Gray matter alterations in restless legs syndrome: A coordinate-based meta-analysis

BACKGROUND

Voxel-based morphometry (VBM) is an objective structural magnetic resonance imaging (MRI) technique which allows researchers to investigate group-level differences in regional gray matter (GM) volume or density over the whole brain. In the last decade, VBM studies in restless leg syndrome (RLS) have exhibited inconsistent and conflicting findings.

METHODS

Studies will be identified through a computerized literature search of the following databases: PubMed, Web of Science, and Embase until October 1, 2018 and updated on March 1, 2020. This protocol will be performed in accordance with the Preferred Reporting Items for Systematic review and Meta-Analysis Protocols (PRISMA-P). In addition, we will follow the recent guidelines and recommendations for coordinate-based meta-analysis (CBMA). This CBMA will be performed with the seed-based d mapping with permutation of subject images (SDM-PSI) software.

RESULTS

This CBMA will offer the latest evidence of GM alterations in RLS.

CONCLUSIONS

To our knowledge, this will be the first CBMA that pooled VBM findings in RLS. This quantitative evidence of GM alterations will characterize brain morphometry of RLS.

PROSPERO REGISTRATION NUMBER

CRD42018117014.

[Restless legs syndrome in ischemic stroke patients: clinical features and significance]

OBJECTIVE

To investigate the clinical features and implication of restless legs syndrome (RLS) in ischemic stroke patients.

METHODS

A total of 199 ischemic stroke patients were enrolled and assessed by polysomnography (PSG). RLS was identified according to criteria of International Restless Legs Syndrome Study Group. Epworth Sleepiness Scale (ESS), Mini-mental State Examination (MMSE) and Patient Health Questionnaire (PHQ-9) were used to evaluate the sleep quality, cognitive function and post-stroke depression, respectively. The National Institute of Health Stroke Scale (NIHSS) was used to evaluate the neurological function 3 months after stroke onset. Gender-and age-matched non-ischemic stroke patients with RLS (primary PLS) were selected as controls.

RESULTS

Twenty-two cases of RLS were identified among 199 ischemic stroke patients (11.1%). Generalized linear model and logistic regression showed that low serum ferritin level (β=-133.3 mg/L, 95%CI:-200.4--0.1, P<0.01), subcortical infarction (OR=4.05, 95%CI:1.15-14.18, P<0.05) and female (OR=2.54, 95%CI:1.04-6.23, P<0.05) were identified as the risk factors of RLS in ischemic stroke patients. Compared with ischemic stroke patients without RLS, ESS increased by 4.37 (95%CI:2.33-6.41, P<0.01), PHQ-9 increased by 2.17 (95%CI:0.39--3.94, P<0.05), and reduced NIHSS from the baseline deceased by 0.97 (95%CI:-1.79--0.15, P<0.05) in ischemic stroke patients with RLS. In addition, the incidence of moderate-severe depression increased (OR=4.27, 95%CI:1.40-13.10, P<0.05) in ischemic stroke patients with RLS. The index of periodic leg movements of sleep (PLMS) with arousal in ischemic stroke patients with RLS was significantly higher than that in patients with primary RLS (β=12.85, 95%CI:2.04-23.67, P<0.05).

CONCLUSIONS

RLS is common in ischemic stroke patients and has adverse influences on patients.

Is There an Association between Restless Legs Syndrome and Urticaria?

Restless legs syndrome (RLS) is a disease characterized by the urge to move the legs and sleep disturbances. Similarly, chronic spontaneous urticaria (CSU) is a dermatological disease characterized by pruritus and sleep disorders. In this study, we aimed to determine the prevalence and severity of RLS in patients with chronic spontaneous urticaria (CSU) and to compare the quality of sleep of patients with and without RLS in the CSU group using the Pittsburgh Sleep Quality Index. A total of 130 patients with CSU and 100 healthy controls were included in this study. The frequency of RLS, frequency of sleep disturbances, and average score of RLS in patients with CSU were statistically significantly higher than control groups (respectively P = 0.008, P = 0.009, P = 0.004). Subjective sleep quality, sleep latency and habitual sleep efficiency scores in patients with RLS were statistically significantly higher than patients without RLS (respectively P = 0.016, P = 0.007, P = 0.035). We claimed that pruritus of urticaria may decrease the quality of sleep in patients with RLS and it may trigger and worsen the restless legs syndrome. Furthermore, RLS and CSU may share a common etiology.

DTI and VBM reveal white matter changes without associated gray matter changes in patients with idiopathic restless legs syndrome

BACKGROUND AND PURPOSE

We evaluated cerebral white and gray matter changes in patients with iRLS in order to shed light on the pathophysiology of this disease.

METHODS

Twelve patients with iRLS were compared to 12 age- and sex-matched controls using whole-head diffusion tensor imaging (DTI) and voxel-based morphometry (VBM) techniques. Evaluation of the DTI scans included the voxelwise analysis of the fractional anisotropy (FA), radial diffusivity (RD), and axial diffusivity (AD).

RESULTS

Diffusion tensor imaging revealed areas of altered FA in subcortical white matter bilaterally, mainly in temporal regions as well as in the right internal capsule, the pons, and the right cerebellum. These changes overlapped with changes in RD. Voxel-based morphometry did not reveal any gray matter alterations.

CONCLUSIONS

We showed altered diffusion properties in several white matter regions in patients with iRLS. White matter changes could mainly be attributed to changes in RD, a parameter thought to reflect altered myelination. Areas with altered white matter microstructure included areas in the internal capsule which include the corticospinal tract to the lower limbs, thereby supporting studies that suggest changes in sensorimotor pathways associated with RLS.

