Surface EMG activity during REM sleep in Parkinson's disease correlates with disease severity

ObjectivesOver 40% of individuals with Parkinson's disease (PD) have rapid eye movement sleep behavior disorder (RBD). This is associated with excessive sustained (tonic) or intermittent (phasic) muscle activity instead of the muscle atonia normally seen during REM sleep. We examined characteristics of manually-quantitated surface EMG activity in PD to ascertain whether the extent of muscle activity during REM sleep is associated with specific clinical features and measures of disease severity.MethodsIn a convenience sample of outpatients with idiopathic PD, REM sleep behavior disorder was diagnosed based on clinical history and polysomnogram, and severity was measured using the RBD sleep questionnaire. Surface EMG activity in the mentalis, extensor muscle group of the forearms, and anterior tibialis was manually quantitated. Percentage of REM time with excessive tonic or phasic muscle activity was calculated and compared across PD and RBD characteristics.ResultsAmong 65 patients, 31 had confirmed RBD. In univariate analyses, higher amounts of surface EMG activity were associated with longer PD disease duration (srho = 0.34; p = 0.006) and greater disease severity (p < 0.001). In a multivariate regression model, surface EMG activity was significantly associated with RBD severity (p < 0.001) after adjustment for age, PD disease duration, PD severity and co-morbid sleep abnormalities.ConclusionSurface EMG activity during REM sleep was associated with severity of both PD and RBD. This measure may be useful as a PD biomarker and, if confirmed, may aid in determining which PD patients warrant treatment for their dream enactment to reduce risk of injury.     

A comparative study of methods for automatic detection of rapid eye movement abnormal muscular activity in narcolepsy

ObjectiveTo evaluate rapid eye movement (REM) muscular activity in narcolepsy by applying five algorithms to electromyogram (EMG) recordings, and to investigate its value for narcolepsy diagnosis.Patients/methodsA modified version of phasic EMG metric (mPEM), muscle activity index (MAI), REM atonia index (RAI), supra-threshold REM EMG activity metric (STREAM), and Frandsen method (FR) were calculated from polysomnography recordings of 20 healthy controls, 18 clinic controls (subjects suspected with narcolepsy but finally diagnosed without any sleep abnormality), 16 narcolepsy type one without REM sleep behavior disorder (RBD), nine narcolepsy type one with RBD, and 18 narcolepsy type two. Diagnostic value of metrics in differentiating between groups was quantified by area under the receiver operating characteristic curve (AUC). Correlations among the metrics and cerebrospinal fluid hypocretin-1 (CSF-hcrt-1) values were calculated using linear models.ResultsAll metrics excluding STREAM found significantly higher muscular activity in narcolepsy one cases versus controls (p < 0.05). Moreover, RAI showed high sensitivity in the detection of RBD. The mPEM achieved the highest AUC in differentiating healthy controls from narcoleptic subjects. The RAI best differentiated between narcolepsy 1 and 2. Lower CSF-hcrt-1 values correlated with high muscular activity quantified by mPEM, sMAI, lMAI, PEM and FR (p < 0.05).ConclusionsThis automatic analysis showed higher number of muscle activations in narcolepsy 1 compared to controls. This finding might play a supportive role in diagnosing narcolepsy and in discriminating narcolepsy subtypes. Moreover, the negative correlation between CSF-hcrt-1 level and REM muscular activity supported a role for hypocretin in the control of motor tone during REM sleep.     

Clinical manifestations of Parkinson disease and the onset of rapid eye movement sleep behavior disorder

