Less is more: pathophysiology of dopaminergic-therapy-related augmentation in restless legs syndrome

[Practical guidelines for diagnosis and therapy of restless legs syndrome]

Restless legs syndrome (RLS) is the most common neurological sleep disorder affecting 10 % of the Caucasian population. The disorder is characterized by painful sensations in the lower limbs, especially during the evening, at night and during rest, resulting in an urge to move the legs and insomnia. As a result the quality of life is significantly reduced. Dopaminergic agents, opioids and anticonvulsants have proven to be effective for RLS with only the former being currently licensed; however, affected patients have to be identified, which is not always the case, especially in outpatient settings. Possible impediments to the adequate management of patients with RLS may include a lack of awareness, comorbidities and other medical conditions mimicking RLS. To overcome some of these difficulties practical guidelines for the diagnosis and therapy of RLS are provided.

Restless legs syndrome and its associated risk factors in Parkinson's disease

Introduction. Restless legs syndrome has been shown to negatively impact the quality of life of patients. Studies have shown an association between restless legs syndrome and Parkinson's disease. We attempted to investigate the prevalence of restless legs syndrome in Parkinson's disease patients and to identify associated risk factors. Method. This was a cross-sectional study among patients with idiopathic Parkinson's disease. Exclusion criterion was a Mini Mental State Examination score of less than 21/30. The International Restless Legs Syndrome Study Group criterion was used to identify patients with restless legs syndrome. Results. A total of 113 patients were recruited. The prevalence rate of restless legs syndrome in our cohort was 9.7% and was significantly associated with a younger onset of Parkinson's disease (P = 0.023), male gender (P = 0.045), higher Mini Mental State Examination score (P = 0.004), and less advanced Hoehn & Yahr stage (P = 0.014). Conclusion. The prevalence rate of restless legs syndrome in our Parkinson's disease population is in keeping with other studies published worldwide. The significance of the association between a younger onset of Parkinson's disease and restless legs syndrome needs to be further investigated.

The role of descending inhibitory pathways on chronic pain modulation and clinical implications

The treatment and management of chronic pain is a major challenge for clinicians. Chronic pain is often underdiagnosed and undertreated, and there is a lack of awareness of the pathophysiologic mechanisms that contribute to chronic pain. Chronic pain involves peripheral and central sensitization, as well as the alteration of the pain modulatory pathways. Imbalance between the descending facilitatory systems and the descending inhibitory systems is believed to be involved in chronic pain in pathological conditions. A pharmacological treatment that could restore the balance between these 2 pathways by diminishing the descending facilitatory pain pathways and enhancing the descending inhibitory pain pathways would be a valuable therapeutic option for patients with chronic pain. Due to the lack of evidence for pharmacological options that act on descending facilitation pathways, in this review we summarize the role of the descending inhibitory pain pathways in pain perception. This review will focus primarily on monoaminergic descending inhibitory pain pathways and their contribution to the mechanism of chronic pain and several pharmacological treatment options that enhance these pathways to reduce chronic pain. We describe anatomical structures and neurotransmitters of the descending inhibitory pain pathways that are activated in response to nociceptive pain and altered in response to sustained and persistent pain which leads to chronic pain in various pathological conditions.

Uremic restless legs syndrome (RLS) and sleep quality in patients with end-stage renal disease on hemodialysis: potential role of homocysteine and parathyroid hormone

BACKGROUND

The aetiology of uremic restless legs syndrome (RLS) remains unclear. Our research investigated whether an elevated plasma concentration of the excitatory amino acid homocysteine might be associated with RLS occurrence in patients with chronic renal insufficiency on hemodialysis.

METHODS

Total plasma homocysteine as well as creatinine, urea, folate, parathyroid hormone, hemoglobin, iron, ferritin, phosphate, calcium, magnesium, and albumin levels were compared between 26 RLS-affected (RLSpos) and 26 non-affected (RLSneg) patients on chronic hemodialysis. We further compared subjective sleep quality between RLSpos and RLSneg patients using the Pittsburgh-Sleep-Quality-Index and investigated possible relationships between laboratory parameters and sleep quality.

RESULTS

Taking individual albumin concentrations into account, a significant positive correlation between total plasma homocysteine and RLS occurrence was observed (r= 0.246; p=0.045). Sleep quality was significantly more reduced in RLSpos compared to RLSneg patients and RLS severity correlated positively with impairment of sleep quality. Bad sleep quality in all patients was associated with higher concentrations of parathyroid hormone.

CONCLUSION

Our results suggest a possible aetiological role of homocysteine in uremic RLS. They confirm that uremic RLS is an important factor causing sleep impairment in patients on hemodialysis. Higher parathyroid hormone levels might also be associated with bad sleep quality in these patients.

