Postmortem and imaging based analyses reveal CNS decreased myelination in restless legs syndrome

From brain to spinal cord: neuromodulation by direct current stimulation and its promising effects as a treatment option for restless legs syndrome

Neuromodulation is a fast-growing field of mostly non-invasive therapies, which includes spinal cord stimulation (SCS), transcranial direct current stimulation (tDCS), vagal nerve stimulation (VNS), peripheral nerve stimulation, transcranial magnetic stimulation (TMS) and transcutaneous spinal direct current stimulation (tsDCS). This narrative review offers an overview of the therapy options, especially of tDCS and tsDCS for chronic pain and spinal cord injury. Finally, we discuss the potential of tsDCS in Restless Legs Syndrome as a promising non-invasive, alternative therapy to medication therapy.

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.

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.

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.

Impact of chronic sleep deprivation and sleep recovery on hippocampal oligodendrocytes, anxiety-like behavior, spatial learning and memory of rats

Sleep and its quality play an important role in memory, cognition, and quality of life. Sleep deprivation-induced changes in hippocampal neurons and behavior have been studied widely, in contrast, the extent of damage to oligodendrocytes have not been fully understood. The present study aims to investigate chronic sleep deprivation (CSD) and sleep recovery-induced changes in oligodendrocytes of the hippocampus, cognition, and behavior of rats. Male Sprague-Dawley rats (n = 48) were grouped as control, sham control (SC), CSD, and CSD+sleep recovery (CSD+SR) (n = 12/group). CSD and CSD+SR group rats were sleep deprived for 21-days. After CSD, the CSD+SR group rats sleep recovered for 21-days. Oxidative markers, CNPase+ve oligodendrocytes, CNPase intensity, and CNPase gene expression were measured in the hippocampus, and the anxiety-like behavior, spatial learning, and memory were assessed. The 21-days of CSD significantly (p < 0.001) increased oxidative stress and significantly (p < 0.001) reduced the number of CNPase+ve oligodendrocytes, CNPase intensity, and CNPase gene expression when compared to controls. The increased oxidative stress was correlated with reduced CNPase+ve oligodendrocytes, CNPase intensity, and CNPase gene expression (r = -0.9). In-line with cellular changes, an increased (p < 0.01) anxiety-like behavior and impaired spatial memory were observed in the CSD group compared to controls. The 21-days of sleep recovery significantly (p < 0.01) reduced oxidative stress and anxiety-like behavior, improved spatial memory, increased CNPase intensity and CNPase gene expression, and non-significant (p > 0.05) increase in CNPase+ve oligodendrocytes compared to CSD. Overall, the 21-days of CSD reduced the number of CNPase+ve oligodendrocytes in the hippocampus, increased anxiety, and impaired spatial memory in rats. Though the 21-day sleep recovery showed an improvement in all parameters, it was not sufficient to completely reverse the CSD-induced changes to the control level.

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.

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.

Voxel-wise lesion mapping of restless legs syndrome in multiple sclerosis

Objective

Restless legs syndrome (RLS) is known to be associated with multiple sclerosis (MS) and may be caused by MS lesions in specific cerebral brain regions. Applying a voxel-wise lesion analysis, we tried to identify the contribution of cerebral MS lesions to RLS.

Methods

In this retrospective study, we established a cohort of people with MS with documented RLS and controls of people with MS without RLS matched disease severity. Diagnosis of MS and RLS was based on the current guidelines. The MS lesions were analyzed on T2-weighted magnetic resonance imaging scans (1.5 or 3 T). After manual delineation, lesion maps were converted into stereotaxic space. We generated a lesion overlap and performed a Liebermeister test with 4000 permutations to compare the absence or presence of RLS voxel-wise between patients with and without lesions in a given voxel.

Results

Forty of the patients with RLS and MS fulfilled the inclusion criteria. The voxel-wise analysis yielded associations between RLS and MS in the subcortex of the left gyrus precentralis.

Conclusion

Our voxel-wise analysis shows associations in the subcortex of the left gyrus precentralis. Thus, our data suggests that a dysfunction of the efferent motor system due to cerebral lesions may contribute to the pathophysiology of RLS in MS.

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: 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.

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.

Prevalence and correlates of restless legs syndrome in men living with HIV

Background

Data on the prevalence and correlates of restless legs syndrome (RLS) in people with HIV are limited. This study sought to determine the prevalence of RLS, associated clinical correlates, and characterize sleep-related differences in men with and without HIV.

Methods

Sleep-related data were collected in men who have sex with men participating in the Multicenter AIDS Cohort Study (MACS). Demographic, health behaviors, HIV status, comorbidities, and serological data were obtained from the MACS visit coinciding with sleep assessments. Participants completed questionnaires, home polysomnography, and wrist actigraphy. RLS status was determined with the Cambridge-Hopkins RLS questionnaire. RLS prevalence was compared in men with and without HIV. Multinomial logistic regression was used to examine correlates of RLS among all participants and men with HIV alone. Sleep-related differences were examined in men with and without HIV by RLS status.

