Motor pattern of periodic limb movements in sleep in idiopathic RLS patients

Periodic limb movements in sleep are linked to decreased hippocampus and amygdala volumes in the population-based BiDirect Study

STUDY OBJECTIVES

Even though numerous studies indicate that sleep disorders are associated with altered brain morphology, MRI studies focusing on periodic limb movements in sleep (PLMS) are scarce. Our aim was to investigate the association of PLMS with global and regional gray matter volumes as well as white matter hyperintensity (WMH) volume.

METHODS

One hundred and eighty-nine subjects (57.0 ± 7.8 years, women: 50.5%) of the population-based BiDirect Study underwent a single-night polysomnography (PSG). Standard criteria of the American Academy of Sleep Medicine were applied to evaluate sleep characteristics and calculate the PLMS index (PLMSI). T1w and FLAIR images were acquired with cerebral MRI at 3 Tesla. Voxel-based morphometry was performed to determine the total gray matter volume as well as the volume of cortical segments and subcortical gray matter areas using SPM12 and CAT12. The WMH volume was quantified with the Brain Intensity AbNormality Classification Algorithm. The independent relationship between MRI markers and PLMSI was analyzed using multivariable linear regression with adjustment for age, sex, body mass index, intracranial volume, PSG scorer, PSG device, sleep apnea, and the use of antidepressants.

RESULTS

PLMSI was not significantly related to global gray matter volume and WMH volume. However, significant inverse associations of the PLMSI with the volume of the hippocampus (left and right hemisphere) and left amygdala were observed.

CONCLUSIONS

A significant relationship between a higher PLMSI and lower volumes of the hippocampus and amygdala was found among the participants of the BiDirect Study. Since these associations are based on exploratory analyses, further replications are required before drawing firm conclusions.

Systematic review of neuromuscular diurnal activity in restless legs syndrome

Purpose.

The aim of this review was to systematically summarize the current literature on corticospinal excitation and muscle activity in restless legs syndrome (RLS) patients during daytime and diurnal activities. Three models of muscle activation in RLS directed this review: (i) evoked neuromuscular activation; (ii) sensory reflex responsiveness; (iii) voluntary muscle activation.

Methods.

A literature search was conducted in PubMed and Google Scholar, and 51 articles met the primary inclusion criteria. After a quality analysis, a total 13 articles were deemed of sufficient quality for data extraction.

Results.

Three studies on evoked neuromuscular activation demonstrated increased motor excitability associated with RLS. Sensory reflex responsiveness studies in RLS patients revealed increased reflex responsiveness, indicating increased spinal excitability and a possible dysfunction in afferent inhibition. Voluntary muscle activation studies showed both diurnal muscle electromyography abnormalities and an increased circadian variation in the musculature of the lower leg in RLS patients.

Conclusions.

Although a number of mechanisms have been evaluated increasing the understanding of RLS, few studies have evaluated RLS during daytime and diurnal muscle activity in patients with RLS. Furthermore, potential associations with the circadian rhythm have not been thoroughly investigated, nor have methodologies been combined. Future research should aim to establish differences in muscle activity of RLS patients and associate these differences with the duration and severity of symptoms. Suggestions for further studies are provided.

RestEaze: An Emerging Technology to Characterize Leg Movements During Sleep

Several sleep disorders are characterized by periodic leg movements during sleep including Restless Leg Syndrome, and can indicate disrupted sleep in otherwise healthy individuals. Current technologies to measure periodic leg movements during sleep are limited. Polysomnography and some home sleep tests use surface electromyography to measure electrical activity from the anterior tibilias muscle. Actigraphy uses 3-axis accelerometers to measure movement of the ankle. Electromyography misses periodic leg movements that involve other leg muscles and is obtrusive because of the wires needed to carry the signal. Actigraphy based devices require large amplitude movements of the ankle to detect leg movements (missing the significant number of more subtle leg movements) and can be worn in multiple configurations precluding precision measurement. These limitations have contributed to their lack of adoption as a standard of care for several sleep disorders. In this study, we develop the RestEaze sleep assessment tool as an ankle-worn wearable device that combines capacitive sensors and a 6-axis inertial measurement unit to precisely measure periodic leg movements during sleep. This unique combination of sensors and the form-factor of the device addresses current limitations of periodic leg movements during sleep measurement techniques. Pilot data collected shows high correlation with polysomnography across a heterogeneous participant sample and high usability ratings. RestEaze shows promise in providing ecologically valid, longitudinal measures of leg movements that will be useful for clinicians, researchers, and patients to better understand sleep.

