The dopamine transporter is decreased in the striatum of subjects with restless legs syndrome

An expedited model for identifying potential patients with periodic leg movements

Periodic leg movements during sleep (PLMS) may have crucial consequences in adults. This study aimed to identify baseline characteristics, symptoms, or questionnaires that could help to identify sleep-disordered breathing patients with significant PLMS. Patients aged 20-80 years who underwent polysomnography for assessing sleep disturbance were included. Various factors such as sex, age, body measurements, symptoms, apnea-hypopnea index (AHI), and sleep quality scales were analysed to determine the presence of PLMS. The study included 1480 patients with a mean age of 46.4 ± 13.4 years, among whom 110 (7.4%) had significant PLMS with a PLM index of 15 or higher. There were no significant differences observed in terms of sex or BMI between patients with and without significant PLMS. However, the odds ratios (OR) for PLMS were 4.33, 4.41, and 4.23 in patients who were aged over 50 years, had insomnia, or had an ESS score of less than 10, respectively. Notably, the OR increased up to 67.89 times in patients who presented with all three risk factors. Our analysis identified significant risk factors for PLMS: age over 50, self-reported insomnia, and lower daytime sleepiness levels. These findings aid in identifying potential PLMS patients, facilitating confirmatory examinations and managing associated comorbidities.

Association of low serum ferritin levels with augmentation in patients with restless legs syndrome: A systematic review and meta-analysis

BACKGROUND

Augmentation of restless legs syndrome (RLS) is an iatrogenic side effect induced by dopaminergic agents, and it is a major cause of therapeutic failure. Iron deficiency is a risk factor for RLS, but its effects on the development of RLS augmentation are unclear. This meta-analysis aimed to elucidate the association between serum ferritin and RLS augmentation.

METHODS

We searched the PubMed, Cochrane Library, Embase, ClinicalKey, ScienceDirect, and ProQuest databases for studies comparing the serum ferritin levels of patients with augmented RLS and nonaugmented RLS. A meta-analysis based on a random-effects model was conducted. Levodopa equivalent dose (LED), International Restless Legs Study Group Severity Rating Scale (IRLS), and serum hemoglobin levels were also analyzed.

RESULTS

Six observational studies fulfilled the eligibility criteria of this meta-analysis. A total of 220 RLS patients with augmentation and 687 RLS patients without augmentation were included. The results revealed that augmented RLS was significantly associated with low serum ferritin levels (p = 0.002), high LEDs (p = 0.026), and nonsignificantly associated with high IRLS scores (p = 0.227).

CONCLUSIONS

A low serum ferritin level is associated with RLS augmentation. For patients with RLS who are iron deficient, iron supplements can not only relieve their fundamental RLS symptoms but also lower the risk of RLS augmentation. Moreover, non-dopminergic agents should be considered as the first-line treatment for patients with persistent low serum ferritin levels or those with moderate to severe RLS to prevent augmentation.

Cerebellum drives functional dysfunctions in restless leg syndrome

OBJECTIVE

Restless legs syndrome (RLS) has serious effects on patients' sleep quality, physical and mental health. However, the pathophysiological mechanisms of RLS remain unclear. This study utilized both static and dynamic functional activity and connectivity analyses approaches as well as effective connectivity analysis to reveal the neurophysiological basis of RLS.

METHODS

The resting-state functional MRI (rs-fMRI) data from 32 patients with RLS and 33 age-, and gender-matched healthy control (HC) were collected. Dynamic and static amplitude of low frequency fluctuation (ALFF), functional connectivity (FC), and Granger causality analysis (GCA) were employed to reveal the abnormal functional activities and couplings in patients with RLS.

RESULTS

RLS patients showed over-activities in left parahippocampus and right cerebellum, hyper-connectivities of right cerebellum with left basal ganglia, left postcentral gyrus and right precentral gyrus, and enhanced effective connectivity from right cerebellum to left postcentral gyrus compared to HC.

CONCLUSIONS

Abnormal cerebellum-basal ganglia-sensorimotor cortex circuit may be the underlying neuropathological basis of RLS. Our findings highlight the important role of right cerebellum in the onset of RLS and suggest right cerebellum may be a potential target for precision therapy.

Alterations of the thalamic nuclei volumes and intrinsic thalamic network in patients with restless legs syndrome

We aimed to investigate the alterations of thalamic nuclei volumes and intrinsic thalamic network in patients with primary restless legs syndrome (RLS) compared to healthy controls. Seventy-one patients with primary RLS and 55 healthy controls were recruited. They underwent brain MRI using a three-tesla MRI scanner, including three-dimensional T1-weighted images. The intrinsic thalamic network was determined using graph theoretical analysis. The right and left whole thalamic volumes, and the right pulvinar inferior, left ventral posterolateral, left medial ventral, and left pulvinar inferior nuclei volumes in the patients with RLS were lower than those in healthy controls (0.433 vs. 0.447%, p = 0.034; 0.482 vs. 0.502%, p = 0.016; 0.013 vs. 0.015%, p = 0.031; 0.062 vs. 0.065%, p = 0.035; 0.001 vs. 0.001%, p = 0.034; 0.018 vs. 0.020%, p = 0.043; respectively). There was also a difference in the intrinsic thalamic network between the groups. The assortative coefficient in patients with RLS was higher than that in healthy controls (0.0318 vs. - 0.0358, p = 0.048). We demonstrated the alterations of thalamic nuclei volumes and intrinsic thalamic network in patients with RLS compared to healthy controls. These changes might be related to RLS pathophysiology and suggest the pivotal role of the thalamus in RLS symptoms.

The relationship of the prevalence and severity of restless legs syndrome in primary Sjögren syndrome with insomnia status, anxiety, depression, and neuropathic pain

Background and aims

In this study, we aimed to compare the prevalence of restless legs syndrome (RLS) between primary Sjögren syndrome (PSS) patients and the healthy population and investigate the relationships between RLS and insomnia status, anxiety, depression, neuropathic pain, and lower extremity pain. Our case-control study, included 55 patients aged 18–65 who were diagnosed with PSS based on the 2016 ACR/EULAR criteria and 60 healthy controls aged 18–65. The pain levels of the participants were evaluated using the pain DETECT Questionnaire, the lower-extremity visual analog scale, and an algometer, all participants were screened for fibromyalgia syndrome, and their psychiatric parameters were evaluated with the Beck Depression Inventory and the Beck Anxiety Inventory. Insomnia status was assessed using the Insomnia Severity Index. The cases in the PSS group with and without restless legs syndrome were compared.

Results

While the rate of RLS in the PSS group was 26.7%, that in the control group was found as 9%, and the difference between the two groups was significant (p < 0.05). The severity of RLS in the PSS group was found to be significantly higher in comparison to that in the control group (p < 0.05). The PSS group had significantly higher lower-extremity pain, fibromyalgia, insomnia, depression, anxiety, and pain scores, as well as a significantly higher mean number of painful points, than the control group (p > 0.05). In the results of the multivariate regression analysis, depression and insomnia scores were identified as independent predictors for the presence of RLS in PSS cases (p < 0.05).

