Circadian variation in restless legs syndrome

Potential Effect of Vortioxetine on Restless Leg Syndrome

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

Restless legs syndrome in multiple sclerosis is related to retinal thinning

BACKGROUND

Restless legs syndrome (RLS) is one of the most frequent comorbidities accompanying multiple sclerosis. Patients with multiple sclerosis (MS) show thinning in the retinal layers throughout the disease. The thinning is related to acute attacks and progression and atrophy of the brain. Optical coherence tomography (OCT) provides relevant information on the pathophysiology of MS. We aimed to evaluate OCT parameters in patients with MS to investigate any changes related to the coexistence of RLS.

METHODS

We consecutively enrolled 75 adults with relapsing-remitting MS. Participants were assessed by using demographic and clinical parameters along with the excessive sleepiness in the daytime (ESS), fatigue severity scale (FSS), and RLS severity scale (IRLSSG). The thickness of the peripapillary retinal nerve fiber layer (pRNFL), macular thickness (MT), and macular ganglion cell - inner plexiform layer (MGCIPL) complex was measured with spectral-domain OCT.

RESULTS

Of the 75 participants, 20 were found to have RLS, and 55 did not. Scores of ESS, FSS, and MS disability (EDSS) were worse in patients with RLS. There was no significant difference in retinal nerve fiber layer thickness except for the inferior quadrant(p = 0.029). The mean inferior pRNFL thickness was 104.5 ± 22.6 μm in the RLS (+) group and 114.2 ± 21.6 μm in the RLS (-) group.

CONCLUSION

Patients with RLS had excessive daytime sleepiness, were more fatigued, had higher EDSS scores, and had a thinner retinal layer in the inferior quadrant. Overall, data from the study suggest a possible relationship between retinal volume changes in MS patients with RLS.

Does physical activity timing differentially correlate with symptoms of restless legs syndrome in adults with multiple sclerosis?

OBJECTIVE/BACKGROUND

The present study examined the associations among physical activity during different times of the day(i.e., morning, midday,evening) and days of the week(i.e., weekdays, weekend days) with restless legs syndrome(RLS) severity and sleep quality in adults with multiple sclerosis(MS).

PATIENTS/METHODS

Participants(N = 39) completed the International Restless Legs Syndrome Study Group Scale and the Pittsburgh Sleep Quality Index as measures of RLS severity and global sleep quality, respectively, and wore an ActiGraph GT3X + on the non-dominant hip for seven days for measuring physical activity(i.e., light physical activity[LPA], moderate-to-vigorous physical activity[MVPA], and steps).

RESULTS

There was a significant effect of time of day wherein participants had more midday activity compared with morning or evening for LPA, MVPA, and steps; there was no effect of day of the week. Spearman's rho correlations across the week indicated higher evening LPA, evening steps, and overall daily steps (ρ = -0.42,ρ = -0.51,ρ = -0.40,respectively) were associated with lower RLS severity. Similar associations were demonstrated for weekdays(ρ = -0.39,ρ = -0.50,ρ = -0.41,respectively) and weekend days(ρ = -0.44,ρ = -0.51,ρ = -0.39,respectively). Higher evening MVPA on weekend days(ρ = -0.42) was associated with lower RLS severity. Higher morning and overall daily LPA(ρ = 0.34,ρ = 0.33,respecitvely) were associated with worse sleep quality. Similar associations were demonstrated on weekdays(ρ = 0.33,ρ = 0.37,respectively) and more evening MVPA(ρ = 0.32) was associated with worse sleep quality. On weekend days, more morning MVPA(ρ = 0.42) was associated with worse sleep quality.

CONCLUSIONS

Our results suggest that undertaking physical activity, particularly LPA and steps, in evenings may be important for managing symptoms of RLS without worsening sleep quality.

Hypothalamic A11 Nuclei Regulate the Circadian Rhythm of Spinal Mechanonociception through Dopamine Receptors and Clock Gene Expression

