Putting the periodicity back into the periodic leg movement index: an alternative data-driven algorithm for the computation of this index during sleep and wakefulness

Periodic limb movement disorder in children: A systematic review

This systematic review evaluates the scientific literature on pediatric periodic limb movement disorder (PLMD), adhering to PRISMA guidelines and utilizing PICOS criteria. The search across PubMed, EMBASE, and Scopus yielded 331 articles, with 17 meeting inclusion criteria. Diagnostic criteria evolved, with polysomnography and PLMS index ≥5 required since 2003. Also, PLMD diagnosis mandates clinical consequences like insomnia, hypersomnia, and fatigue, excluding comorbidities causing sleep disruption. Prevalence in children is low (0.3%), emphasizing the need for meticulous investigation. Comorbidities, particularly the bidirectional relationship with ADHD, were explored. Challenges in diagnosis and understanding arise from overlapping conditions such as sleep disordered breathing, psychotropic medication, and criteria non-adherence. Despite generally good study quality, weaknesses include sample size justification and biases. The periodic leg movement index shows high sensitivity but low specificity, underscoring strict diagnostic criteria adherence. Diverse metrics for symptoms necessitate standardized approaches. Family history of RLS in children with PLMD suggests unexplored aspects. Treatment, mainly iron supplementation, lacks standardized assessment metrics. The review emphasizes diagnostic and treatment challenges, recommending unbiased studies with precise techniques. Comprehensive research, quantifying PLMS and objectively assessing sleep parameters, is crucial for advancing understanding in pediatric PLMD. PROSPERO REGISTRATION NUMBER: CRD42021251406.

Changes in time structure of periodic leg movements during sleep in restless legs syndrome: Effects of sex and age

BACKGROUND

The objective of this study was to check the hypothesis that in women with restless legs syndrome (RLS) different changes occur in periodic leg movements during sleep (PLMS) during the post-menopausal period (using >50 years as a proxy) than in men of the same age.

METHODS

We recruited 36 untreated patients aged 18-50 years (19 men, median age 40 years, and 17 women, median age 37 years) while the remaining 67 were >50 years old (24 men, median age 66.6 years, and 43 women, median age 60.0 years). Leg movement activity during sleep was analyzed by means of an approach utilizing indexes especially suitable to assess leg movement periodicity.

RESULTS

No significant difference was seen between men in the two age groups; conversely, in women, a clear and significant increase in Periodicity Index was observed in the older group, along with a decrease in isolated leg movements. In women, a clear age-related enhancement of PLMS was found in the intermovement interval graphs, especially in the 16-22 s range, which was more evident than that observed in men. The results remained unchanged also when they were replicated by selecting only subjects aged 18-45 years vs. those aged >55 years.

CONCLUSIONS

Our findings indicate that assessing PLMS in women after menopause is clinically relevant because they are probably connected with the hormonal fluctuations of this period of life. Translationally, identifying and addressing PLMS in post-menopausal women is crucial for optimizing their sleep health and addressing potential health risks associated with sleep disturbances.

Restless sleep disorder, restless legs syndrome, and periodic limb movement disorder-Sleep in motion!

Sleep-related movement disorders (SRMDs) represent an important part of pediatric sleep disorders. The most common complaint in SRMD is restless sleep at night. Restless sleep is reported in up to 80% of children with restless legs syndrome (RLS) and children with periodic limb movements of sleep (PLMS) disorder (PLMD). However, restless sleep causing daytime behavioral consequences can be seen in children without another apparent condition and has recently been identified as a new independent primary pediatric sleep disorder, called restless sleep disorder (RSD). This study describes these three main SRMDs (RSD, RLS, and PLMD), explains the new consensus criteria for RSD, emphasizes the rapidly evolving areas of research in this field, and proposes recommendations for future research. In particular, the published data constitute convincing evidence that sleep-related movements are disruptors of sleep quality and continuity. However, while important advancements have recently been reported in adults, a detailed analysis of the phenomenology and consequences of sleep-related movements has just started in children. New approaches, standardized diagnostic methods, and specific guidelines are needed in the field of pediatric SRMD.

Periodic limb movements during sleep: a narrative review

Objective

Using narrative review techniques, this paper evaluates the evidence for separable underlying patho-mechanisms of periodic limb movements (PLMs) to separable PLM motor patterns and phenotypes, in order to elucidate potential new treatment modalities.