ObjectiveTo identify whether the presence and/or timing of rapid eye movement (REM) sleep behavior disorder (RBD) onset were associated with differences in clinical features and sleep parameters of Parkinson disease (PD).MethodsIn all, 112 PD patients were enrolled and all underwent extensive clinical evaluations and video-polysomnography (PSG). Clinical features and PSG parameters were compared in PD patients with (PD + RBD) or without (PD − RBD) RBD, RBD preceding (RBD > PD), or not (PD ⩾ RBD) PD onset.ResultsSixty-three of the 112 PD patients were affected by RBD. Adjusted for age, gender, education, body mass index (BMI), levodopa equivalent daily dose (LED) and PD duration, PD + RBD patients had higher Hoehn & Yahr stage, higher scores for UPDRS parts I, II and III, more dyskinesia, higher ratio of axial/limb manifestations, and more hallucinations. Their cognitive and quality-of-life status was significantly lower (all P < 0.05). For PSG, PD + RBD patients exhibited higher percentages of phasic and tonic EMG activities, lower apnea hypopnea (AHI) and oxygen desaturation index (ODI), and less time in arterial oxygen saturation (SaO₂) <90% during REM sleep (all P < 0.05). PD ⩾ RBD (n = 22) patients did not significantly differ from RBD > PD (n = 41) patients in clinical manifestations, whereas the PD ⩾ RBD subgroup had significantly higher UPDRS part I score, lower PDQ score and lower AHI during REM than the PD − RBD group (all P < 0.05), but not RBD > PD subgroup. Correlation analysis showed that worse cognition was associated with shorter interval of RBD preceding PD onset (r = 0.297, P = 0.018), but not RBD duration (P = 0.202).ConclusionsClinical manifestations of PD may vary depending on the presence and timing of RBD onset. These findings are compatible with the hypothesis that RBD may be a marker of complex subtypes of PD.     

Decreased sleep spindle density in patients with idiopathic REM sleep behavior disorder and patients with Parkinson’s disease

ObjectiveTo determine whether sleep spindles (SS) are potentially a biomarker for Parkinson’s disease (PD).MethodsFifteen PD patients with REM sleep behavior disorder (PD + RBD), 15 PD patients without RBD (PD − RBD), 15 idiopathic RBD (iRBD) patients and 15 age-matched controls underwent polysomnography (PSG). SS were scored in an extract of data from control subjects. An automatic SS detector using a Matching Pursuit (MP) algorithm and a Support Vector Machine (SVM) was developed and applied to the PSG recordings. The SS densities in N1, N2, N3, all NREM combined and REM sleep were obtained and evaluated across the groups.ResultsThe SS detector achieved a sensitivity of 84.7% and a specificity of 84.5%. At a significance level of α = 1%, the iRBD and PD + RBD patients had a significantly lower SS density than the control group in N2, N3 and all NREM stages combined. At a significance level of α = 5%, PD − RBD had a significantly lower SS density in N2 and all NREM stages combined.ConclusionsThe lower SS density suggests involvement in pre-thalamic fibers involved in SS generation. SS density is a potential early PD biomarker.SignificanceIt is likely that an automatic SS detector could be a supportive diagnostic tool in the evaluation of iRBD and PD patients.     

Characteristics of early- and late-onset rapid eye movement sleep behavior disorder in China: a case–control study

ObjectiveTo investigate demography and clinic and polysomnographic characteristics in Chinese rapid eye movement (REM) sleep behavior disorder (RBD) patients across onset ages.MethodsNinety consecutive patients fulfilling the criteria for RBD were recruited for study in our sleep center. Patients were separated into early- and late-onset groups according to age when symptoms began (⩽50 and >50 years, respectively). Ninety age- and gender-matched healthy subjects served as controls. All subjects were interviewed for their clinical history, completed an RBD questionnaire, and underwent an overnight video polysomnography assessment. Demographics, comorbidities, scores on the RBD questionnaire, sleep architecture, and EMG activity were compared between the patients and controls and between the early- and late-onset groups.ResultsOf all RBD patients, 63 were male, and mean age of RBD onset was 54.3 ± 15.7 years. In 25 patients (28%), RBD was secondary and associated with neurodegenerative disease, narcolepsy or antidepressant use. Twenty-three patients (26%) had early-onset RBD and 67 (74%) were in the late-onset group. RBD patients had significantly more comorbidities, dreams and dream-enacting behaviors, and poorer sleep quality than did controls. The early-onset group had a high proportion of females (48%) and an increased proportion of cases associated with narcolepsy. The early-onset group also had fewer movements, lower EMG activity during REM sleep, and better sleep quality when compared to the late-onset group. EMG activity was positively correlated with age of onset. The mean follow-up time was 1.57 ± 0.82 years, and four patients in the late-onset group were subsequently diagnosed with neurodegenerative diseases.ConclusionsStratifying patients into early and late-onset RBD revealed different characteristics from those previously described as typical for RBD. EMG activity during REM sleep was positively correlated with age of onset. We suggest that it will be valuable to explore the relationship between age of onset conversion and neurodegenerative diseases.     

