EEG-based machine learning models for the prediction of phenoconversion time and subtype in isolated rapid eye movement sleep behavior disorder

STUDY OBJECTIVES

Isolated rapid eye movement sleep behavior disorder (iRBD) is a prodromal stage of α-synucleinopathies and eventually phenoconverts to overt neurodegenerative diseases including Parkinson's disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA). Associations of baseline resting-state electroencephalography (EEG) with phenoconversion have been reported. In this study, we aimed to develop machine learning models to predict phenoconversion time and subtype using baseline EEG features in patients with iRBD.

METHODS

At baseline, resting-state EEG and neurological assessments were performed on patients with iRBD. Calculated EEG features included spectral power, weighted phase lag index, and Shannon entropy. Three models were used for survival prediction, and four models were used for α-synucleinopathy subtype prediction. The models were externally validated using data from a different institution.

RESULTS

A total of 236 iRBD patients were followed up for up to 8 years (mean 3.5 years), and 31 patients converted to α-synucleinopathies (16 PD, 9 DLB, 6 MSA). The best model for survival prediction was the random survival forest model with an integrated Brier score of 0.114 and a concordance index of 0.775. The K-nearest neighbor model was the best model for subtype prediction with an area under the receiver operating characteristic curve of 0.901. Slowing of the EEG was an important feature for both models.

CONCLUSIONS

Machine learning models using baseline EEG features can be used to predict phenoconversion time and its subtype in patients with iRBD. Further research including large sample data from many countries is needed to make a more robust model.

Using spectral and temporal filters with EEG signal to predict the temporal lobe epilepsy outcome after antiseizure medication via machine learning

Epilepsy is a neurological disorder in which the brain is transiently altered. Predicting outcomes in epilepsy is essential for providing feedback that can foster improved outcomes in the future. This study aimed to investigate whether applying spectral and temporal filters to resting-state electroencephalography (EEG) signals could improve the prediction of outcomes for patients taking antiseizure medication to treat temporal lobe epilepsy (TLE). We collected EEG data from a total of 46 patients (divided into a seizure-free group (SF, n = 22) and a non-seizure-free group (NSF, n = 24)) with TLE and retrospectively reviewed their clinical data. We segmented spectral and temporal ranges with various time-domain features (Hjorth parameters, statistical parameters, energy, zero-crossing rate, inter-channel correlation, inter-channel phase locking value and spectral information derived from Fourier transform, Stockwell transform, and wavelet transform) and compared their performance by applying an optimal frequency strategy, an optimal duration strategy, and a combination strategy. For all time-domain features, the optimal frequency and time combination strategy showed the highest performance in distinguishing SF patients from NSF patients (area under the curve (AUC) = 0.790 ± 0.159). Furthermore, optimal performance was achieved by utilizing a feature vector derived from statistical parameters within the 39- to 41-Hz frequency band with a window length of 210 s, as evidenced by an AUC of 0.748. By identifying the optimal parameters, we improved the performance of the prediction model. These parameters can serve as standard parameters for predicting outcomes based on resting-state EEG signals.

Quantitative measurement of motor activity during sleep in isolated REM sleep behavior disorder patients using actigraphy before and after treatment with clonazepam

STUDY OBJECTIVES

We conducted a prospective study to quantify motor activity during sleep measured by actigraphy before and after 3 months of treatment with clonazepam in patients with video-polysomnography (vPSG) confirmed isolated rapid eye movement (REM) sleep behavior disorder (iRBD).

METHODS

The motor activity amount (MAA) and the motor activity block (MAB) during sleep were obtained from actigraphy. Then, we compared quantitative actigraphic measures with the results of the REM sleep behavior disorder questionnaire for the previous 3-month period (RBDQ-3M) and of the Clinical Global Impression-Improvement scale (CGI-I), and analyzed correlations between baseline vPSG measures and actigraphic measures.

RESULTS

Twenty-three iRBD patients were included in the study. After medication treatment, large activity MAA dropped in 39% of patients, and the number of MABs decreased in 30% of patients when applying 50% reduction criteria. 52% of patients showed more than 50% improvement in either one. On the other hand, 43% of patients answered "much or very much improved" on the CGI-I, and RBDQ-3M was reduced by more than half in 35% of patients. However, there was no significant association between the subjective and objective measures. Phasic submental muscle activity during REM sleep was highly correlated with small activity MAA (Spearman's rho = 0.78, p < .001) while proximal and axial movements during REM sleep correlated with large activity MAA (rho = 0.47, p = .030 for proximal movements, rho = 0.47, p = .032 for axial movements).

CONCLUSIONS

Our findings imply that quantifying motor activity during sleep using actigraphy can objectively assess therapeutic response in drug trials in patients with iRBD.

Diet quality and prodromal Parkinson's disease probability in isolated REM sleep behavior disorder

INTRODUCTION

It is reported that a diet that lowers oxidative stress reduces the prodromal Parkinson's disease (pPD) probability as well as the risk of Parkinson's disease (PD). In this study, we evaluated whether the diet quality of patients with isolated rapid eye movement (REM) sleep behavior disorder (iRBD) were associated with the pPD probability score, PD risk markers, or prodromal markers.

METHODS

Polysomnography (PSG)-confirmed iRBD patients from the Neurology Department at Seoul National University Hospital were enrolled. We calculated the pPD probability using the "Web-based Medical Calculator for Prodromal Risk in Parkinsonism" Diet quality was assessed using the Recommended Food Score (RFS).

RESULTS

We enrolled 101 patients with iRBD. The mean RFS score of patients with iRBD was 28.23 ± 9.29, which did not differ from the general population. Among patients with iRBD, the probability of pPD did not differ between the high and low RFS groups. In patients aged <70 years, although total RFS was not correlated with pPD probability (p = 0.529, Spearman rank correlation), legume consumption was negatively correlated with pPD probability (p = 0.032): furthermore, legume consumption was significantly higher in patients with fewer prodromal markers (p = 0.016).

CONCLUSION

Diet quality assessed by RFS did not differ between the general population and patients with iRBD in Korea. Further studies are needed to confirm these protective effects of legume consumption on iRBD, which may have strong implications for the prevention and management of PD.

Quantitative Network Comparisons of REM Sleep Without Atonia Across the α-Synucleinopathy Spectrum: A Systematic Review

Purpose

Isolated rapid eye movement (REM) sleep behavior disorder (iRBD) is characterized by REM sleep without atonia (RWA) and is regarded as the prodromal stage of α-synucleinopathies, such as Parkinson's disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA). RWA is also associated with neurodegeneration driven by α-synucleinopathy. However, the level of RWA across the α-synucleinopathy spectrum remains elusive. We aimed to rate the percentage of RWA across the α-synucleinopathy spectrum, encompassing prodromal and overt phenotypes.

Methods

A systematic search was conducted in the PubMed, Embase, Web of Science, and Cochrane Library databases. We included cohort, cross-sectional, and case-control studies comparing the RWA percentage during REM sleep evaluated by tonic chin activity (RWA%-T) or by phasic chin activity (RWA%-P) across the α-synucleinopathy spectrum. Bayesian network meta-analysis was used to combine both direct and indirect evidence regarding the group differences in the RWA%-T and RWA%-P. The surface under the cumulative ranking curve was used to estimate the ranked probability.

Results

Fifteen articles met the inclusion criteria. The investigations included 204 iRBD, 295 PD with RBD (PDwtRBD), 187 PD without RBD (PDwoRBD), 42 MSAwtRBD, 9 DLBwtRBD patients, and 246 controls. MSAwtRBD ranked first in RWA%-T, whereas iRBD ranked first in RWA%-P. RWA% in PDwoRBD patients was comparable to that in the controls and was lower than that in PDwtRBD patients.

Conclusion

Overt phenotypes such as MSAwtRBD and PDwtRBD ranked high in RWA%-T, whereas iRBD, a prodromal type, ranked highest in RWA%-P. Taken together, our data suggest that the percentage of neurodegeneration in RBD patients may be associated with RWA%-T rather than RWA%-P.

Prospero Registration Number

CRD42021276445.

Change of iron content in brain regions after intravenous iron therapy in restless legs syndrome: quantitative susceptibility mapping study

STUDY OBJECTIVES

The pathomechanism of restless legs syndrome (RLS) is related to brain iron deficiency and iron therapy is effective for RLS; however, the effect of iron therapy on human brain iron state has never been studied with magnetic resonance imaging. This study aimed to investigate the change of brain iron concentrations in patients with RLS after intravenous iron therapy using quantitative susceptibility mapping (QSM).

