Altered brain iron homeostasis and dopaminergic function in Restless Legs Syndrome (Willis-Ekbom Disease)

The complexities in the differential diagnosis of restless legs syndrome (Willis-Ekbom disease)

INTRODUCTION

We present a literature review on the clinical conundrums surrounding the differential diagnosis of restless legs syndrome (RLS, Willis-Ekbom disease), as well as conditions that can mimic RLS. An extensive literature search showed that secondary causes of RLS ranged from commonly recognized causes, such as iron deficiency anemia, to less widely noted causes, such as rheumatoid disorders and hypothyroidism. There is a controversial association with Parkinson's disease, essential tremor, and RLS, whereby RLS is proposed as a prodromal feature.

AREAS COVERED

The clinical presentation of restless legs syndrome (RLS), a highly prevalent movement disorder usually during sleep with a circadian variation. The review highlights differences between commonly established secondary causes of RLS, RLS mimics, genetic and drug-induced RLS. A flowchart presents some key features of different and overlapping secondary RLS and mimics and genetic RLS.

EXPERT OPINION

RLS is one of the commonest movement disorders and the International Restless Legs Syndrome Study Group has suggested five-point criteria for robust diagnosis of RLS. However, even in expert hands, diagnosis is accurate in about 85% and misdiagnosis, especially with 'RLS mimics,' appears to be high. There are wide variations in the way RLS can present, and this includes different types of secondary RLS as well as drug induced or genetic patterns of RLS. Secondary RLS is highly complex and can be associated with Parkinson's disease as well as prodromal stage of Parkinson and essential tremor. Other known causes of secondary RLS are many and include end-stage kidney disease as well as metabolic disorders to painful conditions such as rheumatic disorders and fibromyalgia and polyradiculopathy.

Serum alpha-synuclein in restless legs syndrome

STUDY OBJECTIVES

To determine any correlation between serum alpha-synuclein (α-syn) concentrations and restless legs syndrome (RLS), and to explore the impact of intravenous iron supplementation on serum α-syn levels.

METHODS

We collected clinical data on 113 RLS patients in whom serum α-syn levels were quantified using an ELISA kit and compared to a group of 45 age-matched controls. A subset of nine RLS patients who received intravenous (IV) iron underwent pre- and post-treatment blood sampling to assess α-syn and ferritin response.

RESULTS

A family history of RLS was reported by 62.8% of patients, and current dopaminergic augmentation was observed in 31.0%. Low serum ferritin levels below 75 μg/L were seen in 39.8%. Serum α-syn levels were found to be significantly decreased in RLS patients (mean: 7.7 ng/mL) compared to controls (mean: 10.7 ng/mL), p < .05. Stratification based on sex, age, and age of onset, did not reveal significant differences in α-syn levels. In nine RLS patients who received IV iron treatment, a linear correlation between fold change in α-syn and ferritin was observed (R: 0.7, p < .05). The temporal relation between serum α-syn and IV iron treatment showed a gradual decline of α-syn and ferritin by time correlation (p = .023, R: -.739).

CONCLUSION

In our study of 113 RLS participants, serum α-syn levels were decreased in RLS patients compared to healthy controls, and increased in the nine patients who received IV iron treatment in correlation with ferritin. This correlation could suggest a mechanism for reduced dopamine transmission in RLS.

Prospective study of restless legs syndrome in a blood donors' sample

BACKGROUND AND OBJECTIVES

Blood donation is suggested to increase the risk of restless legs syndrome (RLS). This study aims to assess the prevalence of RLS in Spanish blood donors and determined its potential correlation with iron metabolism parameters.

MATERIALS AND METHODS

Prospective cohort study of 129 blood donors (54.3% men, 39.44 years ± 11.0) that underwent a physical examination, blood analysis (hemoglobin, ferritin, transferrin saturation index and soluble transferrin receptor) and a RLS screening questionnaire followed by a prospective follow-up study including a clinical phone interview. A multivariate logistic regression model was performed to examine the association between RLS and other variables.

RESULTS

Eighty-four (65.1%) participants were repeat blood donors (mean of 2.11 donations/year) at inclusion and 61 (47.4%) at follow-up (mean of 2.09 donations/year). Non-anemic iron deficiency (ferritin < 50 µg/l) was high in women p < 0.001 and in repeat donors (p = 0.003). The prevalence of RLS was 14.1% at inclusion increasing prospectively (19.5%; p = 0.065). On multivariate analysis, gender was the only variable significantly associated with a RLS diagnosis, being higher in women (OR 5.1; 95% CI 1.71-15.3; p = 0.003).

CONCLUSIONS

Despite the high prevalence of non-anemic iron deficiency there was no association between ferritin, transferrin saturation index, soluble transferrin receptor concentration values and RLS diagnosis. Gender was associated with RLS diagnosis regardless of other variables.

Treatment of restless legs syndrome and periodic limb movement disorder: an American Academy of Sleep Medicine clinical practice guideline

INTRODUCTION

This guideline establishes clinical practice recommendations for treatment of restless legs syndrome (RLS) and periodic limb movement disorder (PLMD) in adults and pediatric patients.

METHODS

The American Academy of Sleep Medicine (AASM) commissioned a task force of experts in sleep medicine to develop recommendations and assign strengths based on a systematic review of the literature and an assessment of the evidence using the grading of recommendations assessment, development, and evaluation methodology. The task force provided a summary of the relevant literature and the certainty of evidence, the balance of benefits and harms, patient values and preferences, and resource use considerations that support the recommendations. The AASM Board of Directors approved the final recommendations.

GOOD PRACTICE STATEMENT

The following good practice statement is based on expert consensus, and its implementation is necessary for the appropriate and effective management of patients with RLS.

1. In all patients with clinically significant RLS, clinicians should regularly test serum iron studies including ferritin and transferrin saturation (calculated from iron and total iron binding capacity). Testing should ideally be administered in the morning avoiding all iron-containing supplements and foods at least 24 hours prior to blood draw. Analysis of iron studies greatly influences the decision to use oral or intravenous (IV) iron treatment. Consensus guidelines, which have not been empirically tested, suggest that supplementation of iron in adults with RLS should be instituted with oral or IV iron if serum ferritin ≤ 75 ng/mL or transferrin saturation < 20%, and only with IV iron if serum ferritin is between 75 and 100 ng/mL. In children, supplementation of iron should be instituted for serum ferritin < 50 ng/mL with oral or IV formulations. These iron supplementation guidelines are different than for the general population.

2. The first step in the management of RLS should be addressing exacerbating factors, such as alcohol, caffeine, antihistaminergic, serotonergic, antidopaminergic medications, and untreated obstructive sleep apnea.

3. RLS is common in pregnancy; prescribers should consider the pregnancy-specific safety profile of each treatment being considered.

RECOMMENDATIONS

The following recommendations are intended as a guide for clinicians in choosing a specific treatment for RLS and PLMD in adults and children. Each recommendation statement is assigned a strength ("strong" or "conditional"). A "strong" recommendation (ie, "We recommend…") is one that clinicians should follow under most circumstances. The recommendations listed below are ranked in the order of strength of recommendations and grouped by class of treatments within each PICO (Patient, Intervention, Comparator, Outcome) question. Some recommendations include remarks that provide additional context to guide clinicians with implementation of this recommendation.

ADULTS WITH RLS

1. In adults with RLS, the AASM recommends the use of gabapentin enacarbil over no gabapentin enacarbil (strong recommendation, moderate certainty of evidence).

2. In adults with RLS, the AASM recommends the use of gabapentin over no gabapentin (strong recommendation, moderate certainty of evidence).

3. In adults with RLS, the AASM recommends the use of pregabalin over no pregabalin (strong recommendation, moderate certainty of evidence).

4. In adults with RLS, the AASM recommends the use of IV ferric carboxymaltose over no IV ferric carboxymaltose in patients with appropriate iron status (see good practice statement for iron parameters) (strong recommendation, moderate certainty of evidence).

5. In adults with RLS, the AASM suggests the use of IV low molecular weight iron dextran over no IV low molecular weight iron dextran in patients with appropriate iron status (see good practice statement for iron parameters) (conditional recommendation, very low certainty of evidence).

6. In adults with RLS, the AASM suggests the use of IV ferumoxytol over no IV ferumoxytol in patients with appropriate iron status (see good practice statement for iron parameters) (conditional recommendation, very low certainty of evidence).

7. In adults with RLS, the AASM suggests the use of ferrous sulfate over no ferrous sulfate in patients with appropriate iron status (see good practice statement for iron parameters) (conditional recommendation, moderate certainty of evidence).

8. In adults with RLS, the AASM suggests the use of dipyridamole over no dipyridamole (conditional recommendation, low certainty of evidence).

9. In adults with RLS, the AASM suggests the use of extended-release oxycodone and other opioids over no opioids (conditional recommendation, moderate certainty of evidence).

10. In adults with RLS, the AASM suggests the use of bilateral high-frequency peroneal nerve stimulation over no peroneal nerve stimulation (conditional recommendation, moderate certainty of evidence).

11. In adults with RLS, the AASM suggests against the standard use of levodopa (conditional recommendation, very low certainty of evidence).

Remarks: levodopa may be used to treat RLS in patients who place a higher value on the reduction of restless legs symptoms with short-term use and a lower value on adverse effects with long-term use (particularly augmentation).

12. In adults with RLS, the AASM suggests against the standard use of pramipexole (conditional recommendation, moderate certainty of evidence).