First rapid eye movement sleep periods and sleep-onset rapid eye movement periods in sleep-stage sequencing of hypersomnias

ObjectivesDiscrimination between narcolepsy, idiopathic hypersomnia, and behavior-induced inadequate sleep syndrome (BIISS) is based on clinical features and on specific nocturnal polysomnography (NPSG) and multiple sleep latency test (MSLT) results. However, previous studies have cast doubt on the specificity and sensitivity of these diagnostic tools.MethodsEleven variables of the NPSG were analyzed in 101 patients who were retrospectively diagnosed with narcolepsy with cataplexy (N + C) (n = 24), narcolepsy without cataplexy (N−C) (n = 38), idiopathic hypersomnia with long sleep period (IHL) (n = 21), and BIISS (n = 18).ResultsFifteen out of 24 N + C and 8 out of 38 N−C entered the first rapid eye movement (REM) sleep period (FREMP) from sleep stage 1 (N1) or wake (W), though this sleep-stage sequence did not arise in the other patient groups. FREMP stage sequence was a function of REM sleep latency (REML) for both N + C and N−C groups. FREMP stage sequence was not associated with mean sleep latency (MSL) in N + C but was associated in N−C, which implies heterogeneity within the N−C group. REML also was a useful discriminator. Depending on the cutoff period, REML had a sensitivity and specificity of up to 85.5% and 97.4%, respectively.ConclusionsThe FREMP stage sequence may be a useful tool in the diagnosis of narcolepsy, particularly in conjunction with sleep-stage sequence analysis of sleep-onset REM periods (SOREMPs) in the MSLT; it also may provide a helpful intermediate phenotype in the clarification of heterogeneity in the N−C diagnostic group. However, larger prospective studies are necessary to confirm these findings.     

Improved computation of the atonia index in normal controls and patients with REM sleep behavior disorder

ObjectiveThe aim of this study was to evaluate the effects of a simple method of noise reduction before the calculation of the REM sleep atonia index (AI) on a large number of recordings from different normal controls and patient groups.Subjects and methodsEighty-nine subjects were included: 25 young controls, 10 aged controls, 31 untreated patients with idiopathic REM sleep behavior disorder (iRBD), 8 treated patients with iRBD, 10 patients with multiple system atrophy (MSA) and 5 patients with obstructive sleep apnea syndrome (OSAS). The average amplitude of the rectified submentalis muscle EMG signal was then obtained for all 1-s mini epochs of REM sleep. The new correction method was implemented by subtracting from each mini epoch the minimum value found in a moving window including the 60 mini epochs surrounding it.ResultsTwo arbitrary thresholds were established at AI < 0.8 and 0.8 < AI < 0.9; all young controls presented AI > 0.9; this was not true for aged controls, 3 of whom presented 0.8 < AI < 0.9 but none had AI < 0.8; on the contrary 74.4% of all iRBD showed AI < 0.9, with 38.5% of the whole group having AI < 0.8 and only 25.6% with AI > 0.9. All MSA patients showed AI < 0.8.ConclusionsAfter the introduction of this new method for noise reduction, REM sleep AI index values lower than 0.8 were strongly indicative of altered (reduced) chin EMG atonia during REM sleep; values of AI between 0.8 and 0.9 indicated a less evident involvement of atonia, and values above 0.9 characterized the majority of normal recordings.     

REM sleep behavior disorder in Parkinson disease: Association with abnormal ocular motor findings

BackgroundThe anatomical substrates associated with generalized muscle atonia during REM sleep are located on the pontine tegmentum and medial medulla oblongata. We examined whether patients with REM sleep behavior disorder (RBD) have abnormal ocular movements suggesting brainstem or cerebellar dysfunction in Parkinson's disease (PD).MethodsCross-sectional survey for the existence of RBD and abnormal ocular movements. Ocular movements were examined by video-oculography (VOG).ResultsA total of 202 patients were included in this study. One hundred and sixteen (57.4%) of the 202 patients have clinically probable RBD, and 28 (24.1%) of the 116 with clinically probable RBD patients had abnormal VOG findings suggesting brainstem or cerebellar dysfunction; whereas 86 of the 202 patients did not have clinically probable RBD, and only 7 (8.1%) of the 86 patients had abnormal VOG findings suggesting brainstem or cerebellar dysfunction (P = 0.001).ConclusionThis study suggests that the presence of RBD is associated with more severe or extensive brainstem pathology or different distribution of pathology in PD.     