Treatment of restless legs syndrome

OPINION STATEMENT

Restless legs syndrome (RLS) is a common, sensorimotor, circadian sleep disorder characterized by the urge to move the legs, particularly at nighttime. It is important to differentiate primary and secondary RLS from other conditions, which can mimic the symptoms of RLS, in particular neuropathy and cramps. Despite considerable advances, the understanding of RLS pathophysiology remains incomplete. Many hypotheses focus on central nervous system structures, although there is increasing evidence that peripheral structures may also be important. There is insufficient evidence at the moment to recommend changes in lifestyle, nutritional supplements and any specific nonpharmacologic treatments. The first-line drugs continue to be dopaminergic medications, including pramipexole, ropinirole, rotigotine transdermal patch and levodopa. However, the phenomenon of RLS augmentation, a paradoxical worsening of symptoms by dopaminergic treatment remains as major problem in treatment of RLS, and prevention of augmentation is one of the main goals in the management of RLS. RLS requires treatment only if it has a significant impact on the patient's nighttime sleep or daily activities. Doses of dopamine agonists should be kept to the minimum required for acceptable symptom reduction. Augmentation may require treatment withdrawal, with prescription of alternate medication. Alternative or additional pharmacologic treatment with a lower level of overall quality of evidence includes opioids (codeine, tramadol, and oxycodone) and anticonvulsants (gabapentin, gabapentin enacarbil, and pregabalin). The choice of the medication should be based on the severity of RLS and the effectiveness of medication for the short-term or long-term treatment of RLS. Iron deficiency must be identified at diagnosis; treatment may improve RLS symptoms and potentially may lower risk of augmentation. There is no clear evidence for treatment of secondary RLS, but agents used in primary RLS should be tried. Comparative long-term trials are required to assess differences in efficacy and augmentation rates between medications used for treatment of RLS.

Restless legs syndrome: pathophysiology and modern management

Restless legs syndrome (RLS) is a common sensory motor neurological disorder that is characterised by an irresistible urge to move the legs that significantly affects the quality of life of the patient. Prevalence in the general population is 5-25% and it is twice as prevalent in women as in men. RLS is the most common movement disorder in pregnancy with a fourfold increased risk of developing this disorder later in life. The pathophysiology of RLS is centred on dopaminergic dysfunction, reduced central nervous system iron, genetic linkages, or alteration in neurotransmitters such as hypocretins, endorphins levels and immune dysfunction and inflammatory mechanisms. With the emergence of new evidence, there are changes to the previous treatment recommendations for RLS. There is sufficient evidence to conclude that dopamine agonists such as rotigotine transdermal patch, pramipexole, ropinirole, gabapentin enacarbil, pregabalin and gabapentin are effective in the short-term treatment of RLS and rotigotine, followed by gabapentin enacarbil, ropinirole, pramipexole and gabapentin for long-term treatment. Based on expert consensus, the recommendation for daily RLS is dopamine agonists or gabapentin or low-potency opioids. Levodopa is less preferred for treating daily RLS due to its high risk of augmentation. For intermittent RLS, it is levodopa or dopamine agonists or low-potency opioids or benzodiazepines. For refractory RLS, the choice is to change to gabapentin or a different dopamine agonist, addition of a second agent like gabapentin or benzodiazepine to the existing drug or changing to a high-potency opioid or tramadol. Medications with safety record in pregnancy include opioids and antiepileptics such as carbamazepine and gabapentin. There are concerns that patients with RLS are at risk for metabolic deregulation, autonomic dysfunction and cardiovascular morbidity. However, a recent study concluded that RLS is not associated with increased risk of cardiovascular complications.

Efficacy, safety and risk of augmentation of rotigotine for treating restless legs syndrome

The present study aimed to examine the long-term efficacy and safety of rotigotine treatment for restless legs syndrome (RLS), as well as the rate of clinically significant augmentation, in a 1-year open-label study of Japanese subjects. Japanese patients with RLS who had been treated with rotigotine or placebo in a double-blind trial were enrolled in a 1-year, open-label, uncontrolled extension study and treated with rotigotine at a dose of up to 3 mg/24 h after an 8-week titration phase. Outcomes included International Restless Legs Syndrome Study Group rating scale (IRLS scale), Pittsburgh Sleep Quality Index (PSQI), safety, and investigator-/expert panel-assessed augmentation (including Augmentation Severity Rating Scale). Overall, 185 patients entered the open-label study and 133 completed the study. IRLS and PSQI total scores improved throughout the 52-week treatment period (IRLS, from 23.2±5.1 to 7.8±7.6 and PSQI, from 8.0±3.1 to 5.0±2.9). Treatment-emergent adverse events were mild to moderate in severity, and included application site reactions (52.4%) and nausea (28.6%). Clinically significant augmentation occurred in five patients (2.7%). These results indicate a good long-term efficacy of rotigotine for treating RLS, with a relatively low risk of clinically significant augmentation.