Remarks: pramipexole may be used to treat RLS in patients who place a higher value on the reduction of restless legs symptoms with short-term use and a lower value on adverse effects with long-term use (particularly augmentation).

13. In adults with RLS, the AASM suggests against the standard use of transdermal rotigotine (conditional recommendation, low certainty of evidence).

Remarks: transdermal rotigotine may be used to treat RLS in patients who place a higher value on the reduction of restless legs symptoms with short-term use and a lower value on adverse effects with long-term use (particularly augmentation).

14. In adults with RLS, the AASM suggests against the standard use of ropinirole (conditional recommendation, moderate certainty of evidence).

Remarks: ropinirole may be used to treat RLS in patients who place a higher value on the reduction of restless legs symptoms with short-term use and a lower value on adverse effects with long-term use (particularly augmentation).

15. In adults with RLS, the AASM suggests against the use of bupropion for the treatment of RLS (conditional recommendation, moderate certainty of evidence).

16. In adults with RLS, the AASM suggests against the use of carbamazepine (conditional recommendation, low certainty of evidence).

17. In adults with RLS, the AASM suggests against the use of clonazepam (conditional recommendation, very low certainty of evidence).

18. In adults with RLS, the AASM suggests against the use of valerian (conditional recommendation, very low certainty of evidence).

19. In adults with RLS, the AASM suggests against the use of valproic acid (conditional recommendation, low certainty of evidence).

20. In adults with RLS, the AASM recommends against the use of cabergoline (strong recommendation, moderate certainty of evidence).

SPECIAL ADULT POPULATIONS WITH RLS

21. In adults with RLS and end-stage renal disease (ESRD), the AASM suggests the use of gabapentin over no gabapentin (conditional recommendation, very low certainty of evidence).

22. In adults with RLS and ESRD, the AASM suggests the use of IV iron sucrose over no IV iron sucrose in patients with ferritin < 200 ng/mL and transferrin saturation < 20% (conditional recommendation, moderate certainty of evidence).

23. In adults with RLS and ESRD, the AASM suggests the use of vitamin C over no vitamin C (conditional recommendation, low certainty of evidence).

24. In adults with RLS and ESRD, the AASM suggests against the standard use of levodopa (conditional recommendation, low certainty of evidence).

Remarks: levodopa may be used to treat RLS in patients who place a higher value on the reduction of restless legs symptoms with short-term use and a lower value on adverse effects with long-term use (particularly augmentation).

25. In adults with RLS and ESRD, the AASM suggests against the standard use of rotigotine (conditional recommendation, very low certainty of evidence).

Remarks: rotigotine may be used to treat RLS in patients who place a higher value on the reduction of restless legs symptoms with short-term use and a lower value on adverse effects with long-term use (particularly augmentation).

ADULTS WITH PLMD

26. In adults with PLMD, the AASM suggests against the use of triazolam (conditional recommendation, very low certainty of evidence).

27. In adults with PLMD, the AASM suggests against the use of valproic acid (conditional recommendation, very low certainty of evidence).

CHILDREN WITH RLS

28. In children with RLS, the AASM suggests the use of ferrous sulfate over no ferrous sulfate in patients with appropriate iron status (see good practice statement for iron parameters) (conditional recommendation, very low certainty of evidence).

CITATION

Winkelman JW, Berkowski JA, DelRosso LM, et al. Treatment of restless legs syndrome and periodic limb movement disorder: an American Academy of Sleep Medicine clinical practice guideline. J Clin Sleep Med. 2025;21(1):137-152.

Alterations in spontaneous brain activity of maintenance hemodialysis patients with restless legs syndrome: a cross-sectional case-control study

OBJECTIVE

Through resting state functional magnetic resonance imaging (rs-fMRI) we evaluate the spontaneous brain activity changes of maintenance hemodialysis (MHD) patients with restless legs syndrome (RSL) and analyzed the imaging features and related mechanisms of RLS in patients with MHD.

METHOD

We select 27 MHD patients with RLS and 27 patients without RSL matched by age, gender, cognitive function. Both groups underwent neuropsychological tests and MRI scans. MRI data analysis was performed to obtain and compare the amplitude of low-frequency fluctuation (ALFF), fractional amplitude of low-frequency fluctuations (fALFF), and regional homogeneity (ReHo) values, which were mALFF, mfALFF, and mReHo. Clinical data were collected and compared. Differentiated indicators and RLS scores conduct Pearson correlation analysis.

RESULT

Compared with the MHD-nRLS group, the MHD-RLS group showed significantly lower mALFF values in the left precentral, right precentral gyrus, and right postcentral gyrus, lower mfALFF values in the left precentral gyrus, right precentral gyrus, left calcarine fissure, left lingual gyrus, left postcentral gyrus, and right postcentral gyrus, and lower mReHo values in the left precentral gyrus, right precentral gyrus, left calcarine fissure, left lingual gyrus, left postcentral gyrus, and right postcentral gyrus, and right postcentral gyrus (P < 0.05). The MHD-RLS group exhibited lower hemoglobin levels (P = 0.001), higher total iron-binding capacity levels (P = 0.011), and higher folic acid levels (P = 0.022). The above indicators were correlated with RLS scores using Pearson correlation analysis, and it was found that the mfALFF value of the right precentral gyrus and the right postcentral gyrus, and the mReHo values of the right precentral gyrus and right postcentral gyrus were negatively correlated with the RLS score (r = -0.567, P = 0.002;r = -0.705, P < 0.001;r = -0.414, P = 0.032; r = -0.410, P = 0.034), and the hemoglobin concentration was negatively correlated with the RLS scores (r = -0.394, P = 0.042).

CONCLUSION

Patients with MHD-RLS exhibit abnormal spontaneous brain activity in the right precentral gyrus and right postcentral gyrus within the sensorimotor network, along with lower hemoglobin levels, which may be associated with the pathogenesis and severity of MHD-RLS.

Circadian Pattern in Restless Legs Syndrome: Implications for Treatment Posology

The symptoms of restless legs syndrome (RLS) follow a circadian pattern, as inducated in the current RLS diagnostic criteria. Indeed, subjects with mild-to-moderate RLS suffer or not from RLS symptoms depending on the time of day, resembling an above-threshold state periodically followed by a below-threshold state. Although the circadian clock is crucial in the clinical features of RLS, research assessing the ultimate drivers of circadian rhythmicity is still very limited. In the present review, we show current evidence on circadian variations of neurotransmitters involved in the pathophysiology of RLS (systemic iron metabolism, brain iron homeostasis, adenosine, dopamine, glutamate, and endogenous opioids). Secondly, an overview of available therapies for RLS is presented, including information on current recommendations for symptomatic treatments in RLS. We discuss the importance of further research into the circadian oscillations that occur in RLS, so that they can be managed, and a protective below-threshold state can be established on an individualized basis. In addition, we also discuss the current dosing of the medications prescribed in RLS symptomatic treatments, and how circadian factors should be considered to better adjust dosing on an individualized basis and increase the therapeutic benefit.

Pediatric acute-onset neuropsychiatric syndrome and pediatric autoimmune neuropsychiatric disorder associated with streptococcal infections: a delphi study and consensus document about definition, diagnostic criteria, treatment and follow-up

Pediatric Autoimmune Neuropsychiatric Disorder Associated with Streptococcal Infections (PANDAS) and Pediatric Acute-onset Neuropsychiatric Syndrome (PANS) are broad diagnoses that encompass a range of sudden-onset neuropsychiatric symptoms in children, which can include obsessive-compulsive disorder (OCD), tics, anxiety, emotional instability, and cognitive difficulties. Unlike PANDAS, PANS is not strictly linked to group A streptococcal infections but can be triggered by various infectious or environmental factors. Lights and shadows remain upon the management of children with PANS and PANDAS and there is no clear consensus regarding definition, diagnostic criteria, treatment, and follow-up. The aim of the present study was to evaluate the level of agreement on PANS and PANDAS definition, diagnostic criteria, treatment and follow-up and to assess on the basis of recent studies whether there is a need to modify the current recommendations used by primary care pediatricians and hospital pediatricians in clinical practice in order to improve outcomes. Using the Delphi method, this consensus provides shared indications on PANS and PANDAS management in pediatric age, based on the most updated literature. This work represents, in our opinion, the most complete and up-to-date information on the diagnosis of PANS and PANDAS, as well as consensus statements about several aspects of clinical care. Undoubtedly, more randomized and controlled trials are needed in the pediatric population to better define the best management, also in terms of adequate follow-up examinations and period of observation.

Brain Iron Dysregulation in Iron Deficiency Anemia-Related Restless Leg Syndrome Revealed by Neuron-Derived Extracellular Vesicles: A Case-Control Study

Brain iron deficiency (ID) and, to a degree, systemic ID have been implicated in restless leg syndrome (RLS) pathogenesis. Previously, we found increased ferritin in neuron-derived extracellular vesicles (NDEVs) in RLS, suggesting a mechanism for depleting intracellular iron by secreting ferritin-loaded NDEVs. In this study, we hypothesized that increased NDEV ferritin occurs even in RLS accompanied by systemic ID and that neuronal intracellular iron depletion in RLS also manifests as NDEV abnormalities in other iron regulatory proteins, specifically, decreased transferrin receptor (TfR) and increased ferroportin. To address these hypotheses, we studied 71 women with ID anemia, 36 with RLS, and 35 without RLS. Subjects with RLS again showed higher NDEV ferritin and also decreased TfR, suggesting diminished neuronal capacity for iron uptake. Findings inform a more complete understanding of the pathogenic role of neuronal iron homeostasis and dissociate it from peripheral ID. ANN NEUROL 2024;96:560-564.