Observations on muscle activity in REM sleep behavior disorder assessed with a semi-automated scoring algorithm

Objectives

Rapid eye movement (REM) sleep behavior disorder (RBD) is defined by dream enactment due to a failure of normal muscle atonia. Visual assessment of this muscle activity is time consuming and rater-dependent.

Susceptibility to life-threatening ventricular arrhythmias in an animal model of paradoxical sleep deprivation

BackgroundAccording to some reports regarding the increase of cardiac events following sleep deprivation, our study was conducted to clarify the effects of rapid eye movement (REM) sleep deprivation on susceptibility to lethal ventricular arrhythmias in rat.MethodsThe animal groups included the control group; the sham 48 and sham 72 groups (without sleep deprivation); and the test 48 and test 72 groups, who experienced REM sleep deprivation for 48 h and 72 h, respectively. For induction of cardiac arrhythmia, aconitine was infused via the tail vein of the animals.ResultsAfter 72 h of REM sleep deprivation, the blood pressure (BP) levels and the QTc interval of the electrocardiogram (ECG) were significantly increased (P < .05 and P < .01, respectively). However, the sleep deprivation had no significant effect on the heart rate (HR), myocardial oxygen consumption index, and plasma corticosterone level. Furthermore, sleep deprivation increased the latency times of premature ventricular contraction (PVC), ventricular tachycardia (VT), and also the PVC number; however, it did not increase the number, duration, and severity of VT and ventricular fibrillation (VF).ConclusionOur findings suggest that 72 h of REM sleep deprivation is associated with increased risk for hypertension and QT interval prolongation under nonstressful conditions; however, it does not increase the susceptibility to lethal ventricular arrhythmia in rat.     

Polysomnographic diagnosis of idiopathic REM sleep behavior disorder

The presence of either excessive tonic chin EMG activity during REM sleep, or excessive phasic submental or limb EMG twitching is required to diagnose REM sleep behavior disorder (RBD). The aim was to identify cut‐off values and to assess the sensitivity and specificity of these values taken separately or combined to diagnose idiopathic RBD patients. Eighty patients presenting with a clinical diagnosis of idiopathic RBD and 80 age‐ and gender‐matched normal controls were studied in the sleep laboratory. Receiver operating characteristic curves were drawn to find optimal cut‐off values for three REM sleep EMG parameters. Tonic and phasic EMG activity were measured in the chin, but not in the limbs. Videos were examined during the recording but were not systematically reviewed by the authors. Total correct classification of 81.9% was found for tonic chin EMG density ≥30%; 83.8% for phasic chin EMG density ≥15% and 75.6% for ≥24 leg movements per hour of REM sleep. Five patients did not fulfill any of these three polysomnographic (PSG) criteria. Conversely, one subject of the control group met the PSG criteria for RBD. This study estimates the diagnostic value of a visual scoring method for the diagnosis of idiopathic RBD and establishes cut‐off values to be used in clinical and research set‐ups. For the five RBD patients who did not show chin EMG abnormalities, it cannot be excluded that they had increased phasic EMG activity in the upper limbs and presented visible motor activity. © 2010 Movement Disorder Society     

The importance of polysomnography in the evaluation of prolonged disorders of consciousness: sleep recordings more adequately correlate than stimulus-related evoked potentials with patients’ clinical status