METHODS

We enrolled 31 RLS patients and 20 healthy controls. All participants underwent initial baseline (t0) assessment using brain magnetic resonance imaging, serum iron status, and sleep questionnaires including international RLS Study Group rating scale (IRLS). RLS patients underwent follow-up tests at 6 and 24 weeks (t1 and t2) after receiving 1000 mg ferric carboxymaltose. Iron content of region-of-interest on QSM images was measured for 13 neural substrates using the fixed-shaped method.

RESULTS

RLS symptoms evaluated using IRLS were significantly improved after iron treatment (t0: 29.7 ± 6.5, t1: 19.5 ± 8.5, t2: 21.3 ± 10.1; p < .001). There was no significant difference in susceptibility values between the controls and RLS patients at t0. In the caudate nucleus, putamen, and pulvinar thalamus of RLS patients, the QSM values differed significantly for three timepoints (p = .035, .048, and .032, respectively). The post-hoc analysis revealed that the QSM values increased at t1 in the caudate nucleus (66.8 ± 18.0 vs 76.4 ± 16.6, p = .037) and decreased from t1 to t2 in the putamen (69.4 ± 16.3 vs 62.5 ± 13.6, p = .025). Changes in the QSM values for the pulvinar and caudate nuclei at t1 were positively and negatively correlated with symptomatic improvement, respectively (r = 0.361 and -0.466, respectively).

CONCLUSIONS

Intravenous iron treatment results in changes in brain iron content which correlate to reductions in RLS severity. This suggests a connection between symptom improvement and the associated specific brain regions constituting the sensorimotor network.

The effect of continuous positive airway pressure (CPAP) on the quality of life in patients with multiple system atrophy

PURPOSE

To evaluate the effect of continuous positive airway pressure (CPAP) on the quality of life (QoL) in patients with multiple system atrophy (MSA) and their caregivers.

METHODS

We reviewed the electronic medical records of patients with MSA treated with CPAP (n = 15). After CPAP treatment, we checked the patient global impression of change (PGI-C) scale for sleep complaints and QoL for six patients who continued to use CPAP. QoL was also assessed for five caregivers of these patients.

RESULTS

A total of 15 patients (6 women) were included. The mean age was 63.6 ± 8.1 years old and the mean disease duration was 4.9 years. The mean duration of CPAP treatment was 22.1 ± 10.6 months and the average compliance was 90%. Three patients died during CPAP treatment, and two patients discontinued CPAP after tracheostomy. For six patients who continued to use CPAP, sleep complaints minimally improved. Five patients reported an improved QoL, and all five caregivers reported improved caregivers' QoL.

CONCLUSION

This study showed that the use of CPAP has a beneficial effect on sleep complaints and QoL of patients with MSA and their caregivers.

Five-Year Retention of Perampanel and Polytherapy Patterns: 328 Patients From a Single Center in South Korea

BACKGROUND AND PURPOSE

Perampanel (PER) is an α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid antagonist used to treat focal and generalized epilepsy. Comprehensive data from real-world settings with long-term follow-ups are still scarce. This study aimed to determine the factors related to PER retention and the polytherapy pattern with PER.

METHODS

We reviewed all patients with epilepsy with a history of PER prescription during 2008-2017 and over a follow-up of >3 years. PER usage patterns and associated factors were analyzed.

RESULTS

Among the 2,655 patients in the cohort, 328 (150 females, 178 males) were enrolled. The ages at onset and diagnosis were 21.1±14.7 years and 25.6±16.1 years (mean±standard deviation), respectively. The age at the first visit to our center was 31.8±13.8 years. Seizure types were focal, generalized, and unknown onset in 83.8%, 15.9%, and 0.3% of patients, respectively. The most common etiology was structural (n=109, 33.2%). The maintenance duration of PER was 22.6±19.2 months (range=1-66 months). The initial number of concomitant antiseizure medications was 2.4±1.4 (range=0-9). The most common regimen was PER plus levetiracetam (n=41, 12.5%). The median number of 1-year seizures before PER usage was 8 (range=0-1,400). A seizure reduction of >50% was recorded in 34.7% of patients (52.0% and 29.2% in generalized and focal seizures, respectively). The 1-, 2-, 3-, 4-, and 5-year retention rates for PER were 65.3%, 50.4%, 40.4%, 35.3%, and 21.5%, respectively. A multivariate analysis indicated that lower age at onset was associated with longer retention (p=0.01).

CONCLUSIONS

PER was safely used in patients with diverse characteristics and was maintained for a long time in a real-world setting, especially in patients with a lower age at onset.

A case of disorder of arousal with prolonged postarousal hypersynchronous delta activity

Disorder of arousal (DOA) is a form of non-rapid eye movement sleep parasomnia caused by partial or incomplete arousal from deep sleep. Most previous studies of patients with DOA analyzed prearousal hypersynchronous delta activity (HSDA), but few studies have described postarousal HSDA. Herein, we report a 23-year-old man with a history of abrupt arousal during sleep and confused behavior and speech since he was 14 years old. During video electroencephalography monitoring, he had 9 arousal events of getting up, sitting on the bed, looking around, or simple arousal, including eyes open, looking at the ceiling, or head flexion. During all arousal events, the postarousal electroencephalography pattern was prolonged HSDA for approximately 40 seconds. The patient was treated unsuccessfully for more than 2 years with an antiseizure medication (lacosamide); eventually, he responded to clonazepam that was administered for the possibility of DOA. Prolonged rhythmic HSDA without spatiotemporal evolution can appear as a postarousal electroencephalography pattern of DOA. When diagnosing DOA, it is important to recognize that postarousal HSDA can appear as a characteristic electroencephalography pattern of DOA.

CITATION

Kang M, Shin D, Lee HC, Provini F, Jung KY. A case of disorder of arousal with prolonged postarousal hypersynchronous delta activity. J Clin Sleep Med. 2023;19(7):1365-1368.

Characterization of attentional event-related potential from REM sleep behavior disorder patients based on explainable machine learning

BACKGROUND AND OBJECTIVE

Idiopathic rapid eye movement sleep behavior disorder (iRBD) is a prodromal stage of neurodegeneration and is associated with cortical dysfunction. The purpose of this study was to investigate the spatiotemporal characteristics of cortical activities underlying impaired visuospatial attention in iRBD patients using an explainable machine-learning approach.

METHODS

An algorithm based on a convolutional neural network (CNN) was devised to discriminate cortical current source activities of iRBD patients due to single-trial event-related potentials (ERPs), from those of normal controls. The ERPs from 16 iRBD patients and 19 age- and sex-matched normal controls were recorded while the subjects were performing visuospatial attentional task, and converted to two-dimensional images representing current source densities on flattened cortical surface. The CNN classifier was trained based on overall data, and then, a transfer learning approach was applied for the fine-tuning to each patient.

RESULTS

The trained classifier yielded high classification accuracy. The critical features for the classification were determined by layer-wise relevance propagation, so that the spatiotemporal characteristics of cortical activities that were most relevant to cognitive impairment in iRBD were revealed.

CONCLUSIONS

These results suggest that the recognized dysfunction in visuospatial attention of iRBD patients originates from neural activity impairment in relevant cortical regions and may contribute to the development of useful iRBD biomarkers based on neural activity.

Altered functional connectivity of the ascending reticular activating system in obstructive sleep apnea

Repeated arousals during sleep in obstructive sleep apnea (OSA) may lead to altered functional connectivity (FC) of the ascending reticular activating system (ARAS). We evaluated resting-state FC between eight ARAS nuclei and 105 cortical/subcortical regions in OSA patients and healthy controls. Fifty patients with moderate to severe OSA and 20 controls underwent overnight polysomnography and resting-state functional magnetic resonance imaging. Seed-to-voxel analysis of ARAS-cortex FC was compared between OSA patients and controls. The ARAS nuclei included the locus coeruleus (LC), laterodorsal tegmental nucleus (LDTg), and ventral tegmental area (VTA). FC values of three ARAS nuclei (the LC, LDTg, and VTA) significantly differed between the groups. FC of the LC with the precuneus, posterior cingulate gyrus, and right lateral occipital cortex (LOC) was stronger in OSA patients than controls. FC between the LDTg and right LOC was stronger in OSA patients than controls, but FC between the VTA and right LOC was weaker. Average LC-cortex FC values positively correlated with the arousal, apnea, and apnea-hypopnea index in OSA patients. Alterations in ARAS-cortex FC were observed in OSA patients. The strength of LC-cortex noradrenergic FC was related to arousal or OSA severity in patients.