Results

The sample consisted of 942 men (56% HIV+; mean age 57 years; 69% white). The prevalence of definite RLS was comparable in men with and without HIV (9.1% vs 8.7%). In multinomial regression, HIV status was not associated with RLS prevalence. However, white race, anemia, depression, and antidepressant use were each independently associated with RLS. HIV disease duration was also associated with RLS. Men with HIV and RLS reported poorer sleep quality, greater sleepiness, and had worse objective sleep efficiency/fragmentation than men without HIV/RLS.

Conclusions

The prevalence of RLS in men with and without HIV was similar. Screening for RLS may be considered among people with HIV with insomnia and with long-standing disease.

Restless arm syndrome: a rare disease?

Restless legs syndrome (RLS) is a common neurological disorder characterised by an irresistible urge to move the lower limbs, often accompanied by unpleasant sensations in the legs, typically occurring in the evening and at night and improving with movement. Restless arms syndrome (RAS) predominantly affects the arms, while the legs are rarely affected. RAS appears to be very rare, with very few cases described to date, but the diagnosis of RAS is probably made too infrequently, especially for milder and transient forms. The patient reported here even had severe symptoms for years that could have indicated RAS. He observed an immediate improvement in all RAS-related symptoms after administration of 100 mg L-dopa +25 mg benserazide, which continues to this day. Clinicians should always be alert for RLS-like symptoms in one or both arms that worsen at rest and improve with movement, thinking of possible RAS.

White matter tract-specific alterations in patients with primary restless legs syndrome

Prior diffusion tensor imaging (DTI) studies have investigated white matter (WM) changes in patients with primary restless legs syndrome (RLS), but the results were inconsistent. Here, we proposed using tract-specific statistical analysis (TSSA) to find alterations in specific WM tracts to clarify the pathophysiological mechanisms of RLS. We enrolled 30 patients with RLS and 31 age- and sex- matched controls who underwent brain magnetic resonance imaging, neuropsychological tests, and polysomnography. Fractional anisotropy (FA) maps obtained from whole-brain diffusion tensor imaging and TSSA were used to localize WM changes in patients with RLS. Subsequently, a comparison of FA values for each tract between patients and controls was performed. The associations between FA values and clinical, polysomnographic, and neuropsychological parameters in RLS patients were assessed. RLS patients demonstrated decreased FA values in the left corticospinal tract (CST) and cingulum, and in the right anterior thalamic radiation (ATR) and inferior fronto-occipital fasciculus (IFO). Patients’ attention/executive function and visual memory scores positively correlated with FA values in the right ATR, and anxiety levels negatively correlated with FA values in the right IFO. Additionally, the number of periodic leg movements and movement arousal index were negatively correlated with FA values in the left CST. The TSSA method identified previously unknown tract-specific alterations in patients with RLS and significant associations with distinct clinical manifestations of RLS.

Bidirectional association between irritable bowel syndrome and restless legs syndrome: a systematic review and meta-analysis

BACKGROUND

Several observational studies have shown that patients with irritable bowel syndrome (IBS) may have a high risk of restless legs syndrome (RLS). This systematic review and meta-analysis aimed to comprehensively investigate the bidirectional association between IBS and RLS.

METHODS

All conservational studies on IBS and RLS were searched in MEDLINE (assessed by PubMed), Embase, Web of Science, CINAHL, the Cochrane Library database and Google Scholar from inception to June 14, 2020. The Newcastle-Ottawa Scale and Agency for Healthcare Research and Quality were used to assess the methodological quality of the cohort and cross-sectional studies, respectively. The pooled odds ratio (OR) and 95% confidence interval (CI) were calculated using Reviewer Manager 5.3.

RESULT

A total of five cross-sectional studies of moderate methodological quality and one cohort study of high methodological quality were included in our review. Four cross-sectional studies and one cohort study involving 86 438 individuals met the criteria of IBS predicating the onset of RLS. Patients with IBS had a nearly three-fold increased odds of RLS compared with controls (OR = 2.60, 95%CI: 2.17-3.12, P < 0.00001; I² = 48%, P = 0.11). Three sensitivity analyses confirmed the robustness of the pooled result. Two cross-sectional studies involving 3581 individuals met the criteria of RLS predicating the onset of IBS. RLS patients had a nearly four-fold increased odds of IBS compared with controls without RLS (OR = 3.87, 95%CI: 1.73-8.66, P = 0.0010; I² = 77%, P = 0.04).

CONCLUSION

In this systematic review and meta-analysis, we found a substantial bidirectional association between IBS and RLS. More prospective, high-quality, population-based studies are warranted in the future.

Which Factors in Spinocerebellar Ataxia Type 3 Patients Are Associated with Restless Legs Syndrome/Willis-Ekbom Disease?