Altered white matter integrity in primary restless legs syndrome patients: diffusion tensor imaging study

OBJECTIVES

A prior diffusion tensor imaging (DTI) of restless legs syndrome (RLS) subjects found alterations in brain white matter (WM). The aim of this study was to explore the possible mechanism of altered integrity of brain WM in RLS patients.

METHODS

The DTI measurement was performed in 22 subjects with RLS and 22 age-matched control subjects. Using a voxel-based analysis, fractional anisotropy (FA) and axial and radial diffusivities (AD and RD) were compared between RLS and control subjects with a two-sample t-test, and correlation analysis was performed in RLS subjects.

RESULTS

RLS subjects demonstrated decreased FA in the genu of the corpus callosum and frontal WM adjacent to the inferior frontal gyrus compared with the control subjects. For areas of decreased FA, both the AD and RD were higher than that in the control subjects.

DISCUSSION

Our findings suggest that loss of axonal density and myelin may account for WM changes seen in a prior study of RLS subjects.

Periodic leg movements in sleep in patients with supratentorial cerebral infarction

The pathophysiology of periodic leg movements in sleep (PLMS) is complex, and still lacks a consensus. Consecutive 35 patients with the diagnosis of acute supratentorial ischemic stroke and 35 age- and sex-matched control subjects were prospectively investigated. Clinical and sociodemographic evaluation and a whole-night polysomnographic recording were performed. In patients with supratentorial ischemic stroke, 27 patients (77.2%) had PLMS-index more than 5/h, and 19 out of 35 patients (54.3%) had PLMS-index more than 15/h; while only 10 participants (28.5%) in control group had PLMS-index more than 5/h, and 6 participants (17.1%) had PLMS-index more than 15/h (p < 0.05). None of the demographic variables showed statistically significant relationship with PLMS, such as gender (p = 0.952) and age (p = 0.435). Territorial localization of ischemic lesions showed no relation with the presence of PLMS (p = 0.867), PLMS-index (p = 0.432), or restless legs syndrome (p = 0.833). All patients demonstrated PLMS contralateral to ischemic lesion except eight patients with bilateral PLMS; these were also more prominent contralaterally. Our study supports the hypothesis that destructive lesions causing the loss of cortical or subcortical inhibition exerting on the reticular formation on spinal pathways could lead to the development of PLMS.

A comparison of gray matter density in restless legs syndrome patients and matched controls using voxel-based morphometry

BACKGROUND

Restless legs syndrome (RLS) is a common neurological disorder the pathophysiology of which is incompletely understood. Four studies have examined structural differences between the brains of RLS patients and healthy controls, using voxel-based morphometry (VBM). All 4 studies have provided different results.

METHODS

Optimized VBM was used to search for structural differences in gray matter density. Sixteen RLS patients naïve to dopaminergic drugs and 16 age- and sex-matched controls received structural T1-weighted MR scans. Structural data were analyzed using FSL-VBM.

RESULTS

No difference in gray matter density was detected between the two groups (voxel-wise significance: no significant voxels at P= .89 (whole brain Family Wise Error (FWE) corrected); no significant voxels at P < .05 (whole brain False Discovery Rate (FDR) corrected; smallest achievable FDR threshold .99).

CONCLUSION/DISCUSSION

The present study did not replicate (confirm) previous findings of structural brain changes in RLS, but instead supported the findings of a recent study showing a lack of gray matter alteration in an elderly RLS population. More specifically, the results do not support neuronal loss as an underlying disease mechanism in RLS. Potential limitations in the application of VBM are also discussed.

A case of a patient with both chorea and restless legs syndrome

The patient was a 44-yr-old man with end-stage renal disease who had developed chorea as a result of hypoglycemic injury to the basal ganglia and thalamus and who was subsequently diagnosed with depression and restless legs syndrome (RLS). For proper management, the presence of a complex medical condition including two contrasting diseases, chorea and RLS, had to be considered. Tramadol improved the pain and dysesthetic restlessness in his feet and legs, and this was gradually followed by improvements in his depressed mood, insomnia, lethargy, and feelings of hopelessness. This case suggests that the dopaminergic system participates intricately with the opioid, serotoninergic, and noradrenergic systems in the pathophysiology of RLS and pain and indirectly of depression and insomnia.

Cortical grey matter alterations in idiopathic restless legs syndrome: An optimized voxel-based morphometry study

An impairment of central somatosensory processing is assumed in restless legs syndrome (RLS). Although functional neuroimaging in RLS gave evidence to the presence of widespread functional changes in various brain areas, structural changes at the cortical level were not reported to be RLS-associated to date. Here, an analysis of high-resolution three-dimensional magnetic resonance imaging (MRI) was performed in 63 patients with idiopathic RLS by use of optimized voxel-based morphometry, in order to investigate if cortical areas might be altered in volume at group level according to the phenomenology of RLS. The comparison of the RLS patients versus controls yielded significant regional decreases of gray matter volume at corrected P < 0.05 in the bihemispheric primary somatosensory cortex, which additionally extended into left-sided primary motor areas. All clusters correlated both with the severity of RLS symptoms and with disease duration. These results, for the first time, give in vivo evidence to structural neocortical gray matter alterations in RLS patients. The alterations in the sensorimotor cortices might add to the pathophysiological concepts of idiopathic RLS.