Prevalence and clinical profile of patients with restless legs syndrome in Parkinson's disease: A meta-analysis

INTRODUCTION

Restless legs syndrome (RLS) is a sensorimotor disorder of sleep/wake regulation characterized by an urge to move the legs accompanied by a wide range of sensory symptoms, mainly affecting the lower limbs. An increased incidence of RLS has been demonstrated in Parkinson's disease (PD) and has been associated with severe motor and non-motor manifestations. We aimed to provide a reliable estimate of RLS prevalence and the clinical features associated with its occurrence in PD (PD-RLS).

METHODS

We performed a systematic literature search up to January 2024 using PubMed, Scopus, and PsycINFO databases. Articles were included if they provided data on PD patients with or without RLS, and these proportions were used to estimate the prevalence of PD-RLS. Clinical profile associated with PD-RLS was explored by comparing the clinical characteristics of PD patients with and without RLS.

RESULTS

Forty-six studies were included in the meta-analysis. Pooled RLS prevalence was 20 % of a total sample of 6990 PD patients and was associated with female sex, mixed motor phenotype, worse motor disturbances and functional disability, and a wide range of non-motor symptoms such as sleep disorders, cognitive and autonomic dysfunctions, and more severe neuropsychiatric manifestations. Sensitivity analyses indicated significant associations of PD-RLS with variables related to dopaminergic therapy. No association was found with serum ferritin, serum iron and hemoglobin levels.

CONCLUSIONS

The prevalence of PD-RLS exceeds that reported in the general population, suggesting the existence of a relationship between the two disorders. Dopaminergic treatment seems to play an ambivalent role relieving, worsening or "mimicking" RLS manifestations. However, the clinical profile of PD-RLS patients, characterized by a greater severity of non-motor symptoms, also suggests that neurotransmitter systems other than the dopaminergic one are involved in PD-RLS etiology.

Effects of Dietary Supplementation in Patients with Restless Legs Syndrome: A Systematic Review

Restless legs syndrome (RLS) is a common neurological disorder. It disrupts sleep and well-being and is often associated with other conditions. This review examines the potential of dietary supplements to manage RLS symptoms and reduce reliance on medications. A total of 10 randomized clinical trials involving 482 participants were analyzed, focusing on the impact of various supplements on symptom severity, sleep quality, and daytime sleepiness. Findings suggest some supplements may have positive results. Magnesium oxide and vitamin B6 significantly improved sleep quality and RLS symptoms, with magnesium showing greater effectiveness. Vitamin D supplementation did not show significant benefits. Oral iron has promising results, indicating potential efficacy but issues related to compliance and absorption. Both vitamins C and E positively affect RLS symptoms, likely due to their antioxidant properties. Valerian improved RLS and sleep but did not show a statistically significant improvement. Despite these encouraging results, a high risk of bias was noted in half of the studies, emphasizing the need for more rigorous research. Overall, this review suggests that dietary supplements may be a promising approach to managing RLS. However, further investigation is required to confirm the efficacy and safety.

Clinical efficacy and safety of intravenous ferric carboxymaltose for treatment of restless legs syndrome: a multicenter, randomized, placebo-controlled clinical trial

STUDY OBJECTIVES

Iron therapy is associated with improvements in restless legs syndrome (RLS). This multicenter, randomized, double-blind study evaluated the effect of intravenous ferric carboxymaltose (FCM) on RLS.

METHODS

A total of 209 adult patients with a baseline International RLS (IRLS) score ≥ 15 were randomized (1:1) to FCM (750 mg/15 mL) or placebo on study days 0 and 5. Ongoing RLS medication was tapered starting on Day 5, with the goal of discontinuing treatment or achieving the lowest effective dose. Co-primary efficacy endpoints were changed from baseline in IRLS total score and the proportion of patients rated as much/very much improved on the Clinical Global Impression (CGI)-investigator (CGI-I) scale at day 42 in the "As-Treated" population.

RESULTS

The "As-Treated" population comprised 107 FCM and 101 placebo recipients; 88 (82.2%) and 68 (67.3%), respectively, completed the day 42 assessment. The IRLS score reduction was significantly greater with FCM versus placebo: least-squares mean (95% confidence interval [CI]) -8.0 (-9.5, -6.4) versus -4.8 (-6.4, -3.1); p = .0036. No significant difference was observed in the proportion of FCM (35.5%) and placebo (28.7%) recipients with a CGI-I response (odds ratio 1.37 [95% CI: 0.76, 2.47]; p = .2987). Fewer patients treated with FCM (32.7%) than placebo (59.4%) received RLS interventions between day 5 and study end (p = .0002). FCM was well tolerated.

CONCLUSIONS

The IRLS score improved with intravenous FCM versus placebo, although the combination of both co-primary endpoints was not met. Potential methodological problems in the study design are discussed.

Attention-deficit/hyperactivity and obsessive-compulsive symptoms in adult patients with primary restless legs syndrome

Comorbidity between Restless Legs Syndrome and Attention-Deficit/Hyperactivity Disorder remains a matter of debate. This putative association, possibly reflecting a shared brain iron homeostasis and dopaminergic dysfunction, supports the hypothesis of a neurodevelopmental component in Restless Legs Syndrome pathogenesis. The aim of this study was to investigate Attention-Deficit/Hyperactivity Disorder and Obsessive-Compulsive Disorder symptoms prevalence in adult patients with primary Restless Legs Syndrome compared to another ill group of patients with obstructive sleep apnea syndrome to control for the disease specific effects on psychiatric symptoms and a healthy individuals control group. Clinical data were obtained through standardized and validated self-administrated questionnaires evaluating Attention-Deficit/Hyperactivity Disorder and Obsessive-Compulsive Disorder symptoms frequencies in 139 outpatients with idiopathic Restless Legs Syndrome, 111 patients with treated obstructive sleep apnea syndrome and 136 healthy subjects. Our findings demonstrate a higher prevalence of Attention-Deficit/Hyperactivity Disorder symptoms among both male and female patients with Restless Legs Syndrome, compared to obstructive sleep apnea syndrome patients and healthy subjects (33.3 and 43.5%, respectively, p < 0.001). Only women presented a strong relationship between Attention-Deficit/Hyperactivity Disorder and Restless Legs Syndrome severity (p < 0.001). Male and female in the three groups showed similar Obsessive-Compulsive Disorder symptom prevalence. These findings indicate that Attention-Deficit/Hyperactivity Disorder symptoms among adult patients with Restless Legs Syndrome populations are a robust phenomenon. These data provide arguments in favor of an enlargement of the clinical neuropsychological presentation of Restless Legs Syndrome and question the role of decreased brain iron of these psychiatric symptoms.

A survey-based approach on restless legs syndrome: practices and perspectives among Italian neurologists

INTRODUCTION

Restless Legs Syndrome (RLS) is a widely prevalent and complex neurological disorder. Despite notable advancements in managing RLS, the disorder continues to face challenges related to its recognition and management.

OBJECTIVE

This study seeks to gain comprehensive insights into the knowledge and clinical practices among Italian neurologists regarding RLS diagnosis, management, and treatment, comparing approaches among general neurologists, movement disorder specialists, and sleep experts.

METHODS

Members of the Italian Society of Neurology, the Italian Society of Parkinson and Movement Disorders, and the Italian Association of Sleep Medicine were invited to participate in a 19-question online survey.

RESULTS

Among the 343 surveyed neurologists, 60% categorized RLS as a "sleep-related movement disorder." Forty% indicated managing 5-15 RLS patients annually, with sleep specialists handling the highest patient volume. Of note, only 34% adhered strictly to all five essential diagnostic criteria. The majority (69%) favored low-dosage dopamine agonists as their first-line treatment, with movement disorder specialists predominantly endorsing this approach, while sleep experts preferred iron supplementation. Regular screening for iron levels was widespread (91%), with supplementation typically guided by serum iron alterations. In cases of ineffective initial treatments, escalating dopamine agonist dosage was the preferred strategy (40%).

CONCLUSIONS

These findings underscore a lack of a clear conceptualization of RLS, with a widespread misconception of the disorder as solely a movement disorder significantly influencing treatment approaches. Disparities in RLS understanding across neurology subspecialties underscore the necessity for improved diagnostic accuracy, targeted educational initiatives, and management guidelines to ensure consistent and effective RLS management.

Iron deficiency in children with a focus on inflammatory conditions

Iron deficiency (ID) tends to be overlooked compared with anemia. However, its prevalence is estimated to be twice as high as that of ID anemia, and ID without anemia can be accompanied by clinical and functional impairments. The symptoms of ID are nonspecific, such as fatigue and lethargy, but can lead to neurodevelopmental disorders in children, restless legs syndrome, and recurrent infections due to immune system dysregulation. In particular, the risk of ID is high in the context of chronic inflammatory diseases (CIDs) due to the reaction of various cytokines and the resulting increase in hepcidin levels; ID further exacerbates these diseases and increases mortality. Therefore, the diagnosis of ID should not be overlooked through ID screening especially in high-risk groups. Ferritin and transferrin saturation levels are the primary laboratory parameters used to diagnose ID. However, as ferritin levels respond to inflammation, the diagnostic criteria differ among guidelines. Therefore, new tools and criteria for accurately diagnosing ID should be developed. Treatment can be initiated only with an accurate diagnosis. Oral iron is typically the first-line treatment for ID; however, the efficacy and safety of intravenous iron have recently been recognized. Symptoms improve quickly after treatment, and the prognosis of accompanying diseases can also be improved. This review highlights the need to improve global awareness of ID diagnosis and treatment, even in the absence of anemia, to improve the quality of life of affected children, especially those with CIDs.