There is evidence of a higher prevalence of restless legs syndrome/Willis-Ekbom disease (RLS/WED) in individuals with spinocerebellar ataxia type 3 (SCA3), although the factors underlying this association remain unknown. The present study aimed to determine the prevalence of RLS/WED in SCA3 patients and to investigate which factors of SCA3 patients are associated with presence of RLS/WED. From February to August of 2006, we carried out clinical interviews in 40 controls and 40 SCA3 patients, diagnosed and followed up at Faculty of Medicine of Ribeirão Preto, University of São Paulo. Twenty-seven SCA3 patients were submitted to a detailed clinical protocol, electroneuromyography, blood work up, polysomnography (PSG), suggested immobilization test (SIT), and magnetic resonance image (MRI). RLS/WED was found in 27.5% of SCA3 patients and 2.5% of normal controls (p = 0.003). The factors related to RLS/WED in SCA3 patients were female gender, age at start of the symptoms of ataxia after 30 years, presence of peripheral neuropathy, and documented iron deficiency. Among SCA3 patients, those with RLS showed higher values of maximal discomfort level and discomfort level sum compared to non-RLS individuals on SIT. There is a relation between RLS/WED and SCA3, which seems to be resultant of different factors whose identification could improve the quality of assistance to those patients as well as to promote a better comprehension of the pathophysiology of both RLS/WED and SCA3.

Patterns of Gray Matter Volume Alterations in Hemodialysis Patients With and Without Restless Legs Syndrome: Evidence From a Voxel-Based Morphometry Study

PURPOSE

The purpose of this study was to investigate the differences of gray matter volume (GMV) alteration patterns between hemodialysis with restless legs syndrome (HD-RLS) and hemodialysis without restless legs syndrome (HD-nRLS) patients using voxel-based morphometry.

METHODS

Twenty-three HD-RLS patients, 27 HD-nRLS patients, and 27 age-, sex-, and education-matched healthy controls were included in this study. One-way analysis of covariance and post hoc analyses were used to assess differences in GMV, demographics, and clinical data among the 3 groups. Pearson correlation analysis was conducted between altered GMV in the HD-RLS group and clinical data.

RESULTS

Compared with HD-nRLS patients, HD-RLS patients showed decreased GMV in the left primary motor cortex (false discovery rate corrected, P < 0.05). Compared with the healthy controls, both HD subgroups (ie, those with and without RLS) exhibited consistent GMV changes, including decreased GMV in the bilateral anterior cingulate and paracingulate gyrus and left middle temporal gyrus (false discovery rate corrected, P < 0.05). The GMV values in the left precentral gyrus were negatively correlated with the RLS rating scores (r = 0.2138, P = 0.0263).

CONCLUSIONS

This abnormal decreased GMV in the sensorimotor cortex provides evidence for a sensory processing disorder in RLS that may be involved in the pathogenesis of RLS in HD patients.

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.

Sensorimotor white matter projections and disease severity in primary Restless Legs Syndrome/Willis-Ekbom disease: a multimodal DTI analysis

BACKGROUND

Restless Legs Syndrome, a potentially disabling sleep disorder, also known as Willis-Ekbom disease (RLS/WED), may be caused by loss of inhibitory modulation of descending central motor pathways, structural changes in the somatosensory cortex, abnormal connectivity between motor and sensory areas, as well as by subtle abnormalities in white matter micro-organization.

OBJECTIVE

To compare diffusion-tensor imaging (DTI) metrics in areas associated with sensory or motor function, as well as sensorimotor integration, between subjects with primary mild-to-severe RLS/WED and controls.

METHODS

DTI metrics were assessed in 38 subjects with RLS/WED (14 mild to moderate, 24 severe to very severe) and 24 healthy age-matched controls with whole-brain Tract Based Spatial Statistics (TBSS), Region-of-interest (ROI) and probabilistic tractography based analyses. The ROIs corresponded to the corticospinal tract (CST) at the level of the cerebral peduncle; the superior, middle and inferior cerebellar peduncles. Subgroup analyses were made according to the severity of RLS/WED symptoms. The corticospinal tract was evaluated with probabilistic tractography. We also explored associations between significant findings and severity of symptoms with the Spearman's correlation coefficient.

RESULTS

TBSS analysis revealed decreased axial diffusivity (AD) in the left posterior thalamic radiation in RLS/WED. In subjects with severe RLS/WED, AD was reduced in the left posterior corona radiata and this reduction was negatively correlated with severity of symptoms. ROI-based analysis showed that radial diffusivity (RD) was increased in the superior cerebellar peduncles of individuals with severe RLS/WED. Tractography did not show between-group or subgroup differences.

CONCLUSIONS

Our results are consistent with subtle white matter changes, prominently in RLS/WED subjects with more severe symptoms, in areas related to sensory or motor function, as well as to sensorimotor integration, compared to controls. These findings support the hypothesis, raised by prior pathophysiological studies, of defective integration within these networks.

Statistical shape analysis of corpus callosum in restless leg syndrome

OBJECTIVES

In this study we aimed to investigate corpus callosum shape differences between restless leg syndrome patients and healthy controls, and to determine whether disease severity and duration are indicators for corpus callosum deformation in RLS patients.

METHODS

This study was conducted using the magnetic resonance imaging scans of 33 restless leg syndrome patients and 33 control subjects. Landmarks were marked on the digital images and callosal landmark coordinate data were used to assess shape difference by performing Generalized Procrustes analysis. The shape deformation from controls to the patients was evaluated performing the Thin Plate Spline approach.