Spatiotemporal characteristics of cortical activities of REM sleep behavior disorder revealed by explainable machine learning using 3D convolutional neural network

Isolated rapid eye movement sleep behavior disorder (iRBD) is a sleep disorder characterized by dream enactment behavior without any neurological disease and is frequently accompanied by cognitive dysfunction. The purpose of this study was to reveal the spatiotemporal characteristics of abnormal cortical activities underlying cognitive dysfunction in patients with iRBD based on an explainable machine learning approach. A convolutional neural network (CNN) was trained to discriminate the cortical activities of patients with iRBD and normal controls based on three-dimensional input data representing spatiotemporal cortical activities during an attention task. The input nodes critical for classification were determined to reveal the spatiotemporal characteristics of the cortical activities that were most relevant to cognitive impairment in iRBD. The trained classifiers showed high classification accuracy, while the identified critical input nodes were in line with preliminary knowledge of cortical dysfunction associated with iRBD in terms of both spatial location and temporal epoch for relevant cortical information processing for visuospatial attention tasks.

Anti-seizure medication prescription in epilepsy patients in South Korea: A seven-year population-based retrospective cohort study

BACKGROUND AND OBJECTIVES

This study aimed to explore the natural history of patients with epilepsy using overall antiseizure-medication (ASM) treatment patterns on a nationwide scale in South Korea.

METHODS

We investigated a retrospective longitudinal cohort of patients with epilepsy in South Korea using nationwide data from the Korean National Health Information Database of the Health Insurance and Review Assessment Service between January 1st, 2009, and December 31st, 2018. Histories of each patient's ASM prescription were followed for up to 7 years from the index date, the first observed date of ICD-10 epilepsy diagnosis codes with at least one ASM prescription.

RESULTS

Of 82,390 incident patients analyzed, ten thousand and fifty-nine were followed up to seven years, and nearly 60% of them discontinued the ASM(s). The proportion of patients with possible drug-resistant epilepsy (DRE), who experience three or more types of ASMs, gradually increased, reaching approximately 8.8% of the total number of patients in the seventh year (6.45% for adults, 21.8% for children). The duration of progression for half of the patients with possible DRE was 1.29 years for children, 1.79 years for adults, and 1.62 years for mixed-age patients. However, even in the sixth year, 72 cases progressed to possible DRE, and 6 cases with possible DRE discontinued ASMs in the next year, showing a dynamic process.

DISCUSSION

Our population-based study showed the dynamic changes of anti-seizure medication prescription in epilepsy patients with real-world data, which slowly stabilizes over years after the first diagnosis of epilepsy.

Progression of clinical markers in prodromal Parkinson's disease and dementia with Lewy bodies: a multicentre study

The neurodegenerative synucleinopathies, including Parkinson's disease and dementia with Lewy bodies, are characterized by a typically lengthy prodromal period of progressive subclinical motor and non-motor manifestations. Among these, idiopathic REM sleep behavior disorder (iRBD) is a powerful early predictor of eventual phenoconversion, and therefore represents a critical opportunity to intervene with neuroprotective therapy. To inform the design of randomized trials, it is essential to study the natural progression of clinical markers during the prodromal stages of disease in order to establish optimal clinical endpoints. In this study, we combined prospective follow-up data from 28 centers of the International REM Sleep Behavior Disorder Study Group representing 12 countries. Polysomnogram-confirmed REM sleep behavior disorder subjects were assessed for prodromal Parkinson's disease using the Movement Disorder Society criteria and underwent periodic structured sleep, motor, cognitive, autonomic and olfactory testing. We used linear mixed-effect modelling to estimate annual rates of clinical marker progression stratified by disease subtype, including prodromal Parkinson's disease and prodromal dementia with Lewy bodies. In addition, we calculated sample size requirements to demonstrate slowing of progression under different anticipated treatment effects. Overall, 1160 subjects were followed over an average of 3.3 ± 2.2 years. Among clinical variables assessed continuously, motor variables tended to progress faster and required the lowest sample sizes, ranging from 151-560 per group (at 50% drug efficacy and 2-year follow-up). By contrast, cognitive, olfactory, and autonomic variables showed modest progression with higher variability, resulting in high sample sizes. The most efficient design was a time-to-event analysis using combined milestones of motor and cognitive decline, estimating 117 per group at 50% drug efficacy and 2-year trial duration. Finally, while phenoconverters showed overall greater progression than non-converters in motor, olfactory, cognitive, and certain autonomic markers, the only robust difference in progression between Parkinson's disease and dementia with Lewy bodies phenoconverters was in cognitive testing. This large multicenter study demonstrates the evolution of motor and non-motor manifestations in prodromal synucleinopathy. These findings provide optimized clinical endpoints and sample size estimates to inform future neuroprotective trials.

Trends in sleep duration in Korea: The Korean time use survey

OBJECTIVES

An accurate assessment of sleep duration is important in that it can be one of the indicators of a country's overall health and well-being. The global trend in sleep duration is controversial according to study types. We investigated trends in sleep duration in South Korea with a time diary method.

METHODS

Data from the Korean Time Use Survey (KTUS) in 2004, 2009, 2014, and 2019, were analyzed. The KTUS is a nationwide, cross-sectional survey that measures daily time use patterns of individuals and has been performed every five years by Statistics Korea. For this survey, all participants were asked to record their activities for 2 continuous days in 10-min intervals.

RESULTS

Among the 168,682 people who completed the survey in 2004 through 2019, the final analytical sample consisted of 91,998 individuals. Over 15 years, the sleep duration of the Korean population increased from 411.1 min (SD 22.5) in 2004 to 434.5 min (SD 26.1) in 2019 (p for trend <0.001). This increase was observed for all age groups. Over the study period, while bedtime showed no significant change, wake time was generally delayed for all age groups. The increase in sleep duration in the Korean population was largely due to catch-up sleep on Saturdays, which was substantially prolonged with belated wake times.

CONCLUSION

Our nationwide time use survey data showed that sleep duration in South Korea has increased over the past 15 years but still has room for improvement in terms of weekday sleep duration.

Comparative efficacy of prolonged-release melatonin versus clonazepam for isolated rapid eye movement sleep behavior disorder

PURPOSE

Clonazepam and melatonin are recommended as first-line treatments for isolated rapid eye movement (REM) sleep behavior disorder (iRBD). This study aimed to compare their efficacy and safety in REM sleep without atonia (RWA) and RBD-related symptoms.

METHODS

This prospective, open-label, randomized trial included patients with video-polysomnography-confirmed iRBD. The patients were randomly assigned to receive either clonazepam 0.5 mg or prolonged-release (PR) melatonin 2 mg 30 min before bedtime for 4 weeks. The primary outcome was changes in RWA on follow-up polysomnography (PSG). Secondary endpoints were changes in other PSG parameters, clinical global improvement-impression scale (CGI-I) scores, and sleep questionnaire scores. The safety endpoint was adverse events.

RESULTS

Of 40 patients with probable RBD considered, 34 were enrolled in the study and randomized. Visual scoring parameters of RWA indices were reduced, and automatic scoring parameters tended to be improved after clonazepam treatment but not after PR melatonin treatment. The proportion of N2 sleep was increased, and N3 and REM sleep were decreased only in the clonazepam group. The clonazepam group tended to answer "much or very much improvement" on the CGI-I more frequently than the PR melatonin group (p = 0.068). Daytime sleepiness and insomnia symptoms were reduced after PR melatonin but not after clonazepam. Depressive symptoms increased after clonazepam. Four of the patients (13.3%) reported mild to moderate adverse events, which were similar between the two groups.

CONCLUSION

Four weeks of clonazepam, but not PR melatonin, improved RWA. RBD symptom improvement tended to be better after clonazepam than PR melatonin in exchange for increased depressive symptoms and daytime sleepiness.

CLINICALTRIALS

gov identifier: NCT03255642 (first submitted August 21, 2017).

Altered intrinsic brain functional network dynamics in moderate-to-severe obstructive sleep apnea

OBJECTIVES

Obstructive sleep apnea (OSA) can affect temporal fluctuations in brain activity during rest. Dynamic functional connectivity (dFC) captures the fluctuations in FC during the resting state. This study aimed to investigate differences in dFC between moderate-to-severe OSA patients and healthy controls using resting-state functional magnetic resonance imaging (fMRI) and sliding-window analysis.