A randomized double-blind pilot study to evaluate the efficacy, safety, and tolerability of intravenous iron versus oral iron for the treatment of restless legs syndrome in patients with iron deficiency anemia

Restless legs syndrome (RLS) is a neurological disorder that can have a profound effect on sleep and quality of life. Idiopathic RLS is associated with brain iron insufficiency despite normal peripheral iron stores. There is, however, a five- to six-fold increase in prevalence of RLS in patients with iron deficiency anemia (IDA). Several open-label trials have demonstrated symptomatic improvement in RLS following treatment of IDA using oral or intravenous iron supplementation. To date, there have been no randomized double-blind controlled trials of intravenous iron compared with oral iron for the treatment of RLS patients with IDA. In the current study, oral ferrous sulfate and ferumoxytol were compared for efficacy and speed of response for treatment of RLS occurring in patients with IDA. The planned recruitment for this study was 70 patients with RLS and IDA, to be randomly assigned 1:1 to oral or intravenous iron, using double-blind, double-dummy procedures. At Week 6, the primary outcomes of Clinical Global Impression-Improvement score and change from baseline in the International Restless Legs Syndrome Study Group rating scale score were assessed. Due to challenges, performing the clinical trial during the COVID-19 pandemic, final-week data were found missing for 30 patients. As a result, in order to maintain the prespecified statistical analysis, an additional 30 patients were recruited. Both IV and oral iron were associated with a marked improvement in RLS symptoms, with no statistically significant difference between treatment groups. No serious adverse events were observed in either treatment group.

Current updates in Restless Legs Syndrome: A pragmatic review

Restless legs syndrome (RLS), also called Willis–Ekbom disease (WED), affects approximately 3% of the global population, with higher incidence in Caucasians and women. This review explores the latest advancements in the diagnosis, pathophysiology, and management of RLS, and it highlights the recent changes in diagnostic criteria that improve specificity. The diagnostic spectrum now includes atypical presentations involving the upper limbs and other body parts. The new diagnostic specifiers categorize RLS more effectively into chronic-persistent or intermittent types, and a clinical significance specifier has been introduced to better address the disorder’s effects on daily life. RLS management has shifted toward a balanced approach with non-pharmacological strategies and lifestyle changes, supported by updated pharmacological treatment protocols including iron therapy designed to mitigate risks such as augmentation. Notably, gabapentinoids have emerged as a superior treatment option over dopamine agonists owing to their lower risk of augmentation and superior safety profile. Innovative treatments, such as the FDA-approved tonic motor activation device and new pharmacological agents, serve as alternatives for treating medication-refractory RLS, thereby expanding the therapeutic landscape. Additionally, this review addresses the specific considerations for managing RLS in special groups, including pregnant women, individuals with chronic kidney disease, and patients with comorbid conditions such as Parkinson’s disease and multiple sclerosis. We emphasizes the dynamic nature of RLS research and highlight the critical need for ongoing studies to further elucidate the complex mechanisms underlying RLS, as well as to refine the treatment modalities to enhance patient outcomes.

Associations of anxiety and depression with restless leg syndrome: a systematic review and meta-analysis

Background

The levels of anxiety and depression among patients with restless leg syndrome (RLS) are controversial. The aim of this systematic review and meta-analysis was to compare the levels of depression and anxiety among individuals with RLS with those of healthy controls.

Methods

We conducted an extensive electronic search of the PubMed, Web of Science, EMBASE, and Cochrane Library databases from their inception dates to 20 June 2023. Studies presenting data on depression and anxiety in individuals with RLS were included, and a comprehensive meta-analysis was performed.

Results

Twenty-one studies matched the inclusion criteria. Significantly more depressive symptoms were present in the individuals with RLS than in those without RLS, as measured by the Beck Depression Inventory [mean difference (MD) = 6.58, 95% confidence interval (CI) = 5.54-7.62, p < 0.01; heterogeneity I2 = 0%, p = 0.99]. Similarly, the results from the Beck Anxiety Inventory indicated that there were significantly more pronounced anxiety symptoms in the individuals with RLS than in those without RLS (MD = 9.30, 95%CI = 7.65-10.94, p < 0.01; heterogeneity I2 = 0%, p = 0.92). The other anxiety and depression scales also yielded statistically significant results. Significant heterogeneity was observed in the Hamilton Depression Rating Scale and Hamilton Anxiety Rating Scale, with the primary contributing factor probably being the scoring criteria of the scales.

Conclusion

This meta-analysis found that the levels of depression and anxiety symptoms were significantly higher in individuals with RLS than in their healthy counterparts.Systematic review registration:https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42023410364, (identifier CRD42023410364).

Review of the role of the endogenous opioid and melanocortin systems in the restless legs syndrome

Restless legs syndrome (RLS) is responsive to opioid, dopaminergic and iron-based treatments. Receptor blocker studies in RLS patients suggest that the therapeutic efficacy of opioids is specific to the opioid receptor and mediated indirectly through the dopaminergic system. An RLS autopsy study reveals decreases in endogenous opioids, β-endorphin and perhaps Met-enkephalin in the thalamus of RLS patients. A total opioid receptor knock-out (mu, delta and kappa) and a mu-opioid receptor knock-out mouse model of RLS show circadian motor changes akin to RLS and, although both models show sensory changes, the mu-opioid receptor knock mouse shows circadian sensory changes closest to those seen in idiopathic RLS. Both models show changes in striatal dopamine, anaemia and low serum iron. However, only in the total receptor knock-out mouse do we see the decreases in serum ferritin that are normally found in RLS. There are also decreases in serum iron when wild-type mice are administered a mu-opioid receptor blocker. In addition, the mu-opioid receptor knock-out mouse also shows increases in striatal zinc paralleling similar changes in RLS. Adrenocorticotropic hormone and α-melanocyte stimulating hormone are derived from pro-opiomelanocortin as is β-endorphin. However, they cause RLS-like symptoms and periodic limb movements when injected intraventricularly into rats. These results collectively suggest that an endogenous opioid deficiency is pathogenetic to RLS and that an altered melanocortin system may be causal to RLS as well.

Prevalence and clinical correlates of restless legs syndrome in psychiatric patients: A cross-sectional study from North India

Background

Restless legs syndrome (RLS) is a neuro-sensorimotor disorder which is scarcely researched and is commonly missed in routine psychiatry practice.

Aim

To evaluate the prevalence of RLS and its correlates in patients with anxiety, depression, and somatoform disorders.

Methods

A cross-sectional single-center study was undertaken in patients aged 18-65 years suffering from ICD-10 (International Statistical Classification of Diseases-10th edition) diagnosis of anxiety, depressive, and somatoform disorders. RLS was evaluated by using diagnostic criteria of International Restless Legs Syndrome Study Group (IRLSSG) and severity measured on IRLSSG scale. Depression and anxiety were rated on Hamilton Depression and Anxiety Rating Scales respectively, insomnia severity measured by Insomnia Severity Index (ISI), and quality of life measured by WHO Quality of Life-Brief version (WHO-QOL BREF) scale. Serum ferritin levels were measured for evaluating iron deficiency.

Results

The rate of RLS was 66.7%, 50%, and 48% in patients with depressive, anxiety, and somatoform disorders, respectively, with no significant inter-group difference. Nearly one-third of patients suffered from severe to very severe symptoms of RLS, and quality of life was poorest in those with depressive disorders. RLS was significantly higher in females (P = 0.019), who were married (P = 0.040), diagnosed with severe depression (P = 0.029), and abused benzodiazepines (P = 0.045). On binary logistic regression, female gender and presence of clinical insomnia predicted occurrence of RLS.

Conclusion

The prevalence of RLS is very high in patients with common psychiatric disorders which is often missed. Clinical enquiry and examination for reversible causes such as iron deficiency may assist in its diagnosis and improve clinical outcome.

Evaluation of emotional dysregulation in patients with restless legs syndrome

The aim of this study is to examine patients with restless legs syndrome (RLS) in terms of difficulty in emotion regulation and insomnia. A total of 52 patients with RLS and 57 healthy volunteers were enrolled. Difficulties in Emotion Regulation Scale Short Form (DERS-16), Insomnia Severity Index (ISI), Hospital Anxiety and Depression Scale (HADS), and International Restless Legs Syndrome rating scale were applied to participants. The mean age was 34.00 ± 8.27 years in patients and 31.70 ± 9.12 years in control. The scores of DERS-16, ISI, HADS-A, and HADS-D were significantly higher in the patients than the controls (p = 0.000). The DERS-16 total score showed a significant correlation with age (r = 0.404, p = 0.003), ISI (r = 0.281, p = 0.043), IRLS score (r = 0.422, p = 0.002), HADS-A (r = 0.409, p = 0.003), and HADS-D (r = 0.416, p = 0.002). The factors (age, gender, ferritin, ISI, and IRLS scores) that may be associated with the DERS-16 total scores were assessed with stepwise regression analysis. It was seen that the IRLSs variable had the most ability and could predict 45% (β = 0.625, p < 0.001, ∆R2 = 0.450) of difficulty in emotion regulation. In addition, the variable of insomnia could predict difficulty in emotion regulation by 17% (β = 0.097, p = 0.001, ∆R2 = 0.170). Patients with RLS may experience more emotion regulation difficulties than healthy controls. RLS severity and insomnia may be factors affecting emotion regulation difficulties in patients with RLS. According to our knowledge and our literature review, this finding seems to be the first report in the literature.