Background

Periodic limb movement disorder (PLMD) is estimated to occur in 5–8% of the paediatric population and 4–11% of the general adult population. Due to significant sleep fragmentation, PLMD can lead to functional impairment, including hyperactivity and delayed language development in children, and poor concentration and work performance in adults. Longitudinal data demonstrate that those with PLMD are at greater risk of depression and anxiety, and a 4-fold greater risk of developing dementia. PLMD has been extensively studied over the past two decades, and several key insights into the genetic, pathophysiological, and neural correlates have been proposed. Amongst these proposals is the concept of separable PLM phenotypes, proposed on the basis of nocturnal features such as the ratio of limb movements and distribution throughout the night. PLM phenotype and presentation, however, varies significantly depending on the scoring utilized and the nocturnal features examined, across age, and co-morbid clinical conditions. Furthermore, associations between these phenotypes with major neurologic and psychiatric disorders remain controversial.

Methods

In order to elucidate potential divergent biological pathways that may help clarify important new treatment modalities, this paper utilizes narrative review and evaluates the evidence linking PLM motor patterns and phenotypes with hypothesised underlying patho-mechanisms. Distinctive, underlying patho-mechanisms include: a pure motor mechanism originating in the spinal cord, iron deficiency, dopamine system dysfunction, thalamic glutamatergic hyperactivity, and a more cortical-subcortical interplay. In support of the latter hypothesis, PLM rhythmicity appears tightly linked to the microarchitecture of sleep, not dissimilarly to the apnoeic/hypopneic events seen in obstructive sleep apnea (OSA).

Conclusions

This review closes with a proposal for greater investigation into the identification of potential, divergent biological pathways. To do so would require prospective, multimodal imaging clinical studies which may delineate differential responses to treatment in restless legs syndrome (RLS) without PLMS and PLMS without RLS. This could pave the way toward important new treatment modalities.

Leg Movements during Sleep in Children Treated with Serotonergic Antidepressants

STUDY OBJECTIVES

To evaluate leg movements during sleep (LMS) in children taking serotonergic antidepressants, compared to those of children with restless legs syndrome (RLS) and controls, and to assess the time structure of intermovement intervals (IMI).

METHODS

Twenty-three children (12 girls, mean age 14.1 years) on antidepressants and with a total LMS index ≥15/hour, 21 drug-naïve RLS children (11 girls, mean age 13.6 years) also with total LMS index ≥15/hour, and 35 control children (17 girls, mean age 14.3 years) were recruited. LMS were scored and a series of parameters was calculated, along with the analysis of their time structure.

RESULTS

Children taking antidepressants showed higher total and periodic LMS (PLMS) indexes than both controls and RLS children, as well as higher short-interval and isolated LMS indexes than controls. LMS periodicity was highest in children on antidepressants. In children taking antidepressants, a well-defined PLMS IMI peak corresponding to ~10-60 s, with a maximum at ~20 s was present, which was much less evident in RLS patients and absent in controls. A progressive decrease of PLMS during the night and more frequent arousals were found in children on antidepressants and with RLS.

CONCLUSIONS

Children taking serotonergic antidepressants show higher periodicity LMS than children with RLS or controls and have a higher number of PLMS through the night. Antidepressant-associated PLMS in children seem to have features similar to PLMS of adults with RLS. Whether this is a marker of an increased risk to develop RLS later in life needs to be determined.

A Polysomnographic and Cluster Analysis of Periodic Limb Movements in Sleep of Restless Legs Syndrome Patients with Psychiatric Conditions

Only survey studies have linked specific individual psychiatric disorders such as anxiety, depression and schizophrenia to Restless Legs Syndrome (RLS), Periodic Limb Movements in Sleep (PLMS) or both. We therefore aim to polysomnographically characterize sleep in a sample of physician-based, newly diagnosed cases of RLS with various ICD-10 psychiatric diagnoses. Retrospective analysis of data from a convenience sample of psychiatric patients (n = 43) per standard clinical sleep disorder cut-offs was conducted. Next, a cluster analysis was performed on the sleep data, taking into account the psychiatric diagnosis, comorbid non-psychiatric somatic problems and medication. We found that 37.2% of our sample showed clinically significant PLMS ≥ 15 and 76.5% exhibited an apnea hypopnea index (AHI) ≥ 5. Sleep structure was unaltered apart from the PLMS-related parameters. Two clusters were statistically identified: Cluster 1 primarily representing recurrent major depressive issues and Cluster 2 representing present but not predominant mood symptomatology as well as mixed disorders with personality problems. The known confounders were controlled. A PLMS index ≥ 15 was differentially distributed among the two clusters with Cluster 1: 10 out of 17 with PLMS index ≥ 15; Cluster 2: 1 out of 16 with PLMS index ≥15; whilst AHI was not different. Patients in Cluster 1 have a higher rate of periodic leg movements than patients in Cluster 2. This suggests that the high association with PLMS is primarily driven by affective disorders. Our findings warrant questioning of RLS symptomatology in patients with psychiatric conditions.