Several types of sensory perception have circadian rhythms. The spinal cord can be considered a center for controlling circadian rhythms by changing clock gene expression. However, to date, it is not known if mechanonociception itself has a circadian rhythm. The hypothalamic A11 area represents the primary source of dopamine (DA) in the spinal cord and has been found to be involved in clock gene expression and circadian rhythmicity. Here, we investigate if the paw withdrawal threshold (PWT) has a circadian rhythm, as well as the role of the dopaminergic A11 nucleus, DA, and DA receptors (DR) in the PWT circadian rhythm and if they modify clock gene expression in the lumbar spinal cord. Naïve rats showed a circadian rhythm of the PWT of almost 24 h, beginning during the night–day interphase and peaking at 14.63 h. Similarly, DA and DOPAC’s spinal contents increased at dusk and reached their maximum contents at noon. The injection of 6-hydroxydopamine (6-OHDA) into the A11 nucleus completely abolished the circadian rhythm of the PWT, reduced DA tissue content in the lumbar spinal cord, and induced tactile allodynia. Likewise, the repeated intrathecal administration of D1-like and D2-like DA receptor antagonists blunted the circadian rhythm of PWT. 6-OHDA reduced the expression of Clock and Per1 and increased Per2 gene expression during the day. In contrast, 6-OHDA diminished Clock, Bmal, Per1, Per2, Per3, Cry1, and Cry2 at night. The repeated intrathecal administration of the D1-like antagonist (SCH-23390) reduced clock genes throughout the day (Clock and Per2) and throughout the night (Clock, Per2 and Cry1), whereas it increased Bmal and Per1 throughout the day. In contrast, the intrathecal injection of the D2 receptor antagonists (L-741,626) increased the clock genes Bmal, Per2, and Per3 and decreased Per1 throughout the day. This study provides evidence that the circadian rhythm of the PWT results from the descending dopaminergic modulation of spinal clock genes induced by the differential activation of spinal DR.

Uncovering the dynamics of a circadian-dopamine model influenced by the light-dark cycle

The neurotransmitter dopamine (DA) is known to be influenced by the circadian timekeeping system in the mammalian brain. We have previously created a single-cell differential equations model to understand the mechanisms behind circadian rhythms of extracellular DA. In this paper, we investigate the dynamics in our model and study different behaviors such as entrainment to the 24-hour light-dark cycle and robust periodicity versus decoupling, quasiperiodicity, and chaos. Imbalances in DA are often accompanied by disrupted circadian rhythms, such as in Parkinson's disease, hyperactivity, and mood disorders. Our model provides new insights into the links between the circadian clock and DA. We show that the daily rhythmicity of DA can be disrupted by decoupling between interlocked loops of the clock circuitry or by quasiperiodic clock behaviors caused by misalignment with the light-dark cycle. The model can be used to further study how the circadian clock affects the dopaminergic system, and to help develop therapeutic strategies for disrupted DA rhythms. .

Association Between CLOCK Gene Variants and Restless Legs Syndrome in Koreans

OBJECTIVE

Previous studies have suggested various causes of restless legs syndrome (RLS), including iron and dopamine concentrations in the brain. Genetic influences have also been reported in many studies. There is also a possibility that circadian clock genes may be involved because symptoms of RLS worsen at night. We investigated whether CLOCK and NPAS2 gene polymorphisms were associated with RLS.

METHODS

A total of 227 patients with RLS and 229 non-RLS matched controls were assessed according to the International Restless Legs Syndrome Study Group diagnostic criteria. Genotyping was performed using reverse transcription polymerase chain reaction and high-resolution melting curve analyses.

RESULTS

Although the genotype distributions of the CLOCK variants (rs1801260 and rs2412646) were not significantly different between patients with RLS and non-RLS controls, the allele frequencies of CLOCK rs1801260 showed marginally significant differences between the two groups (X2 =2.98, p=0.085). Furthermore, there was a significant difference in the distribution of CLOCK haplotypes (rs1801260-rs2412646) between patients with RLS and non-RLS controls (p=0.013). The distributions of allelic, genotypic, and haplotypic variants of NPAS2 (rs2305160 and rs6725296) were not significantly different between the two groups.

CONCLUSION

Our results suggest that CLOCK variants may be associated with decreased susceptibility to RLS.

Noninvasive neuromodulation reduces symptoms of restless legs syndrome

STUDY OBJECTIVES

Restless legs syndrome (RLS) is a common neurological disorder characterized by an uncontrollable nocturnal urge to move the legs and often associated with chronic sleep disturbances. The most common treatments for RLS are medications that can have debilitating side-effects. Here, we evaluated a novel alternative modality of RLS treatment, noninvasive bilateral electrical stimulation of the common peroneal nerve.

METHODS

To assess the impact of this noninvasive peripheral nerve stimulation (NPNS) approach on RLS symptomatology, we conducted a multi-site randomized crossover study comparing NPNS to sham. RLS patients with moderate to severe RLS (n=37) self-administered NPNS and sham nightly for 14 days per treatment in randomized order.