RESULTS

There was a statistically significant shape difference between the groups. Highest deformation was determined at the posterior midbody of the corpus callosum. Growth curve analyses showed that with the increase in disease duration and severity, the CC size decreased.

DISCUSSION

The present study demonstrated callosal shape differences in restless leg syndrome using a landmark-based geometric morphometric approach, considering the topographic distribution of corpus callosum for the first time.

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.

Frequency of iron deficiency anemia in pregnant and non-pregnant women suffering from restless legs syndrome

Objectives. Restless Legs Syndrome is a movement disorder characterized by unpleasant sensations in the legs described as a burning, tingling, etc. Symptoms become worse in the evening and are relieved by moving the limbs. The idiopathic form of the disease is associated with a lack of dopamine, and the secondary form is associated with iron deficiency anemia, pregnancy, and kidney disease. The aim of this study was to investigate the incidence of iron deficiency anemia in pregnant women and non-pregnant women suffering from RLS.Methods. The study was conducted on a sample of 231 pregnant women aged 18-50. The pregnant women were interviewed at the outpatient clinic of the Department of Gynaecology and Obstetrics. This study also included a control group of 231 age-compatible non-pregnant women. Women who met the international criteria for diagnosing the syndrome filled in a sociodemographic questionnaire.Results. A statistically significant association between the existence of iron deficiency anemia and RLS in the sample of the examined women was proven (p < 0.001). It was also shown that RLS is more frequent in a sample of anemic pregnant women than non-anemic pregnant women (p = 0.008).Conclusion. Iron deficiency anemia is related with RLS. Pregnant women with RLS are more likely to be anemic than pregnant women without RLS.

Iron-deficient diet induces distinct protein profile related to energy metabolism in the striatum and hippocampus of adult rats

Iron deficiency is a public health problem that affects all age groups. Its main consequence is anemia, but it can also affect cognitive functions. Although the negative effects of iron deficiency on cognitive function have been extensively described, the underlying mechanism has not been fully investigated. Thus, to gain an unbiased insight into the effects of iron deficiency (ID) on discrete brain regions, we performed a proteomic analysis of the striatum and hippocampus of adult rats subjected to an iron restricted (IR) diets for 30 days. We found that an IR diet caused major alterations in proteins related to glycolysis and lipid catabolism in the striatum. In the hippocampus, a larger portion of proteins related to oxidative phosphorylation and neurodegenerative diseases were altered. These alterations in the striatum and hippocampus occurred without a reduction in local iron levels, although there was a drastic reduction in liver iron and ferritin. Moreover, the IR group showed higher fasting glycaemia than the control group. These results suggest that brain iron content is preserved during acute iron deficiency, but the alterations of other systemic metabolites such as glucose may trigger distinct metabolic adaptations in each brain region. Abnormal energy metabolism precedes and persists in many neurological disorders. Thus, altered energy metabolism can be one of the mechanisms by which iron deficiency affects cognitive functions.

Brain regions associated with periodic leg movements during sleep in restless legs syndrome

The neural substrates related to periodic leg movements during sleep (PLMS) remain uncertain, and the specific brain regions involved in PLMS have not been evaluated. We investigated the brain regions associated with PLMS and their severity using the electroencephalographic (EEG) source localization method. Polysomnographic data, including electromyographic, electrocardiographic, and 19-channel EEG signals, of 15 patients with restless legs syndrome were analyzed. We first identified the source locations of delta-band (2–4 Hz) spectral power prior to the onset of PLMS using a standardized low-resolution brain electromagnetic tomography method. Next, correlation analysis was conducted between current densities and PLMS index. Delta power initially and most prominently increased before leg movement (LM) onset in the PLMS series. Sources of delta power at −4~−3 seconds were located in the right pericentral, bilateral dorsolateral prefrontal, and cingulate regions. PLMS index was correlated with current densities at the right inferior parietal, temporoparietal junction, and middle frontal regions. In conclusion, our results suggest that the brain regions activated before periodic LM onset or associated with their severity are the large-scale motor network and provide insight into the cortical contribution of PLMS pathomechanism.

Increased Gray Matter Density and Functional Connectivity of the Pons in Restless Legs Syndrome

BACKGROUND

Neurophysiological and radiological studies provide accumulating evidence for the involvement of the brainstem in the pathogenesis of restless legs syndrome (RLS). The analysis of the various subregions of the brainstem may help us better understand the pathophysiological mechanisms underlying the disorder. In this study, we investigated the structural and functional changes in the various subregions of the brainstem in RLS patients.

METHODS

The subregional changes in gray matter density and functional connectivity in the brainstem were analyzed in 20 drug-naive idiopathic RLS patients, as well as 18 normal control (NC) subjects for comparison. Correlation analyses and multivariate pattern analyses using linear support vector machine (SVM) were conducted.