Health-related quality of life and economic burden in patients with restless legs syndrome

Restless legs syndrome (RLS) is characterized by a distressing, irresistible need or urge to move the legs. It often co-exists with an uncomfortable, though not usually painful, sensation in the legs. Although clear diagnostic criteria and effective treatment options exist, RLS is generally underdiagnosed and under-treated. RLS patients often suffer from sleep disturbances that may severely disrupt normal life functioning. Furthermore, it is one of the most common neurological disorders. In this communication, we provide a systematic review of the literature on health-related quality of life (HRQoL) and health economic issues in patients suffering from RLS. RLS has a considerable impact on the HRQoL of patients, which is comparable to other neurological and chronic diseases. The most important factors contributing to the impairment of HRQoL are the severity of RLS symptoms and the associated sleep disturbances. Although little work has been published on cost-of-illness of RLS, available studies suggest that a considerable economic burden is caused by RLS. Because of the large number of patients requiring treatment and the considerable increase in the number of treatment studies performed in recent years, as well as approval of several drugs for this indication, we assume a considerable increase in treatment frequency. Very few of the RLS treatment options, however, have been evaluated for their cost-effectiveness, and further research is needed on both quality-of-life issues and the economic impact of RLS.

Augmentation in the treatment of restless legs syndrome with transdermal rotigotine

OBJECTIVE

To assess the risk of augmentation under treatment with the transdermally delivered dopamine agonist rotigotine for restless legs syndrome (RLS).

METHODS

Experts in RLS augmentation retrospectively reviewed data from two double-blind, placebo-controlled 6-month trials (745 rotigotine and 214 placebo subjects, NCT00136045 and NCT00135993) and from two open-label 1-year trials (620 rotigotine subjects, NCT00498108 and NCT00263068). All study visits were systematically evaluated applying the Max Planck Institute (MPI) criteria for the diagnosis of both augmentation and clinically relevant augmentation.

RESULTS

MPI criteria for augmentation were met on at least one visit by 8.2% of all subjects in the double-blind trials with 12 subjects meeting the criteria for clinically relevant augmentation: 11 under rotigotine (1.5%) and one under placebo treatment. In the open-label trials, 9.7% of all subjects met the MPI criteria for augmentation and 2.9% met the criteria for clinically relevant augmentation. None of the patients treated with rotigotine for up to 1.5 years (double-blind plus open-label trial) discontinued prematurely owing to augmentation. Neither could dose-dependency or a time pattern for clinically relevant augmentation episodes be detected.

CONCLUSIONS

Our analyses suggest that the risk for clinically relevant augmentation for the duration of up to 18 months of rotigotine treatment is low.

Burning mouth syndrome in Parkinson's disease: dopamine as cure or cause?

Burning mouth syndrome has been reported as being more common in Parkinson’s disease patients than the general population. While the pathophysiology is unclear, decreased dopamine levels and dopamine dysregulation are hypothesized to play a role. We report a patient with Parkinson’s disease who developed burning mouth syndrome with carbidopa/levodopa. Our patient had resolution of burning mouth symptoms when carbidopa/levodopa was replaced with a dopamine agonist. Based on our patient’s clinical course, in conjunction with earlier studies assessing the relationship between burning mouth syndrome and Parkinson’s disease, we discuss a potential role for dopamine in burning mouth syndrome in Parkinson’s disease.

Sleep-related movement disorders

Several movement disorders may occur during nocturnal rest disrupting sleep. A part of these complaints is characterized by relatively simple, non-purposeful and usually stereotyped movements. The last version of the International Classification of Sleep Disorders includes these clinical conditions (i.e. restless legs syndrome, periodic limb movement disorder, sleep-related leg cramps, sleep-related bruxism and sleep-related rhythmic movement disorder) under the category entitled sleep-related movement disorders. Moreover, apparently physiological movements (e.g. alternating leg muscle activation and excessive hypnic fragmentary myoclonus) can show a high frequency and severity impairing sleep quality. Clinical and, in specific cases, neurophysiological assessments are required to detect the presence of nocturnal movement complaints. Patients reporting poor sleep due to these abnormal movements should undergo non-pharmacological or pharmacological treatments.

Transcranial electrical stimulation (tES - tDCS; tRNS, tACS) methods

Weak transcranial direct current stimulation (tDCS) with a homogenous DC field at intensities of around 1 mA induces long-lasting changes in the brain. tDCS can be used to manipulate brain excitability via membrane polarisation: cathodal stimulation hyperpolarises, while anodal stimulation depolarises the resting membrane potential, whereby the induced after-effects depend on polarity, duration and intensity of the stimulation. A variety of other parameters influence tDCS effects; co-application of neuropharmacologically active drugs may most impressively prolong or even reverse stimulation effects. Transcranial alternating stimulation (tACS) and random noise stimulation (tRNS) are used to interfere with ongoing neuronal oscillations and also finally produce neuroplastic effects if applied with appropriate parameters.

Restless legs syndrome, periodic leg movements, and periodic limb movement disorder in children

The characteristic symptoms of restless legs syndrome (RLS) have been known for hundreds of years and were first reported in medicine in the 1600s. Clinicians must consider potential mimics, comorbid, and associated conditions when evaluating children with RLS symptoms. The traditional differentiation of RLS from periodic limb movement disorder (PLMD) is noted in children as well as adults. Because current pediatric RLS research is sparse, this article provides the most up-to-date evidence-based as well as consensus opinion-based information on the subject of childhood RLS and PLMD. Prevalence, pathophysiology, diagnosis, treatment, and clinical associations are discussed.