Conclusions

We found the prevalence and severity of restless legs syndrome higher in the primary Sjögren syndrome patients compared to the healthy participants in the control group. We identified depression and insomnia as independent predictors of the presence of restless legs syndrome in primary Sjögren syndrome cases.

Putative Animal Models of Restless Legs Syndrome: A Systematic Review and Evaluation of Their Face and Construct Validity

Restless legs syndrome (RLS) is a sensorimotor disorder that severely affects sleep. It is characterized by an urge to move the legs, which is often accompanied by periodic limb movements during sleep. RLS has a high prevalence in the population and is usually a life-long condition. While its origins remain unclear, RLS is initially highly responsive to treatment with dopaminergic agonists that target D2-like receptors, in particular D2 and D3, but the long-term response is often unsatisfactory. Over the years, several putative animal models for RLS have been developed, mainly based on the epidemiological and neurochemical link with iron deficiency, treatment efficacy of D2-like dopaminergic agonists, or genome-wide association studies that identified risk factors in the patient population. Here, we present the first systematic review of putative animal models of RLS, provide information about their face and construct validity, and report their role in deciphering the underlying pathophysiological mechanisms that may cause or contribute to RLS. We propose that identifying the causal links between genetic risk factors, altered organ functions, and changes to molecular pathways in neural circuitry will eventually lead to more effective new treatment options that bypass the side effects of the currently used therapeutics in RLS, especially for long-term therapy.

Polysomnographic features of idiopathic restless legs syndrome: a systematic review and meta-analysis of 13 sleep parameters and 23 leg movement parameters

STUDY OBJECTIVES

This study aims to explore the polysomnographically measured sleep and leg movement differences between idiopathic restless legs syndrome (RLS) patients and healthy controls.

METHODS

An electronic literature search was conducted in EMBASE, MEDLINE, all EBM databases, CINAHL, and PsycINFO. Only observational case-control studies were included in the meta-analysis. The differences in 13 sleep parameters and 23 leg movement parameters between RLS patients and healthy controls were explored.

RESULTS

Thirty-eight studies were identified for systematic review, 31 of which were used for meta-analysis. Meta-analyses revealed significant reductions in total sleep time, sleep efficiency, stage N2 and rapid eye movement (REM) sleep percentages, and increases in wake time after sleep onset, stage shifts per hour, stage N1 percentage, REM latency, arousal index, and apnea-hypopnea index. Some leg movement parameters, such as periodic limb movement during sleep (PLMS) index, PLMS sequence duration, number of PLMS sequence, and periodicity index, were higher in RLS patients compared with healthy controls. Further, our meta-analysis revealed a higher PLMS index during non-REM sleep compared with that during REM sleep.

CONCLUSIONS

RLS patients manifest a lightening of sleep, increased sleep fragmentation, and greater sleep-related breathing disruption and limb movements during sleep relative to healthy normal individuals. The distributions of PLMS during a night's sleep may provide more information to clarify the specific characteristics of leg movements in RLS. PLMS in RLS are concentrated in non-REM sleep. The periodicity index may be a more sensitive and specific marker of RLS than the PLMS index.

CITATION

Zhang H, Zhang Y, Ren R, et al. Polysomnographic features of idiopathic restless legs syndrome: a systematic review and meta-analysis of 13 sleep parameters and 23 leg movement parameters. J Clin Sleep Med. 2022;18(11):2561-2575.

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.

Neuroanatomy and Functional Connectivity in Patients with Parkinson's Disease with or without Restless Legs Syndrome

INTRODUCTION

Restless legs syndrome (RLS) is a common non-motor symptom in Parkinson's disease (PD), but its pathogenesis remains unclear. This study aimed to explore the potential neural substrates of RLS in a large sample of patients with PD.

METHODS

A total of 42 patients with PD with RLS and 124 patients with PD without RLS were prospectively recruited at our hospital between February 2019 and October 2020 and underwent structural and resting-state functional magnetic resonance imaging. Differences between the two patient groups were assessed using voxel-based morphometry and functional connectivity analysis. PD duration, Part III of the Movement Disorder Society's Unified Parkinson's Disease Rating Scale (MDS-UPDRS-III) score, and levodopa equivalent daily dose were treated as covariates.

RESULTS

Patients with PD with RLS had significantly larger gray matter volume in the bilateral posterior cingulate cortex than patients with PD without RLS (FDR-adjusted P < 0.05). Compared to patients without RLS, those with RLS had significantly lower functional connectivity between the left central opercular cortex and the bilateral precentral gyri and postcentral gyri (FDR-adjusted P < 0.001).

CONCLUSION

Our study provides the first evidence that in patients with PD, RLS is associated with significantly larger gray matter volume in the posterior cingulate cortex and lower resting-state functional connectivity within the sensorimotor network. Our results may help clarify the pathophysiology of RLS in PD and identify possible therapeutic targets.

Morphological analysis of the brain subcortical gray structures in restless legs syndrome

BACKGROUND

Although several studies have shown the involvement of specific structures of the central nervous system, the dopaminergic system, and iron metabolism in restless legs syndrome (RLS), the exact location and extent of its anatomical substrate is not yet known. The scope of this new study was to investigate the brain subcortical gray structures, by means of structural magnetic resonance imaging (MRI) studies, in RLS patients in order to assess the presence of any volume or shape abnormalities involving these structures.

METHODS

Thirty-three normal controls (24 females and nine males) and 45 RLS patients (34 females and 11 males) were retrospectively recruited and underwent a 1.5 Tesla MRI study with two-dimensional T1 sequences in the sagittal plane. Post-processing was performed by means of the Functional Magnetic Resonance Imaging of the Brain Analysis Group Integrated Registration and Segmentation Tool (FIRST) software, and both volumetric and morphological analyses of the thalamus, caudate, putamen, globus pallidus, brainstem, hippocampus, and amygdala, bilaterally, were carried out.

RESULTS

A statistically significant volumetric reduction in the left amygdala and left globus pallidus was found in subjects with RLS, as well as large surface morphological alterations affecting the amygdala bilaterally and other less widespread surface changes in both hippocampi, the right caudate, the left globus pallidus, and the left putamen.

CONCLUSIONS

These findings seem to indicate that the basic mechanisms of RLS might include a pathway involving not only the hypothalamus-spinal dopaminergic circuit (nucleus A11), but also pathways including the basal ganglia and structures that are part of the limbic system; moreover, structural alterations in RLS seem to concern the morphology as well as the volume of the above structures. The role of basal ganglia in the complex neurophysiological and neurochemical mechanism of RLS needs to carefully reconsidered.

