painful RLS had higher Pain Rating Index (PRI) scores [median (interquartile range) 21 (17-28) vs. 14 (7.5-21) p=0.0008] and IRLS scores [23 (17-28) vs. 18 (11.5-22.5) p=0.0175] than the participants with non-painful RLS. Patients with painful RLS symptoms selected more pain-related literature terms, chose significantly different words in eight of the MPQ subclasses (both sensory and affective) and selected more intense descriptors from certain MPQ subclasses than the non-painful RLS group. The terms that characterised painful RLS were "aching", "painful", "cramping" and "unbearable". Conclusions Descriptors of RLS sensations are changed by the presence of pain, which may indicate an aetiological difference in the patients who have painful RLS. Clinically, patients complaining of cramping and painful sensations may be diagnosed with a condition that mimics RLS. Thus, it is important that the most accurate set of descriptors for RLS are used to enable recognition of RLS and optimised treatment according to the RLS phenotype. Implications The diagnosis of RLS may be improved by overcoming language and cultural barriers and obtaining differential diagnostic terms for painful conditions mimicking RLS.

French Consensus: How to diagnose restless legs syndrome

Correct diagnosis of restless legs syndrome (RLS) is essential to patient care and treatment. Diagnosis is most often clinical and based on diagnostic criteria: the need to move the legs accompanied to varying degrees by unpleasant sensations, predominantly during the evening and improved by movement. In rare cases, clinical examination is insufficient and a polysomnography is necessary. Once a positive diagnosis has been made, a neurological examination and an assessment of iron status are required. The severity of the RLS must be evaluated to determine whether a specific treatment is necessary. Before treatment, it is essential to ensure that a definite diagnosis of RLS has been made and the phenotype characterised. This enables a personal treatment plan and limits the risk of augmentation syndrome.

Effectiveness of fixed-site high-frequency transcutaneous electrical nerve stimulation in chronic pain: a large-scale, observational study

Objective

The objective of this study was to assess the effectiveness of fixed-site high-frequency transcutaneous electrical nerve stimulation (FS-TENS) in a real-world chronic pain sample.

Background

There is a need for nonpharmacological treatment options for chronic pain. FS-TENS improved multisite chronic pain in a previous interventional study. Large observational studies are needed to further characterize its effectiveness.

Methods

This retrospective observational cohort study examined changes in chronic pain measures following 60 days of FS-TENS use. The study data were obtained from FS-TENS users who uploaded their device utilization and clinical data to an online database. The primary outcome measures were changes in pain intensity and pain interference with sleep, activity, and mood on an 11-point numerical rating scale. Dose-response associations were evaluated by stratifying subjects into low (≤30 days), intermediate (31-56 days), and high (≥57 days) utilization subgroups. FS-TENS effectiveness was quantified by baseline to follow-up group differences and a responder analysis (≥30% improvement in pain intensity or ≥2-point improvement in pain interference domains).

Results

Utilization and clinical data were collected from 11,900 people using FS-TENS for chronic pain, with 713 device users meeting the inclusion and exclusion criteria. Study subjects were generally older, overweight adults. Subjects reported multisite pain with a mean of 4.8 (standard deviation [SD] 2.5) pain sites. A total of 97.2% of subjects identified low back and/or lower extremity pain, and 72.9% of subjects reported upper body pain. All pain measures exhibited statistically significant group differences from baseline to 60-day follow-up. The largest changes were pain interference with activity (-0.99±2.69 points) and mood (-1.02±2.78 points). A total of 48.7% of subjects exhibited a clinically meaningful reduction in pain interference with activity or mood. This proportion increased to 57.1% for the high utilization subgroup.

Conclusion

FS-TENS is a practical option for treating multisite chronic pain. The greatest impact is on pain interference with activity and mood. FS-TENS utilization and effectiveness exhibit a dose-response association, suggesting that daily use maximizes pain relief.

Central and peripheral nervous system excitability in restless legs syndrome

Neurophysiological techniques have been applied in restless legs syndrome (RLS) to obtain direct and indirect measures of central and peripheral nervous system excitability, as well as to probe different neurotransmission pathways. Data converge on the hypothesis that, from a pure electrophysiological perspective, RLS should be regarded as a complex sensorimotor disorder in which cortical, subcortical, spinal cord, and peripheral nerve generators are all involved in a network disorder, resulting in an enhanced excitability and/or decreased inhibition. Although the spinal component may have dominated in neurophysiological assessment, possibly because of better accessibility compared to the brainstem or cerebral components of a hypothetical dysfunction of the diencephalic A11 area, multiple mechanisms, such as reduced central inhibition and abnormal peripheral nerve function, contribute to the pathogenesis of RLS similarly to some chronic pain conditions. Dopamine transmission dysfunction, either primary or triggered by low iron and ferritin concentrations, may also bridge the gap between RLS and chronic pain entities. Further support of disturbed central and peripheral excitability in RLS is provided by the effectiveness of nonpharmacological tools, such as repetitive transcranial magnetic stimulation and transcutaneous spinal direct current stimulation, in transiently modulating neural excitability, thereby extending the therapeutic repertoire. Understanding the complex interaction of central and peripheral neuronal circuits in generating the symptoms of RLS is mandatory for a better refinement of its therapeutic support.