Long-term management issues in restless legs syndrome

Restless legs syndrome is a neurologic movement and sleep disorder with lifelong symptoms causing considerable morbidity. Several short-term and some long-term open-label and double-blind clinical trials have demonstrated the efficacy and safety of dopaminergic treatment in restless legs syndrome. Long-term treatment, however, is associated with the emergence of vexing long-term side effects that pose a challenge for physicians. These long-term complications can be broadly categorized as disease-related (impact on sleep and acute exacerbation of restless legs syndrome symptoms), and medication issues (augmentation, sleep attacks, impulse control disorders, addiction and dependence, site reaction, occasionally sleep apnea, fibrotic complications, and weight gain).

Dopamine D3 receptor specifically modulates motor and sensory symptoms in iron-deficient mice

Restless legs syndrome (RLS) is a common neurological disorder whose exact pathophysiological mechanism remains unclear despite the successful use of dopaminergic treatment and recent discovery of predisposing genetic factors. As iron deficiency has been associated with RLS for some patients and there is evidence for decreased spinal dopamine D(3)-receptor (D3R) signaling in RLS, we aimed at establishing whether D3R activity and iron deficiency share common pathways within the pathophysiology of RLS sensory and motor symptoms. Using a combined mouse model of iron deficiency and dopamine D(3)-receptor deficiency (D3R-/-), circadian motor symptoms were evaluated by continuous recording of spontaneous wheel running activity. Testing the acute and persistent pain responses with the hot-plate test and formalin test, respectively, assessed sensory symptoms. A 15 week iron-deficient (ID) diet alone increased acute and persistent pain responses as compared to control diet. As compared to C57BL/6 (WT), homozygous D3R-/- mice already exhibited elevated responses to acute and persistent pain stimuli, where the latter was further elevated by concurrent iron deficiency. ID changed the circadian activity pattern toward an increased running wheel usage before the resting period, which resembled the RLS symptom of restlessness before sleep. Interestingly, D3R-/- shifted this effect of iron deficiency to a time point 3-4 h earlier. The results confirm the ability of iron deficiency and D3R-/- to evoke sensory and motor symptoms in mice resembling those observed in RLS patients. Furthermore this study suggests an increase of ID-related sensory symptoms and modification of ID-related motor symptoms by D3R-/-.

Restless legs syndrome

Restless legs syndrome (RLS) is characterized by a compelling, often insatiable, need to move the legs, accompanied by unpleasant sensations located mainly in the ankles and calves. Because symptoms are brought on by inactivity, distress intrudes upon everyday, sedentary activities such as plane travel, car rides, and attending school, meetings, or the theatre. Symptoms show a diurnal preference for the evening and night, so disruption of sleep onset or maintenance is particularly common. RLS is associated with both lower ratings of quality of life and higher rates of cardiovascular disease. Four common genetic loci associating to RLS have recently been identified, but the molecular pathways by which they increase risk for RLS have yet to be determined. Both sensory (RLS) and motor (periodic limb movements of sleep) symptoms are responsive to dopaminergic medications, yet clear delineation of dopaminergic pathology has not emerged. Brain iron is reduced in many, but not all, patients with RLS. First-line treatment for RLS includes agents acting at D(2) and D(3) dopamine receptors.

Dosage-dependent non-linear effect of L-dopa on human motor cortex plasticity

The neuromodulator dopamine affects learning and memory formation and their likely physiological correlates, long-term depression and potentiation, in animals and humans. It is known from animal experiments that dopamine exerts a dosage-dependent, inverted U-shaped effect on these functions. However, this has not been explored in humans so far. In order to reveal a non-linear dose-dependent effect of dopamine on cortical plasticity in humans, we explored the impact of 25, 100 and 200 mg of L-dopa on transcranial direct current (tDCS)-induced plasticity in twelve healthy human subjects. The primary motor cortex served as a model system, and plasticity was monitored by motor evoked potential amplitudes elicited by transcranial magnetic stimulation. As compared to placebo medication, low and high dosages of L-dopa abolished facilitatory as well as inhibitory plasticity, whereas the medium dosage prolonged inhibitory plasticity, and turned facilitatory plasticity into inhibition. Thus the results show clear non-linear, dosage-dependent effects of dopamine on both facilitatory and inhibitory plasticity, and support the assumption of the importance of a specific dosage of dopamine optimally suited to improve plasticity. This might be important for the therapeutic application of dopaminergic agents, especially for rehabilitative purposes, and explain some opposing results in former studies.

Dopaminergic augmentation of restless legs syndrome

Dopaminergic agents are the first-line treatment of restless legs syndrome (RLS), and have been used for the treatment of this disorder since the 1980s. The major issue with this class of drugs is augmentation of RLS symptoms during treatment. The first report of augmentation found an occurrence among 73% of patients treated with levodopa. Subsequent studies have reported somewhat lower incidences, but augmentation remains a clinically significant issue with all dopaminergic agents. It was not until 2007 that an operational, empirical definition of augmentation (Max Planck Institute Criteria) was made. This late development and the fact that studies have not been specifically designed to assess augmentation, have made it particularly difficult to compare the incidence rates for the different RLS treatments. As the primary neural and molecular substrates underlying idiopathic RLS are not known, the pathophysiology of augmentation remains unclear, however there are several hypotheses that concern the role of dopaminergic hyperstimulation, of iron deficiency, the genetic component, the effect of a reduction in responsiveness of tubero-infundibular dopamine receptors, and the role of chronobiotic mechanisms. RLS is treated by maintaining low doses of dopaminergic agents and ensuring iron sufficiency. Non-dopaminergics and opiates can be used when patients experience augmentation with more than one dopaminergic agent.