Iron deficiency in pregnancy: Influence on sleep, behavior, and molecular markers of adult male offspring

Iron restriction during pregnancy can lead to iron deficiency and changes in the dopaminergic system in the adulthood of offspring, and restless legs syndrome (RLS) is closely related to these changes. Objectives: Analyze whether iron restriction during pregnancy would cause changes in the behavior, sleep, and dopaminergic system of the male offspring. In addition, we aimed to assess whether exercise would be able to modulate these variables. The pregnant rats (Wistar) were divided into four groups with different concentrations of iron in the diet: standard (St), supplementation (Su), restriction since weaning (R1), and restriction only during pregnancy (R2). After birth, the offspring were assigned to their respective groups according to the dams diet (St, Su, R1, and R2) and distributed into sedentary (SD) and exercised (EX) (for 8 weeks of training), reaching eight groups of offspring (O): OSt SD, OSt EX, OSu SD, OSu EX, OR1 SD, OR1 EX, OR2 SD, and OR2 EX. Sleep, behavior, and analysis of key genes of dopaminergic system (D2, DAT) were performed after 8 weeks. The results for trained offspring that the mother received supplementation diet were the most expressive, with increased freezing and the OR1 SD group showed an increase in DAT protein content. These changes may have been due to the association between the dams diet during pregnancy and the practice of exercise by the offspring. The different concentrations of iron during pregnancy caused changes in the offspring, however, they were not associated with fetal programming in the context of RLS.

Sleep disturbance in movement disorders: insights, treatments and challenges

Sleep and circadian rhythm disturbances are central features of many movement disorders, exacerbating motor and non-motor symptoms and impairing quality of life. Understanding these disturbances to sleep is clinically important and may further our understanding of the underlying movement disorder. This review evaluates the current anatomical and neurochemical understanding of normal sleep and the recognised primary sleep disorders. In addition, we undertook a systematic review of the evidence for disruption to sleep across multiple movement disorders. Rapid eye movement sleep behaviour disorder has emerged as the most reliable prodromal biomarker for the alpha synucleinopathies, including Parkinson's disease and multiple system atrophy, often preceding motor symptom onset by several years. Abnormal sleep has also been described for many other movement disorders, but further evidence is needed to determine whether this is a primary or secondary phenotypic component of the underlying condition. Medication used in the treatment of motor symptoms also affects sleep and can aggravate or cause certain sleep disorders. Within the context of movement disorders, there is also some suggestion of a shared underlying mechanism for motor and sleep pathophysiology, with evidence implicating thalamic and brainstem structures and monoaminergic neurotransmission. This review highlights the need for an understanding of normal and abnormal sleep within the movement disorder clinic, an ability to screen for specific causes of poor sleep and to treat sleep disturbance to improve quality of life. Key sleep disorders also act as important biomarkers and have implications in diagnosis, prognosis and the development of future therapies.

Sleep Disorders in Mitochondrial Diseases

PURPOSE OF REVIEW

We aim to summarize the sleep disorders reported in patients affected by primary mitochondrial dysfunctions and describe the association with their clinical and molecular characteristics.

RECENT FINDINGS

Sleep complaints are prevalent in mitochondrial disorders. Sleep-disordered breathing is the main sleep disorder reported in mitochondrial diseases. OSA and CSA are, respectively, more frequently associated with patients characterized by the prevalent involvement of the skeletal muscle and the predominant involvement of the central nervous system. Other sleep disorders, such as restless legs syndrome, have been rarely described. Sleep disorders are frequently associated with primary mitochondrial disorders, and the clinical phenotypes affect the type of sleep disturbance associated with the mitochondrial dysfunction. A polysomnographic study should be performed in every subject with this neurogenetic disorder both at diagnosis and during follow-up for the numerous adverse clinical outcomes associated with sleep disorders and the frailty of mitochondrial patients.

[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.

Pharmacologic Treatment of Restless Legs Syndrome

Restless legs syndrome (RLS)/Willis-Ekbom disease is a neurologic disorder characterized by a strong desire to move when at rest (usually in the evening) and paraesthesia in their lower legs. The most widely used therapies for first-line treatment of RLS are dopaminergic drugs; however, their long-term use can lead to augmentation. α2δ Ligands, opioids, iron, glutamatergic drugs, adenosine, and sleep aids have been investigated as alternatives. The pathogenesis of RLS is not well understood. Despite the efficacy of dopaminergic drugs in the treatment of this disorder, unlike in Parkinson’s disease dopaminergic cell loss in the substantia nigra has not been observed in RLS. The etiology of RLS is likely complex, involving multiple neural pathways. RLS-related genes identified in genome-wide association studies can provide insight into the mechanistic basis and pathophysiology of RLS. Here we review the current treatments and knowledge of the mechanisms underlying RLS.

Cannabis for Restless Legs Syndrome

Restless legs syndrome (RLS) is a chronic sensorimotor disorder characterized by an urge to move the legs. This urge is often accompanied by pain or other uncomfortable and unpleasant sensations, it either occurs or worsens during rest, particularly in the evening and/or at night, and temporarily improves with activity. Affecting nearly 3% of the North American and European populations in its moderate-to-severe form, RLS has a considerable negative impact on the quality of life, and sleep and is associated with significant morbidity. Although new developments have deepened our understanding of the disorder, yet, the corresponding pathophysiologic features that underlie the sensorimotor presentation are still not fully understood. Usually, symptoms respond well to dopamine agonists (DA), anticonvulsants, or opiates, used either alone or in any combination, but still, a subset of patients remains refractory to medical therapy and serious side effects such as augmentation and impulse control disorder may occur in patients with RLS under DA. Convincing treatment alternative are lacking but recently patients' spontaneous reports of a remarkable and total remission of RLS symptoms following cannabis use has been reported. The antinociceptive effect of marijuana has been documented in many painful neurological conditions and the potential benefit of cannabis use in patients with refractory RLS should, therefore, be questioned by robust clinical trials. Here, we review basic knowledge of RLS and the putative mechanisms by which cannabis may exert its analgesic effects.

Searching for Novel Candidate Biomarkers of RLS in Blood by Proteomic Analysis

PURPOSE

We performed comparative proteomic analyses of blood of patients with RLS and healthy individuals aiming to identify potential biomarker and therapeutic target candidate for RLS.

PATIENTS AND METHODS

Blood serum samples from 12 patients with a clinical diagnosis of RLS (8 females and 4 males, with a mean age of 68.52 years) and 10 healthy controls (5 females and 5 males, with a mean age of 67.61 years) underwent proteomic profiling by liquid chromatography coupled with tandem mass spectrometry. Pathway analysis incorporating protein-protein interaction networks was carried out to identify pathological processes linked to the differentially expressed proteins.

RESULTS

We quantified 272 proteins in patients with RLS and healthy controls, of which 243 were shared. Five proteins - apolipoprotein C-II, leucine-rich alpha-2-glycoprotein 1, FLJ92374, extracellular matrix protein 1, and FLJ93143 - were substantially increased in RLS patients, whereas nine proteins - vitamin D-binding protein, FLJ78071, alpha-1-antitrypsin, CD5 antigen-like, haptoglobin, fibrinogen alpha chain, complement factor H-related protein 1, platelet factor 4, and plasma protease C1 inhibitor - were decreased. Bioinformatics analyses revealed that these proteins were linked to 1) inflammatory and immune response, and complement activation, 2) brain-related development, cell aging, and memory disorders, 3) pregnancy and associated complications, 4) myocardial infarction, and 5) reactive oxygen species generation and subsequent diabetes mellitus.

CONCLUSION

Our findings shed light on the multifactorial nature of RLS and identified a set of circulating proteins that may have clinical importance as biomarkers and therapeutic targets.