RESULTS

We found significantly increased gray matter density in two clusters in the pons (designated pons_1 and pons_2) and in one cluster in the midbrain in RLS patients compared with NC subjects. Further functional connectivity analyses revealed significantly decreased functional connectivity between the midbrain and the right middle occipital gyrus, between pons_1 and the right orbital part of the superior frontal gyrus, and between pons_2 and the right parahippocampus in RLS compared with NC. Moreover, the functional connectivity between pons_2 and the right supplementary motor area (SMA) was significantly increased in RLS compared with NC. This change in RLS was marginally correlated with RS_RLS scores in the RLS patients. SVM-based classification showed an AUC of 0.955 using gray matter density of pons_2, and functional connectivity between pons_2 and SMA as features.

CONCLUSION

Collectively, our findings suggest that changes in gray matter density and functional connectivity in the pons may play a pathologic role in RLS. Furthermore, these abnormal changes in the pons might help to discriminate RLS from healthy subjects.

The role of BTBD9 in the cerebral cortex and the pathogenesis of restless legs syndrome

Restless legs syndrome (RLS) is a nocturnal neurological disorder affecting up to 10% of the population. It is characterized by an urge to move and uncomfortable sensations in the legs which can be relieved by movements. Mutations in BTBD9 may confer a higher risk of RLS. We developed Btbd9 knockout mice as an animal model. Functional alterations in the cerebral cortex, especially the sensorimotor cortex, have been found in RLS patients in several imaging studies. However, the role of cerebral cortex in the pathogenesis of RLS remains unclear. To explore this, we used in vivo manganese-enhanced MRI and found that the Btbd9 knockout mice had significantly increased neural activities in the primary somatosensory cortex (S1) and the rostral piriform cortex. Morphometry study revealed a decreased thickness in a part of S1 representing the hindlimb (S1HL) and M1. The electrophysiological recording showed Btbd9 knockout mice had enhanced short-term plasticity at the corticostriatal terminals to D1 medium spiny neurons (MSNs). Furthermore, we specifically knocked out Btbd9 in the cerebral cortex of mice (Btbd9 cKO). The Btbd9 cKO mice showed a rest-phase specific motor restlessness, decreased thermal sensation, and a thinner S1HL and M1. Both Btbd9 knockout and Btbd9 cKO exhibited motor deficits. Our results indicate that systematic BTBD9 deficiency leads to both functional and morphometrical changes of the cerebral cortex, and an alteration in the corticostriatal pathway to D1 MSNs. Loss of BTBD9 only in the cerebral cortex is sufficient to cause similar phenotypes as observed in the Btbd9 complete knockout mice.

Short-interval intracortical inhibition is decreased in restless legs syndrome across a range of severity

BACKGROUND

Decreased short-interval intracortical inhibition (SICI) to transcranial magnetic stimulation (TMS) of the primary motor cortex was described in subjects with restless legs syndrome/Willis-Ekbom disease (RLS/WED). It remained to be determined whether the magnitude of SICI decrease would be similar across levels of RLS/WED severity. Moreover, it was unknown whether, in addition to decreases in SICI, changes in cortical thickness or area could be detected in subjects with RLS/WED compared to controls. The objective of this study was to compare SICI, cortical thickness, and cortical area in subjects with idiopathic mild to moderate RLS/WED, severe to very severe RLS/WED, and controls.

METHODS

The severity of RLS/WED was assessed by the International Restless Legs Syndrome Severity Scale (IRLSS). SICI and 3T magnetic resonance imaging (MRI) data of subjects with RLS/WED and controls were compared. A receiver operating characteristic curve for SICI was designed for discrimination of participants with RLS/WED from controls. Cortical thickness and area were assessed by automated surface-based analysis.

RESULTS

SICI was significantly reduced in patients with mild to moderate and severe to very severe RLS/WED, compared to controls (one-way analysis of variance: F = 9.62, p < 0.001). Receiver operating characteristic curve analysis predicted RLS/WED when SICI was above 35% (area under the curve = 0.79, 95% CI 0.67-0.91, p < 0.001). Analyses of the whole brain and of regions of interest did not reveal differences in gray matter thickness or area between controls and subjects with RLS/WED.

CONCLUSION

SICI is an accurate cortical biomarker that can support the diagnosis of RLS/WED even in subjects with mild symptoms, but cortical thickness and area were not useful for discriminating subjects with this condition from controls.

Multimodal Magnetic Resonance Imaging reveals alterations of sensorimotor circuits in restless legs syndrome

Study Objectives

Integrated information on brain microstructural integrity and iron storage and its impact on the morphometric profile is not available in restless legs syndrome (RLS). We applied multimodal magnetic resonance imaging (MRI) including diffusion tensor imaging, the transverse relaxation rate (R2*), a marker for iron storage, as well as gray and white matter volume measures to characterize RLS-related MRI signal distribution patterns and to analyze their associations with clinical parameters.

Methods

Eighty-seven patients with RLS (mean age 51, range 20–72 years; disease duration, mean 13 years, range 1–46 years, of those untreated n = 30) and 87 healthy control subjects, individually matched for age and gender, were investigated with multimodal 3T MRI.