Update on the management of restless legs syndrome: existing and emerging treatment options

Restless legs syndrome (RLS) is a sensorimotor disorder, characterized by a circadian variation of symptoms involving an urge to move the limbs (usually the legs) as well as paresthesias. There is a primary (familial) and a secondary (acquired) form, which affects a wide variety of individuals, such as pregnant women, patients with end-stage renal disease, iron deficiency, rheumatic disease, and persons taking medications. The symptoms reflect a circadian fluctuation of dopamine in the substantia nigra. RLS patients have lower dopamine and iron levels in the substantia nigra and respond to both dopaminergic therapy and iron administration. Iron, as a cofactor of dopamine production and a regulator of the expression of dopamine type 2-receptor, has an important role in the RLS etiology. In the management of the disease, the first step is to investigate possible secondary causes and their treatment. Dopaminergic agents are considered as the first-line therapy for moderate to severe RLS. If dopaminergic drugs are contraindicated or not efficacious, or if symptoms are resistant and unremitting, gabapentin or other antiepileptic agents, benzodiazepines, or opioids can be used for RLS therapy. Undiagnosed, wrongly diagnosed, and untreated RLS is associated with a significant impairment of the quality of life.

Compulsive habits in restless legs syndrome patients under dopaminergic treatment

Since the introduction of levodopa therapy and dopaminergic replacement therapy to abate symptoms of idiopathic Parkinson's disease, repetitive compulsive behaviors have been reported and are now considered to be drug-related response complications. As dopamine (DA) agonists are the licensed treatment in Restless Legs Syndrome (RLS), a survey was conducted to determine the extent to which patients with RLS present compulsive behaviors. The aim of this study was to investigate the relationship between DA agonists and the occurrence of motor or behavioral compulsions, stress, depression, and sleep disturbance in RLS patients. A questionnaire was mailed three times, at four-month intervals over a period of 8 months to all patients of the Quebec Memory and Motor Skills Disorders Clinic diagnosed with RLS. In addition to recording all medication information for RLS treatment, patients were assessed on the International Restless Legs Syndrome Study Group Rating Scale (IRLS), the Beck Depression Inventory-II (BDI-II), the Sleep Scale from the Medical Outcomes Study (MOS) and on a visual analog scale for current level of stress. A section pertaining to hobby, mania, and compulsion was also included. Analyses are based on 97 out of 151 patients (64.2%) with RLS who returned the three questionnaires. Twelve patients (12.4%) on stable DA agonist therapy (average dose 0.52+/-0.59 mg Pramipexole equivalent) developed a new compulsive behavioral repertoire. Eating (3 women, 1 man), buying food or clothes (2 women, 1 man), trichotillomania (1 woman, 1 man), and gambling (1man) were among the compulsions developed under DA treatment. In addition, two women presented new tic-like phenomena. In contrast to the RLS patients without compulsive behaviors (53 treated with DA agonist; 32 untreated), those with compulsive habits reported experiencing more stress, depression and sleep problems. Patients with RLS with mood and stress states may be at greater risk of developing compulsive behaviors while receiving standard dosage DA agonist treatment. These behaviors are clearly linked to short-term satisfaction and underline the role of dopaminergic mesolimbic stimulation in the reinforcement process of rewarding behavioral sequences.

New approaches for the treatment of sleep disorders

Epidemiological studies have established that sleep disorders are common and often untreated. Besides having a negative impact on overall health, these conditions can significantly disrupt normal daily functions. While a number of drugs are employed in the treatment of sleep disorders, safety, tolerability, and variable efficacy limit their utility. Clinical developments in the area have been facilitated especially by advances in neurobiology and neuropharmacology. In this regard, a wide array of neuroactive substances has been found to be responsible for regulating sleep and wakefulness. Advances in the understanding of neurotransmitter and hormone receptor mechanisms and classifications have led to new opportunities for developing novel therapeutics for treating sleep disorders. Provided in this report is an overview of some of the more prevalent sleep disorders, including narcolepsy, insomnia, obstructive sleep apnea syndrome, and restless legs syndrome, with a summary and critique of medications used to treat these conditions. For each disorder, information is provided on recent approaches taken to develop novel therapeutics based on laboratory findings relating to the underlying biological abnormalities associated with the condition, in addition to approaches that leverage existing therapeutics to develop new treatment options for patients. Significant advances in the future await a better understanding of the underlying pathophysiology of these conditions and of the neurobiological alterations associated with these disorders. It is hoped that some of the research directions described herein will stimulate additional research in this area and thereby help foster the discovery of novel agents for treating major sleep disorders.