Developing a biomarker for restless leg syndrome using genome wide DNA methylation data

This study reports on an epigenetic biomarker for restless leg syndrome (RLS) developed using whole genome DNA methylation data. Lymphocyte-derived DNA methylation was examined in 15 subjects with and without RLS (discovery cohort). T-tests and linear regressions were used followed by a principal component analysis (PCA). The principal component model from the discovery cohort was used to predict RLS status in a peripheral blood (N = 24; including 12 cases and 12 controls) and a post-mortem neural tissue (N = 71; including 36 cases and 35 controls) replication cohort as well as iron deficiency anemia status in a publicly available dataset (N = 71, 59 cases with iron deficiency anemia, 12 controls). Using receiver-operating characteristic analysis the optimum biomarker model - that included 49 probes - predicted RLS status in the blood-based replication cohort with an area under the curve (AUC) of 87.5% (confidence interval = 71.9%-100%). In the neural tissue samples, the model predicted RLS status with an AUC of 73.4% (confidence interval = 61.5%-85.3%). An AUC of 83% was found for predictions of iron deficiency anemia. Thus, the blood-based biomarker model reported here and built with epigenome-wide data showed reasonable replicability in lymphocytes and neural tissue samples. A limitation of this study is that we could not determine the metabolic or neurobiological pathways linking epigenetic changes with RLS. Further research is needed to fine-tune this model for prospective predictions of RLS and to enable translation for clinical use.

Prevalence of restless legs syndrome and quality of sleep in type 2 diabetics

INTRODUCTION

Restless legs syndrome (RLS) is characterized by an irresistible urge to move, with or without paraesthesia occurring or worsening at rest and relieved by activity. Only a few reports of prevalence of RLS with type 2 diabetes are available in India.

AIMS

To estimate the occurrence and risk factors of RLS among Indian patients with type 2 diabetes mellitus.

METHOD

This cross-sectional study was done in consecutive adult patients with type 2 diabetes. Demographic and comorbidity profile were collected. RLS diagnosis was made based on revised international RLS study group (IRLSSG) criteria.

RESULTS

Two hundred and ten diabetic patients were interviewed. Mean age was 56 ± 13.5 years. Male-female ratio was 139: 71. Mean duration of diabetes was 8.3 years. Treatment received for diabetes included oral hypoglycaemic agents (153 patients) and insulin (85 patients). Forty-five patients had polyneuropathy, 18 had retinopathy and 22 had nephropathy. Majority (103) of subjects reported their bedtime as 9-10 pm. Average sleep duration was 8.4 h per night. RLS was diagnosed in 17 (8%) subjects. Mean sleep onset in subjects with RLS was 56 min versus 29 min in diabetics without RLS (p-0.01). The mean Pittsburgh Sleep Quality Index score was 5 in RLS and 3.3 in non-RLS patients (p-0.01).

DISCUSSION AND CONCLUSIONS

RLS resulted in poor sleep quality and affected overall quality of life in diabetics. As poor sleep is a known risk factor for uncontrolled diabetes, early identification and treatment of RLS would help improve glycaemic control and quality of life in these patients.

SNCA-Rep1 polymorphism correlates with susceptibility and iron deficiency in restless legs syndrome

BACKGROUND

Brain iron disequilibrium and dopaminergic dysfunction are key pathophysiological features of Restless Legs Syndrome (RLS). Rep1 polymorphism in the promotor region of SNCA is associated with risk of Parkinson's disease, however its association with RLS and iron status is unclear.

OBJECTIVE

To investigate SNCA-Rep1 polymorphism in RLS and its phenotypes.

METHODS

We recruited RLS patients as well as age and gender matched healthy controls. Demographic information and clinical features of RLS were recorded. Laboratory examinations were performed to exclude possible secondary causes.

RESULTS

215 RLS patients and 369 healthy controls were included. We found that the Rep1 allele 0 homozygosity significantly decreased RLS risk (OR: 0.345; P < 0.0001, and remained significant after the Bonferroni correction). Phenotypic analysis demonstrated that longer Rep1 alleles were associated with increased susceptibility to iron deficiency (53.0% vs 36.1%, P = 0.017), however had no phenotypic significant effects on age, gender, onset age, duration, RLS family history, severity, laterality, extra body involvement and seasonal fluctuation. Multivariate logistic regression analyses confirmed long Rep1 allele was associated with higher risk of iron deficiency in RLS after adjusting for potential confounding factors. In detail, Rep1 allele 2 homozygosity was prone to a higher risk of peripheral iron deficiency in RLS (OR: 4.550, P = 0.006, remained significant after the Bonferroni correction).

CONCLUSION

The SNCA-Rep1 variability modified RLS risk and influenced peripheral iron deficiency in this group of Chinese RLS patients. Rep1 allele 0 homozygosity decreased the risk of RLS, while homozygous allele 2 increased the risk of nonanemic iron deficiency in RLS.

Iron-deficiency and dopaminergic treatment effects on RLS-Like behaviors of an animal model with the brain iron deficiency pattern of the restless legs syndrome

BACKGROUND

Brain iron deficiency (BID), especially for the substantia nigra (SN), without peripheral iron deficiency (ID) has been well documented as a ubiquitous finding for restless legs syndrome (RLS) patients. This close association suggests the biology of RLS BID can produce RLS symptoms. Association, however, cannot establish such a direct relationship. Instead, the BID of RLS could be experimentally produced to determine if it then produces significant RLS-like biological or behavioral features. Forward genetics approach led to identification from the BXD strains the BXD40 females (BXD40f) as a putative animal model for the RLS BID. The BXD40f on an iron-sufficient diet have a lower iron in the VMB (containing the SN) during the active but not inactive period. This was not found for the other BXD strains evaluated. The BXD40f on an ID diet uniquely have even greater reduced VMB but not peripheral iron, matching the RLS BID pathophysiology. A prior report found that the BXD40f on an iron-sufficient diet had an RLS-like behavior of increased activity occurring only in the last part of the active period that was not present in the other strains without the low VMB iron. This increased activity matches the circadian pattern of symptoms in RLS patients with increased urge or drive to move in the last part of the day. This study asks first: if you decrease the VMB iron by an iron deficient diet do the RLS-like behaviors worsen; and second will the dopaminergic treatments effective for RLS also reduce the worsened RLSlike behaviors.

METHODS

In sum, 13 BXD40f mice post weaning were randomly assigned for 100 days to either a iron-sufficient diet (n = 6) or an ID diet (N = 7). They were then evaluated for 24-h activity in their home cage using implanted G2 EMitter telemetry device. At 3 h before the end of the active period IP doses were given every other day of either: saline (vehicle only), 12.5 mg levodopa, 25 mg levodopa, 0.5 mg quinpirole, or 1 0.0 mg quinpirole.

RESULTS

The ID compared to irons-sufficient diet produced earlier onset of the RLS-like behavior matching the earlier onset of symptoms with increasing severity of RLS. The dopaminergic treatments significantly reduced the RLS-like behavior. Added analyses of the RLS-like behaviors as decreased resting times showed similar results to activity increases.