Voxel-based morphometry in unmedicated patients with restless legs syndrome

BACKGROUND

The pathophysiology of restless legs syndrome (RLS) is not yet understood. A prior voxel-based morphometry (VBM) study reported gray matter increase in the pulvinar of the thalamus in a group of patients, most of whom were on medical treatment. Since there is evidence that medication can change the volume of cerebral structures, the question arises as to whether the reported morphometric alterations are caused by the RLS itself or, alternatively, are a consequence of drug treatment. To address this issue, we performed VBM in unmedicated RLS patients.

METHODS

Fourteen patients with idiopathic RLS with no (n=11) or only minimal (n=3) treatment exposure in the past and 14 age- and sex-matched healthy subjects were investigated. All subjects were free of psychotropic drugs for at least 4 months. Morphological data were analyzed by using optimized VBM.

RESULTS

We did not detect any structural changes except for slightly increased gray matter density in the ventral hippocampus (p=0.046 on the left and p=0.055 on the right side) and in the middle orbitofrontal gyrus (p=0.046 on the right and p=0.097 on the left side).

CONCLUSION

Our study could not confirm the findings of a prior study. A possible explanation for the divergent findings is the difference between the populations examined. Since, in our study, essentially treatment-naïve patients were investigated, it is possible that the prior findings reflect treatment-induced effects on cerebral morphology in RLS.

Estrogen therapy reduces nocturnal periodic limb movements

It is believed that periodic limb movement (PLM) and more specifically, restless leg syndrome (RLS), are a common cause of insomnia. And one study in the literature examined PLM when associated to the use of estrogens. Polo-Kantola et al. [Polo-Kantola P, Rauhala E, Erkkola R, Irjala K, Polo O. Estrogen replacement therapy and nocturnal periodic limb movements: a randomized controlled trial. Obstet Gynecol 2001;97(4):548-54] observed that estrogen therapy improved subjective sleep quality regardless of periodic limb movements or related arousals. Herein is a case of a symptomatic postmenopausal patient with high PLM index who complained of insomnia and leg pain. Given that the patient had hot flashes and a high Kupperman Menopausal Index (which evaluates climacteric symptoms), we decided to administer transdermal ESTRADOT 25 microg (Novartis, Brazil) twice-a-week. Our patient experienced a significant decrease in PLM as well as a great increase in REM and a slight increase in slow wave sleep (stages 3 and 4), as shown in the polysomnography. The patient reported an overall improvement in her condition.

Restless legs syndrome and Parkinson's disease: is there an etiologic link?

The etiologic link between restless legs syndrome (RLS) and Parkinson's disease (PD) has been debated. Since dopaminergic dysfunction and response to dopaminergic agents are consistent features in RLS and PD, some authors have suggested that these two diseases may share common pathophysiology. However, presently there is not enough evidence to suggest that the actual pathophysiologic mechanism in both diseases is identical. The nigrostriatal dopaminergic system is primarily involved in PD and it is possible that the extrastriatal dopaminergic system may be variably involved in those PD patients with RLS symptoms. Further clinical, imaging, pharmacologic, and genetic studies will be needed to address the many unanswered questions related to the link between RLS and PD.

Restless legs syndrome: diagnostic assessment and the advantages and risks of dopaminergic treatment

In the past few years, major advances have been made in the field of restless legs syndrome (RLS). New tools have been developed to assess the presence and severity of RLS and its complications. Furthermore new concepts of the phenotype are emerging.With a high likelihood a slight dopaminergic hypofunction contributes essentially to the pathophysiology of most phenotypes of RLS. Dopaminergic substitution either with L-DOPA or with dopamine agonists ameliorates symptoms in the large majority of patients. Too high of doses of either type of drug may be involved in the development of augmentation caused by treatment-induced alterations in dopaminergic neurotransmission. Dopaminergic agents are currently the agents of first choice to treat RLS, and large multicenter trials support the evidence of efficacy. Very careful tailoring of the dose is required to avoid the development of treatment complications, specifically augmentation.

Skeletal Muscle Morphology in Patients with Restless Legs Syndrome

AIM

The aim of the study was to assess the cellular and structural properties of skeletal muscle in restless legs syndrome (RLS).

METHOD

Twenty patients and 16 controls were included. Aerobic performance was assessed using a submaximal test. On muscle biopsies taken from the tibialis anterior, fiber distribution and fiber area were analyzed together with parameters surveying the microvascularization, especially the tortuosity, which is expressed as a percent of muscle fiber perimeter in contact with the wall of the microvessel, length of capillary/perimeter of fiber (LC/PF) index.

RESULTS

The RLS group had significantly lower predicted maximal oxygen uptake (p = 0.01) and significantly higher LC/PF index (p = 0.01) compared to the controls.

CONCLUSION

The higher capillary tortuosity in RLS patients indicates the occurrence of significant remodeling in capillary geometry in RLS.

Pathophysiological concepts of restless legs syndrome

Pathophysiological concepts of restless legs syndrome (RLS) are based mainly on neuroimaging and on neurophysiological data. Furthermore treatment effects contribute essentially to the present understanding of the disease, unless the genetic progress expected in the near future will clarify substantially open issues. The concept agreed on assumes a dysfunction of the dopaminergic system, possibly on the level of striatal and/or spinal dopamine receptors, and the A11 neuron group localized in the hypothalamus as an integrated part of the system. These neurons modulate spinal excitability, alterations of which in turn affect sensory processing predominantly of leg afferents in brain stem structures. Neurophysiologically excitability alterations can be measured by a variety of methods such as determination of pain thresholds, H-reflex testing, and quantitative sensory testing.