RESULTS

NPNS resulted in a reduction in RLS severity of 6.81 points on the International RLS Rating Scale (IRLS) relative to 3.38 for sham (p<0.01) and a 66% clinically significant responder rate on the Clinical Global Impressions-Improvement (CGI-I) scale compared to 17% for sham (p<0.01). Subgroup analysis indicated that medication-resistant and medication-naïve participants both exhibited similarly robust responses. There were no moderate or serious device-related adverse events.

CONCLUSIONS

These results suggest that NPNS could be a promising alternative to pharmacological therapies for RLS and could provide a solution for medication-resistant RLS patients and for medication-naïve RLS patients who are unwilling or unable to take medication.

CLINICAL TRIAL REGISTRATION

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

Abnormal Circadian Modification of Aδ-Fiber Pathway Excitability in Idiopathic Restless Legs Syndrome

Restless legs syndrome (RLS) is characterized by unpleasant sensations generally localized to legs, associated with an urge to move. A likely pathogenetic mechanism is a central dopaminergic dysfunction. The exact role of pain system is unclear. The purpose of the study was to investigate the nociceptive pathways in idiopathic RLS patients. We enrolled 11 patients (mean age 53.2 ± 19.7 years; 7 men) suffering from severe, primary RLS. We recorded scalp laser-evoked potentials (LEPs) to stimulation of different sites (hands and feet) and during two different time conditions (daytime and nighttime). Finally, we compared the results with a matched control group of healthy subjects. The Aδ responses obtained from patients did not differ from those recorded from control subjects. However, the N1 and the N2-P2 amplitudes' night/day ratios after foot stimulation were increased in patients, as compared to controls (N1: patients: 133.91 ± 50.42%; controls: 83.74 ± 34.45%; p = 0.016; Aδ-N2-P2: patients: 119.15 ± 15.56%; controls: 88.42 ± 23.41%; p = 0.003). These results suggest that RLS patients present circadian modifications in the pain system, which are not present in healthy controls. Both sensory-discriminative and affective-emotional components of pain experience show parallel changes. This study confirms the structural integrity of Aδ nociceptive system in idiopathic RLS, but it also suggests that RLS patients present circadian modifications in the pain system. These findings could potentially help clinicians and contribute to identify new therapeutic approaches.

Evaluation of Optical Coherence Tomography Results and Cognitive Functions in Patients with Restless Legs Syndrome

Introduction

The aim of this study was to evaluate whether retinal neural network was impaired and cognitive functions were disturbed in restless legs syndrome (RLS) considering the hypothesis that there may be a dysfunction in dopaminergic pathways in RLS like in Parkinson's disease. Therefore, we evaluated retinal neural network with optical coherence tomography (OCT) and presence of cognitive impairment with Montreal Cognitive Assessment (MOCA).

Methods

OCT evaluations were performed for 30 RLS patients and 30 healthy controls. Ganglion cell complex was segmented to retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), and inner plexiform layer (IPL) automatically by the device, and recorded. Additionally, all the patients and the controls were evaluated using MOCA.

Results

No statistically significant difference was detected between RLS and controls in RNFL, GCL, IPL, and choroidal thicknesses. However, total MOCA score and all of its subscale scores were significantly lower in the RLS patients compared with the controls. No significant correlation was detected between OCT and MOCA parameters.

Conclusion

No degeneration was detected in retinal neurons (RNFL, GCL, and IPL) of RLS patients. However, impairments were seen in MOCA total and subscale scores of these patients. On the other hand, no significant correlation was detected between MOCA scores and RNFL, GCL, or IPL thicknesses. These findings suggest decrease in cognitive functions of RLS patients probably due to dopaminergic dysfunction regardless of anatomical neural degeneration. Longitudinal follow-up studies are warranted to evaluate whether neuronal degeneration will develop.