Results

Volume of the white matter compartment adjacent to the post- and precentral cortex and fractional anisotropy (FA) of the frontopontine tract were both significantly reduced in RLS compared to healthy controls, and these alterations were associated with disease duration (r = 0.25, p = 0.025 and r = 0.23, p = 0.037, respectively). Corresponding gray matter volume increases of the right primary motor cortex in RLS (p &lt; 0.001) were negatively correlated with the right FA signal of the frontopontine tract (r = −0.22; p &lt; 0.05). Iron content evaluated with R2* was reduced in the putamen as well as in temporal and occipital compartments of the RLS cohort compared to the control group (p &lt; 0.01).

Conclusions

Multimodal MRI identified progressing white matter decline of key somatosensory circuits that may underlie the perception of sensory leg discomfort. Increases of gray matter volume of the premotor cortex are likely to be a consequence of functional neuronal reorganization.

A study for the mechanism of sensory disorder in restless legs syndrome based on magnetoencephalography

In spite of the relatively high incidence rate, the etiology and pathogenesis of restless legs syndrome (RLS) are still unclear. Long-term drug treatments fail to achieve satisfying curative effects, which is reflected by rebound and augmentation of related symptoms. An electrophysiological endophenotype experiment was done to investigate the mechanism of somatosensory disorder among RLS patients. Together with 15 normal subjects as the control group, with comparable ages and genders to the RLS patients, 15 primitive RLS patients were scanned by Magnetoencephalography (MEG) under natural conditions; furthermore, the somatosensory evoked magnetic field (SEF) with single and paired stimuli, was also measured. Compared to the control group, the SEF intensities of RLS patients' lower limbs were higher, and the paired-pulse depression (PPD) for SEF in RLS patients was attenuated. It was also revealed by time-frequency analysis of somatosensory induced oscillation (SIO) in RLS patients, that 93.3% of somatosensory induced Alpha (8-12 Hz) oscillations were successfully elicited, while 0% somatosensory induced Gamma (30-55 Hz) oscillations were elicited; which was significantly different from the control group. Additionally, in RLS patients exhibit increased excitability of the sensorimotor cortex, a remarkable abnormality existing in early somatosensory gating control (GC) and an attenuated inhibitory interneuron network, which consequently results in a compensatory mechanism through which RLS patients increase their attention-driven lower limb sensory gating control via somatosensory-induced Alpha (8-12 Hz) oscillation. This hyperexcitability, partially due to an electrocortical disinhibition, may have an important therapeutical implication, and become an important target of neuromodulatory interventions.

Genetic variation in 117 myelination-related genes in schizophrenia: Replication of association to lipid biosynthesis genes

Schizophrenia is a serious psychotic disorder with high heritability. Several common genetic variants, rare copy number variants and ultra-rare gene-disrupting mutations have been linked to disease susceptibility, but there is still a large gap between the estimated and explained heritability. Since several studies have indicated brain myelination abnormalities in schizophrenia, we aimed to examine whether variants in myelination-related genes could be associated with risk for schizophrenia. We established a set of 117 myelination genes by database searches and manual curation. We used a combination of GWAS (SCZ_N = 35,476; CTRL_N = 46,839), exome chip (SCZ_N = 269; CTRL_N = 336) and exome sequencing data (SCZ_N = 2,527; CTRL_N = 2,536) from schizophrenia cases and healthy controls to examine common and rare variants. We found that a subset of lipid-related genes was nominally associated with schizophrenia (p = 0.037), but this signal did not survive multiple testing correction (FWER = 0.16) and was mainly driven by the SREBF1 and SREBF2 genes that have already been linked to schizophrenia. Further analysis demonstrated that the lowest nominal p-values were p = 0.0018 for a single common variant (rs8539) and p = 0.012 for burden of rare variants (LRP1 gene), but none of them survived multiple testing correction. Our findings suggest that variation in myelination-related genes is not a major risk factor for schizophrenia.

Involvement of the central somatosensory system in restless legs syndrome

Objective

To investigate morphologic changes in the somatosensory cortex and the thickness of the corpus callosum subdivisions that provide interhemispheric connections between the 2 somatosensory cortical areas.

Methods

Twenty-eight patients with severe restless legs syndrome (RLS) symptoms and 51 age-matched healthy controls were examined with high-resolution MRI at 3.0 tesla. The vertex-wise analysis in conjunction with a novel cortical surface classification method was performed to assess the cortical thickness across the whole-brain structures. In addition, the thickness of the midbody of the corpus callosum that links postcentral gyri in the 2 hemispheres was measured.

Results

We demonstrated that a morphologic change occurred in the brain somatosensory system in patients with RLS compared to controls. Patients with RLS exhibited a 7.5% decrease in average cortical thickness in the bilateral postcentral gyrus (p < 0.0001). Accordingly, there was a substantial decrease in the corpus callosum posterior midbody (p < 0.008) wherein the callosal fibers are connected to the postcentral gyrus, suggesting altered white matter properties in the somatosensory pathway.

Conclusion

Our results provide in vivo evidence of morphologic changes in the primary somatosensory system, which could be responsible for the sensory functional symptoms of RLS. These results provide a better understanding of the pathophysiology underlying the RLS sensory symptoms and could lead to a potential imaging marker for RLS.