ObjectivesThe aim of our study was to evaluate the importance of sleep recordings and stimulus-related evoked potentials (EPs) in patients with prolonged disorders of consciousness (DOCs) by correlating neurophysiologic variables with clinical evaluation obtained using specific standardized scales.MethodsThere were 27 vegetative state (VS) and 5 minimally conscious state (MCS) patients who were evaluated from a clinical and neurophysiologic perspective. Clinical evaluation included the Coma Recovery Scale-Revised (CRS-R), Disability Rating Scale (DRS), and Glasgow Coma Scale (GCS). Neurophysiologic evaluation included 24-h polysomnography (PSG), somatosensory EPs (SEPs), brainstem auditory EPs (BAEPs), and visual EPs (VEPs).ResultsPatients with preservation of each single sleep element (sleep–wake cycle, sleep spindles, K-complexes, and rapid eye movement [REM] sleep) always showed better clinical scores compared to those who did not have preservation. Statistical significance was only achieved for REM sleep. In 7 patients PSG showed the presence of all considered sleep elements, and they had a CRS-R score of 8.29 ± 1.38. In contrast, 25 patients who lacked one or more of the sleep elements had a CRS-R score of 4.84 ± 1.46 (P < .05). Our multivariate analysis clarified that concurrent presence of sleep spindles and REM sleep were associated with a much higher CRS-R score (positive interaction, P < .0001). On the other hand, no significant associations were found between EPs and CRS-R scores.ConclusionsPSG recordings have proved to be a reliable tool in the neurophysiologic assessment of patients with prolonged DOCs, correlating more adequately than EPs with the clinical evaluation and the level of consciousness. The main contribution to higher clinical scores was determined by the concomitant presence of REM sleep and sleep spindles. PSG recordings may be considered inexpensive, noninvasive, and easy-to-perform examinations to provide supplementary information in patients with prolonged DOCs.     

Effects of long-term use of clonazepam on nonrapid eye movement sleep patterns in rapid eye movement sleep behavior disorder

ObjectiveWe aim to analyze in detail the characteristics of nonrapid eye movement (NREM) sleep in drug-free patients with idiopathic rapid eye movement sleep behavior disorder (iRBD). We compare drug-free iRBD patients to both normal controls and drug-free patients with narcolepsy/RBD and evaluate the changes following the long-term use of bedtime clonazepam.Participants and methodsForty-six participants were recruited: 15 with iRBD (13 men, 2 women; mean age, 65.8 ± 4.39 years), 13 with narcolepsy/RBD (10 men, 3 women; mean age, 63.0 ± 6.73 years), and 18 normal controls (10 men, 8 women; mean age 69.4 ± 7.72 years). Sleep was video polysomnographically recorded and the RBD severity scale (RBDSS) was obtained. Chin electromyography (EMG) amplitude was quantitatively assessed and the atonia index was computed. Additionally, NREM sleep instability was evaluated using an automatic quantitative analysis. Participants with iRBD were re-evaluated after 2.75 ± 1.62 years of regular therapy with 0.5 to 1-mg clonazepam at bedtime.ResultsSlow transient electroencephalography (EEG) events were increased in iRBD and decreased in narcolepsy/RBD, while fast transient events decreased in iRBD and increased in narcolepsy/RBD. During rapid eye movement (REM) sleep the atonia index was reduced in both iRBD and narcolepsy/RBD groups and during NREM sleep atonia index was increased in iRBD participants, remaining low in narcolepsy/RBD participants. After long-term therapy with clonazepam, wakefulness after sleep onset was decreased together with an increase in both slow-wave sleep (SWS) and sleep stage 2, in which the latter reached statistical significance; sleep stages 1 and 2 instability significantly decreased and the duration of EEG transients also slightly but significantly decreased. Finally, chin tone was not modified by clonazepam.ConclusionsOur study confirms that clonazepam modifies some aspects of NREM sleep in iRBD participants with a decrease in its instability. Moreover, we also show that a complex modification of sleep chin atonia exists in these participants, which also involves NREM sleep; for iRBD more complex neuropathologic models encompassing REM sleep and NREM sleep mechanisms are needed.     

Revisiting the impact of REM sleep behavior disorder on motor progression in Parkinson's disease

BackgroundEstimation of progression in Parkinson's disease (PD) is useful to guide clinical decisions and to enable patients to plan and manage their life with PD. Rapid eye movement (REM) sleep behavior disorder (RBD) and REM sleep without atonia (RWA) are recognized as early harbingers of neurodegeneration and may precede motor symptoms by years. However, their impact on motor progression remains elusive.MethodsWe retrospectively analyzed polysomnographic and clinical data of 59 PD patients, grouping them into patients with RBD (n = 15), RWA (n = 22) and those with normal muscle atonia (n = 22). We compared the three groups with regard to motor progression, defined as changes in Unified Parkinson's Disease Rating Scale (UPDRS) III values per year, and selected PD specific characteristics.ResultsMotor disability at first visit and time interval between first and last visits were similar between groups. We observed a significantly faster motor progression in PD patients with RBD and RWA than in those with preserved REM sleep atonia.ConclusionOur findings suggest that impaired muscle atonia during REM sleep might represent a marker of faster motor progression in PD.     