Restless legs syndrome in diabetic neuropathy: a frequent manifestation of small fiber neuropathy

As the occurrence of restless legs syndrome (RLS) in diabetes is controversial, the aim of this study was to assess the prevalence of RLS in a cohort of patients with diabetic neuropathy and to analyze the features of the associated neuropathy. We investigated the occurrence of RLS diagnosed in accordance with the criteria of the International Restless Legs Syndrome Study Group in a cohort of patients with polyneuropathy and mononeuropathy multiplex associated with diabetes mellitus (DM), or impaired glucose tolerance (IGT), or impaired fasting glucose (IFG) in a retrospective study. RLS was present in 33/99 patients with neuropathy associated with DM/IGT/IFG (84 with distal polyneuropathy and 15 with multiple mononeuropathy). Comparing patients with or without RLS, small fiber sensory neuropathy was more common in the RLS patients (15/33 vs. 15/66), as were symptoms of burning feet (10/33 vs. 6/66). In several patients, RLS was responsive to neuropathic pain medications. The frequent occurrence of RLS in association with thermal dysesthesias may reflect the involvement of small sensory fibers in the form of hyperexcitable C fibers or A-delta fiber deafferentation. We suggest that RLS may be triggered by abnormal sensory inputs from small fibers, especially involved in neuropathy associated with DM/IGT/IFG. Our data show that RLS is a relevant feature of diabetic neuropathy, as a frequent and potentially treatable manifestation of small fiber involvement in the course of DM and IGT/IFG.

Animal studies in restless legs syndrome

Although restless legs syndrome (RLS) is a common disorder that has been studied thoroughly in the past decades, the underlying pathophysiology is still not fully understood. However, some attractive hypotheses on the pathogenesis of the disorder have been forwarded. Animal models are an important tool to verify hypotheses and to dissect out the details of pathophysiological mechanisms. Ideally they might serve the development of future treatment strategies. This review discusses the general and specific prerequisites necessary for the establishment of animal models for RLS and summarizes the approaches that have been made.

Support for dopaminergic hypoactivity in restless legs syndrome: a PET study on D2-receptor binding

Clinical observations support a central role of the dopamine system in restless legs syndrome (RLS) but previous imaging studies of striatal dopamine D2-receptors have yielded inconclusive results. Extrastriatal dopaminergic function has hitherto not been investigated. Sixteen RLS patients naïve to dopaminergic drugs and sixteen matched control subjects were examined with PET. [11C]Raclopride and [11C]FLB 457 were used to estimate D2-receptor availability in striatum and extrastriatal regions, respectively. Examinations were performed both in the morning (starting between 10:00 and 12:00 h) and evening (starting at 18:00 h). Measures were taken to monitor and control for head movement during data acquisition. In the striatum, patients had significantly higher [11C]raclopride binding potential (BP) values than controls. In extrastriatal regions, [11C]FLB 457 BP was higher in patients than controls, and in the regional analysis the difference was statistically significant in subregions of thalamus and the anterior cingulate cortex. The diurnal variability in BP with [11C]FLB 457 and [11C]raclopride was within the previously reported test-retest reproducibility for both radioligands. The study supports involvement of the dopamine system in both striatal and extrastriatal brain regions in the pathophysiology of RLS. The brain regions where differences in D2-receptor binding were shown are implicated in the regulation of affective and motivational aspects of sensory processing, suggesting a possible pathway for sensory symptoms in RLS. Increased D2-receptor availability in RLS may correspond to higher receptor densities or lower levels of endogenous dopamine. Both interpretations are consistent with the hypothesis of hypoactive dopaminergic neurotransmission in RLS, as increased receptor levels can be owing to receptor upregulation in response to low levels of endogenous dopamine. The results do not support variations in dopamine D2-receptor availability as a correlate to the diurnal rhythm of RLS symptoms.

Emerging drugs for restless legs syndrome

Restless legs syndrome (RLS) is a common, but often underdiagnosed, neurological disorder, which is characterised by an imperative urge to move the extremities associated with paraesthesias, worsening of symptoms at rest and in the evening or at night, and, as a consequence, sleep disturbances. RLS affects 1-10% of the population. The aetiology of RLS is unknown, but besides genetic factors the dopaminergic and opioidergic system may play a crucial role and new developments also point to an exciting iron-dopamine connection in the pathophysiology of this burdening disorder. Due to the limited disease-specific knowledge, current treatment strategies are not curative, but nevertheless may produce an effective and lasting relief of symptoms. Although clinically based treatment has focused on levodopa, opioids and benzodiazepines for a long time, evidence-based and clinical guidelines identify dopamine agonists as a first-line treatment for daily restless legs symptoms. These substances are now in the process of registration for this indication. Ropinirole is the first dopamine agonist that has been approved by the FDA in May 2005. In addition, several promising new therapies with nondopamine profiles are under development for RLS.

Neuroimaging of sleep and sleep disorders

Herein are presented the results of research in the area of sleep neuroimaging over the past year. Significant work has been performed to clarify the basic mechanisms of sleep in humans. New studies also extend prior observations regarding altered brain activation in response to sleep deprivation by adding information regarding vulnerability to sleep deprivation and regarding the influence of task difficulty on aberrant responses. Studies in sleep disorder medicine have yielded significant findings in insomnia, depression, and restless legs syndrome. Extensive advances have been made in the area of sleep apnea where physiologic challenges have been used to probe brain activity in the pathophysiology of sleep apnea syndrome.