Impact of different stages of chronic kidney disease on the severity of Willis-Ekbom disease

INTRODUCTION

Willis-Ekbom disease (WED)/restless legs syndrome (RLS) is a disorder in which the patient has neurologic features such as urge of rhythmic limb movement that may decrease or stop when the limb is moved. In this study, we had tried to compare the severity of WED in different stages of chronic kidney disease (CKD).

MATERIALS AND METHODS

In this study, a total of 300 patients with CKD who were >18 years of age were included. All the participants were subjected to questionnaire for the diagnosis of RLS (essential clinical criteria for the diagnosis of RLS) and a questionnaire on International Restless Legs Syndrome Study Group Rating Scale for its severity.

OBSERVATION AND RESULTS

Our study showed a prevalence of 20% of WED in patients with CKD. Patients with CKD on hemodialysis had significantly more WED than the conservative group (P = 0.0001). Patients with a history of diabetes mellitus showed significant correlation with WED (P = 0.026), while patients who had a history of hypertension showed both diabetes mellitus and hypertension and smoking had no significant relation with WED (P = 0.27, P = 0.23, and P = 0.22, respectively). The different stages of CKD showed significant correlation with WED (P = 0.002), with more WED among patients with stage V CKD. WED was more in patients on hemodialysis (P = 0.0001). The correlation of different stages of CKD with the severity of WED was statistically significant (P = 0.029), with WED being more severe among stage V CKD.

CONCLUSION

WED was more prevalent among patients with CKD who are on maintenance hemodialysis and diabetes mellitus. However, no such relation could be established for hypertension alone. Patients with higher grades of CKD were more prone to have WED symptoms, and the severity of these symptoms increases with the stages of CKD.

The neurophysiology of hyperarousal in restless legs syndrome: Hints for a role of glutamate/GABA

Restless legs syndrome (RLS) is a common sensory-motor circadian disorder, whose basic components include urge to move the legs, unpleasant sensory experience, and periodic leg movements during sleep, all associated with an enhancement of the individual's arousal state. Brain iron deficiency (BID) is considered to be a key initial pathobiological factor, based on alterations of iron acquisition by the brain, also moderated by genetic factors. In addition to the well-known dopaminergic involvement in RLS, previous studies pointed out that BID brings also a hyperglutamatergic state that influences a dysfunctional cortico-striatal-thalamic-cortical circuit in genetically vulnerable individuals. However, the enhancement of arousal mechanisms in RLS may also be explained by functional changes of the ascending arousal systems and by deficitary GABA-mediated inhibitory control. Very recently, it was also suggested that BID induces a hypoadenosinergic state in RLS, thus possibly providing a link for a putative unified pathophysiological mechanism accounting for both hyperarousal and sensory-motor signs. Consequently, RLS might be viewed as a multitransmitter neurochemical disorder, globally resulting in enhanced excitability and decreased inhibition. In this framework, understanding the complex interaction of different neuronal circuits in generating the symptoms of RLS is mandatory both for a better diagnostic refinement and for an innovative therapeutic support. Notably, multiple neurotransmission dysfunction, either primary or triggered by BID, may also bridge the gap between RLS and other chronic pain disorders. This chapter summarizes the current experimental and clinical findings into a heuristic model of the electrophysiology and neurochemistry underlying RLS.

The level of observed physical movement accompanying periodic limb movements measured in a clinical sleep population

STUDY OBJECTIVES

Periodic limb movements (PLMs) are routinely measured during polysomnogram (PSG) testing. During the early years of sleep testing, physical movements were identified and over time, consensus ultimately led to the current definitions of movement disorders including criteria used to measure PLMs on PSG testing. There has been considerable debate about the clinical importance of the PLMs measured during PSG testing. Over the last decade, the author has observed significant variations in the actual visible physical movements observed with a PLM event. This report is the result of work to quantify the amount of movement and the frequency of movements observed among individuals who have PLMs.

METHODS/PRINCIPAL FINDINGS

Consecutive PSGs performed in a suburban sleep center for an initial diagnosis of a sleep disorder were retrospectively reviewed to identify those with measured PLMs. Of 646 studies on patients >18 years, 460 met criteria for inclusion. Visual assessment of movements was carried out on all of those with PLM events measured using American Academy of Sleep Medicine guidelines. The movements were quantified based on the number of extremities observed to move. PLMs were observed in 237 of the 460 studies that met inclusion criteria (52%). As expected, the PLMs occurred more frequently in older individuals. PLMs occurred with equal frequency in both sexes. Apnea occurred with equal frequency in those with and without observed physical movements. Of those with PLMs, 62% (147) demonstrated observable physical movements. Significant movements involving three or four extremities occurred in 16% of individuals with PLMs. No physical movements were observed in 38%.