Two polysomnographic features of REM sleep behavior disorder: Clinical variations insight for Parkinson's disease

IntroductionLoss of REM sleep muscle atonia (RWA) and dream-enactment behavior (DEB) are two associated features of REM sleep behavior disorder (RBD), which is frequently associated with Parkinson's disease (PD). Few studies have examined both DEB and RWA simultaneously in patients with PD. This study aimed to evaluate relationships between RWA, DEB and clinical characteristics of PD.MethodsWe conducted overnight polysomnography in 145 patients with PD. DEB (motor behaviors and/or vocalizations during REM) and increased RWA (IRWA; tonic and phasic chin EMG density ≥ 30% and ≥15%, respectively) were identified. Patients were categorized as clinical RBD (DEB and IRWA), sub-DEB positive (DEB only), subclinical RBD (IRWA only), or normal REM sleep.ResultsPatients with DEB had higher Hoehn and Yahr (H&Y) stage, Unified Parkinson's Disease Rating Scale (UPDRS) III score, levodopa equivalent dose(LEDs), and worse cognition. RWA was associated with H&Y stage, LEDs, cognition, and sleep structure in all patients. PD duration was associated with RWA, but not DEB. The PD patients who exhibited clinical or subclinical RBD, compared to sub-DEB positive, had higher H&Y stage, UPDRS III score and LEDs, lower cognitive score, worse sleep structure than the PD + cREM group.ConclusionBoth DEB and RWA were associated with severity of PD illness. Subclinical RBD might have different disease progression from sub-DEB positive. DEB symptoms may fluctuate or disappear whereas RWA may continue to develop as PD progresses. Differences in the course of DEB and RWA may reflect the difference in the degeneration process of neurodegenerative disorders.     

The relation between abnormal behaviors and REM sleep microstructure in patients with REM sleep behavior disorder

ObjectiveTo investigate the temporal relation between rapid eye movement (REM) sleep microstructure (REMs, EMG activity) and motor events in REM sleep behavior disorder (RBD).MethodsPolysomnographic records of eight patients with RBD were analyzed and compared with those of eight sex- and age-matched controls. We examined sleep microstructure for REM sleep with and without REMs and phasic chin EMG activity and their temporal relation to motor events on video.ResultsAll types of motor events were either more frequent in RBD patients than in controls (P ? 0.007) or present solely in RBD patients. In RBD, major motor events were significantly more frequent during REM sleep with REMs than during REM sleep without REMs (violent, 84.0% vs. 16.0%, P < 0.001; complex/scenic behavior, 78.1% vs. 23.2%, P < 0.001; major jerks, 77.5% vs. 20.3%, P < 0.001), whereas minor motor activity was evenly distributed (54.1% vs. 45.9%, P = 0.889). Controls showed predominantly minor motor activity with rare myoclonic body jerks. The distribution of motor events did not differ between REM sleep with and without REMs (40.9% vs. 59.1%, P = 0.262).ConclusionsIn RBD, major motor activity is closely associated with REM sleep with REMs, whereas minor jerks occur throughout REM sleep. This finding further supports the concept of a dual nature of REM sleep with REMs and REM sleep without REMs and implies a potential gate control mechanism of REM sleep with REMs for the manifestation of elaborate or violent behaviors in RBD.     

Power spectral analysis of surface electromyography (EMG) at matched contraction levels of the first dorsal interosseous muscle in stroke survivors