Periodic Leg Movements During Sleep

Periodic leg movements during sleep (PLMS) are a frequent finding in nocturnal sleep registrations that include tibialis anterior electromyographic signals. Different PLMS scoring rules exist and can have a major impact on PLMS frequency, which tends to be underappreciated. There is no consistent evidence that frequent PLMS are a causal risk factor for clinically significant outcomes. Several critical open questions are identified that need to be addressed, including but not limited to the consideration of the full range of all sleep-related leg movement activity.

Electroclinical Features of Sleep-Related Head Jerk

STUDY OBJECTIVES

To evaluate clinical and electrophysiological features of sleep-related head jerk (SRHJ) and electromyographic activity of superficial neck muscles during head jerk.

METHODS

Totally, 850 cases with video-polysomnography recording were collected, among which 50 presented with SRHJ. In these 50 patients, 15 underwent electromyography (EMG) check on bilateral sternocleidomastoid (SCM) and trapezius muscles as well as chin, while 35 had only chin EMG check. Further, the sensitivity and specificity of the both EMGs were calculated and compared.

RESULTS

Six among the 50 SRHJ patients had a primary complaint of involuntary head jerks associated with impaired sleep. Approximately 76.1% of head jerks occurred during REM sleep with the median head jerk index of 5.9/h, 64.5% of which were associated with electroencephalogram arousals and 66.4% with body movements. One patient showed SRHJ predominantly in NREM sleep but also in wakefulness. Surface EMG of SCM/trapezius muscles showed a sensitivity of 92% and a specificity of 97.8%, whereas chin EMG had a sensitivity of 14.5% and a specificity of 98.8%.

CONCLUSION

SRHJ was associated with electroencephalogram arousals and might interfere with sleep. Surface EMG of SCM/trapezius muscles exhibited a good accuracy in the revelation of SRHJ.

Effects of new PLM scoring rules on PLM rate in relation to sleep and resting wake for RLS and healthy controls

PURPOSE

This study evaluates the differences in periodic leg movement (PLM) rates for Restless Legs Syndrome (RLS) and healthy controls when using the updated PLM scoring criteria developed by IRLSSG in 2016 versus the prior PLM scoring criteria developed by IRLSSG in 2006. Four major problems with the prior standards had been objectively identified, i.e. minimum inter-movement interval should be 10 not 5 s, non-PLM leg movements should end any preceding PLM sequence, a leg movement (LM) can be any length > 0.5 s, and a PLM should be a persisting movement not a couple or a series of closely spaced, very brief events. Each of these led to including, erroneously, various random leg movements as PLM. Correcting these problems was expected to increase specificity, reducing the number of PLM detected, particularly in situations producing relatively more random leg movements, e.g. wake vs. sleep and controls without PLMD vs. RLS patients.

METHODS

This study evaluated the putative benefits of the updated, 2016-scoring criteria. The LMs from 42 RLS patients and 30 age- and gender-matched controls were scored for PLMS and PLMW from standard all-night PSG recordings using both 2006 and 2016 WASM criteria.

RESULTS/CONCLUSION

The results confirmed that that the 2016 compared to the 2006 criteria generally decreased the PLM rates with particularly large decreases for the conditions with more random non-PLM events, e.g. wake times and normal healthy controls. This supported the view that the new criteria succeeded in increasing the specificity of PLM detection. Moreover, the changes in PLM rates were generally small for the conditions with relatively few random LM, e.g. RLS and sleep. Thus the bulk of existing PLMS research does not require reconsideration of results, with possible exception of special situations with relatively more random leg movements than periodic leg movements, e.g. wake, healthy normals and children.

Limb movements during sleep in children: effects of age, sex, and iron status in more than 1,000 patients referred to a pediatric sleep center

STUDY OBJECTIVES

Limb movements during sleep (LMS) and periodic limb movements during sleep (PLMS) have been shown to vary by age in children. In the current study, we examined this relationship in more detail in a large clinically referred sample adjusting for iron status and sex.