METHODS

Thirty-seven consecutive patients with moderate-to-severe OSA and 16 age- and sex-matched controls underwent resting-state fMRI in the morning following overnight polysomnography. The dynamics of aberrant FC between the groups and the correlation between the dynamics and clinical variables were evaluated.

RESULTS

dFC analysis revealed two distinct connectivity states: hypoconnected (State I) and hyperconnected (State II). In OSA patients, State I occurred 34% more often than in the controls and the occurrence of State II was proportionally reduced. The time in State I positively correlated with the Pittsburg Sleep Quality Index score in the OSA patients.

CONCLUSIONS

This study showed dFC alterations in moderate-to-severe OSA patients, which may serve as a novel physiological biomarker for OSA.

Lesion Detection Through MRI Postprocessing in Pathology-Proven Focal Cortical Dysplasia: Experience at a Single Institution in the Republic of Korea

BACKGROUND AND PURPOSE

Focal cortical dysplasia (FCD) is one of the most common causes of drug-resistant epilepsy, and necessitates a multimodal evaluation to ensure optimal surgical treatment. This study aimed to determine the supportive value of the morphometric analysis program (MAP) in detecting FCD using data from a single institution in Korea.

METHODS

To develop a standard reference for the MAP, normal-looking MRIs by two scanners that are frequently used in this center were chosen. Patients with drug-resistant epilepsy and FCD after surgery were candidates for the analysis. The three-dimensional T1-weighted MRI scans of the patients were analyzed as test cases using the MAP.

RESULTS

The MRI scans of 87 patients were included in the analysis. The radiologist detected abnormal findings correlated with FCD (RAD positive [RAD(+)]) in 34 cases (39.1%), while the MAP could detect FCD in 25.3% of cases. A combination of the MAP (MAP[+] cases) with interpretations by the radiologist increased the detection to 42.5% (37 cases). The lesion detection rate was not different according to the type of reference scanners except in one case. MAP(+)/RAD(-) presented in three cases, all of which had FCD type IIa. The detection rate was slightly higher using the same kind of scanner as a reference, but not significantly (35.0% vs. 22.4% p=0.26).

CONCLUSIONS

The results of postprocessing in the MAP for detecting FCD did not depend on the type of reference scanner, and the MAP was the strongest in detecting FCD IIa. We suggested that the MAP could be widely utilized without developing institutional standards and could become an effective tool for detecting FCD lesions.

Comparative Analysis of Pupillometry in Idiopathic Rapid Eye Movement Sleep Behavior Disorder and Parkinson’s Disease

Background and Objective Pupillary light reflex (PLR) abnormalities have been reported in patients with Parkinson’s disease (PD). However, few studies have been conducted on the abnormality of PLR in patients with idiopathic rapid eye movement sleep behavior disorder (iRBD), which is a prodromal stage of α-synucleinopathy. We herein quantitatively analyzed the PLR of iRBD using an automated pupillometer, and compared the results with those of PD.Methods In this cross-sectional study, we prospectively enrolled 27 patients with polysomnography-confirmed iRBD, and 23 patients with PD. Pupillometry was performed three times in each eye, alternating left and right. We compared seven pupillometric parameters between the iRBD and PD patients.Results Maximum and minimum pupil diameters were significantly larger in PD patients than in iRBD patients. However, the other pupillometric parameters, such as mean constriction velocity, maximum constriction velocity, reflex amplitude, latency, and mean dilation velocity, did not differ between the two groups. Among iRBD patients, the pupillometric parameters were not correlated with any clinical characteristics related to autonomic dysfunction or neurodegeneration.Conclusions We found that the pupillary constriction and dilation in response to light of iRBD were not different from those of PD. These findings suggest that autonomic pupillary dysfunction already existed in the prodromal stage of α-synucleinopathy to a degree comparable to that in PD. Larger pupil diameters in PD than in iRBD may reflect the pharmacological effect of dopaminergic medications. Future studies are needed to elucidate the association between the PLR abnormalities and the risk of phenoconversion in iRBD.

Deep learning signature of brain [18F]FDG PET associated with cognitive outcome of rapid eye movement sleep behavior disorder

An objective biomarker to predict the outcome of isolated rapid eye movement sleep behavior disorder (iRBD) is crucial for the management. This study aimed to investigate cognitive signature of brain [¹⁸F]FDG PET based on deep learning (DL) for evaluating patients with iRBD. Fifty iRBD patients, 19 with mild cognitive impairment (MCI) (RBD-MCI) and 31 without MCI (RBD-nonMCI), were prospectively enrolled. A DL model for the cognitive signature was trained by using Alzheimer's Disease Neuroimaging Initiative database and transferred to baseline [¹⁸F]FDG PET from the iRBD cohort. The results showed that the DL-based cognitive dysfunction score was significantly higher in RBD-MCI than in RBD-nonMCI. The AUC of ROC curve for differentiating RBD-MCI from RBD-nonMCI was 0.70 (95% CI 0.56-0.82). The baseline DL-based cognitive dysfunction score was significantly higher in iRBD patients who showed a decrease in CERAD scores during 2 years than in those who did not. Brain metabolic features related to cognitive dysfunction-related regions of individual iRBD patients mainly included posterior cortical regions. This work demonstrates that the cognitive signature based on DL could be used to objectively evaluate cognitive function in iRBD. We suggest that this approach could be extended to an objective biomarker predicting cognitive decline and neurodegeneration in iRBD.

Explainable Machine-Learning-Based Characterization of Abnormal Cortical Activities for Working Memory of Restless Legs Syndrome Patients

Restless legs syndrome (RLS) is a sensorimotor disorder accompanied by a strong urge to move the legs and an unpleasant sensation in the legs, and is known to accompany prefrontal dysfunction. Here, we aimed to clarify the neural mechanism of working memory deficits associated with RLS using machine-learning-based analysis of single-trial neural activities. A convolutional neural network classifier was developed to discriminate the cortical activities between RLS patients and normal controls. A layer-wise relevance propagation was applied to the trained classifier in order to determine the critical nodes in the input layer for the output decision, i.e., the time/location of cortical activities discriminating RLS patients and normal controls during working memory tasks. Our method provided high classification accuracy (~94%) from single-trial event-related potentials, which are known to suffer from high inter-trial/inter-subject variation and low signal-to-noise ratio, after strict separation of training/test/validation data according to leave-one-subject-out cross-validation. The determined critical areas overlapped with the cortical substrates of working memory, and the neural activities in these areas were correlated with some significant clinical scores of RLS.

Comparison of rapid eye movement without atonia quantification methods to diagnose rapid eye movement sleep behavior disorder: a systematic review

Study Objectives

Rapid eye movement (REM) sleep without atonia (RWA) is essential for diagnosing REM sleep behavior disorder (RBD). Manual and automatic quantifications of RWA that use different criteria have been validated. This study compared the RWA quantification methods for diagnosing RBD.

Methods

The PubMed, EMBASE, Web of Science, and Cochrane Library databases were systemically searched for studies published from inception to December 2021. The inclusion criteria were cohort, cross-sectional, and case-control studies assessing the sensitivity and specificity of RWA quantification methods. Pooled estimates of the sensitivity, specificity, diagnostic odds ratio (DOR), and area under the curve (AUC) were determined. Risk of bias and certainty of evidence was assessed using the Quality Assessment of Diagnostic Accuracy Studies tool and the Grading of Recommendations, Assessment, Development, and Evaluations framework, respectively.

Results

Fourteen articles including 402 patients with RBD met the inclusion criteria. Manual methods evaluating any chin and phasic flexor digitorum superficialis (FDS) activity had the highest DOR (138.8, 95% CI = 21.8% to 881.7%) and AUC (0.9686). The automatic REM atonia index (RAI) showed similar or higher sensitivity (89.1%, 95% CI = 84.6% to 92.7%) but a lower specificity (73.5%), DOR (43.1), and AUC (0.9369) than the manual techniques.

Conclusions

In this meta-analysis, manual RWA quantification that employed chin or phasic FDS activity had the best RBD diagnostic performance. The automatic RAI method may be useful for screening patients with RBD. The results should be interpreted carefully because of the high risk of bias in patient selection and significant heterogeneity among the studies.

PROSPERO Registration number

CRD42021276445.

White matter tract-specific microstructural disruption is associated with depressive symptoms in isolated RBD

OBJECTIVE

White matter (WM) tract-specific changes may precede gray matter loss in isolated rapid eye movement sleep behavior disorder (iRBD). We aimed to evaluate tract-specific WM changes using tract-specific statistical analysis (TSSA) and their correlation with clinical variables in iRBD patients.