Exploring the causes of augmentation in restless legs syndrome

Long-term drug treatment for Restless Legs Syndrome (RLS) patients can frequently result in augmentation, which is the deterioration of symptoms with an increased drug dose. The cause of augmentation, especially derived from dopamine therapy, remains elusive. Here, we review recent research and clinical progress on the possible mechanism underlying RLS augmentation. Dysfunction of the dopamine system highly possibly plays a role in the development of RLS augmentation, as dopamine agonists improve desensitization of dopamine receptors, disturb receptor interactions within or outside the dopamine receptor family, and interfere with the natural regulation of dopamine synthesis and release in the neural system. Iron deficiency is also indicated to contribute to RLS augmentation, as low iron levels can affect the function of the dopamine system. Furthermore, genetic risk factors, such as variations in the BTBD9 and MEIS1 genes, have been linked to an increased risk of RLS initiation and augmentation. Additionally, circadian rhythm, which controls the sleep-wake cycle, may also contribute to the worsening of RLS symptoms and the development of augmentation. Recently, Vitamin D deficiency has been suggested to be involved in RLS augmentation. Based on these findings, we propose that the progressive reduction of selective receptors, influenced by various pathological factors, reverses the overcompensation of the dopamine intensity promoted by short-term, low-dose dopaminergic therapy in the development of augmentation. More research is needed to uncover a deeper understanding of the mechanisms underlying the RLS symptom and to develop effective RLS augmentation treatments.

Potential Effect of Vortioxetine on Restless Leg Syndrome

Restless legs syndrome (RLS) is a chronic progressive movement disorder characterized by abnormal sensations, especially at rest and at night, as the need and urge to move the lower extremity. It has been reported that RLS severity and frequency increase in patients with anxiety and depression. It has been reported that serotonin-noradrenaline reuptake inhibitors such as venlafaxine and selective serotonin reuptake inhibitors such as citalopram, fluoxetine, paroxetine, and sertraline can cause RLS symptoms. No adverse effects of vortioxetine on RLS have been reported in the literature. In this case series, we report the effect of vortioxetine in patients with RLS with symptoms of depression and anxiety. In this case series, the effect of adding vortioxetine to treatment on RLS symptoms is reported in 7 patients (5 female). After the use of vortioxetine, 5 of 7 patients' symptoms regressed without the need to start a separate drug for primary movement disorder. In conclusion, we believe that studies should be conducted to investigate the efficacy of vortioxetine in the treatment of RLS. Therefore, randomized controlled studies are needed to determine the effect and safety of vortioxetine on RLS symptoms.

Change of iron content in brain regions after intravenous iron therapy in restless legs syndrome: quantitative susceptibility mapping study

STUDY OBJECTIVES

The pathomechanism of restless legs syndrome (RLS) is related to brain iron deficiency and iron therapy is effective for RLS; however, the effect of iron therapy on human brain iron state has never been studied with magnetic resonance imaging. This study aimed to investigate the change of brain iron concentrations in patients with RLS after intravenous iron therapy using quantitative susceptibility mapping (QSM).

METHODS

We enrolled 31 RLS patients and 20 healthy controls. All participants underwent initial baseline (t0) assessment using brain magnetic resonance imaging, serum iron status, and sleep questionnaires including international RLS Study Group rating scale (IRLS). RLS patients underwent follow-up tests at 6 and 24 weeks (t1 and t2) after receiving 1000 mg ferric carboxymaltose. Iron content of region-of-interest on QSM images was measured for 13 neural substrates using the fixed-shaped method.

RESULTS

RLS symptoms evaluated using IRLS were significantly improved after iron treatment (t0: 29.7 ± 6.5, t1: 19.5 ± 8.5, t2: 21.3 ± 10.1; p < .001). There was no significant difference in susceptibility values between the controls and RLS patients at t0. In the caudate nucleus, putamen, and pulvinar thalamus of RLS patients, the QSM values differed significantly for three timepoints (p = .035, .048, and .032, respectively). The post-hoc analysis revealed that the QSM values increased at t1 in the caudate nucleus (66.8 ± 18.0 vs 76.4 ± 16.6, p = .037) and decreased from t1 to t2 in the putamen (69.4 ± 16.3 vs 62.5 ± 13.6, p = .025). Changes in the QSM values for the pulvinar and caudate nuclei at t1 were positively and negatively correlated with symptomatic improvement, respectively (r = 0.361 and -0.466, respectively).

CONCLUSIONS

Intravenous iron treatment results in changes in brain iron content which correlate to reductions in RLS severity. This suggests a connection between symptom improvement and the associated specific brain regions constituting the sensorimotor network.

Epigenetic Association Analyses and Risk Prediction of RLS

BACKGROUND

As opposed to other neurobehavioral disorders, epigenetic analyses and biomarkers are largely missing in the case of idiopathic restless legs syndrome (RLS).

OBJECTIVES

Our aims were to develop a biomarker for RLS based on DNA methylation in blood and to examine DNA methylation in brain tissues for dissecting RLS pathophysiology.

METHODS

Methylation of blood DNA from three independent cohorts (n = 2283) and post-mortem brain DNA from two cohorts (n = 61) was assessed by Infinium EPIC 850 K BeadChip. Epigenome-wide association study (EWAS) results of individual cohorts were combined by random-effect meta-analysis. A three-stage selection procedure (discovery, n = 884; testing, n = 520; validation, n = 879) established an epigenetic risk score including 30 CpG sites. Epigenetic age was assessed by Horvath's multi-tissue clock and Shireby's cortical clock.

RESULTS

EWAS meta-analysis revealed 149 CpG sites linked to 136 genes (P < 0.05 after Bonferroni correction) in blood and 23 CpG linked to 18 genes in brain (false discovery rate [FDR] < 5%). Gene-set analyses of blood EWAS results suggested enrichments in brain tissue types and in subunits of the kainate-selective glutamate receptor complex. Individual candidate genes of the brain EWAS could be assigned to neurodevelopmental or metabolic traits. The blood epigenetic risk score achieved an area under the curve (AUC) of 0.70 (0.67-0.73) in the validation set, comparable to analogous scores in other neurobehavioral disorders. A significant difference in biological age in blood or brain of RLS patients was not detectable.

CONCLUSIONS

DNA methylation supports the notion of altered neurodevelopment in RLS. Epigenetic risk scores are reliably associated with RLS but require even higher accuracy to be useful as biomarkers. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Sleep Disorders in Childhood

OBJECTIVE

This article provides a comprehensive review of pediatric sleep disorders including the clinical features, diagnosis, and treatment of sleep-disordered breathing, insomnia, parasomnias, restless sleep disorder, restless legs syndrome, narcolepsy in childhood, and Kleine-Levin syndrome.

LATEST DEVELOPMENTS

Our understanding of pediatric sleep pathophysiology continues to evolve, and diagnostic and treatment modalities have expanded. A low-sodium oxybate formulation was approved in July 2020 in the United States to treat cataplexy and excessive daytime sleepiness in patients 7 years old and older with narcolepsy. A validated pediatric hypersomnolence survey for pediatric narcolepsy and idiopathic hypersomnia with high sensitivity, specificity, and interrater reliability is now available.

ESSENTIAL POINTS

The clinical presentation, diagnostics, and treatment of children with sleep disorders differ from those of adults. Untreated sleep disorders in childhood can lead to adverse physical and psychological consequences in adults. Correctly diagnosing and treating sleep disorders in youth can prevent a significant burden of disease in adulthood.

Bilateral high-frequency noninvasive peroneal nerve stimulation evokes tonic leg muscle activation for sleep-compatible reduction of restless legs syndrome symptoms

STUDY OBJECTIVES

Restless legs syndrome (RLS) is a prevalent sleep disorder with limited treatment options. Bilateral high-frequency noninvasive peroneal nerve stimulation (NPNS) reduces RLS symptoms. Here, we sought to characterize the mechanism of action for NPNS and identify predictors of treatment response. We hypothesized that, similar to voluntary leg movements, NPNS reduces RLS symptoms by activating leg muscles.

METHODS

For 20 adults with moderate-severe RLS, we tested this hypothesis by recording surface electromyography (EMG) from the tibialis anterior leg muscle while administering NPNS at varying amplitudes to determine the minimum NPNS amplitude that evoked EMG activity (motor threshold) and maximal NPNS amplitude that was not distracting (therapeutic intensity level). Afterwards, participants self-administered NPNS (at the therapeutic intensity level) and sham control for 14 days, each in randomized order. Efficacy was defined as International RLS Study Group Rating Scale (IRLS) score difference for NPNS compared with sham.

RESULTS

NPNS consistently activated leg muscles; NPNS evoked EMG activity at the therapeutic intensity level for 19 of 20 participants (mean TIL: 26.6 mA, mean MT: 18.3 mA). Evoked EMG activity was tonic (not phasic) and sustained over time. Evoked EMG activity predicted efficacy; participants with lower motor thresholds had greater IRLS improvement (r = .45, P = .046). NPNS treatment did not interfere with self-reported sleep onset (NPNS: 16% of nights; sham: 11%; P = .629) and frequently improved self-reported sleep onset (NPNS: 52% of nights; sham: 15%; P = .002).

CONCLUSIONS

These results demonstrate that NPNS reduces RLS symptoms by activating afferent pathways, thereby generating tonic and sustained leg muscle activity without interfering with sleep.