METHODS

Retrospective data analysis was done on a large pediatric population who underwent an overnight sleep study and had ferritin levels measured within 30 days of sleep study between May 2013 and October 2017 at pediatric sleep center. Patients with obstructive or central sleep apneas were excluded.

RESULTS

A total of 1,070 patients were included in the study, with 60% males. Younger age and male sex were associated with increased PLMS and LMS. In addition, there was an increase in PLMS and LMS during adolescence that subsided at a later age, independent of sex. These associations remained significant in models controlling for ferritin level. Ferritin level, in contrast, was not a significant predictor of PLMS or LMS when controlling for sex and age.

CONCLUSIONS

Age and sex may need to be considered when interpreting limb movement indices in pediatric sleep patients regardless of ferritin level.

Leg Movement Activity During Sleep in Adults With Attention-Deficit/Hyperactivity Disorder

Objectives: To conduct a first detailed analysis of the pattern of leg movement (LM) activity during sleep in adult subjects with Attention-Deficit/Hyperactivity Disorder (ADHD) compared to healthy controls. Methods: Fifteen ADHD patients and 18 control subjects underwent an in-lab polysomnographic sleep study. The periodic character of LMs was evaluated with established markers of "periodicity," i.e., the periodicity index, intermovement intervals, and time distribution of LM during sleep, in addition to standard parameters such as the periodic leg movement during sleep index (PLMSI) and the periodic leg movement during sleep arousal index (PLMSAI). Subjective sleep and psychiatric symptoms were assessed using several, self-administered, screening questionnaires. Results: Objective sleep parameters from the baseline night did not significantly differ between ADHD and control subjects, except for a longer sleep latency (SL), a longer duration of the periodic leg movements during sleep (PLMS) in REM sleep and a higher PLMSI also in REM sleep. Data from the sleep questionnaires showed perception of poor sleep quality in ADHD patients. Conclusions: Leg movements during sleep in ADHD adults are not significantly more frequent than in healthy controls and the nocturnal motor events do not show an increased periodicity in these patients. The non-periodic character of LMs in ADHD has already been shown in children and seems to differentiate ADHD from other pathophysiological related conditions like restless legs syndrome (RLS) or periodic limb movement disorder (PLMD). The reduced subjective sleep quality reported by ADHD adults contrasted with the normal objective polysomnographic parameters, which could suggest a sleep-state misperception in these individuals or more subtle sleep abnormalities not picked up by the traditional sleep staging.

Isolated rapid eye movement sleep without atonia in amyotrophic lateral sclerosis

OBJECTIVE

The aim of this study was to quantitatively analyze, with the most recent and advanced tools, the presence of periodic leg movements during sleep (PLMS) and/or rapid eye movement (REM) sleep without atonia (RSWA), in a group of patients with amyotrophic lateral sclerosis (ALS), and to assess their eventual correlation with the clinical severity of the disease.

METHODS

Twenty-nine ALS patients were enrolled (mean age 63.6 years) along with 28 age-matched "normal" controls (mean age 63.8 years). Functional impairment due to ALS was evaluated using the ALS-Functional Rating Scale-Revised (ALS-FRS) and the ALS severity scale (ALSSS). Full video polysomnographic night recordings were obtained, and PLMS were analyzed by considering their number/hour of sleep and periodicity index, the distribution of intermovement intervals, and the distribution during the night. The characteristics of the chin electromyogram (EMG) amplitude during REM sleep were analyzed by means of the automatic atonia index and the number of chin EMG activations (movements).

RESULTS

The ALS patients showed longer sleep latency than the controls, together with an increase in number of stage shifts, increased sleep stage 1, and decreased sleep stage 2. None of the leg PLMS parameters were different between the ALS patients and controls. The REM atonia index was significantly decreased in the ALS patients, and the number of chin movements/hour tended to increase. Both REM atonia index and number of chin movements/hour correlated significantly with the ALS-FRS; REM atonia was higher and chin movements were less in ALS patients with more preserved function (higher scores on the ALS-FRS).

CONCLUSION

Abnormal REM sleep atonia seemed to be a genuine effect of ALS pathology per se and correlated with the clinical severity of the disease. It is unclear if this might constitute the basis of a possible risk for the development of REM sleep behavior disorder or represent a form of isolated RSWA in ALS.