Factors contributing to the development of restless legs syndrome in patients with Parkinson disease

Although restless legs syndrome (RLS) commonly accompanies Parkinson disease (PD), the mechanism of RLS development in PD is still unclear. We investigated the prevalence of RLS in Korean patients with PD, and the possible contributing factors to the development of RLS in those patients. Four hundred forty-seven consecutive patients with PD were interviewed and examined. Among them, 73 patients (16.3%) were diagnosed with RLS. PD patients with RLS had a longer duration of PD symptoms, more severe PD disability, a greater degree of cognitive decline, and a longer duration of antiparkinson therapy than those without RLS. Multivariate logistic regression analysis revealed that the duration of antiparkinson therapy was the most significant factor contributing to the development of RLS in patients with PD. The present results support a higher prevalence of RLS in patients with PD and suggest that long-term antiparkinson therapy, rather than PD itself, may contribute to the development of RLS.

Dose-dependent inverted U-shaped effect of dopamine (D2-like) receptor activation on focal and nonfocal plasticity in humans

The neuromodulator dopamine (DA) has multiple modes of action on neuroplasticity induction and modulation, depending on subreceptor specificity, concentration level, and the kind of stimulation-induced plasticity. To determine the dosage-dependent effects of D(2)-like receptor activation on nonfocal and focal neuroplasticity in the human motor cortex, different doses of ropinirole (0.125, 0.25, 0.5, and 1.0 mg), a D(2)/D(3) dopamine agonist, or placebo medication were combined with anodal and cathodal transcranial direct current stimulation (tDCS) protocols, which induce nonfocal plasticity, or paired associative stimulation (PAS, ISI of 10 or 25 ms), which generates focal plasticity, in healthy volunteers. D(2)-like receptor activation produced an inverted "U"-shaped dose-response curve on plasticity for facilitatory tDCS and PAS and for inhibitory tDCS. Here, high or low dosages of ropinirole impaired plasticity. However, no dose-dependent response effect of D(2)-like receptor activation was evident for focal inhibitory plasticity. In general, our study supports the assumption that modulation of D(2)-like receptor activity exerts dose-dependent inhibitory or facilitatory effects on neuroplasticity in the human motor cortex depending on the topographic specificity of plasticity.

Treatment options for restless legs syndrome

BACKGROUND

Restless legs syndrome (RLS) is a common condition characterized by dysesthesia and an urge to move. Predominantly, symptoms occur at rest in the evening or at night, and they are alleviated by moving the affected extremity or by walking. Although the etiopathogenesis of RLS is still unknown, the rapid and dramatic improvement of RLS with dopaminergic agents suggests that dopaminergic system dysfunction may be a basic mechanism. Dopaminergic agents are the best-studied agents, and are considered first-line treatment of RLS.

OBJECTIVE

To review all options for the treatment of RLS, including the non-pharmacological ones.

METHODS

The treatment suggestions are based on evidence from studies published in peer-reviewed journals, or upon a comprehensive review of the medical literature.

RESULTS/CONCLUSION

Extensive data are available for levodopa and dopamine agonists, especially for pramipexole and ropinirole. Pharmacological treatment should be limited to those patients who suffer from clinically relevant RLS with impaired sleep quality or quality of life. A treatment on demand is a clinical need in RLS cases that present intermittent symptoms.

Obesity and restless legs syndrome in men and women

BACKGROUND

Obesity and restless legs syndrome (RLS) are both associated with hypofunction of dopamine in the CNS. We therefore examined whether individuals who are obese have an increased risk of RLS in two ongoing US cohorts, the Nurses' Health Study II and the Health Professional Follow-up Study.

METHODS

We included 65,554 women and 23,119 men free of diabetes, arthritis, and pregnancy in the current analyses. Information on RLS was assessed using a set of standardized questions. Participants were considered to have RLS if they met four RLS diagnostic criteria recommended by the International RLS Study Group and had restless legs > or =5 times/month. Odds ratios (ORs) and 95% confidence intervals (CIs) were computed using logistic regression models adjusting for age, smoking, use of antidepressant, phobic anxiety score, and other covariates. Log ORs from the two cohorts were pooled by a fixed-effects model.

RESULTS

There were 6.4% of women and 4.1% of men who were considered to have RLS. Multivariate adjusted ORs for RLS were 1.42 (95% CI: 1.3, 1.6; p trend <0.0001) for participants with body mass index (BMI) >30 vs <23 kg/m(2) and 1.60 (95% CI: 1.5, 1.8; p trend <0.0001) for highest vs lowest waist circumference quintiles. Greater BMI in early adulthood (age 18-21 years) and weight gain were also associated with a higher prevalence of RLS (p trend <0.01 for both).

CONCLUSIONS

Both overall and abdominal adiposity are associated with increased likelihoods of having restless legs syndrome (RLS). Further prospective studies are warranted to clarify causative association between obesity and risk of developing RLS.

The severity range of restless legs syndrome (RLS) and augmentation in a prospective patient cohort: association with ferritin levels

OBJECTIVES

The aim of the study was to prospectively examine all patients with a diagnosis of RLS consulting a sleep disorders clinic and to assess RLS severity and augmentation and their associations, including ferritin levels.