CLINICAL TRIAL REGISTRATION

Registry: ClinicalTrials.gov; Name: Noninvasive Peripheral Nerve Stimulation for Restless Legs Syndrome; URL: https://clinicaltrials.gov/ct2/show/NCT04700683; Identifier: NCT04700683.

CITATION

Charlesworth JD, Adlou B, Singh H, Buchfuhrer MJ. Bilateral high-frequency noninvasive peroneal nerve stimulation evokes tonic leg muscle activation for sleep-compatible reduction of restless legs syndrome symptoms. J Clin Sleep Med. 2023;19(7):1199-1209.

Effects of iron-deficient diet on sleep onset and spinal reflexes in a rodent model of Restless Legs Syndrome

Restless Legs Syndrome (RLS) is a common sensorimotor and a sleep disorder that affects 2.5-10% of the European and North American populations. RLS is also often associated with periodic leg movements during sleep (PLMS). Despite ample evidence of genetic contributions, the underlying mechanisms that elicit the sensory and motor symptoms remain unidentified. Clinically, RLS has been correlated with an altered central iron metabolism, particularly in the brain. While several animal models have been developed to determine the outcome of an altered iron homeostasis on brain function, the potential role of an altered iron homeostasis on sleep and sensorimotor circuits has not yet been investigated. Here, we utilize a mouse model to assess the effects of an iron-deficient (ID) but non-anemic state on sleep time and episodes, and sensorimotor reflexes in male and female mice. We found that animals on the ID diet displayed an increased expression of the transferrin receptor in the spinal cord, confirming the results of previous studies that focused only on the impact of ID in the brain. We also demonstrate that the ID diet reduced hematocrit levels compared to controls but not into the anemic range, and that animals on the ID diet exhibited RLS-like symptoms with regard to sleep onset and spinal cord reflex excitability. Interestingly, the effects on the spinal cord were stronger in females than in males, and the ID diet-induced behaviors were rescued by the return of the animals to the control diet. Taken together, these results demonstrate that diet-induced ID changes to CNS function are both inducible and reversible, and that they mimic the sleep and sensorimotor RLS symptoms experienced in the clinic. We therefore propose replacing the commonly used phrase "brain iron deficiency" (BID) hypothesis in the RLS research field with the term "iron deficiency in the central nervous system" (ID-CNS), to include possible effects of altered iron levels on spinal cord function.

Restless leg syndrome in spinal cord injury: case report

CASE DESCRIPTION

Restless leg syndrome (RLS) is a condition infrequently reported in spinal cord injury that causes an uncomfortable sensation in the legs and an urge to move them. We report a case involving a 63-year-old man with incomplete paraplegia with an onset of RLS four years post injury.

FINDINGS

Based upon history, pramipexole was prescribed for the presumptive diagnosis of RLS, with good effect. Initial workup revealed an anemia (hemoglobin of 9.3 gram/deciliter (g/dl)) and iron deficiency (ferritin of 10 microgram/liter (μg/L)), necessitating further evaluation.

CONCLUSION

Due to the complexities in diagnosing RLS in patients with SCI, it is important to be cognizant of symptoms and to consider this diagnosis to initiate the appropriate work-up for an etiology, of which iron deficiency anemia is common.

Iron Deficiency in Attention-Deficit Hyperactivity Disorder, Autism Spectrum Disorder, Internalizing and Externalizing Disorders, and Movement Disorders

This article reviews the role of iron in brain development and function, with a focus on the association between iron deficiency (ID) and neuropsychiatric conditions. First, we describe how ID is defined and diagnosed. Second, the role of iron in brain development and function is summarized. Third, we review current findings implicating ID in a number of neuropsychiatric conditions in children and adolescents, including attention deficit hyperactivity disorder and other disruptive behavior disorders, depressive and anxiety disorders, autism spectrum disorder, movement disorders, and other situations relevant to mental health providers. Last, we discuss the impact of psychotropic medication on iron homeostasis.

Presynaptic adenosine receptor heteromers as key modulators of glutamatergic and dopaminergic neurotransmission in the striatum

Adenosine plays a very significant role in modulating striatal glutamatergic and dopaminergic neurotransmission. In the present essay we first review the extensive evidence that indicates this modulation is mediated by adenosine A₁ and A_2A receptors (A₁Rs and A_2ARs) differentially expressed by the components of the striatal microcircuit that include cortico-striatal glutamatergic and mesencephalic dopaminergic terminals, and the cholinergic interneuron. This microcircuit mediates the ability of striatal glutamate release to locally promote dopamine release through the intermediate activation of cholinergic interneurons. A₁Rs and A_2ARs are colocalized in the cortico-striatal glutamatergic terminals, where they form A₁R-A_2AR and A_2AR-cannabinoid CB₁ receptor (CB₁R) heteromers. We then evaluate recent findings on the unique properties of A₁R-A_2AR and A_2AR-CB₁R heteromers, which depend on their different quaternary tetrameric structure. These properties involve different allosteric mechanisms in the two receptor heteromers that provide fine-tune modulation of adenosine and endocannabinoid-mediated striatal glutamate release. Finally, we evaluate the evidence supporting the use of different heteromers containing striatal adenosine receptors as targets for drug development for neuropsychiatric disorders, such as Parkinson's disease and restless legs syndrome, based on the ability or inability of the A_2AR to demonstrate constitutive activity in the different heteromers, and the ability of some A_2AR ligands to act preferentially as neutral antagonists or inverse agonists, or to have preferential affinity for a specific A_2AR heteromer.

Circadian rhythm in restless legs syndrome

Restless legs syndrome (RLS) is a sensorimotor disorder with a obvious circadian rhythm, as its symptoms often occur or worsen only in the evening or at night. The mechanisms behind the rhythms of RLS have not yet been fully elucidated. This review explores possible causes for the circadian fluctuations of the symptomatology, including the levels of iron, dopamine, melatonin, melanocortin, and thyroid-stimulating hormone in the brain, as well as conditions such as peripheral hypoxia and microvascular function disorders. The metabolic disturbances of the substances above can create a pathological imbalance, which is further aggravated by physiological fluctuations of circadian rhythms, and results in the worsening of RLS symptoms at night. The review concludes with the suggestions for RLS treatment and research directions in the future.

Clonazepam for the management of sleep disorders

BACKGROUND

The objectives of this review and meta-analysis of polysomnographic data are those to focus on the clinical use of clonazepam for the management of sleep disorders by re-analyzing clinical trials and randomized clinical trials which have been published in peer-reviewed journals.

METHODS

A review of the literature including clinical trials and randomized controlled trials was performed in PubMed®, in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement protocol. A random effects model meta-analysis was then carried out for the four more frequently reported polysomnographic measures: total sleep time, sleep latency, sleep efficiency, and periodic leg movement during sleep (PLMS) index.

RESULTS

A total of 33 articles were retrieved and screened in full text, of which 18 met the criteria for review; among the latter, nine met the criteria for meta-analysis. The studies included in the review involved patients with insomnia, REM sleep behavior disorder, sleep bruxism, and restless leg syndrome or PLMS which reported, most often, an increase in total sleep time with clonazepam. A clear sleep-promoting effect of clonazepam was found also by meta-analysis.

DISCUSSION AND CONCLUSIONS

Our results indicate that the pharmacological treatment of sleep disorders with clonazepam must always be personalized according to the type of patient, the risk of addiction and the concomitant presence of respiratory disorders are key factors to take into account. However, in light of the clinical evidence of the few studies in the literature on the different types of disorders, more studies on the use of clonazepam (also in association with first choice treatments) are definitely needed.

Genetics of circadian rhythms and sleep in human health and disease

Circadian rhythms and sleep are fundamental biological processes integral to human health. Their disruption is associated with detrimental physiological consequences, including cognitive, metabolic, cardiovascular and immunological dysfunctions. Yet many of the molecular underpinnings of sleep regulation in health and disease have remained elusive. Given the moderate heritability of circadian and sleep traits, genetics offers an opportunity that complements insights from model organism studies to advance our fundamental molecular understanding of human circadian and sleep physiology and linked chronic disease biology. Here, we review recent discoveries of the genetics of circadian and sleep physiology and disorders with a focus on those that reveal causal contributions to complex diseases.

Peripheral Iron Metabolism is Associated with Leg Movements on Polysomnography but Not with the Severity of Restless Legs Syndrome or Its Impact on Patients

Purpose

This study investigated the associations of peripheral iron status with different manifestations of restless legs syndrome (RLS), including leg movements (LMs) on polysomnography (PSG), disease severity, and impact on patients.

Patients and Methods

In this cross-sectional study, 108 patients with RLS were enrolled at Sir Run Run Shaw Hospital's Center for Sleep Medicine. Demographic information, disease characteristics, RLS severity, and impact on patients were assessed through a semi-structured questionnaire. Peripheral iron indicators [serum ferritin, iron, and transferrin concentrations; unsaturated iron-binding capacity (UIBC) and total iron-binding capacity (TIBC); transferrin saturation (TSAT)] were measured following PSG to assess sleep stages, respiratory events, microarousals and LM parameters. Data from patients with and without ferritin concentration < 50 µg/L were compared in crude analyses, and Spearman correlations of other iron indicators with RLS data were examined. An ordinal logistic regression model was used to adjust for age, sex, body mass index, years of education, age at the time of RLS onset, prior treatment (yes/no), C-reactive protein (CRP)/hemoglobin level, total sleep time and apnea-hypopnea index.