CONCLUSION

In this uncontrolled, nonrandom, observational series, visual physical movements with a PLM event identify a unique subset of individuals with PLMs. The presence of any visual movements or more pronounced visual movements involving multiple extremities may represent markers for PLM disorder, for clinically significant PLMs with other disorders, or for other clinical conditions or physiologic variables.

Central and peripheral nervous system excitability in restless legs syndrome

Neurophysiological techniques have been applied in restless legs syndrome (RLS) to obtain direct and indirect measures of central and peripheral nervous system excitability, as well as to probe different neurotransmission pathways. Data converge on the hypothesis that, from a pure electrophysiological perspective, RLS should be regarded as a complex sensorimotor disorder in which cortical, subcortical, spinal cord, and peripheral nerve generators are all involved in a network disorder, resulting in an enhanced excitability and/or decreased inhibition. Although the spinal component may have dominated in neurophysiological assessment, possibly because of better accessibility compared to the brainstem or cerebral components of a hypothetical dysfunction of the diencephalic A11 area, multiple mechanisms, such as reduced central inhibition and abnormal peripheral nerve function, contribute to the pathogenesis of RLS similarly to some chronic pain conditions. Dopamine transmission dysfunction, either primary or triggered by low iron and ferritin concentrations, may also bridge the gap between RLS and chronic pain entities. Further support of disturbed central and peripheral excitability in RLS is provided by the effectiveness of nonpharmacological tools, such as repetitive transcranial magnetic stimulation and transcutaneous spinal direct current stimulation, in transiently modulating neural excitability, thereby extending the therapeutic repertoire. Understanding the complex interaction of central and peripheral neuronal circuits in generating the symptoms of RLS is mandatory for a better refinement of its therapeutic support.

Alpha-melanocyte stimulating hormone and adrenocorticotropic hormone: an alternative approach when thinking about restless legs syndrome?

Alpha-melanocyte stimulating hormone (alpha-MSH) and adrenocorticotropic hormone (ACTH) possess properties suggesting that they may be involved in the pathogenesis of restless legs syndrome (RLS). We sought to determine if alpha-MSH and ACTH when administered centrally in rat recapitulate features reminiscent of RLS: increased activity, sleep fragmentation, and periodic movements during sleep. Rats were instrumented with electroencephalography, electromyography, and intracerebral cannulae and recorded for the measurement of sleep, periodic movements, and behavior following intracerebroventricular administration of alpha-MSH, ACTH, or saline. Studied behavior included grooming, locomotion, and rearing during wake and limb movements during sleep. Vigilance states included active wake (AW), quiet wake (QW), slow wave sleep I (SWSI), slow wave sleep II (SWSII), and paradoxical sleep (PS). All rats received normal saline acting as their own controls. Different rats received alpha-MSH in doses of 0.05, 0.5, 1.0, 2.0, and 6.0 microg or ACTH in doses of 0.5, 1.0, and 2.0 microg. Administered alpha-MSH caused an increase in waking behavior and prolongation of sleep latency, while ACTH stimulated waking behavior and fragmented sleep, yielding more AW and less SWSII and PS. Both hormones increased periodic movements during sleep. When administered centrally in rat, alpha-MSH and ACTH stimulate motor activity in wake, cause changes in sleep architecture, and increase periodic movements in sleep. These melanocortin hormones may play a role in the pathogenesis of RLS.

Assessment of restless legs syndrome—Methodological approaches for use in practice and clinical trials

The Restless Legs Syndrome (RLS) is a sensorimotor disorder that has only recently been extensively investigated by validated methods. Following the first presentation of diagnostic criteria by the International RLS Study Group in 1995, several methods were specifically developed for clinical trials in RLS or adapted from other areas of medicine and health sciences. We present a critical overview on validated methods to assess (1) severity of RLS symptoms [International RLS Rating Scale (IRLS), John Hopkins RLS Severity Scale (JHRLSSS), the RLS-6 scales, and the investigator-based Clincial Global Impressions (CGI)]; (2) quality of life [RLS Quality of Life Instrument (RLS-QLI), Hopkins RLS Quality of Life Questionnaire (RLSQoL), and the RLS Quality of Life Questionnaire (QoL-RLS)]; (3) sleep disturbances and sudden onset of sleep; (4) sleep laboratory methods (polysomnography, limb activity monitoring by actigraphy) to evaluate sleep and periodic leg movements (including the "suggested immobilization test"); and (5) severity of augmentation (Augmentation Severity Rating Scale, ASRS). It is concluded that several validated methods are available to investigate the main features of RLS in practice and in clinical trials; however, further developments are needed to address new questions like the consequences of RLS on life functioning in areas such as ability to travel, days missed at work or impaired work performance.