The implication of neuronimmunoendocrine (NIE) modulatory network in the pathophysiologic process of Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder implicitly marked by the substantia nigra dopaminergic neuron degeneration and explicitly characterized by the motor and non-motor symptom complexes. Apart from the nigrostriatal dopamine depletion, the immune and endocrine study findings are also frequently reported, which, in fact, have helped to broaden the symptom spectrum and better explain the pathogenesis and progression of PD. Nevertheless, based on the neural, immune, and endocrine findings presented above, it is still difficult to fully recapitulate the pathophysiologic process of PD. Therefore, here, in this review, we have proposed the neuroimmunoendocrine (NIE) modulatory network in PD, aiming to achieve a more comprehensive interpretation of the pathogenesis and progression of this disease. As a matter of fact, in addition to the classical motor symptoms, NIE modulatory network can also underlie the non-motor symptoms such as gastrointestinal, neuropsychiatric, circadian rhythm, and sleep disorders in PD. Moreover, the dopamine (DA)-melatonin imbalance in the retino-diencephalic/mesencephalic-pineal axis also provides an alternative explanation for the motor complications in the process of DA replacement therapy. In conclusion, the NIE network can be expected to deepen our understanding and facilitate the multi-dimensional management and therapy of PD in future clinical practice.

Circadian Dysregulation in Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder that affects over one million individuals in the US alone. PD is characterized by a plethora of motor and non-motor manifestations, resulting from a progressive degeneration of dopaminergic neurons and disbalance of several other neurotransmitters. A growing body of evidence points to significant alterations of the circadian system in PD. This is not surprising given the pivotal role that dopamine plays in circadian regulation as well as the role of circadian influences in dopamine metabolism. In this review we present basic and clinical investigations that examined the function of the circadian system in PD.

Connectome and molecular pharmacological differences in the dopaminergic system in restless legs syndrome (RLS): plastic changes and neuroadaptations that may contribute to augmentation

Restless legs syndrome (RLS) is primarily treated with levodopa and dopaminergics that target the inhibitory dopamine receptor subtypes D3 and D2. The initial success of this therapy led to the idea of a hypodopaminergic state as the mechanism underlying RLS. However, multiple lines of evidence suggest that this simplified concept of a reduced dopamine function as the basis of RLS is incomplete. Moreover, long-term medication with the D2/D3 agonists leads to a reversal of the initial benefits of dopamine agonists and augmentation, which is a worsening of symptoms under therapy. The recent findings on the state of the dopamine system in RLS that support the notion that a dysfunction in the dopamine system may in fact induce a hyperdopaminergic state are summarized. On the basis of these data, the concept of a dynamic nature of the dopamine effects in a circadian context is presented. The possible interactions of cell adhesion molecules expressed by the dopaminergic systems and their possible effects on RLS and augmentation are discussed. Genome-wide association studies (GWAS) indicate a significantly increased risk for RLS in populations with genomic variants of the cell adhesion molecule receptor type protein tyrosine phosphatase D (PTPRD), and PTPRD is abundantly expressed by dopamine neurons. PTPRD may play a role in the reconfiguration of neural circuits, including shaping the interplay of G protein-coupled receptor (GPCR) homomers and heteromers that mediate dopaminergic modulation. Recent animal model data support the concept that interactions between functionally distinct dopamine receptor subtypes can reshape behavioral outcomes and change with normal aging. Additionally, long-term activation of one dopamine receptor subtype can increase the receptor expression of a different receptor subtype with opposite modulatory actions. Such dopamine receptor interactions at both spinal and supraspinal levels appear to play important roles in RLS. In addition, these interactions can extend to the adenosine A₁ and A_2A receptors, which are also prominently expressed in the striatum. Interactions between adenosine and dopamine receptors and dopaminergic cell adhesion molecules, including PTPRD, may provide new pharmacological targets for treating RLS. In summary, new treatment options for RLS that include recovery from augmentation will have to consider dynamic changes in the dopamine system that occur during the circadian cycle, plastic changes that can develop as a function of treatment or with aging, changes in the connectome based on alterations in cell adhesion molecules, and receptor interactions that may extend beyond the dopamine system itself.

A Review of Sleep and Its Disorders in Patients with Parkinson's Disease in Relation to Various Brain Structures

Sleep is an indispensable normal physiology of the human body fundamental for healthy functioning. It has been observed that Parkinson's disease (PD) not only exhibits motor symptoms, but also non-motor symptoms such as metabolic irregularities, altered olfaction, cardiovascular dysfunction, gastrointestinal complications and especially sleep disorders which is the focus of this review. A good understanding and knowledge of the different brain structures involved and how they function in the development of sleep disorders should be well comprehended in order to treat and alleviate these symptoms and enhance quality of life for PD patients. Therefore it is vital that the normal functioning of the body in relation to sleep is well understood before proceeding on to the pathophysiology of PD correlating to its symptoms. Suitable treatment can then be administered toward enhancing the quality of life of these patients, perhaps even discovering the cause for this disease.