Restless legs syndrome and periodic limb movements

The history, clinical aspects, and treatment of restless legs syndrome (RLS), a heterogeneous distressing sensorimotor disorder, and periodic limb movements (PLMs) that are the typical motor accompaniment of the syndrome, are described. A positive family history, a positive response to dopaminergic treatment, and the presence of PLM while awake or asleep are supportive criteria for the diagnosis of the disorder. RLS and PLM occur more frequently at the beginning of night and exponentially decline across sleep cycles, suggesting circadian influences. Altered circadian rhythmicity in dopamine metabolism and enhanced circadian variations in dopaminergic functions have been reported in the disorder. Dysfunction or atrophy of A11 cells from the diencephalic-spinal dopamine A11 system has been suggested to explain the efficacy of dopaminergic drugs in relieving RLS symptoms and the circadian rhythmicity of RLS. Studies support the hypothesis that the A11 dopaminergic neurons and spinal pathways may be more involved in the pathophysiology of RLS than the nigrostriatal system. Neurophysiological evidence indicates that the involuntary movements in RLS may be of spinal or propriospinal origin. Despite these findings, however, the pathogenic mechanisms underlying the peculiar sensory and motor manifestations of RLS remain unexplained. Among the current treatment options offered for the treatment of RLS, dopaminergic agents have provided the best evidence for efficacy in symptom relief.

Functional neuroimaging studies in restless legs syndrome

Functional neuroimaging studies may contribute to elucidate pathophysiological mechanisms of the restless legs syndrome (RLS) which still remain unclear. Studies in patients with RLS have been performed using functional magnetic resonance imaging (fMRI), single photon emission computed tomography (SPECT) and, more recently, positron emission tomography (PET). SPECT and PET studies revealed some controversial results of the pre- and postsynaptic dopaminergic neurotransmission system and cerebral metabolism in RLS probably reflecting a dysfunction of the central dopaminergic system. However, it still has to be determined whether these alterations affect the nigrostriatal and/or other central dopaminergic systems like the diencephalospinal or mesolimbic pathway and whether they are the primary mechanisms or only secondary phenomena within the manifestation of RLS symptoms. A subtle receptor dysfunction or a synaptic dopaminergic deficit may play a major role. fMRI investigations of RLS patients revealed an activation in the red nuclei and brainstem close to the reticular formation during the symptomatic period, suggesting that subcortical cerebral generators are involved in the pathogenesis of RLS. However, both techniques are not yet clinically relevant methods to differentiate RLS from other movement disorders during sleep. Further investigations, especially at night when RLS symptoms are most pronounced, will lead to a better understanding of the mechanisms underlying RLS.

Apomorphine in idiopathic restless legs syndrome: an exploratory study

BACKGROUND

Dopaminergic and opioidergic drugs have been found to be effective in patients with restless legs syndrome (RLS).

OBJECTIVES

To test the effect of apomorphine--a combined opioidergic and dopaminergic agonist--and subsequent selective antagonism by naloxone and metoclopramide on subjective and objective symptoms in patients with idiopathic RLS.

METHODS

Nine patients with RLS were pretreated with oral domperidone for three days. A modified suggested immobilisation test (SIT) was carried out between 8 pm and 1 am under the following conditions of intravenous drug administration: baseline-apomorphine-apomorphine plus naloxone-apomorphine plus metoclopramide. Outcome variables were a visual analogue scale (VAS) of subjective RLS symptoms and EMG documented periodic leg movements while awake (PLMW).

RESULTS

Compared with baseline, apomorphine resulted in a rapid and significant improvement in subjective RLS symptoms as measured by VAS (54.5% improvement; p = 0.011), and an almost immediate cessation of PLMW, measured by PLMW index (98.0% improvement; p = 0.012). Neither additional naloxone nor metoclopramide blocked this effect significantly. While given apomorphine with metoclopramide, there was a trend to reappearance of PLMW.

CONCLUSIONS

Apomorphine may be an effective treatment for idiopathic RLS. Its effectiveness may reflect both to its dopaminergic and its opioidergic activity, and is not diminished significantly by blocking only one of these pathways. The trend to a worsening of the PLMW index with metoclopramide hints at a primarily dopaminergic effect of apomorphine in idiopathic RLS.

Bilateral thalamic gray matter changes in patients with restless legs syndrome

Restless legs syndrome (RLS) is a common neurological disorder of a primary unpleasant sensation with an urge to move the legs occurring at rest. The etiology of idiopathic RLS is unknown and structural cerebral abnormalities have so far not been detected. We studied 51 right-handed patients with an idiopathic restless legs syndrome in two independent samples (Regensburg RLS-group: n = 28, Munich RLS-group: n = 23) and compared them to 51 sex- and age-matched healthy volunteers. High-resolution T1-weighted magnetic resonance imaging (MRI) of each subject was obtained and analyzed using voxel-based morphometry (VBM) to detect regionally specific differences in gray matter between patients and controls. Conjunction analysis was used to combine results from both centers. In patients with idiopathic RLS, both study centers observed independently a bilateral gray matter increase in the pulvinar. In the conjunction analysis including all patients and controls from both study centers, a significant gray matter increase in the pulvinar bilaterally (right: x = 16, y = -21, z = 12, Z = 4.57; left: x = -16, y = -24, z = 12, Z = 4.10) was present. This is the first demonstration of structural changes in the brain of patients with idiopathic RLS. These changes in thalamic structures are either involved in the pathogenesis of RLS or may reflect a consequence of chronic increase in afferent input of behaviorally relevant information.