Results

Multivariate analysis showed that periodic LMs during sleep (PLMS) and other LM parameters were significantly associated with a ferritin concentration < 50 µg/L, UIBC, TIBC, and serum transferrin concentration, but not serum iron or TSAT. By contrast, the severity and impact of RLS were not associated with a ferritin concentration < 50 µg/L or other peripheral iron indicators in the multivariate model.

Conclusion

In this study, peripheral iron status was associated mainly with motor components (LMs on PSG) rather than sensory components (severity and impact of RLS) after adequately controlling for potential confounders, such as CRP and hemoglobin levels. Commonly used peripheral iron metabolism indicators may therefore not be ideal biomarkers of RLS severity or impact on patients.

Brain-iron deficiency models of restless legs syndrome

Restless legs syndrome (RLS) is a common sensorimotor disorder for which two main pathological elements are fairly well accepted: Brain iron deficiency (BID) and an altered dopaminergic system. The ability to better understand the causal and consequential factors related to these two pathological elements, would hopefully lead to the development of better therapeutic strategies for treating, if not curing, this disease. The current understanding of the relationship between these two elements is that BID leads to some alterations in neurotransmitters and subsequent changes in the dopaminergic system. Therefore, rodent models based on diet-induced BID, provide a biological substrate to understand the consequences of BID on dopaminergic pathway and on alternative pathways that may be involved. In this review, we present the current research on dopaminergic changes found in RLS subjects and compare that to what is seen in the BID rodent model to provide a validation of the BID rodent model. We also demonstrate the ability of the BID model to predict changes in other neurotransmitter systems and how that has led to new treatment options. Finally, we will present arguments for the utility of recombinant inbred mouse strains that demonstrate natural variation in brain iron, to explore the genetic basis of altered brain iron homeostasis as a model to understand why in idiopathic RLS there can exist a BID despite normal peripheral iron store. This review is the first to draw on 25 years of human and basic research into the pathophysiology of RLS to provide strong supportive data as to the validity of BID model as an important translational model of the disease. As we will demonstrate here, not only does the BID model closely and accurately mimic what we see in the dopaminergic system of RLS, it is the first model to identify alternative systems from which new treatments have recently been developed.

Association of a History of Sleep Disorder With Risk of Mild Cognitive Impairment and Alzheimer's Disease Dementia

OBJECTIVE

We explored whether a history of sleep disorder affected a current diagnosis of cognitive impairment and clinical conversion in a non-demented elderly population.

METHODS

Comprehensive clinical data collected as part of the Alzheimer's Disease Neuroimaging Initiative (ADNI) was analyzed. A history of sleep disorder was recorded in the recent ADNI medical database. Standard clinical and neuropsychological tests were performed both at baseline and follow-up visit. Multiple logistic regression analysis was performed after adjusting for age, sex, education, apolipoprotein E ε4 status, vascular risk score, body mass index, Geriatric Depression Scale score, and use of sleeping pills.

RESULTS

A total of 391 cognitively normal individuals, 303 with early mild cognitive impairment (MCI) and 364 with late MCI were included. Sleep disorder history was significantly associated with an increased risk of MCI but not with clinical conversion. A history of insomnia or obstructive sleep apnea (OSA) significantly increased the risk of MCI, but only an OSA history predicted progression to Alzheimer's disease (AD) dementia.

CONCLUSION

Our findings suggest that a sleep disorder history usefully aids early detection of cognitive impairment and emphasize that such sleep disorder, particularly OSA, is important as potential target for AD prevention.

Restless legs syndrome due to brainstem stroke: A systematic review

Restless Legs Syndrome (RLS) is a sleep-related movement disorder, which can also result from brainstem pathology. A systematic review of articles published in the electronic databases PubMed and Web of Science was conducted to summarize the existent literature on RLS associated with a brainstem stroke. We identified eight articles including 19 subjects with RLS due to brainstem ischemic lesion. The symptoms occurred simultaneously with the infarction (66.7%) or few days after (33.3%). The most common location of infarction was pons and less commonly medulla. In most cases (68.4%), symptoms were unilateral. In the majority of those cases (92.3%), the contralateral limb was affected due to a lateral pons infarction. RLS symptoms after infarction improved or resolved in almost 90% of cases within a few days up to 3 months. In almost all patients who received dopaminergic treatment (11 out of 13, 91.7%), the symptoms improved significantly or resolved completely. Screening for RLS has to be considered in patients suffering a brainstem stroke, particularly anteromedial pontine infarction. The appearance of acute unilateral RLS symptoms, usually in association with other sensorimotor deficits, should prompt the clinician to consider a vascular event in the brainstem. RLS in these cases seem to have a favorable outcome and respond well to dopaminergic treatment.

Consensus guidelines on the construct validity of rodent models of restless legs syndrome

Our understanding of the causes and natural course of restless legs syndrome (RLS) is incomplete. The lack of objective diagnostic biomarkers remains a challenge for clinical research and for the development of valid animal models. As a task force of preclinical and clinical scientists, we have previously defined face validity parameters for rodent models of RLS. In this article, we establish new guidelines for the construct validity of RLS rodent models. To do so, we first determined and agreed on the risk, and triggering factors and pathophysiological mechanisms that influence RLS expressivity. We then selected 20 items considered to have sufficient support in the literature, which we grouped by sex and genetic factors, iron-related mechanisms, electrophysiological mechanisms, dopaminergic mechanisms, exposure to medications active in the central nervous system, and others. These factors and biological mechanisms were then translated into rodent bioequivalents deemed to be most appropriate for a rodent model of RLS. We also identified parameters by which to assess and quantify these bioequivalents. Investigating these factors, both individually and in combination, will help to identify their specific roles in the expression of rodent RLS-like phenotypes, which should provide significant translational implications for the diagnosis and treatment of RLS.

Restless legs syndrome: Over 50 years of European contribution

Restless legs syndrome (RLS) is a sensorimotor neurological disorder characterised by an urge to move the limbs with a circadian pattern (occurring in the evening/at night), more prominent at rest, and relieved with movements. RLS is one of the most prevalent sleep disorders, occurring in 5%-10% of the European population. Thomas Willis first described RLS clinical cases already in the 17th century, and Karl-Axel Ekbom described the disease as a modern clinical entity in the 20th century. Despite variable severity, RLS can markedly affect sleep (partly through the presence of periodic leg movements) and quality of life, with a relevant socio-economic impact. Thus, its recognition and treatment are essential. However, screening methods present limitations and should be improved. Moreover, available RLS treatment options albeit providing sustained relief to many patients are limited in number. Additionally, the development of augmentation with dopamine agonists represents a major treatment problem. A better understanding of RLS pathomechanisms can bring to light novel treatment possibilities. With emerging new avenues of research in pharmacology, imaging, genetics, and animal models of RLS, this is an interesting and constantly growing field of research. This review will update the reader on the current state of RLS clinical practice and research, with a special focus on the contribution of European researchers.

Revisiting brain iron deficiency in restless legs syndrome using magnetic resonance imaging

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Increased iron in RLS was found in the caudate, putamen and red nucleus.

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A meta-analysis revealed no significant evidence of reduced iron in RLS as assessed by MRI.

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Evidence suggestive of publication bias for results on the substantia nigra was found.

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Our results support the view that brain iron mobilization or homeostasis is impaired in RLS.

Study objectives

Studies on brain iron content in restless legs syndrome (RLS) using magnetic resonance imaging (MRI) are heterogeneous. In this study, we sought to leverage the availability of a large dataset including a range of iron-sensitive MRI techniques to reassess the association between brain iron content and RLS with added statistical power and to compare these results to previous studies.

Methods

The relaxation rates R₂, R₂′, and R₂* and quantitative susceptibility are MRI parameters strongly correlated to iron content. In general, these parameters are sensitive to magnetic field variations caused by iron particles. These parameters were quantified within iron-rich brain regions using a fully automatized approach in a cohort of 72 RLS patients and individually age and gender-matched healthy controls identified from an existing dataset acquired at the Sleep Laboratory of the Department of Neurology, Medical University of Innsbruck. 3 T-MRI measures were corrected for age and volume of the segmented brain nuclei and results were compared with previous findings in a meta-analysis.

Results

In our cohort, RLS patients had increased R₂* signal in the caudate and increased quantitative susceptibility signal in the putamen and the red nucleus compared to controls, suggesting increased iron content in these areas. The meta-analysis revealed no significant pooled effect across all brain regions. Furthermore, potential publication bias was identified for the substantia nigra.

Conclusions

Normal and increased iron content of subcortical brain areas detected in this study is not in line with the hypothesis of reduced brain iron storage, but favors CSF investigations and post mortem studies indicating alteration of brain iron mobilization and homeostasis in RLS.

Prevalence of restless legs syndrome in pregnant women in Oman and its effect on pregnancy and neonatal outcomes

BACKGROUND:

Restless legs syndrome (RLS) is a common sensorimotor disorder during pregnancy. The purpose of this study was to assess the prevalence of RLS and explore the associated risk factors and outcomes in Omani women in the first and third trimester and at 2-week postpartum.

MATERIALS AND METHODS:

This cross-sectional study included 305 pregnant women visiting four health centers in Muscat between May 2018 and October 2020. A structured questionnaire was used and data were collected through review of electronic records and face-to-face interviews. The International RLS Study Group criteria were used to diagnose RLS. Participants were interviewed during their first trimester, their third trimester, and at their 2-week postpartum visit. Results were presented as means and standard deviations or percentages, as appropriate. To assess the association between RLS and various variables, unpaired t-test or McNemar's test were used, as appropriate.