METHODS

This was a cross-sectional single-center study of 50 polysomnography-confirmed iRBD patients and 20 age- and sex-matched controls. We used TSSA to identify tract-specific fractional anisotropy (FA) and mean diffusivity (MD) in fourteen major fiber tracts and analyzed between-group differences in these values. Correlations between FA or MD values and clinical variables, including RBD symptom severity, depression and cognition, were evaluated.

RESULTS

Patients with iRBD showed lower FA in the right anterior thalamic radiation (ATR) and higher MD in the bilateral ATR and right inferior fronto-occipital fasciculus (IF-OF) than controls after adjusting for age, sex, and years of education. MD values in the IF-OF positively correlated with scores on the Korean version of the Rapid Eye Movement Sleep Behavior Disorder Questionnaire-Hong Kong (RBDQ-KR, p = 0.042) and the Korean version of the geriatric depression scale (GDS-K, p = 0.002) in iRBD patients. Only GDS-K scores independently correlated with IF-OF MD values after adjusting for RBDQ-KR scores (adjusted p = 0.026).

CONCLUSION

This study suggests WM microstructural disruption in the bilateral ATR and right IF-OF in patients with iRBD and that alterations in the IF-OF may contribute to depressive symptoms.

Multidimensional Early Prediction Score for Drug-Resistant Epilepsy

Background and Purpose

Achieving favorable postoperative outcomes in patients with drug-resistant epilepsy (DRE) requires early referrals for preoperative examinations. The purpose of this study was to investigate the possibility of a user-friendly early DRE prediction model that is easy for nonexperts to utilize.

Methods

A two-step genotype analysis was performed, by applying 1) whole-exome sequencing (WES) to the initial test set (n=243) and 2) target sequencing to the validation set (n=311). Based on a multicenter case–control study design using the WES data set, 11 genetic and 2 clinical predictors were selected to develop the DRE risk prediction model. The early prediction scores for DRE (EPS-DRE) was calculated for each group of the selected genetic predictors (EPS-DRE_gen), clinical predictors (EPS-DRE_cln), and two types of predictor mix (EPS-DRE_mix) in both the initial test set and the validation set.

Results

The multidimensional EPS-DRE_mix of the predictor mix group provided a better match to the outcome data than did the unidimensional EPS-DRE_gen or EPS-DRE_cln. Unlike previous studies, the EPS-DRE_mix model was developed using only 11 genetic and 2 clinical predictors, but it exhibited good discrimination ability in distinguishing DRE from drug-responsive epilepsy. These results were verified using an unrelated validation set.

Conclusions

Our results suggest that EPS-DRE_mix has good performance in early DRE prediction and is a user-friendly tool that is easy to apply in real clinical trials, especially by nonexperts who do not have detailed knowledge or equipment for assessing DRE. Further studies are needed to improve the performance of the EPS-DRE_mix model.

Association of Nucleus Basalis of Meynert Functional Connectivity and Cognition in Idiopathic Rapid-Eye-Movement Sleep Behavior Disorder

Background and Purpose

Cognitive impairments are common in isolated rapid-eye-movement sleep behavior disorder (iRBD), in which the cholinergic system may play an important role. This study aimed to characterize the cortical cholinergic activity using resting-state functional connectivity (FC) of the nucleus basalis of Meynert (NBM) according to the cognitive status of iRBD patients.

Methods

In this cross-sectional study, 33 patients with polysomnography-confirmed iRBD and 20 controls underwent neuropsychological evaluations and resting-state functional magnetic resonance imaging. Thirteen of the iRBD patients had mild cognitive impairment (iRBD-MCI), and the others were age-matched patients with normal cognition (iRBD-NC). The seed-to-voxel NBM–cortical FC was compared among the patients with iRBD-MCI, patients with iRBD-NC, and controls. Correlations between average values of significant clusters and cognitive function scores were calculated in the patients with iRBD.

Results

There were group differences in the FC of the NBM with the left lateral occipital cortex and lingual gyrus (adjusted for age, sex, and education level). The strength of FC was lower in the iRBD-MCI group than in the iRBD-NC and control groups (each post-hoc p<0.001). The average NBM–lateral occipital cortex FC was positively correlated with the memory-domain score in iRBD patients.

Conclusions

The results obtained in this study support that cortical cholinergic activity is impaired in iRBD patients with MCI. FC between NBM and posterior regions may play a central role in the cognitive function of these patients.

Neuropsychiatric symptoms and seizure related with serum cytokine in epilepsy patients

Neuroinflammation contributes to epileptogenesis and ictogenesis. Various signals of neuroinflammation lead to neuronal hyper-excitability. Since an interplay between epilepsy, psychiatric comorbidities and neuroinflammation has been suggested, we explored psychiatric symptoms in epilepsy patients, and the relationship with neuroinflammation. We screened epilepsy patients who were admitted for video-EEG monitoring between July 2019 and December 2020. Enrolled patients were asked to respond to neuropsychiatric questionnaires (Hospital Anxiety and Depression Scale (HADS) and Neuropsychiatric Inventory-Questionnaire (NPI-Q)) on admission. Serum cytokines (IL-1β, IL-2, IL-6, IFN-γ, CCL2, and CCL5) were measured by ELISA on admission, and within 6 h after a seizure. We enrolled 134 patients, and 32 patients (23.9%) had seizures during monitoring. Cytokine levels did not change after seizures, but IL-2 and IL-6 increased in cases of generalized tonic–clonic seizures. The HADS-A score was lower in Q4 of CCL5 (p-value = 0.016) and anxiety was also less common in Q4 of CCL5 (p-value = 0.042). NPI-Q question 4 (depression) severity was higher in CCL2 (p-value = 0.024). This suggested that psychiatric symptoms may also be related to inflammatory processes in epilepsy patients. Further large, standardized studies are necessary to underpin the inflammatory mechanisms in epilepsy and psychiatric symptoms.

Association of Zolpidem With Increased Mortality in Patients With Brain Cancer: A Retrospective Cohort Study Based on the National Health Insurance Service Database

Background and Purpose

Zolpidem is one of the most common hypnotics prescribed to treat insomnia worldwide. However, there are numerous reports of a positive association between zolpidem and mortality, including an association with increased cancer-specific mortality found in a Taiwanese cohort study. This study aimed to determine the association between zolpidem use and brain-cancer-specific mortality in patients with brain cancer.

Methods

This population-based, retrospective cohort study analyzed data in the National Health Insurance Service database. All incident cases of brain cancer at an age of ≥18 years at the time of brain cancer diagnosis over a 15-year period (2003–2017) were included. A multivariate Cox regression analysis after adjustment for covariables was performed to evaluate the associations of zolpidem exposure with brain-cancer-specific and all-cause mortality.

Results

This study identified 38,037 incident cases of brain cancer, among whom 11,823 (31.1%) patients were exposed to zolpidem. In the multivariate Cox regression model, the brain-cancer-specific mortality rate was significantly higher in patients who were prescribed zolpidem than in those with no zolpidem prescription (adjusted hazard ratio [HR]=1.14, 95% confidence interval [CI]=1.08–1.21, p<0.001). Zolpidem exposure was significantly associated with increased brain-cancer-specific mortality after adjustment in younger adults (age 18–64 years; adjusted HR=1.37, 95% CI=1.27–1.49) but not in older adults (age ≥65 years; adjusted HR=0.94, 95% CI=0.86–1.02).

Conclusions

Zolpidem exposure was significantly associated with increased brain-cancer-specific mortality in patients with brain cancer aged 18–64 years. Further prospective studies are warranted to understand the mechanism underlying the effect of zolpidem on mortality in patients with brain cancer.

Emotional and Environmental Factors Aggravating Dream Enactment Behaviors in Patients with Isolated REM Sleep Behavior Disorder

OBJECTIVE

To identify emotional and environmental factors that aggravate dream enactment behaviors (DEBs) in isolated rapid eye movement (REM) sleep behavior disorder (iRBD).

METHODS

In this cross-sectional study, a total of 96 polysomnography-confirmed iRBD patients (mean age, 68.5 years; men, 68%) and their caregivers completed questionnaires regarding potential aggravating factors related to DEBs, including emotion/feelings (stress, anger, anxiety, depressive mood, fatigue, pain), food (alcohol, caffeine, overeating in the evening, fasting/hunger), activities and sleep patterns (strenuous exercise, sex before bed, conflict/fighting, sleep deprivation, oversleeping, sleeping away from home, watching TV before bed), weather/environmental factors (cloudy or rainy weather, heat, cold, noise) and medication (skipping medication, taking hypnotics).