Neuropathology of primary restless leg syndrome: absence of specific tau- and alpha-synuclein pathology

The neuroanatomical substrate for restless legs syndrome (RLS) is unknown. We identified 4 patients with idiopathic RLS who came to post-mortem examination, where brain and spinal cord tissue were available for neuropathological assessment. Lewy bodies were not identified and alpha-synuclein immunohistochemistry was uniformly negative. Neurofibrillary tangle pathology was variable and nonspecific. These findings suggest that tau- or alpha-synuclein brain pathology is not a component of primary RLS. Although chronic ischemic changes were found in all 4 cases, these were probably incidental. The absence of diagnostic microscopic brain or spinal cord pathology suggests that the pathologic substrate may be neurochemical or receptor based.

Why do restless legs occur at rest?—pathophysiology of neuronal structures in RLS. Neurophysiology of RLS (part 2)

Restless legs syndrome (RLS) is a heterogeneous disorder encompassing genetically caused types with early onset and acquired varieties occurring later in life. Genetic studies in the near future will most likely discover more than one causative gene. The acquired cases too have different etiologies ranging from idiopathic types to secondary forms with uremia, iron depletion, polyneuropathy and others. Here we aim to correlate typical RLS symptoms, such as the sensory symptoms at rest, the reduction of the complaint in response to movement or other physical stimuli, the dominant involvement of the legs, pain, circadian rhythm, and the responsiveness to dopaminergic drugs with neurophysiological features of the central nervous system. We outline the complexity of the neural structures involved and their connections. A diversity of hypothetical affections of different neuronal levels might lead to various combinations of RLS symptomatology. No single pathophysiological explanation has yet been developed that covers all clinical features.

Neuropathological examination suggests impaired brain iron acquisition in restless legs syndrome

OBJECTIVE

To assess neuropathology in individuals with restless legs syndrome (RLS).

METHODS

A standard neuropathologic evaluation was performed on seven brains from individuals who had been diagnosed with RLS. The substantia nigra was examined in greater detail for iron staining and with immunohistochemistry for tyrosine hydroxylase and proteins involved in iron management. Five age-matched individuals with no neurologic history served as controls.

RESULTS

There were no histopathologic abnormalities unique to the RLS brains. Tyrosine hydroxylase staining in the major dopaminergic regions appeared normal in the RLS brains. Iron staining and H-ferritin staining was markedly decreased in the RLS substantia nigra. Although H-ferritin was minimally detected in the RLS brain, L-ferritin staining was strong. However, the cells staining for L-ferritin in RLS brains were morphologically distinct from those in the control brains. Transferrin receptor staining on neuromelanin-containing cells was decreased in the RLS brains compared to normal, whereas transferrin staining in these cells was increased.

CONCLUSIONS

RLS may not be rooted in pathologies associated with traditional neurodegenerative processes but may be a functional disorder resulting from impaired iron acquisition by the neuromelanin cells in RLS. The underlying mechanism may be a defect in regulation of the transferrin receptors.

Linkage analysis of the candidate genes of familial restless legs syndrome

This research was performed to investigate the relationship between 16 candidate genes responsible for dopaminergic transmission or iron metabolism and familial restless legs syndrome. Genotyping was performed in a Han restless legs syndrome family using the technique of fluorescence-based genescan with the microsatellite markers selected in chromosomal regions flanking the candidate genes. Classical linkage analysis was conducted under the autosomal dominant genetic mode. Results showed that all of the LOD scores at recombination fraction 0.00 are smaller than -2.00, which indicated that these loci were not linked to familial restless legs syndrome. No linkage was found between the candidate genes and RLS in this family. Familial restless legs syndrome may be caused by another gene related to dopaminergic transmission and iron metabolism or there is new mechanism involved in this disease.

Subjective sleep quality and suggested immobilization test in restless leg syndrome and periodic limb movement disorder

The severity of restless leg syndrome (RLS) and/or periodic limb movement disorder (PLMD) was investigated by using a suggested immobilization test (SIT) and by measuring the influence of these disorders on the subjective sleep quality as assessed by the Pittsburgh Sleep Quality Index (PSQI). Patients with RLS and those with both RLS and PLMD showed remarkably high values for PSQI and SIT, whereas patients with PLMD only showed normal values for PSQI. These findings suggest that there is only a small pathological significance for periodic limb movements, and demonstrate the efficacy of SIT and PSQI for evaluating the severity of these disorders.