CONCLUSIONS

These data demonstrate both that The BXD40f provide a useful animal model of RLS and also strongly support the hypothesis that the biology of RLS BID can produce RLS symptoms.

BTBD9 and dopaminergic dysfunction in the pathogenesis of restless legs syndrome

Restless legs syndrome (RLS) is characterized by an urge to move legs, usually accompanied by uncomfortable sensations. RLS symptoms generally happen at night and can be relieved by movements. Genetic studies have linked polymorphisms in BTBD9 to a higher risk of RLS. Knockout of BTBD9 homolog in mice (Btbd9) and fly results in RLS-like phenotypes. A dysfunctional dopaminergic system is associated with RLS. However, the function of BTBD9 in the dopaminergic system and RLS is not clear. Here, we made use of the simple Caenorhabditis elegans nervous system. Loss of hpo-9, the worm homolog of BTBD9, resulted in hyperactive egg-laying behavior. Analysis of genetic interactions between hpo-9 and genes for dopamine receptors (dop-1, dop-3) indicated that hpo-9 and dop-1 worked similarly. Reporter assays of dop-1 and dop-3 revealed that hpo-9 knockout led to a significant increase of DOP-3 expression. This appears to be evolutionarily conserved in mice with an increased D₂ receptor (D₂R) mRNA in the striatum of the Btbd9 knockout mice. Furthermore, the striatal D₂R protein was significantly decreased and Dynamin I was increased. Overall, activities of DA neurons in the substantia nigra were not altered, but the peripheral D₁R pathway was potentiated in the Btbd9 knockout mice. Finally, we generated and characterized the dopamine neuron-specific Btbd9 knockout mice and detected an active-phase sleepiness, suggesting that dopamine neuron-specific loss of Btbd9 is sufficient to disturb the sleep. Our results suggest that increased activities in the D₁R pathway, decreased activities in the D₂R pathway, or both may contribute to RLS.

The Role of BTBD9 in the Cerebellum, Sleep-like Behaviors and the Restless Legs Syndrome

Recent genome-wide association studies (GWAS) have found cerebellum as a top hit for sleep regulation. Restless legs syndrome (RLS) is a sleep-related sensorimotor disorder characterized by uncomfortable sensations in the extremities, generally at night, which are often relieved by movements. Clinical studies have found that RLS patients have structural and functional abnormalities in the cerebellum. However, whether and how cerebellar pathology contributes to sleep regulation and RLS is not known. GWAS identified polymorphisms in BTBD9 conferring a higher risk of sleep disruption and RLS. Knockout of the BTBD9 homolog in mice (Btbd9) and fly results in motor restlessness and sleep disruption. We performed manganese-enhanced magnetic resonance imaging on the Btbd9 knockout mice and found decreased neural activities in the cerebellum, especially in lobules VIII, X, and the deep cerebellar nuclei. Electrophysiological recording of Purkinje cells (PCs) from Btbd9 knockout mice revealed an increased number of non-tonic PCs. Tonic PCs showed increased spontaneous activity and intrinsic excitability. To further investigate the cerebellar contribution to RLS and sleep-like behaviors, we generated PC-specific Btbd9 knockout mice (Btbd9 pKO) and performed behavioral studies. Btbd9 pKO mice showed significant motor restlessness during the rest phase but not in the active phase. Btbd9 pKO mice also had an increased probability of waking at rest. Unlike the Btbd9 knockout mice, there was no increased thermal sensation in the Btbd9 pKO. Our results indicate that the Btbd9 knockout influences the PC activity; dysfunction in the cerebellum may contribute to the motor restlessness found in the Btbd9 knockout mice.

Restless Legs Syndrome across the Lifespan: Symptoms, Pathophysiology, Management and Daily Life Impact of the Different Patterns of Disease Presentation

Restless legs syndrome is a common but still underdiagnosed neurologic disorder, characterized by peculiar symptoms typically occurring in the evening and at night, and resulting in sleep disruption and daily functioning impairment. This disease can affect subjects of all age ranges and of both sexes, manifesting itself with a broad spectrum of severity and deserving special attention in certain patient categories, in order to achieve a correct diagnosis and an effective treatment. The diagnosis of restless legs syndrome can be challenging in some patients, especially children and elderly people, and an effective treatment might be far from being easy to achieve after some years of drug therapy, notably when dopaminergic agents are used. Moreover, the pathophysiology of this disorder offers an interesting example of interaction between genetics and the environment, considering strong iron metabolism involvement and its interaction with recognized individual genetic factors. Therefore, this syndrome allows clinicians to verify how lifespan and time can modify diagnosis and treatment of a neurological disorder.

Mu opioid receptor knockout mouse: Phenotypes with implications on restless legs syndrome

Restless legs syndrome (RLS) is characterized by an irresistible need to move the legs while sitting or lying at night with insomnia as a frequent consequence. Human RLS has been associated with abnormalities in the endogenous opioid system, the dopaminergic system, the iron regulatory system, anemia, and inflammatory and auto-immune disorders. Our previous work indicates that mice lacking all three subtypes of opioid receptors have a phenotype similar to that of human RLS. To study the roles of each opioid receptor subtype in RLS, we first used mu opioid receptor knockout (MOR KO) mice based on our earlier studies using postmortem brain and cell culture. The KO mice showed decreased hemoglobin, hematocrit, and red blood cells (RBCs), with an appearance of microcytic RBCs indicating anemia. Together with decreased serum iron and transferrin, but increased ferritin levels, the anemia is similar to that seen with chronic inflammation in humans. A decreased serum iron level was also observed in the wildtype mice treated with an MOR antagonist. Iron was increased in the liver and spleen of the KO mice. Normal circadian variations in the dopaminergic and serotoninergic systems were absent in the KO mice. The KO mice showed hyperactivity and increased thermal sensitivity in wakefulness primarily during what would normally be the sleep phase similar to that seen in human RLS. Deficits in endogenous opioid system transmission could predispose to anemia of inflammation and loss of circadian variations in dopaminergic or serotonergic systems, thereby contributing to an RLS-like phenotype.

Striatal histamine mechanism in the pathogenesis of restless legs syndrome

STUDY OBJECTIVES

Restless legs syndrome (RLS) has been hypothesized to be generated by abnormal striatal dopamine transmission. Dopaminergic drugs are effective for the treatment of RLS. However, long-term use of dopaminergic drugs causes adverse effects. We used iron-deficient (ID) and iron-replacement (IR) rats to address the neuropathology of RLS and to determine if a histamine H3 receptor (H3R) antagonist might be a useful treatment. Histamine H3R antagonists have been shown to decrease motor activity.

METHODS

Control and ID rats were surgically implanted with electrodes for polysomnographic recording. After 3 days of baseline polysomnographic recordings, rats were systemically injected with the H3R agonist, α-methylhistamine, and antagonist, thioperamide. Recordings were continued after drug injection. Striatal H3R levels from control, ID, and IR rats were determined by western blots. Blood from control, ID, and IR rats was collected for the measurement of hematocrit levels.