RESULTS

The patients reported that stress (61%) was the most aggravating factor for DEBs, followed by anxiety (56%), anger (51%), fatigue (49%), and watching TV before bed (46%). Similarly, the caregivers reported that these factors were most relevant to the aggravation of DEBs in the patients, although some factors were ranked differently. In the subgroup analyses, aggravating factors for DEBs did not differ by RBD symptom severity. Interestingly, the proportion of patients experiencing DEB aggravation by stress, anxiety and depressive mood was significantly higher in women than in men. Furthermore, depressed patients reported that stress and cloudy or rainy weather made DEBs worse than nondepressed patients.

CONCLUSION

Our results suggest that DEBs in iRBD patients may be mainly aggravated by emotional factors. These negative effects appeared to be more prominent in female and depressed patients.

Association of autosomal dominant polycystic kidney disease with cerebral small vessel disease

Cilia dysfunction in autosomal-dominant polycystic kidney disease (ADPKD) may impair the integrity of glymphatic system and be implicated in the progression of cerebral small vessel disease (SVD), although the link between the two diseases has not been investigated. We evaluated the association of ADPKD pathology with SVD pattern and severity. Overall, 304 individuals in an ADPKD (chronic kidney disease stage ≤4 and age ≥50 years) cohort and their age, sex, and estimated glomerular filtration rate (eGFR)-matched controls were retrospectively included. ADPKD severity was classified into 1 A-B, 1 C, and 1 D-E, according to age and height-adjusted total kidney volume. SVD parameters included white-matter hyperintensity (WMH) severity scale, enlarged perivascular space (ePVS) score, and degree of lacunes or cerebral microbleeds (CMBs). After adjustments for age, sex, eGFR, and cerebrovascular risk factor parameters, ADPKD was associated with higher ePVS scores (P < 0.001), but not with the WMH severity or degree of lacunes or CMBs. In the ADPKD subgroup, higher ADPKD severity class was associated with higher ePVS scores (P < 0.001), WMH severity (P = 0.003), and degree of lacunes (P = 0.002). ADPKD associated cilia dysfunction may induce chronic cerebral glymphatic system dysfunction, which may contribute to the specific progression of ePVS compared with other SVD markers.

Alerting network alteration in isolated rapid eye movement sleep behavior disorder patients with mild cognitive impairment

OBJECTIVE

Mild cognitive impairment (MCI) was found in 30-50% of the isolated REM sleep behavior disorder (iRBD) patients. Furthermore, it is known that patients with Parkinson's disease have attention network defects. Given that iRBD is known to be the prodromal disease of α-synucleinopathies, our aim was to investigate whether there are attention network dysfunctions in iRBD patients following the presence of MCI.

METHODS

14 healthy controls, 48 iRBD patients, 24 with MCI and 24 without MCI, were included in this study. Attention network task (ANT) was used to assess alerting, orienting, and executive control networks. Event-related potentials (ERPs) and behavioral performances were recorded during the ANT. Parietal N1 and P3 components were analyzed to find effects of the three attention networks.

RESULTS

IRBD patients without MCI showed neuropsychological, behavioral, and ERP results similar to those of healthy controls. On the other hand, iRBD patients with MCI showed a general decline in cognitive domains with no alerting effect (controls, p = 0.043; iRBD-noMCI, p = 0.014; iRBD-MCI, p = 0.130) while preserving orienting and executive control effect. Furthermore, iRBD patients with MCI had impairments in executive function and verbal memory domains, compared to iRBD patients without MCI.

CONCLUSIONS

Our findings indicate that when cognition is reduced to MCI levels in iRBD patients, the attention network, especially the alerting component, is impaired. The attention network and cognition, on the other hand, can be preserved in iRBD patients due to the compensatory mechanism.

Apolipoprotein E ε4 is not associated with cognitive impairment in patients with idiopathic REM sleep behavior disorder

We analyzed 136 patients (age, 67.5 ± 6.9 years; men, 59.6%) with idiopathic rapid eye movement sleep behavior disorder (iRBD). The results of the neuropsychological tests were not significantly different between APOE ε4 carriers and noncarriers, suggesting that the APOE ε4 allele was not associated with cognitive impairment in iRBD.

Serum neurofilament light chain as a severity marker for spinocerebellar ataxia

Since the serum neurofilament light (NfL) chain is known as a promising biomarker in neurodegenerative diseases, we aimed to evaluate serum NfL as a biomarker indicating neuronal damage in autosomal-dominant (AD) spinocerebellar ataxia (SCA). We reviewed patients diagnosed with AD SCA in the outpatient clinic of Seoul National University Hospital's (SNUH) Department of Neurology between May and August of 2019. We reviewed the demographic data, clinical characteristics, Scale for the Assessment and Rating of Ataxia (SARA) score, and brain magnetic resonance imaging (MRI) scans. The serum NfL was measured by electrochemiluminescence (ECL) immunoassay. Forty-nine patients with AD SCA were reviewed and their serum NfL level was determined. The median serum NfL level (109.5 pg/mL) was higher than control (41.1 pg/mL) (p-value < 0.001). Among the AD SCA patients, there was a positive correlation between the serum NfL level and the trinucleotide repeat number (r = 0.47, p-value = 0.001), disease duration (r = 0.35, p-value = 0.019), disease duration/age × trinucleotide repeat number (r = 0.330, p-value = 0.021), and SARA score (n = 33; r = 0.37, p-value = 0.033). This study shows that serum NfL is elevated in AD SCA patients and correlates with clinical severity.

A new rapid titration protocol for lamotrigine that reduces the risk of skin rash

Objective

Lamotrigine is one of the most widely used antiepileptic drugs, but it has a critical issue of a skin rash if the starting dose is too high or the escalation rate is too rapid. We investigated the efficacy and safety of a novel and rapid titration protocol for lamotrigine that takes only 11 days to reach a daily dose of 200 mg.

Methods

We prospectively enrolled 33 adult patients (age 18‐85) who were diagnosed with epilepsy and started lamotrigine administration for the first time at a single tertiary hospital. Our new protocol starts with a subthreshold dose of the drug and then administers a stepwise‐incremental dose until reaching the full therapeutic dose within 11 days.

Results

Of 29 patients analyzed, only two (6.9%) experienced idiosyncratic skin rash before the first follow‐up visit at 2 weeks (±3 days). In addition, a therapeutic concentration was reached in more than 75% of studied patients after 2 weeks of lamotrigine administration.

Significance

These findings demonstrate the value of the novel tolerance induction protocol for lamotrigine, which could widen the available application of lamotrigine in various situations. However, this study is a preliminary study limited by a small number of patients and its nonrandomized and open‐label design, so the current protocol needs more rigorous clinical evaluations before the application to the real clinical setting.

Sleep structure and electroencephalographic spectral power of middle-aged or older adults: Normative values by age and sex in the Korean population

The fine structure of sleep electrocortical activity reflects health and disease. The current study provides normative data for sleep structure and electroencephalography (EEG) spectral power measures derived from overnight polysomnography (PSG) and examines the effect of age and sex among Korean middle-aged and older adults with or without obstructive sleep apnea (OSA). We analysed home PSG data from 1,153 adult participants of an ongoing population-based cohort study, the Korean Genome and Epidemiology Study. Sleep stages were visually scored and spectral power was measured on a single-channel EEG (C4-A1). We computed spectral power for five frequency ranges. The EEG power was reported in relative (%) and log-transformed absolute values (µV² ). With ageing, the proportion of N1 sleep increased, whereas N3 decreased, which is more noticeable in men than in women. The amount of N3 was relatively low in this cohort. With ageing, relative delta power decreased and alpha and sigma power increased for the whole sleep period, which was more pronounced during REM sleep in non-OSA. For men compared with women, relative theta power was lower during REM and sigma and beta were higher during N1 sleep. The differences of relative powers by age and sex in OSA were comparable to those in non-OSA. In a community-based Korean population, we present normative data of sleep structure and spectral power for middle-aged or older adults of a non-Caucasian ethnicity. The values varied with age and sex and were not influenced by sleep apnea.

Reduced sympatho-vagal responses to orthostatic stress in drug-naïve idiopathic restless legs syndrome

STUDY OBJECTIVES

Restless legs syndrome (RLS) is known to be a risk factor for cardiovascular disease. However, there are no electrophysiological biomarkers to assess this risk. This study aimed to evaluate heart rate variability (HRV) and cardiovascular reflexes in the supine and standing positions during wakefulness in patients with RLS.