RESULTS:

The mean age at baseline was 29.8 ± 5.28 years. The prevalence of RLS was significantly higher in the third trimester (41.0%) than in the first trimester (15.7%) and postpartum period (15.1%) (P < 0.001), although there was no significant difference in severity. Family history and personal history of RLS were the only independent correlates of RLS (P < 0.001 and 0.002, respectively). No associations were noted with pregnancy and neonatal outcomes or other comorbidities, including anemia. However, there was a significant relationship between the development of RLS and weight gain during pregnancy (P = 0.023).

CONCLUSION:

One in six pregnant Omani women may be at risk of RLS during the first trimester, while one in 2–3 may be at risk in the third trimester, particularly those with a personal or family history of RLS and those who gain >12 kg during pregnancy.

Genome-wide analysis identified novel susceptible genes of restless legs syndrome in migraineurs

Background

Restless legs syndrome is a highly prevalent comorbidity of migraine; however, its genetic contributions remain unclear.

Objectives

To identify the genetic variants of restless legs syndrome in migraineurs and to investigate their potential pathogenic roles.

Methods

We conducted a two-stage genome-wide association study (GWAS) to identify susceptible genes for restless legs syndrome in 1,647 patients with migraine, including 264 with and 1,383 without restless legs syndrome, and also validated the association of lead variants in normal controls unaffected with restless legs syndrome (n = 1,053). We used morpholino translational knockdown (morphants), CRISPR/dCas9 transcriptional knockdown, transient CRISPR/Cas9 knockout (crispants) and gene rescue in one-cell stage embryos of zebrafish to study the function of the identified genes.

Results

We identified two novel susceptibility loci rs6021854 (in VSTM2L) and rs79823654 (in CCDC141) to be associated with restless legs syndrome in migraineurs, which remained significant when compared to normal controls. Two different morpholinos targeting vstm2l and ccdc141 in zebrafish demonstrated behavioural and cytochemical phenotypes relevant to restless legs syndrome, including hyperkinetic movements of pectoral fins and decreased number in dopaminergic amacrine cells. These phenotypes could be partially reversed with gene rescue, suggesting the specificity of translational knockdown. Transcriptional CRISPR/dCas9 knockdown and transient CRISPR/Cas9 knockout of vstm2l and ccdc141 replicated the findings observed in translationally knocked-down morphants.

Conclusions

Our GWAS and functional analysis suggest VSTM2L and CCDC141 are highly relevant to the pathogenesis of restless legs syndrome in migraineurs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10194-022-01409-9.

Restless Legs Syndrome Prevalence and Clinical Correlates Among Psychiatric Inpatients: A Multicenter Study

Background

There are only limited reports on the prevalence of restless legs syndrome (RLS) in patients with psychiatric disorders. The present study aimed to evaluate the prevalence and clinical correlates in psychiatric inpatients in Germany and Switzerland.

Methods

This is a multicenter cross-sectional study of psychiatric inpatients with an age above 18 years that were diagnosed and evaluated face-to-face using the International RLS Study Group criteria (IRLSSG) and the International RLS severity scale (IRLS). In addition to sociodemographic and biometric data, sleep quality and mood were assessed using the Pittsburgh Sleep Quality Index (PSQI), the Insomnia Severity Index (ISI), the Epworth Sleepiness Scale (ESS), and the Patient Health Questionnaire (PHQ-9). In addition to univariate statistics used to describe and statistically analyze differences in variables of interest between patients with and without RLS, a logistic model was employed to identify predictors for the occurrence of RLS.

Results

The prevalence of RLS in a sample of 317 psychiatric inpatients was 16.4%, and 76.9% of these were diagnosed with RLS for the first time. RLS severity was moderate to severe (IRLS ± SD: 20.3 ± 8.4). The prevalences in women (p = 0.0036) and in first-degree relatives with RLS (p = 0.0108) as well as the body mass index (BMI, p = 0.0161) were significantly higher among patients with RLS, while alcohol consumption was significantly lower in the RLS group. With the exception of atypical antipsychotics, treatment with psychotropic drugs was not associated with RLS symptoms. Regarding subjective sleep quality and mood, scores of the PSQI (p = 0.0007), ISI (p = 0.0003), and ESS (p = 0.0005) were higher in patients with RLS, while PHQ-9 scores were not different. A logistic regression analysis identified gender (OR 2.67; 95% CI [1.25; 5.72]), first-degree relatives with RLS (OR 3.29; 95% CI [1.11; 9.73], ESS score (OR 1.09; 95% CI [1.01; 1.17]), and rare alcohol consumption (OR 0.45; 95% CI [0.22; 0.94] as predictors for RLS.

Conclusions

Clinically significant RLS had a high prevalence in psychiatric patients. RLS was associated with higher BMI, impaired sleep quality, and lower alcohol consumption. A systematic assessment of restless legs symptoms might contribute to improve the treatment of psychiatric patients.

Restless Legs Syndrome among patients receiving antipsychotic and antidepressant drugs

BACKGROUND

Patients with Restless Legs Syndrome (RLS) experience psychological distress and diminished quality of life. Antipsychotics and antidepressants are known to be linked to RLS.

AIMS

This study aims to investigate the presence of RLS in psychiatric patients who receive antipsychotic and antidepressant drugs and to determine potential risk factors for its occurrence.

METHODS

Two hundred patients who received antipsychotic and antidepressant drugs for more than 1 month were recruited from two tertiary psychiatric centers in Cairo, Egypt. One hundred apparently healthy volunteers were also included. All patients and controls were screened using the four-items questionnaire (Arabic version) for RLS. RLS severity was scored according to the validated Arabic version of International Restless Legs Syndrome Study Group rating scale (IRLS). Mimicking conditions were carefully investigated and excluded.

RESULTS

Forty-one percent of the patients who receive antipsychotic and antidepressant drugs were found to have RLS. Family history, past history and smoking are potential risk factors. Trazodone and haloperidol were less associated with RLS.

CONCLUSIONS

Although limited by its cross-sectional design, these findings suggest that patients who receive antipsychotic and antidepressant are susceptible to RLS. However, these results need to be replicated on a wider scale.

Brain Iron Deficiency Changes the Stoichiometry of Adenosine Receptor Subtypes in Cortico-Striatal Terminals: Implications for Restless Legs Syndrome

Brain iron deficiency (BID) constitutes a primary pathophysiological mechanism in restless legs syndrome (RLS). BID in rodents has been widely used as an animal model of RLS, since it recapitulates key neurochemical changes reported in RLS patients and shows an RLS-like behavioral phenotype. Previous studies with the BID-rodent model of RLS demonstrated increased sensitivity of cortical pyramidal cells to release glutamate from their striatal nerve terminals driving striatal circuits, a correlative finding of the cortical motor hyperexcitability of RLS patients. It was also found that BID in rodents leads to changes in the adenosinergic system, a downregulation of the inhibitory adenosine A1 receptors (A1Rs) and upregulation of the excitatory adenosine A2A receptors (A2ARs). It was then hypothesized, but not proven, that the BID-induced increased sensitivity of cortico-striatal glutamatergic terminals could be induced by a change in A1R/A2AR stoichiometry in favor of A2ARs. Here, we used a newly developed FACS-based synaptometric analysis to compare the relative abundance on A1Rs and A2ARs in cortico-striatal and thalamo-striatal glutamatergic terminals (labeled with vesicular glutamate transporters VGLUT1 and VGLUT2, respectively) of control and BID rats. It could be demonstrated that BID (determined by measuring transferrin receptor density in the brain) is associated with a selective decrease in the A1R/A2AR ratio in VGLUT1 positive-striatal terminals.

Sleep and homeostatic control of plasticity

Sleep homeostasis is a complex neurobiologic phenomenon involving a number of molecular pathways, neurotransmitter release, synaptic activity, and factors modulating neural networks. Sleep plasticity allows for homeostatic optimization of neural networks and the replay-based consolidation of specific circuits, especially important for cognition, behavior, and information processing. Furthermore, research is currently moving from an essentially brain-focused to a more comprehensive view involving other systems, such as the immune system, hormonal status, and metabolic pathways. When dysfunctional, these systems contribute to sleep loss and fragmentation as well as to sleep need. In this chapter, the implications of neural plasticity and sleep homeostasis for the diagnosis and treatment of some major sleep disorders, such as insomnia and sleep deprivation, obstructive sleep apnea syndrome, restless legs syndrome, REM sleep behavior disorder, and narcolepsy are discussed in detail with their therapeutical implications. This chapter highlights that sleep is necessary for the maintenance of an optimal brain function and is sensitive to both genetic background and environmental enrichment. Even in pathologic conditions, sleep acts as a resilient plastic state that consolidates prior information and prioritizes network activity for efficient brain functioning.

Restless Legs Syndrome: Known Knowns and Known Unknowns

Although restless legs syndrome (RLS) is a common neurological disorder, it remains poorly understood from both clinical and pathophysiological perspectives. RLS is classified among sleep-related movement disorders, namely, conditions characterized by simple, often stereotyped movements occurring during sleep. However, several clinical, neurophysiological and neuroimaging observations question this view. The aim of the present review is to summarize and query some of the current concepts (known knowns) and to identify open questions (known unknowns) on RLS pathophysiology. Based on several lines of evidence, we propose that RLS should be viewed as a disorder of sensorimotor interaction with a typical circadian pattern of occurrence, possibly arising from neurochemical dysfunction and abnormal excitability in different brain structures.