RESULTS

α-Methylhistamine and thioperamide increased and decreased motor activity, respectively, in control rats. In ID rats, α-methylhistamine had no effect on motor activity, whereas thioperamide decreased periodic leg movement (PLM) in sleep. Sleep-wake states were not significantly altered under any conditions. Striatal H3R levels were highest in ID rats, moderate to low in IR rats, and lowest in control rats. Striatal H3R levels were also found to positively and negatively correlate with PLM in sleep and hematocrit levels, respectively.

CONCLUSIONS

A striatal histamine mechanism may be involved in ID anemia-induced RLS. Histamine H3R antagonists may be useful for the treatment of RLS.

The Role of BTBD9 in Striatum and Restless Legs Syndrome

Restless legs syndrome (RLS) is a sensory-motor neurological disorder characterized by uncomfortable sensations in the extremities, generally at night, which is often relieved by movements. Genome-wide association studies (GWAS) have identified mutations in BTBD9 conferring a higher risk of RLS. Knockout of the BTBD9 homolog in mice (Btbd9) and fly results in motor restlessness and sleep disruption. Clinical studies have found RLS patients have structural and functional abnormalities in the striatum; however, whether and how striatal pathology contributes to the pathogenesis of RLS is not known. Here, we used fMRI to map regions of altered synaptic activity in basal ganglia of systematic Btbd9 knock-out (KO) mice. We further dissected striatal circuits using patch-clamp electrophysiological recordings in brain slices. Two different mouse models were generated to test the effect of specific knockout of Btbd9 in either striatal medium spiny neurons (MSNs) or cholinergic interneurons (ChIs) using the electrophysiological recording, motor and sensory behavioral tests. We found that Btbd9 KO mice showed enhanced neural activity in the striatum, increased postsynaptic currents in the MSNs, and decreased excitability of the striatal ChIs. Knocking out Btbd9 specifically in the striatal MSNs, but not the ChIs, led to rest-phase specific motor restlessness, sleep disturbance, and increased thermal sensation in mice, which are consistent with results obtained from the Btbd9 KO mice. Our data establish the role of Btbd9 in regulating the activity of striatal neurons. Increased activity of the striatal MSNs, possibly through modulation by the striatal ChIs, contributes to the pathogenesis of RLS.

Hyperactivity, dopaminergic abnormalities, iron deficiency and anemia in an in vivo opioid receptors knockout mouse: Implications for the restless legs syndrome

Previous studies have uncovered a potential role of the opioid system in iron hemostasis and dopamine metabolism. Abnormalities in both of these systems have been noted in human RLS. Autopsy studies of human RLS have shown an endogenous opioid deficiency in the thalamus. Opioids, particularly prolonged-release oxycodone/naloxone, have been approved in Europe to be a second-line therapy for severe restless legs syndrome (RLS). To study the role of opioid receptors in the pathogenesis of RLS, we used a triple knockout (KO) mouse strain that lack mu, delta, and kappa opioid receptors and explored the behavioral and biochemical parameters relevant to RLS. The triple KO mice showed hyperactivity and a trend of increased probability of waking during the rest period (day) akin to that in human RLS (night). Surprisingly, triple KO mice also exhibit decreased serum iron concentration, evidence of anemia, a significant dysfunction in dopamine metabolism akin to that noted in human RLS, as well as an increased latency in response to thermal stimuli. To our knowledge, this is the first study to demonstrate that the endogenous opioid system may play a role in iron metabolism and subsequently in the pathogenesis of anemia. It is also the first study showing that opioid receptors are involved in the production of motor restlessness with a circadian predominance. Our findings support the role of endogenous opioids in the pathogenesis of RLS, and the triple KO mice can be used to understand the relationship between iron deficiency, anemia, dopaminergic dysfunction, and RLS.

IL1B polymorphism is associated with essential tremor in Chinese population

BACKGROUND

The aim of the study was to investigate the genetic risk factors of essential tremor (ET) in Chinese Population.

METHODS

A total of 225 ET patients (25 ET patients also had restless legs syndrome (RLS) and were excluded from final analysis) and 229 controls were recruited. The diagnosis of ET was based on the Consensus Statement of the Movement Disorders Society on tremor. Polymerase chain reaction (PCR) and sequencing were used to detect 12 single nucleotide polymorphisms (SNPs) in seven candidate genes for RLS (HMOX1, HMOX2, VDR, IL17A, IL1B, NOS1 and ADH1B).

RESULTS

We found that one SNP was associated with the risk of ET in Chinese population after adjusting for age and gender: rs1143633 of IL1B (odds ratio [OR] =2.57, p = 0.003, recessive model), and the statistical result remained significant after Bonferroni correction. Then, we performed a query in Genotype-tissue Expression (GTEx), Brain eQTL Almanac (Braineac) databases and Blood expression quantitative trait loci (eQTL) browser. The significant association was only found between genotype at rs1143633 and IL1B expression level of putamen and white matter in Braineac database, which was more prominent with homozygous (GG) carriers.

CONCLUSIONS

Our study firstly reported the association of IL1B polymorphism with the risk of ET in Chinese population. However, the association might only suggest a marker of IL1B SNP associated with ET instead of the casual variant. Further studies are needed to confirm our finding.

Caenorhabditis elegans and its applicability to studies on restless legs syndrome

Restless legs syndrome (RLS) is a common neurological disorder in the United States. This disorder is characterized by an irresistible urge to move the legs, although the symptoms vary in a wide range. The pathobiology of RLS has been linked to iron (Fe) deficiency and dopaminergic (DAergic) dysfunction. Several genetic factors have been reported to increase the risk of RLS. Caenorhabditis elegans (C. elegans) is a well-established animal model with a fully sequenced genome, which is highly conserved with mammals. Given the detailed knowledge of its genomic architecture, ease of genetic manipulation and conserved biosynthetic and metabolic pathways, as well as its small size, ease of maintenance, speedy generation time and large brood size, C. elegans provides numerous advantages in studying RLS-associated gene-environment interactions. Here we will review current knowledge about RLS symptoms, pathology and treatments, and discuss the application of C. elegans in RLS study, including the worm homologous genes and methods that could be performed to advance the pathophysiology RLS.

The heterotetrameric structure of the adenosine A1-dopamine D1 receptor complex: Pharmacological implication for restless legs syndrome

Dopaminergic and purinergic signaling play a pivotal role in neurological diseases associated with motor symptoms, including Parkinson's disease (PD), multiple sclerosis, amyotrophic lateral sclerosis, Huntington disease, Restless Legs Syndrome (RLS), spinal cord injury (SCI), and ataxias. Extracellular dopamine and adenosine exert their functions interacting with specific dopamine (DR) or adenosine (AR) receptors, respectively, expressed on the surface of target cells. These receptors are members of the family A of G protein-coupled receptors (GPCRs), which is the largest protein superfamily in mammalian genomes. GPCRs are target of about 40% of all current marketed drugs, highlighting their importance in clinical medicine. The striatum receives the densest dopamine innervations and contains the highest density of dopamine receptors. The modulatory role of adenosine on dopaminergic transmission depends largely on the existence of antagonistic interactions mediated by specific subtypes of DRs and ARs, the so-called A_2AR-D₂R and A₁R-D₁R interactions. Due to the dopamine/adenosine antagonism in the CNS, it was proposed that ARs and DRs could form heteromers in the neuronal cell surface. Therefore, adenosine can affect dopaminergic signaling through receptor-receptor interactions and by modulations in their shared intracellular pathways in the striatum and spinal cord. In this work we describe the allosteric modulations between GPCR protomers, focusing in those of adenosine and dopamine within the A₁R-D₁R heteromeric complex, which is involved in RLS. We also propose that the knowledge about the intricate allosteric interactions within the A₁R-D₁R heterotetramer, may facilitate the treatment of motor alterations, not only when the dopamine pathway is hyperactivated (RLS, chorea, etc.) but also when motor function is decreased (SCI, aging, PD, etc.).