METHODS

Fourteen drug-naïve patients with RLS (12 women and 2 men, mean age, 42.14 ± 7.81 years) and 10 healthy control patients underwent tests for blood pressure, heart rate when in the supine and standing positions, and deep breathing and handgrip tests in controlled laboratory conditions. Data on 5-minute R-R intervals at each position were collected and analyzed for HRV.

RESULTS

Expected cardiovascular reflexes were within the normal range and were similar between the 2 groups. In HRV analysis, the normalized unit of the low-frequency component and the low-frequency/high-frequency ratio during standing were lower in patients with RLS than in the control patients. The low-frequency/high-frequency ratio responses during the change from the supine to the standing position were significantly reduced in patients with RLS (mean ± standard deviation, 2.94 ± 3.11; control patients: 7.51 ± 5.58; P = .042.) On Spearman rank correlation, questionnaires related to sleep problems were associated with the parameters of HRV.

CONCLUSIONS

Patients with RLS showed reduced sympatho-vagal responses during the change from the supine to the upright position during wakefulness, and RLS-related sleep disturbance was a contributing factor for autonomic nervous system dysfunction. This case-control study showed a difference in HRV response to position change in a considerably small group of patients with RLS. The relevance of this finding is uncertain, but it may be worthy of further investigation in longitudinal studies on RLS and cardiovascular disease.

Nonrapid eye movement sleep electroencephalographic oscillations in idiopathic rapid eye movement sleep behavior disorder: a study of sleep spindles and slow oscillations

STUDY OBJECTIVES

We investigated electroencephalographic (EEG) slow oscillations (SOs), sleep spindles (SSs), and their temporal coordination during nonrapid eye movement (NREM) sleep in patients with idiopathic rapid eye movement (REM) sleep behavior disorder (iRBD).

METHODS

We analyzed 16 patients with video-polysomnography-confirmed iRBD (age, 65.4 ± 6.6 years; male, 87.5%) and 10 controls (age, 62.3 ± 7.5 years; male, 70%). SSs and SOs were automatically detected during stage N2 and N3. We analyzed their characteristics, including density, frequency, duration, and amplitude. We additionally identified SO-locked spindles and examined their phase distribution and phase locking with the corresponding SO. For inter-group comparisons, we used the independent samples t-test or Wilcoxon rank-sum test, as appropriate.

RESULTS

The SOs of iRBD patients had significantly lower amplitude, longer duration (p = 0.005 for both), and shallower slope (p < 0.001) than those of controls. The SS power of iRBD patients was significantly lower than that of controls (p = 0.002), although spindle density did not differ significantly. Furthermore, SO-locked spindles of iRBD patients prematurely occurred during the down-to-up-state transition of SOs, whereas those of controls occurred at the up-state peak of SOs (p = 0.009). The phase of SO-locked spindles showed a positive correlation with delayed recall subscores (p = 0.005) but not with tonic or phasic electromyography activity during REM sleep.

CONCLUSIONS

In this study, we found abnormal EEG oscillations during NREM sleep in patients with iRBD. The impaired temporal coupling between SOs and SSs may reflect early neurodegenerative changes in iRBD.

A hospital-based study on etiology and prognosis of bacterial meningitis in adults

Bacterial meningitis is a neurological emergency with high morbidity and mortality. We herein investigated clinical features, etiology, antimicrobial susceptibility profiles, and prognosis of bacterial meningitis in adults from a single tertiary center. We retrospectively reviewed medical records of patients with laboratory-confirmed bacterial meningitis from 2007 to 2016. Patients with recent neurosurgery, head trauma, or indwelling neurosurgical devices were classified as having healthcare-related meningitis. Causative microorganisms were identified by analyzing cerebrospinal fluid (CSF) and blood cultures, and antimicrobial susceptibility profiles were evaluated. We performed multiple logistic regression analysis to identify factors associated with unfavorable outcomes. We identified 161 cases (age, 55.9 ± 15.5 years; male, 50.9%), of which 43 had community-acquired and 118 had healthcare-related meningitis. CSF and blood culture positivity rates were 91.3% and 30.4%, respectively. In community-acquired meningitis patients, Klebsiella pneumoniae (25.6%) was the most common isolate, followed by Streptococcus pneumoniae (18.6%) and Listeria monocytogenes (11.6%). The susceptibility rates of K. pneumoniae to ceftriaxone, cefepime, and meropenem were 85.7%, 81.3%, and 100%, respectively. Among healthcare-related meningitis patients, the most common bacterial isolates were coagulase-negative staphylococci (28.0%), followed by Staphylococcus aureus (16.1%) and Enterobacter spp. (13.6%). Neurological complications occurred in 39.1% of the patients and the 3-month mortality rate was 14.8%. After adjusting for covariates, unfavorable outcome was significantly associated with old age (odds ratio [OR] 1.03, 95% confidence interval [CI] 1.00–1.06), neurological complications (OR 4.53, 95% CI 1.57–13.05), and initial Glasgow coma scale ≤ 8 (OR 19.71, 95% CI 4.35–89.40). Understanding bacterial pathogens and their antibiotic susceptibility may help optimize antimicrobial therapy in adult bacterial meningitis.

Surgical treatment of nonlesional temporal lobe epilepsy

PURPOSE

One-third of the patients with drug-resistant temporal lobe epilepsy (TLE) have a normal MRI, but there are only a few studies regarding the surgical outcomes and the efficacy of anterior temporal lobectomy (ATL) in patients with nonlesional TLE. The objective of this study is to evaluate the surgical outcomes and efficacy of ATL in patients with nonlesional TLE.

METHODS

We included 77 consecutive patients without MRI-identifiable lesions who had undergone surgical resection for drug-resistant TLE. We performed univariate and multivariate logistic regression analyses to identify the predictors of surgical outcomes, and the efficacy of ATL in patients with nonlesional TLE.

RESULTS

More than two-thirds of patients (51/76, 67.3 %) had achieved seizure freedom at the last follow-up. Presence of oroalimentary automatism, localized hypometabolism in FDG-PET, and concordant results in presurgical evaluations were associated with better surgical outcomes. Only 15 out of 77 patients (19.2 %) with nonlesional TLE were treated with ATL, and the surgically resected areas were located within the resection margin of ATL in one-third of the patients (26/77, 33.8 %). Patients with auras suggesting neocortical ictal onset and lateralizing semiological features had a higher chance that their potentially epileptogenic areas were located beyond or outside the resection margin of ATL.

CONCLUSION

Our study showed that the potentially epileptogenic areas were located beyond or outside the margin of the ATL in nearly two-thirds of the patients. Several clinical factors may be useful in predicting the location of an epileptogenic area, which can help optimize a surgical strategy in these patients.

Working memory deficits in patients with idiopathic restless legs syndrome are associated with abnormal theta-band neural synchrony

Cognitive impairment, particularly prefrontal function, has been reported in patients with restless legs syndrome. However, working memory performance in patients with restless legs syndrome remains uncertain. The present study aimed to examine working memory performance in patients with restless legs syndrome by investigating electroencephalography theta-band oscillations within task-relevant brain regions and the synchronization among oscillations during a working memory task. Twelve female idiopathic patients with restless legs syndrome and 12 female healthy controls participated in this study. Nineteen-channel electroencephalography data were recorded while participants performed a Sternberg working memory task. We analysed event-related theta-band activity and interregional theta-band phase synchrony during the memory retrieval phase. The spatial pattern of theta-band phase synchrony was quantified using graph theory measures, including the clustering coefficient, characteristic path length, and small-world propensity. Considerable increases in theta-band activity and theta-band phase synchrony were observed at 600-700 ms in controls and at 650-750 ms in restless legs syndrome subjects after the probe item was presented. During this period, induced theta-band activity showed lower with borderline significance in the restless legs syndrome subjects than in the controls regardless of channel location (F_4,88  = 3.92, p = .06). Theta-band phase synchrony between the frontal and posterior regions was significantly reduced in the restless legs syndrome subjects. Inefficiency in both global and local networks in the restless legs syndrome subjects was revealed by the decreased small-world propensity (t₂₂  = 2.26, p = .03). Small-world propensity was negatively correlated with restless legs syndrome severity (r = -.65, p = .02). Our findings suggest that patients with restless legs syndrome have multiple deficits in cognitive processes, including attentional allocation, evaluation of incoming stimuli, and memory manipulation of encoded information during a working memory task. Abnormal local theta-band neural synchrony and global theta-band neural synchrony may underlie the neurophysiological mechanism of the working memory dysfunction associated with restless legs syndrome.