Iron, dopamine, genetics, and hormones in the pathophysiology of restless legs syndrome

Restless legs syndrome (RLS) is a common, chronic neurologic condition, which causes a persistent urge to move the legs in the evening that interferes with sleep. Human and animal studies have been used to study the pathophysiologic state of RLS and much has been learned about the iron and dopamine systems in relation to RLS. Human neuropathologic and imaging studies have consistently shown decreased iron in different brain regions including substantia nigra and thalamus. These same areas also demonstrate a state of relative dopamine excess. While it is not known how these changes in dopamine or iron produce the symptoms of RLS, genetic and hormone studies of RLS have identified other biologic systems or genes, such as the endogenous opioid and melanocortin systems and BTBD9 and MEIS1, that may explain some of the iron or dopamine changes in relation to RLS. This manuscript will review what is known about the pathophysiology of RLS, especially as it relates to changes in iron, dopamine, genetics, and hormonal systems.

Brain imaging and networks in restless legs syndrome

Several studies provide information useful to our understanding of restless legs syndrome (RLS), using various imaging techniques to investigate different aspects putatively involved in the pathophysiology of RLS, although there are discrepancies between these findings. The majority of magnetic resonance imaging (MRI) studies using iron-sensitive sequences supports the presence of a diffuse, but regionally variable low brain-iron content, mainly at the level of the substantia nigra, but there is increasing evidence of reduced iron levels in the thalamus. Positron emission tomography (PET) and single positron emission computed tomography (SPECT) findings mainly support dysfunction of dopaminergic pathways involving not only the nigrostriatal but also mesolimbic pathways. None or variable brain structural or microstructural abnormalities have been reported in RLS patients; reports are slightly more consistent concerning levels of white matter. Most of the reported changes were in regions belonging to sensorimotor and limbic/nociceptive networks. Functional MRI studies have demonstrated activation or connectivity changes in the same networks. The thalamus, which includes different sensorimotor and limbic/nociceptive networks, appears to have lower iron content, metabolic abnormalities, dopaminergic dysfunction, and changes in activation and functional connectivity. Summarizing these findings, the primary change could be the reduction of brain iron content, which leads to dysfunction of mesolimbic and nigrostriatal dopaminergic pathways, and in turn to a dysregulation of limbic and sensorimotor networks. Future studies in RLS should evaluate the actual causal relationship among these findings, better investigate the role of neurotransmitters other than dopamine, focus on brain networks by connectivity analysis, and test the reversibility of the different imaging findings following therapy.

Restless Legs Syndrome: Current Concepts about Disease Pathophysiology

Background

In the past few decades, much has been learned about the pathophysiology of restless legs syndrome (RLS). Investigators have studied neuropathology, imaging, electrophysiology, and genetics of RLS, identifying brain regions and biological systems affected in RLS. This manuscript will review RLS pathophysiology literature, examining the RLS state through consideration of the neuroanatomy, then the biological, organ, and genetic systems.

Methods

Pubmed (1966 to April 2016) was searched for the term “restless legs syndrome” cross-referenced with “pathophysiology,” “pathogenesis,” “pathology,” or “imaging.” English language papers were reviewed. Studies that focused on RLS in relation to another disease were not reviewed.

Results

Although there are no gross structural brain abnormalities in RLS, widespread brain areas are activated, including the pre- and post-central gyri, cingulate cortex, thalamus, and cerebellum. Pathologically, the most consistent finding is striatal iron deficiency in RLS patients. A host of other biological systems are also altered in RLS, including the dopaminergic, oxygen-sensing, opioid, glutamatergic, and serotonergic systems. Polymorphisms in genes including BTBD9 and MEIS1 are associated with RLS.

Discussion

RLS is a neurologic sensorimotor disorder that involves pathology, most notably iron deficiency, in motor and sensory brain areas. Brain areas not subserving movement or sensation such as the cingulate cortex and cerebellum are also involved. Other biological systems including the dopaminergic, oxygen-sensing, opioid, glutamatergic, and serotonergic systems are involved. Further research is needed to determine which of these anatomic locations or biological systems are affected primarily, and which are affected in a secondary response.

Microstructure of the Midbrain and Cervical Spinal Cord in Idiopathic Restless Legs Syndrome: A Diffusion Tensor Imaging Study

STUDY OBJECTIVES

Diffusion tensor imaging (DTI) allows the study of white matter microstructure in the central nervous system. The aim of this study was to examine the DTI metrics of the cervical spinal cord and the brainstem up to the midbrain in patients with idiopathic restless legs (RLS) compared to matched healthy controls.

METHODS

DTI analysis of the cervical spinal cord and the brainstem up into the midbrain was performed in 25 patients with idiopathic RLS and 25 matched healthy controls. Data analysis in the brain was performed by voxelwise comparison of fractional anisotropy (FA) maps at group level. Cervical spinal cord data analysis was performed by slicewise analysis of averaged FA values in axial slices along the spinal cord.