Reduced daytime intramuscular blood flow in patients with restless legs syndrome/Willis-Ekbom disease

AIM

The aim of this study was to examine possible signs of impairment of the microcirculation in the lower extremities of female patients suffering from primary restless legs syndrome (RLS)/Willis-Ekbom disease.

METHODS

This study was performed in eight female patients, mean age 48 years (range 21-65), diagnosed with primary RLS but otherwise healthy. Eight healthy female control subjects, mean age 47 years (range 27-64), were also included in the study. Laser Doppler flowmetry was used to determine intramuscular blood flow by placing an optical single fiber in the tibialis anterior muscle belly. The studies were performed between 08.00 and 10.00 hours and 20.00 and 22.00 hours. Blood flow was expressed in perfusion units.

RESULTS

The median intramuscular blood flow in the RLS patients' tibialis anterior muscles, recorded from both legs, was significantly higher in the morning, at 17.9 perfusion units, than in the evening, at 12.1 perfusion units (P = 0.004). Corresponding values for the healthy controls were 13.1 perfusion units and 12.0 perfusion units, a non-significant difference. The relative fold changes of microcirculation in the RLS group compared to healthy age-matched controls were 0.7 ± 0.3 and 1.1 ± 0.6, respectively (P = 0.04).

CONCLUSION

Our results suggest that in female patients with primary RLS, the microcirculation in the tibialis anterior muscle is higher in the morning compared with in the evening.

Restless legs syndrome: differential diagnosis and management with rotigotine

RLS is a common sleep disorder with distinctive clinical features. The prevalence of RLS in Caucasians and North Americans ranges from 5% to 10%. However, only some of these subjects (almost the 3% of the general population) report being affected by a frequent and severe form of the sleep disorder. RLS is diagnosed clinically by means of four internationally recognized criteria that summarize the main characteristics of the sleep disorder. Besides the essential criteria, supportive and associated features of RLS have been established by experts in order to help physicians treat patients with doubtful symptoms. Several clinical conditions may mimic this sleep disorder. In order to increase the sensibility and specificity of RLS diagnosis, doctors should perform a meticulous patient history and then an accurate physical and neurological examination. Dopamine agonists are recognized as the preferred first-line treatment for RLS. Rotigotine is a non-ergoline dopamine agonist with selectivity for D1, D2 and D3 receptors. The drug is administered via transdermal patches which release rotigotine for 24 hours. Four clinical trials demonstrated that this compound is able to improve RLS symptomatology with few and moderate adverse events. Head to head trials are required to compare the efficacy and tolerability of rotigotine with other dopamine agonists administered via oral intake. Rotigotine has been approved by the FDA and EMEA for Parkinson's disease. For the treatment of moderate to severe idiopathic RLS, rotigotine has been recommended for approval by the EMEA and is under review by the FDA.

Ropinirole treatment for restless legs syndrome

Restless legs syndrome (RLS) is a chronic neurological disorder associated with sleep disturbance. Ropinirole, a non-ergot dopamine agonist, has been widely studied for the treatment of moderate-to-severe primary RLS in a comprehensive clinical development program. In these studies, ropinirole was effective in significantly improving the symptoms of RLS, compared with placebo, in patients with moderate-to-severe primary RLS. These improvements are supported by data from individual studies, as well as by pooled analyses. Significant improvements in RLS symptoms were observed within 2 nights of treatment. Ropinirole also produced significant benefits on objective measures of RLS motor symptoms, such as periodic leg movements; and on subjective measures of sleep, ropinirole was generally well tolerated. A newly developed extended-release formulation of ropinirole may benefit patients who warrant an extended duration of therapy.

Ropinirole treatment for restless legs syndrome

BACKGROUND

Restless legs syndrome (RLS) is a chronic neurological disorder associated with sleep disturbance.

OBJECTIVE

Prepare a drug evaluation of the non-ergot dopamine agonist ropinirole in RLS.

METHODS

Review of scientific literature on RLS, particularly focusing on treatment with ropinirole.

CONCLUSION

Ropinirole has been studied for treatment of moderate to severe primary RLS in a comprehensive clinical development program. Ropinirole significantly improved symptoms of RLS, versus placebo, in patients with primary RLS. These improvements are supported by data from individual studies and pooled analyses. Significant improvements in RLS symptoms were observed within two nights of treatment. Ropinirole also produced significant benefits on objective measures of RLS motor symptoms, such as periodic leg movements, and subjective measures of sleep. Ropinirole was generally well tolerated.

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.