ObjectiveThe objective of this study was to help assess complex neural and muscular changes induced by stroke using power spectral analysis of surface electromyogram (EMG) signals.MethodsFourteen stroke subjects participated in the study. They were instructed to perform isometric voluntary contractions by abducting the index finger. Surface EMG signals were collected from the paretic and contralateral first dorsal interosseous (FDI) muscles with forces ranging from 30% to 70% maximum voluntary contraction (MVC) of the paretic muscle. Power spectral analysis was performed to characterize features of the surface EMG in paretic and contralateral muscles at matched forces. A Linear Mixed Model was applied to identify the spectral changes in the hemiparetic muscle and to examine the relation between spectral parameters and contraction levels. Regression analysis was performed to examine the correlations between spectral characteristics and clinical features.ResultsDifferences in power spectrum distribution patterns were observed in paretic muscles when compared with their contralateral pairs. Nine subjects showed increased mean power frequency (MPF) in the contralateral side (>15 Hz). No evident spectrum difference was observed in 3 subjects. Only 2 subjects had higher MPF in the paretic muscle than the contralateral muscle. Pooling all subjects’ data, there was a significant reduction of MPF in the paretic muscle compared with the contralateral muscle (paretic: 168.7 ± 7.6 Hz, contralateral: 186.1 ± 8.7 Hz, mean ± standard error, F = 36.56, p < 0.001). Examination of force factor on the surface EMG power spectrum did not confirm a significant correlation between the MPF and contraction force in either hand (F = 0.7, p > 0.5). There was no correlation between spectrum difference and Fugl–Meyer or Chedoke scores, or ratio of paretic and contralateral MVC (p > 0.2).ConclusionsThere appears to be complex muscular and neural processes at work post stroke that may impact the surface EMG power spectrum. The majority of the tested stroke subjects had lower MPF in the paretic muscle than in the contralateral muscle at matched isometric contraction force. The reduced MPF of paretic muscles can be attributed to different factors such as increased motor unit synchronization, impairments in motor unit control properties, loss of large motor units, and atrophy of muscle fibers.SignificanceSurface EMG power spectral analysis can serve as a useful tool to indicate complex neural and muscular changes after stroke.     

Modulation of neck muscle activity induced by intra-oral stimulation in humans

ObjectiveTo investigate the effect of painful electrical stimuli applied to intra-oral tissues around the teeth on the neck muscle activity in healthy humans.MethodsElectromyographic (EMG) responses of the dorsal neck muscles evoked by intra-oral electrical stimulation were recorded before and after local anesthesia to the stimulus site in 17 healthy volunteers.ResultsInhibition of dorsal neck muscle EMG activities on average 80% compared to baseline level was observed with a latency around 50 ms after the electrical stimulation before anesthesia, and the EMG activity inhibition decreased after anesthesia of the intra-oral stimulus site. The perceived intensity of the electrical stimuli as scored on a visual analogue scale (VAS) was 6.1 ± 0.4 cm before anesthesia and 1.5 ± 0.2 cm after anesthesia.ConclusionIntra-oral stimulation can inhibit neck muscle activity. This modulation might be attributed mainly to nociceptive afferent nerves however, non-nociceptive fibers could also be responsible.SignificanceIntra-oral information including nociceptive activity can inhibit neck muscle activity. From a clinical viewpoint, the present findings demonstrate the neural connectivity between the trigeminal region and the cervical region raising the possibility that orofacial pain conditions could influence head, neck and shoulder activity.     

Validation study of REM Sleep Behavior Disorder Questionnaire – Hong Kong (RBDQ-HK) in East China

ObjectiveTo validate the REM Sleep Behavior Disorder (RBD) Questionnaire – Hong Kong (RBDQ-HK) in polysomnography (PSG)-confirmed RBD and non-RBD subjects, and to evaluate its usefulness in different clinical populations.MethodsIn total, 325 subjects (115 RBD and 210 controls) from East China were enrolled. After patients had finished the structured interview, and completed the RBDQ-HK and video-PSG test, we evaluated the reliability of RBDQ-HK (areas under the curves (AUC), the best cut-off values, factor 2 of RBDQ-HK, and overall scale) and validated the usefulness of RBDQ-HK between the Parkinson disease (PD) and obstructive sleep apnea (OSA) groups.ResultsThe best cut-off values for factor 2 of RBDQ-HK were located at 7/8 with a sensitivity of 90% and specificity of 82% (AUC = 0.911), and for RBDQ-HK overall scale were located at 17 with a sensitivity of 85% and specificity of 81% (AUC = 0.892) in all subjects. Both factor 2 and overall scale of RBDQ-HK are valid in all subjects (PD and OSA patients), with a higher accuracy given by factor 2 of RBDQ-HK.ConclusionsRBDQ-HK and its factor 2 are useful and validated RBD screening instruments, and could be used as a tool for screening RBD in patients with PD and OSA.