Symptoms in individuals with small cutaneous veins

The clinical relevance of small cutaneous veins (SCV) is still being discussed. In the Duesseldorf/Essen civil servants study, the prevalence of SCV and the individual symptoms and age-dependent changes were analysed. This cross-sectional study recruited 9935 employees; 9100 could be finally evaluated for this analysis. All volunteers were asked to fill out the questionnaire and were clinically examined. Primarily the clinical findings were documented, adapted to the Basel Study and later modified according to the CEAP classification: (a) class 0 - no visible or palpable clinical signs of venous disease, (b) class 1 - small cutaneous veins, (c) class 1 - reticular veins, (d) class 2 - varicose veins. In all, 64% of the volunteers had no signs of venous disease (class 0: age 41+/-10 years); 10% had small cutaneous veins (class 1: age 44+/-10 years). SCV was more frequent in females (25%) than in males (6%). Only 5% of those with SCV had already consulted a physician. A striking result was that individuals with SCV generally complained about more leg symptoms, of which 'leg swelling' and 'muscle cramps during the night' were the most frequent. 'Continual leg swelling' was reported by 24% of individuals with SCV as opposed to 10% of those without. 'Leg cramps' and 'restless legs' also were more often documented in individuals with SCV (29% vs 22% and 10% vs 7%). These findings were all statistically significant (p<0.001). After adjusting for age and sex, though, there were few or no differences between groups (leg swelling: odds ratio (OR) 1.3; 95% confidence interval (95% CI) 1.1-1.6 and cramps: OR 1.1; 95% CI 0.9-1.3). A gender separate estimation of the rates showed that females suffer more often from any symptom. Regarding 'leg cramps', 'restless legs' and 'itching', the OR were not different for females and males. For 'leg swelling' the age-adjusted OR were significant for women (OR 1.4; 95% Cl 1.1-1.7) compared with men (OR 1.1; 95% Cl 0.7-2). Individuals with SCV seem to have more symptoms compared with healthy people. However, this analysis shows that age and sex are the most relevant explanations for these symptoms.

Restless legs syndrome in spinocerebellar ataxia types 1, 2, and 3

To identify the prevalence and determinants of restless legs syndrome (RLS) in spinocerebellar ataxia (SCA) we studied 58 patients with a molecular diagnosis of SCA1, SCA2 and SCA3. Data on the symptoms of RLS were collected by a standardized questionnaire, and RLS was diagnosed when patients met the four minimal criteria of the syndrome as recently defined by an international study group. In addition, we studied the relationship between RLS and age, age at ataxia onset, CAG repeat length, and nerve conduction and evoked potentials data. RLS was significantly more frequent in SCA patients than in controls (28% vs. 10%). Age at RLS onset in SCA was 49.0 +/- 10.9 years. There were no significant differences in nerve conduction or evoked potentials between RLS and non-RLS SCA patients. The probability of developing RLS increased with age but not with CAG repeat length or higher age of ataxia onset. The data provide evidence that patients with SCA1, SCA2 and SCA3 are per se more susceptible to RLS than non-affected individuals. The probability of developing RLS is related principally to the period over which the CAG repeat mutation exerts its effect and not to CAG repeat length or age of ataxia onset.

A crossover study of gabapentin in treatment of restless legs syndrome among hemodialysis patients

Restless legs syndrome (RLS) is a common entity affecting hemodialysis patients. Although the cause of RLS remains unclear, a number of therapies have been used successfully to treat the disorder. Gabapentin is an anticonvulsant shown to alleviate symptoms of RLS in two small studies of nonhemodialysis patients. Because it is excreted renally, gabapentin has a long half-life among hemodialysis patients and may be advantageous if proven effective. We conducted a randomized, double-blind, placebo-crossover study of gabapentin in the treatment of RLS among a population of hemodialysis patients. Sixteen patients identified with RLS were randomized to either gabapentin or placebo. After 6 weeks of treatment with 200 to 300 mg of gabapentin after each hemodialysis session, patients' RLS was reassessed. After a 1-week washout period, patients were switched from gabapentin to placebo or placebo to gabapentin. After another 6 weeks, patients' RLS was assessed again. Patient data were analyzed using both parametric and nonparametric means. Thirteen of the 16 original patients completed the study. Two patients dropped out because of lethargy (believed to be secondary to gabapentin), and 1 patient died secondary to myocardial infarction. Eleven patients responded to gabapentin, but not placebo (P < 0.01). One patient responded to both, and 1 patient responded to placebo, but not gabapentin. Gabapentin is an effective treatment for RLS in hemodialysis patients.

MRI measurement of brain iron in patients with restless legs syndrome

Brain iron insufficiency in the restless legs syndrome (RLS) has been suggested by a prior CSF study. Using a special MRI measurement (R2'), the authors assessed regional brain iron concentrations in 10 subjects (five with RLS, five controls). R2' was significantly decreased in the substantia nigra, and somewhat less significantly in the putamen, both in proportion to RLS severity. The results show the potential utility of this MRI measurement, and also indicate that brain iron insufficiency may occur in patients with RLS in some brain regions.

Subclinical sensory neuropathy in late-onset restless legs syndrome

OBJECTIVE

To determine the prevalence of different forms of peripheral neuropathy in patients with restless legs syndrome (RLS) and correlate the findings with other clinical characteristics.

BACKGROUND

RLS is characterized by a desire to move the extremities, often associated with paresthesias or dysesthesias, motor restlessness, worsening of symptoms with rest with relief by activity, and worsening of symptoms in the evening or night. The association between RLS and peripheral neuropathy remains controversial. The observation that many patients with small-fiber neuropathy also complain of RLS prompted this prospective case series.

METHODS

Twenty-two consecutive patients with RLS were evaluated for evidence of large-fiber neuropathy (LFN) and small sensory fiber loss (SSFL).

RESULTS

In eight of the 22 (36%) patients, neuropathy was identified. Three patients had pure LFN; two had mixed LFN and SSFL; and three had isolated SSFL. The SSFL group had a later onset of RLS (p < 0.009), reported pain in their feet with RLS more frequently (p < 0.001), and tended to have no family history of RLS (p < 0.078). Patients with LFN did not have similar associations with age at onset, family history status, or presence of pain.