Tolerability of lacosamide rapid dose titration: A randomized, multicenter, prospective, open-label study

OBJECTIVE

Currently recommended dosing of lacosamide often necessitates long titration periods. However, the use of a regimen consisting of initial loading dose of 200 mg followed by a maintenance dose of 200 mg/day in practice suggests tolerability of more rapid titration schedules. We aimed to clarify whether the shortened titration schedule affects tolerability of lacosamide.

METHODS

We evaluated the safety of two rapid titration protocols designed to reach the target dose of 400 mg/day within 1 week, and the conventional weekly titration protocol (reaching the target dose of 400 mg/day in three weeks). The ≥50% responder rate and steady-state plasma concentration of lacosamide were also analyzed. Adverse events were assessed at 1 week and 5 weeks after reaching the target dose.

RESULTS

Seventy-five patients with epilepsy were enrolled and evenly distributed to three titration protocols, from which 5 patients were lost to follow-up and excluded from the safety analysis. Discontinuation of lacosamide or dose reductions due to adverse events occurred in 32 patients (46%), of whom a large majority (74%) had experienced adverse events after reaching 400 mg/day, demonstrating apparent dose-dependency. There was no difference in safety outcomes among the three titration groups. Concomitant use of sodium channel blockers significantly increased the risk of adverse events.

CONCLUSION

Rapid titration protocols for lacosamide were not associated with an increased risk of adverse events compared to the conventional weekly titration protocol. Uptitration of lacosamide at shorter intervals to an effective target dosage may be feasible in appropriate clinical situations.

Altered insular functional connectivity in isolated REM sleep behavior disorder: a data-driven functional MRI study

OBJECTIVE

Functional connectivity (FC) changes can occur prior to structural changes. This study aimed to evaluate data-driven whole-brain FC associated with isolated rapid eye movement sleep behavior disorder (iRBD) using multivariate pattern analysis (MVPA).

METHODS

This was a cross-sectional study of 50 polysomnography-confirmed iRBD patients and 20 age- and sex-matched controls. We used MVPA implemented in the connectome-MVPA CONN toolbox to identify data-driven seed regions for post hoc seed-to-voxel connectivity analysis. The association between FC changes and clinical characteristics, including cognition, depression, autonomic function, and daytime sleepiness, was evaluated.

RESULTS

MVPA revealed one significant cluster located in the left posterior insular cortex. Seed-to-voxel FC analysis using the cluster as a seed showed significantly reduced FC with two clusters located in the precuneus in iRBD patients compared to the controls. The degree of FC was associated with the Montreal Cognitive Assessment-Korean version scores (r = 0.317, p = 0.025).

CONCLUSION

This study emphasizes the insula as an important neural correlate associated with iRBD that was associated with cognitive function.

Respiratory virus-related meningoencephalitis in adults

Purpose

Respiratory viruses (RVs) are pathogens that can cause central nervous system (CNS) infection, but previous research has been limited to a pediatric population. In recent years, several cases of adult RV meningoencephalitis have begun to be reported. We decided to research the CNS infection of RV in the entire neuroinfection registry.

Methods

We retrospectively reviewed the neurologic infection registry of Seoul National University (Seoul, Korea). Among a total of 661 patients in the registry, 10 adult patients were diagnosed with RV-related meningoencephalitis on RV multiplex polymerase chain reaction (PCR) screening test. We analyzed the clinical presentation, laboratory findings, and clinical course of the 10 patients.

Results

Three patients were definite RV meningoencephalitis who had positive PCR results from cerebrospinal fluid. The other seven patients were diagnosed with probable RV meningoencephalitis if they had positive PCR results in the sputum and negative results in other extensive workup.

Conclusion

RV-related meningoencephalitis should be considered a possible etiology in adult meningoencephalitis patients. To diagnose these viruses, screening test of RV PCR is recommended even in patients without upper respiratory infection symptoms.

Dynamic changes in nocturnal blood glucose levels are associated with sleep-related features in patients with obstructive sleep apnea

Obstructive sleep apnea (OSA) has a bidirectional relationship with insulin resistance conditions; however, the mechanism remains unclear. This study aimed to compare dynamic nocturnal glucose changes among patients with OSA of varying levels of severity and evaluate temporal changes associated with the cardinal features of OSA (sympathetic hyperactivation, intermittent hypoxemia, and sleep fragmentation) in nondiabetic subjects. Nocturnal glucose was measured with a continuous glucose monitoring device every 5 min during polysomnography (PSG). The OSA features were evaluated using heart rate variability (HRV), minimum saturation, and electroencephalography. Eleven subjects with moderate to severe OSA and 12 subjects with no or mild OSA were evaluated. Those with moderate to severe OSA showed an increasing trend in blood glucose levels after sleep onset, whereas those without or with mild OSA showed a decreasing trend (F = 8.933, p < 0.001). Delta band power also showed different trends during sleep between the two groups (F = 2.991, p = 0.009), and minimum saturation remained lower in the moderate to severe OSA group than in the no or mild OSA group. High degrees of coupling between nocturnal glucose levels and each OSA feature were observed. Altered trends in nocturnal glucose in moderate to severe OSA may reflect glucose intolerance and result in metabolic consequences. Managing the features of sleep-related OSA may have implications for metabolic management in the future.

Bioinformatic analysis of proteomic data for iron, inflammation, and hypoxic pathways in restless legs syndrome

OBJECTIVE/BACKGROUND

We performed bioinformatic analysis of proteomic data to identify the biomarkers of restless legs syndrome (RLS) and provide insights into the putative pathomechanisms, including iron deficiency, inflammation, and hypoxic pathways.

PATIENTS/METHODS

Patients with drug-naïve idiopathic RLS were recruited at a university hospital from June 2017 to February 2018. Serum samples from patients with RLS (n = 7) and healthy sex- and age-matched controls (n = 6) were evaluated by proteomic analysis. For differentially expressed proteins (DEPs) in patients with RLS, compared to those in controls, the expression profiles and protein-protein interaction (PPI) network were characterized between dysregulated proteins and extracted proteins involved in iron deficiency, hypoxia, and inflammation responses using the String database (http://string-DB.org). The PPI network was visualized by Cytoscape ver. 3. 7. 1. Statistical analyses of the validation Western blot assays were performed using a Student's t-test.

RESULTS

Interactome network analysis revealed a relationship among the eight proteins, their associated genes, and 150, 47, and 11 proteins related to iron deficiency, inflammation, and hypoxic pathways, respectively. All DEPs were well associated with inflammation, and complement 3, complement C4A, alpha-2 HS glycoprotein, and alpha-2 macroglobulin precursor were found to be in hub positions of networks involved in PPIs including iron deficiency, hypoxia pathway, and inflammation. C3 and C4A were verified using western blotting.

CONCLUSIONS

We identified key molecules that represent the selected cellular pathways as protein biomarkers by PPI network analysis. Changes in inflammation can mediate or affect the pathomechanism of RLS and can thus act as systemic biomarkers.

HLAs associated with perampanel-induced psychiatric adverse effects in a Korean population

Perampanel (PER) is a new-generation antiepileptic drug that has an occasional but significant shortcoming, psychiatric adverse effects (PAEs). Recently, antiepileptic drug-related adverse reactions, such as skin rash and even PAEs, have been discovered to be correlated with certain human leukocyte antigen (HLA) types. Thus, we aimed to analyze specific HLA alleles as risk factors for PER-PAEs. We prospectively enrolled 17 patients with epilepsy who were prescribed PER between May 2016 and Jul 2018 at Seoul National University Hospital and developed PAEs while taking PER. Their HLA types were analyzed compared to those of 19 patients in the PAE-tolerant group and the general Korean population. In silico docking was performed with two different computational programs, AutoDock Vina and SwissDock, to theoretically evaluate the binding affinity of PER in the grooves of the specific HLA alleles. The HLA-DQB1*06:01, DRB1*08:03, and B*54:01 alleles were significantly associated with the patients who developed PER-PAEs compared with the general Korean population (odds ratio [OR] 3.94, p = 0.008, OR 9.24, p = 0.037, and OR 3.25, p = 0.041, respectively). As a haplotype, the combination of the three alleles was significantly more frequent in the PER-PAE group than in both the PER-tolerant group and the general Korean population. DQB1*06:01 and B*54:01 also demonstrated higher docking scores with PER than other alleles. This is the first study to analyze the association of PER-PAEs with specific HLA genotypes. Our results suggest that an HLA-associated genetic predisposition and a possible immunological mechanism are involved in the occurrence of PER-PAEs.