Fixed-site high-frequency transcutaneous electrical nerve stimulation for treatment of chronic low back and lower extremity pain

Objective

The objective of this study was to determine if fixed-site high-frequency transcutaneous electrical nerve stimulation (FS-TENS) is effective in treating chronic low back and lower extremity pain.

Background

Transcutaneous electrical nerve stimulation is widely used for treatment of chronic pain. General-purpose transcutaneous electrical nerve stimulation devices are designed for stimulation anywhere on the body and often cannot be used while the user is active or sleeping. FS-TENS devices are designed for placement at a pre-determined location, which enables development of a wearable device for use over extended time periods.

Methods

Study participants with chronic low back and/or lower extremity pain self-administered an FS-TENS device for 60 days. Baseline, 30-, and 60-day follow-up data were obtained through an online questionnaire. The primary outcome measure was the patient global impression of change. Pain intensity and interference were assessed using the Brief Pain Inventory. Changes in use of concomitant pain medications were evaluated with a single-item global self-rating.

Results

One hundred and thirty participants were enrolled, with 88 completing the 60-day follow-up questionnaire. Most participants (73.9%) were 50 years of age or older. At baseline, low back pain was identified by 85.3%, lower extremity pain by 71.6%, and upper extremity pain by 62.5%. Participants reported widespread pain, at baseline, with a mean of 3.4 (standard deviation 1.1) pain sites. At the 60-day follow-up, 80.7% of participants reported that their chronic pain had improved and they were classified as responders. Baseline characteristics did not differentiate non-responders from responders. There were numerical trends toward reduced pain interference with walking ability and sleep, and greater pain relief in responders. There was a large difference in use of concomitant pain medications, with 80.3% of responders reporting a reduction compared to 11.8% of non-responders.

Conclusion

FS-TENS is a safe and effective option for treating chronic low back and lower extremity pain. These results motivate the use of FS-TENS in development of wearable analgesic devices.

The Effect of Gabapentin Enacarbil on Pain Associated with Moderate-to-Severe Primary Restless Legs Syndrome in Adults: Pooled Analyses from Three Randomized Controlled Trials

BACKGROUND

Adults with moderate-to-severe primary restless legs syndrome (RLS) often experience painful dysesthesias, which may lead to impaired quality of life.

OBJECTIVES

The aim of this study was to assess the effects of gabapentin enacarbil (GEn) on pain associated with moderate-to-severe primary RLS in adults.

METHODS

Data were pooled from three double-blind, randomized, placebo-controlled, 12-week trials (NCT00298623, NCT00365352, NCT01332305) for adults receiving GEn or placebo once daily. Change in average daily RLS pain score and a combined International Restless Legs Scale (IRLS)-pain response were examined.

RESULTS

The modified intention-to-treat population included 671 adults (placebo, n = 244; GEn 600 mg, n = 161; GEn 1200 mg, n = 266). Both GEn doses significantly improved average daily RLS pain score at week 12 (p < 0.001 for GEn 600 mg vs. placebo and GEn 1200 mg vs. placebo). The combined IRLS-pain response subanalysis included 366 patients with a baseline IRLS total score ≥15 and pain score ≥4 (placebo, n = 133; GEn 600 mg, n = 86; GEn 1200 mg, n = 147). Most patients were both IRLS and pain responders (placebo, 40 %; GEn 600 mg, 70 %; GEn 1200 mg, 67 %). Spearman rank correlations between IRLS total and pain score (change from baseline to week 12) were moderate or strong. The most frequent treatment-emergent adverse events were somnolence (placebo, 5 %; GEn 600 mg, 20 %; GEn 1200 mg, 23 %) and dizziness (placebo, 4 %; GEn 600 mg, 13 %; GEn 1200 mg, 22 %).

CONCLUSIONS

This post hoc pooled analysis suggests that GEn (600 and 1200 mg) once daily significantly improved pain associated with moderate-to-severe primary RLS in adults; however, the analysis was not powered to detect statistical differences between the two GEn doses. Numerically, more GEn-treated patients had a combined IRLS-pain response than placebo-treated patients.