Clinical and radiological characteristics of restless legs syndrome following acute lacunar infarction

BACKGROUND

Recent studies have suggested that cerebral ischemic infarction may contribute to the development of restless legs syndrome (RLS). This study analyzed the clinical and radiological profiles of RLS with onset after acute lacunar infarction.

METHODS

In this retrospective study we enrolled 244 consecutive patients with acute lacunar infarction between January 2012 and June 2014. RLS was identified and evaluated based on the International RLS Rating Scale (IRLS-RS). Individual sleep quality was assessed using the Epworth Sleepiness Scale (ESS). Psychological state was also assessed using the Hamilton Depression Scale (HDS) and the Hamilton Anxiety Scale (HAS).

RESULTS

The incidence of RLS in patients with lacunar infarction was 5.33%. Our participant group consisted of nine males and four females. Three patients had symptoms in bilateral limbs, and 10 patients had symptoms only contralateral to the cerebral infarction. The infarctions were localized to the pons, centrum semiovale, thalamus, putamen, medulla, and occipital lobe. Contralateral paralysis was found in 13 patients, and contralateral sensory deficit in seven patients. The average IRLS-RS, ESS, HDS, HAS scores were 19.07 ± 8.70, 4.69 ± 5.82, 4.38 ± 4.68, and 3.85 ± 4.76, respectively. Nine patients had diabetes mellitus. After administration of dopaminergic drugs, patients' RLS significantly improved.

CONCLUSIONS

The incidence of RLS after acute lacunar infarction was 5.33%. Pons, centrum semiovale, and basal ganglia were the common locations of responsible lesions. Compared to idiopathic RLS, symptoms of RLS after acute lacunar infarction appeared more unilateral and more likely involved the arm. Moreover, diabetes mellitus may be a risk factor for RLS in stroke patients.

Pharmacological insights into impulsive-compulsive spectrum disorders associated with dopaminergic therapy

Impulsive-compulsive spectrum disorders are associated with dopamine agonist therapy in some patients. These untoward outcomes occur with direct-acting, full and partial agonists at D2 dopamine family receptors. The disorders typically emerge during chronic treatment, and exhibit common features that are independent of the neurological or psychiatric pathology for which the initial therapy was indicated. It is well-documented that the brain is 'plastic', changing in response to alterations to internal factors (e.g., disease processes), as well as external factors (e.g., therapies). The complexities of these clinical scenarios have eluded a clear depiction of the neurobiology for impulsive-compulsive spectrum disorders and engendered considerable debate regarding the mechanistic underpinnings of the disorders. In this opinion, we use pharmacological concepts related to homeostatic compensation subsequent to chronic receptor activation to provide a unifying construct. This construct helps explain the occurrence of impulsive-compulsive spectrum disorders across disease states, and during therapy with full and partial agonists.

Neuroimaging of Sleep Disturbances in Movement Disorders

Sleep dysfunction is recognized as a distinct clinical manifestation in movement disorders, often reported early on in the disease course. Excessive daytime sleepiness, rapid eye movement sleep behavior disorder and restless leg syndrome, amidst several others, are common sleep disturbances that often result in significant morbidity. In this article, we review the spectrum of sleep abnormalities across atypical Parkinsonian disorders including multiple system atrophy (MSA), progressive supranuclear palsy (PSP) and corticobasal syndrome (CBS), as well as Parkinson's disease (PD) and Huntington's disease (HD). We also explore the current concepts on the neurobiological underpinnings of sleep disorders, including the role of dopaminergic and non-dopaminergic pathways, by evaluating the molecular, structural and functional neuroimaging evidence based on several novel techniques including magnetic resonance imaging (MRI), functional magnetic resonance imaging (fMRI), diffusion tensor imaging (DTI), single-photon emission computed tomography (SPECT) and positron emission tomography (PET). Based on the current state of research, we suggest that neuroimaging is an invaluable tool for assessing structural and functional correlates of sleep disturbances, harboring the ability to shed light on the sleep problems attached to the limited treatment options available today. As our understanding of the pathophysiology of sleep and wake disruption heightens, novel therapeutic approaches are certain to transpire.

Deep brain stimulation improves restless legs syndrome in patients with Parkinson disease

OBJECTIVE

To study the effect of subthalamic nucleus (STN) deep brain stimulation (DBS) in patients with Parkinson disease (PD) and moderate to severe restless legs syndrome (RLS) on their RLS symptoms.

METHODS

Patients undergoing STN DBS surgery for PD completed the International RLS Study Group Rating Scale (IRLS) and RLS Quality of Life (QoL) questionnaires preoperatively and postoperatively at 6 months, 1 year, and 2 years. The primary outcome measure was IRLS sum score and subscales (severity and impact) and the secondary measure was RLS QoL scores. Differences among the mean scores over time were analyzed using mixed model regression.

RESULTS

Twenty-two patients were enrolled. The preoperative IRLS sum scores were 19.59 ± 6.95, severity subscale 12.91 ± 4.33, impact subscale 4.45 ± 2.72, and transformed RLS QoL score 68.30 ± 20.26. The differences between preoperative and averaged postoperative scores were IRLS sum score -7.80, severity subscale -5.50, impact subscale -1.20, and RLS QoL 4.73. The overall F tests demonstrated differences among the times for the means of the IRLS sum and subscales: p < 0.05. There were no correlations between RLS symptoms improvement and PD motor symptoms improvement or reduction in PD medications. Half of the patients had at least 50% improvement and 27% had resolution of their RLS symptoms (IRLS = 0).

CONCLUSIONS

STN DBS significantly decreased RLS symptoms in patients with PD despite a decrease in dopaminergic treatment. This improvement was sustained over a 2-year period.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that for patients with PD and moderate to severe RLS, STN DBS improves RLS symptoms.

New Insights into the Neurobiology of Restless Legs Syndrome

Restless legs syndrome (RLS) is a common sensorimotor disorder, whose basic components include a sensory experience, akathisia, and a sleep-related motor sign, periodic leg movements during sleep (PLMS), both associated with an enhancement of the individual's arousal state. The present review attempts to integrate the major clinical and experimental neurobiological findings into a heuristic pathogenetic model. The model also integrates the recent findings on RLS genetics indicating that RLS has aspects of a genetically moderated neurodevelopmental disorder involving mainly the cortico-striatal-thalamic-cortical circuits. Brain iron deficiency (BID) remains the key initial pathobiological factor and relates to alterations of iron acquisition by the brain, also moderated by genetic factors. Experimental evidence indicates that BID leads to a hyperdopaminergic and hyperglutamatergic states that determine the dysfunction of cortico-striatal-thalamic-cortical circuits in genetically vulnerable individuals. However, the enhanced arousal mechanisms critical to RLS are better explained by functional changes of the ascending arousal systems. Recent experimental and clinical studies suggest that a BID-induced hypoadenosinergic state provides the link for a putative unified pathophysiological mechanism for sensorimotor signs of RLS and the enhanced arousal state.