CONCLUSION

The results suggest that two forms of RLS exist: one is triggered by painful dysesthesias associated with SSFL, has later onset, and no family history; and one without involvement of SSF, with an earlier onset age, positive family history for RLS, and no pain. The authors hypothesize that patients with the SSFL subtype of RLS will preferentially respond to neuropathic pain medications.

Clinical correlates of 6-hydroxydopamine injections into A11 dopaminergic neurons in rats: a possible model for restless legs syndrome

Pursuant to the clinical suspicion that restless legs syndrome (RLS) may involve dopaminergic diencephalic spinal neurons (A11), we performed stereotaxic bilateral 6-hydroxydopamine (6-OHDA) lesions into the A11 nucleus to observe for any behavioral correlates similar to this clinical condition. Pathologic examination demonstrated a 54% reduction in A11 tyrosine hydroxylase staining cells in rats injected with 6-OHDA versus sham treatment. Multiple blindly rated 90-120-minute video epochs demonstrated an increased average number of standing episodes (14.4+/-11.7 versus 7.3+/-5.5 episodes/epoch) and increased total standing time (38.9+/-20.5 versus 25.3+/-12.2 minutes/epoch) but similar total sleep time in four lesioned rats when compared with two sham rats. Treatment of the lesioned rats with intramuscular pramipexole subsequently resulted in fewer standing episodes (4.4+/-3.3 versus 14.4+/-11.7 episodes/epoch) and less total standing time (20.9+/-12.3 versus 38.9+/-20.5 minutes/epoch) when compared with untreated lesioned rats. Despite a large number of observations, the small number of lesioned animals precluded formal statistical analysis. These behaviors are consistent, although not specific, with what would be expected in an animal model of RLS.

Clinical correlates of 6-hydroxydopamine injections into A11 dopaminergic neurons in rats: a possible model for restless legs syndrome

Pursuant to the clinical suspicion that restless legs syndrome (RLS) may involve dopaminergic diencephalic spinal neurons (A11), we performed stereotaxic bilateral 6-hydroxydopamine (6-OHDA) lesions into the A11 nucleus to observe for any behavioral correlates similar to this clinical condition. Pathologic examination demonstrated a 54% reduction in A11 tyrosine hydroxylase staining cells in rats injected with 6-OHDA versus sham treatment. Multiple blindly rated 90-120-minute video epochs demonstrated an increased average number of standing episodes (14.4+/-11.7 versus 7.3+/-5.5 episodes/epoch) and increased total standing time (38.9+/-20.5 versus 25.3+/-12.2 minutes/epoch) but similar total sleep time in four lesioned rats when compared with two sham rats. Treatment of the lesioned rats with intramuscular pramipexole subsequently resulted in fewer standing episodes (4.4+/-3.3 versus 14.4+/-11.7 episodes/epoch) and less total standing time (20.9+/-12.3 versus 38.9+/-20.5 minutes/epoch) when compared with untreated lesioned rats. Despite a large number of observations, the small number of lesioned animals precluded formal statistical analysis. These behaviors are consistent, although not specific, with what would be expected in an animal model of RLS.

Cerebral generators involved in the pathogenesis of the restless legs syndrome

The pathophysiology of periodic limb movements and sensory leg discomfort in the restless legs syndrome is unknown. With high-resolution functional magnetic resonance imaging, we localized for the first time cerebral generators associated with sensory leg discomfort and periodic limb movements in 19 patients with restless legs syndrome. During sensory leg discomfort there was mainly bilateral activation of the cerebellum and contralateral activation of the thalamus. During the combined periodic limb movement and sensory leg discomfort conditions, patients also showed activity in the cerebellum and thalamus. In contrast to the sensory leg discomfort condition alone, the combined condition was associated with additional activation in the red nuclei and brainstem close to the reticular formation. Voluntary imitation of periodic limb movements by patients and control subjects was not associated with brainstem activity, but with additional activation in the globus pallidus and motor cortex. These findings indicate that cerebellar and thalamic activation may occur because of sensory leg discomfort and that the red nucleus and brainstem are involved in the generation of periodic limb movements in patients with restless legs syndrome.

Evidence of peripheral axonal neuropathy in primary restless legs syndrome

Restless legs syndrome (RLS) is a well-defined clinical entity characterized by an unpleasant creeping sensation arising in the legs with an irresistible need to move them. The trouble is more pronounced when the affected people lie in a prolonged rest position and try to fall asleep. It is known that RLS may be consequent to systemic disorders and to diseases affecting the central or peripheral nervous system. The International Classification of Sleep Disorders states that peripheral neuropathy should be ruled out by medical history and clinical grounds before diagnosing primary RLS (pRLS). The present study extended peripheral nerve investigation in eight consecutive pRLS patients with normal neurological examination results and showed that all patients exhibited two or more electrical, psychophysiological, and/or morphological features of peripheral axonal neuropathy. Morphometric analysis of sural nerve showed a significant reduction in myelinated fiber density and g ratio (axon diameter/fiber diameter) in the pRLS group compared with eight control biopsy specimens. These results suggest that axonal neuropathy is often present in patients with RLS. A comprehensive peripheral nerve investigation should be considered in RLS patients.

Cholesterol crystal microembolization: a cause of the restless leg syndrome

The restless leg syndrome is characterized by unpleasant lower extremity nocturnal aching, muscle cramps, and restless shuffling. Although the cause remains unknown in the majority of cases, two instances are reported of the restless leg syndrome caused by peripheral cholesterol crystal microemboli. The syndrome caused by cholesterol microemboli and the syndromes of the restless leg are reviewed.