METHODS

Patients were stratified into patients with RLS as ancillary diagnosis, RLS sufferers without current augmentation and RLS sufferers with current augmentation. Work-up included RLS severity scales and blood biochemical variables including indices of iron metabolism.

RESULTS

In an 18-month period, 302 patients with RLS (183 women, 119 men; mean age, 59.1+/-13.7 years) were recruited. RLS was considered idiopathic in 291 patients (96.4%). Most patients (240, 79.5%) were RLS sufferers, whereas the remaining 62 (20.5%) had RLS as ancillary diagnosis. Nineteen out of 162 patients treated with dopaminergic agents (11.7%) had current augmentation. Almost one-third of all patients (31.1%) had ferritin levels <50microg/l. Patients with an ancillary diagnosis of RLS had higher ferritin levels than RLS sufferers without current augmentation. The lowest ferritin levels were present in RLS sufferers with current augmentation 132.8+/-98.0microg/l vs. 100.6+/-84.5microg/l vs. 55.8+/-43.6microg/l; p=0.002). Patients with augmentation did not differ from non-augmented patients regarding age, gender, RLS etiology, presence of previous augmentation, or any other documented comorbidity (p>0.05).

CONCLUSION

The severity spectrum of RLS in this clinical cohort ranged from the ancillary diagnosis of RLS to augmented RLS. There was an inverse correlation between RLS severity and ferritin levels. Patients with current augmentation had the lowest ferritin levels. Our data further strengthen a putative role of low iron stores as a potential aggravator of idiopathic RLS. Moreover, low ferritin might represent a potential biomarker of RLS augmentation under dopaminergic therapy.

Diminished iron concentrations increase adenosine A(2A) receptor levels in mouse striatum and cultured human neuroblastoma cells

Brain iron insufficiency has been implicated in several neurological disorders. The dopamine system is consistently altered in studies of iron deficiency in rodent models. Changes in striatal dopamine D(2) receptors are directly proportional to the degree of iron deficiency. In light of the unknown mechanism for the iron deficiency-dopamine connection and because of the known interplay between adenosinergic and dopaminergic systems in the striatum we examined the effects of iron deficiency on the adenosine system. We first attempted to assess whether there is a functional change in the levels of adenosine receptors in response to this low iron. Mice made iron-deficient by diet had an increase in the density of striatal adenosine A(2A) (A(2A)R) but not A(1) receptor (A(1)R) compared to mice on a normal diet. Between two inbred murine strains, which had 2-fold differences in their striatal iron concentrations under normal dietary conditions, the strain with the lower striatal iron had the highest striatal A(2A)R density. Treatment of SH-SY5Y (human neuroblastoma) cells with an iron chelator resulted in increased density of A(2A)R. In these cells, A(2A)R agonist-induced cyclic AMP production was enhanced in response to iron chelation, also demonstrating a functional upregulation of A(2A)R. A significant correlation (r(2)=0.79) was found between a primary marker of cellular iron status (transferrin receptor (TfR)) and A(2A)R protein density. In conclusion, the A(2A)R is increased across different iron-insufficient conditions. The relation between A(2A)R and cellular iron status may be an important pathway by which adenosine may alter the function of the dopaminergic system.

Treatment wish of individuals with known and unknown restless legs syndrome in the community

STUDY OBJECTIVES

Restless legs syndrome (RLS) is a frequent sleep disorder with a prevalence of 5% to 15% in Caucasian populations. Dopaminergic treatment is known to reduce sensorimotor RLS symptoms and is approved for RLS, but not all patients ask for treatment. About 2% to 3% of patients presenting to a primary care physician require RLS-specific treatment. The overall treatment preference of RLS sufferers, however, is still unknown. The aim of this study was to assess the prevalence and treatment preference in patients with previously diagnosed and those with yet undiagnosed RLS in a population-based survey in Germany.

DESIGN AND SETTING

Cross-sectional health survey with face-to-face interviews with 1312 participants in the Dortmund Health Study. RLS was assessed with standardized, validated questions addressing the four minimal diagnostic criteria for RLS defined by the International Restless Legs Syndrome Study Group.

PARTICIPANTS

Participants were aged 25 to 75 years and were randomly selected from the city register.

RESULTS

The overall prevalence of individuals with a known doctor diagnosis of RLS was 2.3%. In addition, 6.5% fulfilled the four minimal criteria but did not know about this diagnosis yielding an overall prevalence of 8.8%. Prevalence was higher in women (10.2%) and German descendents (9.2%) compared to men (7.1%) and migrants (6.7%). Almost 60% of all RLS cases reported symptoms at least once a week. 33.3% of cases with a known RLS diagnosis and 14.1 % with an unknown diagnosis had an RLS treatment wish. The latter is determined by knowledge of the diagnosis, daily symptoms, diabetes and sleep disturbance.

CONCLUSION

About every fourth RLS case knows about the diagnosis and overall every fifth RLS case wishes medication to effectively reduce symptoms, corresponding to 1.6% of the whole study population.