Restless Legs Syndrome and Parkinson Disease: A Causal Relationship Between the Two Disorders?

Restless Legs Syndrome/Willis-Ekbom Disease (RLS/WED) is a common sleep related movement disorder that can be idiopathic or occurs in comorbidity with other medical conditions such as polyneuropathy, iron deficiency anemia, multiple sclerosis, hypertension and cardiovascular diseases. In recent years, a growing body of literature investigated the association between RLS/WED and Parkinson's Disease (PD). Several questions regarding the comorbidity between these two disorders are still unanswered. If the insurgence of RLS/WED may precede the onset of PD, or if RLS/WED could represent a secondary condition of PD and if impaired dopaminergic pathway may represent a bridge between these two conditions are still debatable issues. In this review, we critically discuss the relationship between RLS/WED and PD by reviewing cross sectional and longitudinal studies, as well as the role of dopamine in these disorders. A twofold interpretation have to be taken into account: dopaminergic therapy may have a crucial role in the development of RLS/WED in PD patients or RLS/WED can be conceived as an early manifestation of PD rather than a risk factor. Several studies showed a high prevalence of RLS/WED in PD patients and several findings related to dopaminergic and iron alterations in both disorders, however up to now it is difficult to find a point of agreement between studies. A greater number of systematic and strongly controlled longitudinal studies as well as basic pathophysiological investigations particularly in RLS/WED are needed to clarify this complex relationship.

Restless legs syndrome: a rarity in the Nigerian pregnant population?

OBJECTIVES

The prevalence of RLS in pregnancy is higher when compared with the general population however it remains unknown among indigenous black Africans. Available data indicate that RLS is uncommon in sub-Saharan Africa. We embarked on this study to determine the prevalence and characteristics of RLS in an antenatal clinic sample of Nigerian pregnant women compared with a primary care sample of non-pregnant women.

METHODS

A total of 310 pregnant women and non-pregnant women filled out a questionnaire which incorporated the 2014 minimal criteria of the International Restless Legs Syndrome Study Group. Demographic and clinical data, including sleep duration and samples for blood hemoglobin concentration and urinalysis were obtained.

RESULTS

The mean ages of the pregnant and non-pregnant women were 24.9 ± 5.6 years and 23.6 + 5.4 years, respectively (p = 0.003). There was no case of RLS found among pregnant women while five (1.6%) of the non-pregnant women fulfilled the criteria for RLS. Overall, the prevalence report of RLS symptoms was associated with lower mean habitual nocturnal sleep duration (p < 0.05) coffee (p = 0.013) and kola nut (0.023) consumption, report of leg cramps (p < 0.001) and proteinuria (p = 0.047), Report of leg cramps and proteinuria were independently associated with RLS.

CONCLUSION

The prevalence of restless legs syndrome is low among women of child-bearing age in the Nigerian population and may be lower in pregnancy. Report of leg cramps and proteinuria are independently associated with RLS.

Reflection impulsivity perceptual decision-making in patients with restless legs syndrome

Objectives

The objective of this study was to investigate perceptual decision‐making and reflection impulsivity in drug naïve patients with restless legs syndrome (RLS) and patients with dopaminergic therapy.

Methods

A total of 35 RLS patients (20 who were drug naïve regarding dopaminergic medication and 15 patients treated with dopaminergic therapy without augmentation or impulse control disorders) were included in this study. We used the Beads task and the Pixel task which assess reflection impulsivity and perceptual decision‐making, respectively. Results were compared to 20 healthy controls.

Results

Both RLS patient groups gathered less evidence than healthy controls in the Beads task before making a decision (P < 0.001), but patients with dopaminergic treatment gathered less information than drug naïve patients (P = 0.026). Moreover, both patient groups made more choices against the evidence than healthy controls (both P < 0.01), but there was no difference between the two patient groups. In the Pixel task, we found an effect of task difficulty on reaction times with patients and controls responding faster with reduced task difficulty. There was neither an effect of group on reaction times nor an effect of group on error rates.

Conclusions

Reflection impulsivity is common in RLS patients, regardless whether they are drug naïve or treated with dopaminergic therapy. Thus, RLS patients tend to gather less information compared to healthy controls which could have a negative effect on decision‐making in daily life and should be investigated further.

Motor hyperactivity of the iron-deficient rat - an animal model of restless legs syndrome

Background

Abnormal striatal dopamine transmission has been hypothesized to cause restless legs syndrome. Dopaminergic drugs are commonly used to treat restless legs syndrome. However, they cause adverse effects with long‐term use. An animal model would allow the systematic testing of potential therapeutic drugs. A high prevalence of restless legs syndrome has been reported in iron‐deficient anemic patients. We hypothesized that the iron‐deficient animal would exhibit signs similar to those in restless legs syndrome patients.

Methods

After baseline polysomnographic recordings, iron‐deficient rats received pramipexole injection. Then, iron‐deficient rats were fed a standard rodent diet, and polysomnographic recording were performed for 2 days each week for 4 weeks.

Results

Iron‐deficient rats have low hematocrit levels and show signs of restless legs syndrome: sleep fragmentation and periodic leg movements in wake and in slow‐wave sleep. Iron‐deficient rats had a positive response to pramipexole treatment. After the iron‐deficient rats were fed the standard rodent diet, hematocrit returned to normal levels, and sleep quality improved, with increased average duration of wake and slow‐wave sleep episodes. Periodic leg movements decreased during both waking and sleep. Hematocrit levels positively correlated with the average duration of episodes in wake and in slow‐wave sleep and negatively correlated with periodic leg movements in wake and in sleep. Western blot analysis showed that striatal dopamine transporter levels were higher in iron‐deficient rats.

Conclusions

The iron‐deficient rat is a useful animal model of iron‐deficient anemic restless legs syndrome. © 2017 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society

Imaging the Nonmotor Symptoms in Parkinson's Disease

Parkinson's disease is acknowledged to be a multisystem syndrome, manifesting as a result of multineuropeptide dysfunction, including dopaminergic, cholinergic, serotonergic, and noradrenergic deficits. This multisystem disorder ultimately leads to the presentation of a range of nonmotor symptoms, now appreciated to be an integral part of the disease-specific spectrum of symptoms, often preceding the diagnosis of motor Parkinson's disease. In this chapter, we review the dopaminergic and nondopaminergic basis of these symptoms by exploring the neuroimaging evidence based on several techniques including positron emission tomography, single-photon emission computed tomography molecular imaging, magnetic resonance imaging, functional magnetic resonance imaging, and diffusion tensor imaging. We discuss the role of these neuroimaging techniques in elucidating the underlying pathophysiology of NMS in Parkinson's disease.