RESULTS

Voxelwise comparison of FA maps in the brainstem showed significant microstructural alterations in two clusters in the midbrain bilaterally. Slicewise comparison of the FA maps in the cervical spinal cord showed a trend for lower FA values at the level of the second and third vertebra area in the patient sample.

CONCLUSIONS

The imaging data suggest that significant alterations in the midbrain in RLS can be visualized by DTI and might correlate to a macroscopically subtle process with changes of the tissue microstructure in the corresponding tracts. An additional area of interest is regionally clustered in the upper cervical spinal cord with a tendency toward altered diffusion metrics. These results might be addressed by further studies, e.g., at higher magnetic field strengths.

A comparison of MRI tissue relaxometry and ROI methods used to determine regional brain iron concentrations in restless legs syndrome

Purpose

Magnetic resonance imaging relaxometry studies differed on the relaxometry methods and their approaches to determining the regions of interest (ROIs) in restless legs syndrome (RLS) patients. These differences could account for the variable and inconsistent results found across these studies. The aim of this study was to assess the relationship between the different relaxometry methods and different ROI approaches using each of these methods on a single population of controls and RLS subjects.

Methods

A 3.0-T magnetic resonance imaging with the gradient-echo sampling of free induction decay and echo pulse sequence was used. The regional brain “iron concentrations” were determined using three relaxometry metrics (R2, R2*, and R2′) through two different ROI methods. The substantia nigra (SN) was the primary ROI with red nucleus, caudate, putamen, and globus pallidus as the secondary ROIs.

Results

Thirty-seven RLS patients and 40 controls were enrolled. The iron concentration as determined by R2 did not correlate with either of the other two methods, while R2* and R2′ showed strong correlations, particularly for the substantia nigra and red nucleus. In the fixed-shape ROI method, the RLS group showed a lower iron index compared to the control group in the substantia nigra and several other regions. With the semi-automated ROI method, however, only the red nucleus showed a significant difference between the two groups.

Conclusion

Both the relaxometry and ROI determination methods significantly influenced the outcome of studies that used these methods to estimate regional brain iron concentrations.

Restless Leg Syndrome/Willis-Ekbom Disease Pathophysiology

Restless leg syndrome/Willis-Ekbom disease has brain iron deficiency that produces excessive dopamine and known genetic risks, some of which contribute to the brain iron deficiency. Dopamine treatments work temporarily but may eventually produce further postsynaptic down-regulation and worse restless leg syndrome. This article includes sections focused on pathophysiologic findings from each of these areas: genetics, cortical-spinal excitability, and iron and dopamine.

Neuroimaging in Restless Legs Syndrome

Neuroimaging studies are of crucial relevance in defining the pathophysiology of restless legs syndrome (RLS). MRI studies showed no structural brain lesions and confirmed a central iron deficiency. Structural and functional studies showed an involvement of the thalamus, sensorimotor cortical areas, and cerebellum in RLS and assessed neurotransmission abnormalities in the dopaminergic and opiate systems. Finally, glutamatergic hyperactivity has been proposed as a cause of disrupted and shortened sleep in RLS. Differences among the results of the studies make it difficult to draw any definitive conclusions, thus, suggesting the need for future research.

Restless legs syndrome: clinical presentation diagnosis and treatment

Restless legs syndrome (RLS) is a circadian disorder of sensory-motor integration that may be related to genetically determined dysregulation of iron transport across the blood-brain barrier. Dopamine agonists (DAs) have been considered the first-line therapy, but with the growing appreciation of problems associated with long-term treatment, particularly augmentation and impulse control disorder, alpha-2-delta drugs, such as gabapentin, are now considered the first line of treatment in patients with troublesome RLS. Opioids can be considered as an alternative therapy, particularly in patients with DA-related augmentation. In more severe cases, a combination therapy may be required. Intravenous iron therapy may be considered on those patients with refractory RLS.

Sleep and oligodendrocyte functions

Transcriptomic studies have revealed that the brains of sleeping and awake animals differ significantly at the molecular level, with hundreds of brain transcripts changing their expression across behavioral states. However, it was unclear how sleep affects specific cells types, such as oligodendrocytes, which make myelin in the healthy brain and in response to injury. In this review, I summarize the recent findings showing that several genes expressed at higher levels during sleep are involved in the synthesis/maintenance of all membranes and of myelin in particular. In addition, I will discuss the effect of sleep and wake on oligodendrocyte precursor cells (OPCs), providing a working hypothesis on the function of REM sleep and acetylcholine in OPC proliferation.

Gray matter alteration in patients with restless legs syndrome: a voxel-based morphometry study

The purpose of this study was to demonstrate whether or not restless legs syndrome (RLS) is associated with any morphological change in gray matter. Forty-six RLS subjects and 46 controls were enrolled. We performed voxel-based morphometry analysis and compared the results of the two groups. The RLS subjects showed significant regional decreases of gray matter volume in the left hippocampal gyrus, both parietal lobes, medial frontal areas and cerebellum (uncorrected, P<.001). We found that RLS patients showed structural alteration in the brain and alterations in certain parts of the brain in RLS patients are relevant to RLS.