Clinical trials in restless legs syndrome--recommendations of the European RLS Study Group (EURLSSG)

The European Restless Legs Syndrome (RLS) Study Group (EURLSSG) is an association of European RLS experts who are actively involved in RLS research. A major aim of the Study Group is the development and continuous improvement of standards for diagnosis and treatment of RLS. Several members developed study designs and evaluation methods in investigator-initiated trials early in the 1990s, and all members have since contributed to many pivotal and nonpivotal drug trials for the treatment of RLS. The recommendations on clinical investigations of pharmacological treatment of RLS patients summarize the group's expertise and knowledge acquired through clinical trials. The recommendations primarily address how to plan and conduct confirmatory, randomized clinical studies in patients with idiopathic RLS. Advice is presented for the diagnosis of RLS and clinical and polysomnographic inclusion and exclusion criteria. Primary and secondary endpoints for an evaluation of efficacy are based on a critical description of validated methods for both short- and long-term trials, also in special populations (children, pregnant women, elderly patients). The recommendations include the assessment of augmentation. Finally, general issues including the evaluation of safety and tolerability, as well as specific neurological and cardiovascular risks and sleep attacks/daytime somnolence, are discussed. The aim of these recommendations is to support research groups or pharmaceutical companies in the design of optimized study protocols.

Restless legs syndrome in Parkinson's disease and other neurodegenerative diseases of the central nervous system

The pathophysiology of restless legs syndrome (RLS) is associated with central dopaminergic system dysfunction leading to speculations that RLS may be common in those neurodegenerative diseases with dopaminergic cell loss. However, since RLS is a very common condition, the co-occurrence with less frequent disorders such as the neurodegenerative diseases might be a matter of chance. Currently, no data suggests that patients with sporadic and familial RLS are at increased risk for developing a neurodegenerative disease. In particular, whether RLS is associated with Parkinson's disease has not been established. Only a few studies have directly addressed this issue, and these have methodological limitations yielding conflicting results. Few studies have assessed the frequency of RLS in other neurodegenerative disorders. In several autosomal dominant spinocerebellar ataxias, particularly in Machado-Joseph disease, a higher frequency of RLS is reported than could be accounted for in the general population. Two anecdotal publications have reported the presence of RLS in patients with Huntington's disease and hereditary spastic paraparesis. There are no studies that have examined the association between RLS and other neurodegenerative diseases, such as Alzheimer's disease, frontotemporal dementia, dementia with Lewy bodies, multiple system atrophy, progressive supranuclear palsy, and corticobasal degeneration. .

Update of the pathophysiology of the restless-legs-syndrome

The Restless Legs Syndrome (RLS) is a heterogeneous disease. Symptomatic or secondary forms encompass iron deficiency, uremia, pregnancy, polyneuropathy, and other causes. The so-called idiopathic RLS syndrome preferentially affects patients with a younger onset before the age of 30. Here we summarize pathophysiological results along the anatomical route, beginning at the cortex and followed by the basal ganglia, thalamus, A11 neurones, substantia nigra, brainstem nuclei, and spinal cord. Genetic risk variants for RLS have recently been identified in two genes, one of them the homeobox gene MEIS1, known to be involved in embryonic development and variants in a second locus containing the genes encoding mitogen-activated protein kinase MAP2K5, and the transcription factor LBXCOR1. A third one, the BTBD9 gene with unknown function encodes a BTB(POZ) domain. Accordingly, new concepts on pathophysiology have to bridge conventional knowledge with possible consequences deriving from these findings. Furthermore, this may create a framework to help understand why dopamine, opioid, and some anticonvulsant therapies are effective in RLS patients.

Restless legs syndrome in older adults

Restless legs syndrome (RLS) is a common neurological disorder characterized by an urge to move the legs. The symptoms show a strong circadian rhythmicity, with onset or increase in the evening or at night; thus, sleep disturbances are the most frequent reason for patients seeking medical aid. The prevalence of the disorder increases strongly with age, with an estimated 9% to 20% of sufferers being among the elderly. Dopaminergic drugs are the first-line treatment option in RLS; opioids and anticonvulsants can also be used either as add-on or stand alone therapy options. Secondary forms of RLS and possible interaction with other medications require particular consideration in the elderly.

Restless Legs Syndrome

Restless legs syndrome is a symptomatic urge to move the legs, usually accompanied or caused by uncomfortable/ unpleasant sensations deep within the legs that begin or are worsened during periods of rest or inactivity in the evening or night and are partially or totally relieved by movement. It can occur intermittently or daily. Nonpharmacologic treatments include moderate exercise; good sleep hygiene; elimination of alcohol, caffeine, and nicotine; and hot baths, massage, and stretching. Activities promoting mental alertness may improve symptoms. Moderate exercise and use of nasal continuous positive airway pressure are the only nonpharmacologic treatments with proven benefit. For intermittent restless legs syndrome, carbidopa/levodopa and nonpharmacologic therapy are recommended as primary treatments. For daily restless legs syndrome, dopamine agonists, particularly ropinirole and pramipexole, are suggested as the drugs of choice. Carbidopa/levodopa could be considered for daily restless legs syndrome, but augmentation is a significant drawback to its use. Carbamazepine and gabapentin have limited data to support their use.