Tonic Electromyographic Activity Research Articles

Dysmaturation of sleep state and electroencephalographic activity after hypoxia-ischaemia in preterm fetal sheep.

Antenatal hypoxia-ischaemia (HI) in preterm fetal sheep can trigger delayed evolution of severe, cystic white matter injury (WMI), in a similar timecourse to WMI in preterm infants. We therefore examined how severe hypoxia-ischaemia affects recovery of electroencephalographic (EEG) activity. Chronically instrumented preterm fetal sheep (0.7 gestation) received 25 min of complete umbilical cord occlusion (UCO, n = 9) or sham occlusion (controls, n = 9), and recovered for 21 days. HI was associated with a shift to lower frequency EEG activity for the first 5 days with persisting loss of EEG power in the delta and theta bands, and initial loss of power in the alpha and beta bands in the first 14 days of recovery. In the final 3 days of recovery, there was a marked rhythmic shift towards higher frequency EEG activity after UCO. The UCO group spent less time in high-voltage sleep, and in the early evening (7:02 pm ± 47 min) abruptly stopped cycling between sleep states, with a shift to a high frequency state for 2 h 48 min ± 40 min, with tonic electromyographic activity. These findings demonstrate persisting EEG and sleep state dysmaturation after severe hypoxia-ischaemia. Loss of fetal or neonatal sleep state cycling in the early evening may be a useful biomarker for evolving cystic WMI.

MP60-08 COMPARISON OF LOWER URINARY TRACT DYSFUNCTION AFTER SPINAL CORD INJURY (SCI) BETWEEN FEMALE AND MALE MICE

You have accessJournal of UrologyCME1 Apr 2023MP60-08 COMPARISON OF LOWER URINARY TRACT DYSFUNCTION AFTER SPINAL CORD INJURY (SCI) BETWEEN FEMALE AND MALE MICE Mamoru Hashimoto, Kang Jun Cho, Stephanie L Daugherty, PA Pittsburgh, Nobutaka Shimizu, Pradeep Tyagi, Akihide Hirayama, Hirotsugu Uemura, Jonathan M Beckel, Sergei Karnup, and Naoki Yoshimura Mamoru HashimotoMamoru Hashimoto More articles by this author , Kang Jun ChoKang Jun Cho More articles by this author , Stephanie L DaughertyStephanie L Daugherty More articles by this author , PA PittsburghPA Pittsburgh More articles by this author , Nobutaka ShimizuNobutaka Shimizu More articles by this author , Pradeep TyagiPradeep Tyagi More articles by this author , Akihide HirayamaAkihide Hirayama More articles by this author , Hirotsugu UemuraHirotsugu Uemura More articles by this author , Jonathan M BeckelJonathan M Beckel More articles by this author , Sergei KarnupSergei Karnup More articles by this author , and Naoki YoshimuraNaoki Yoshimura More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003318.08AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: In humans, voiding occurs during synergic relaxation of the external urethral sphincter (EUS), and SCI induces detrusor-sphincter dyssynergia (DSD) shown by tonic EUS contraction during voiding. However, EUS bursting activity is known to be an important mechanism for efficient voiding in spinal intact (SI) and SCI rats while such data are less available in mice. Thus, we evaluated gender-specific EUS function during voiding in male and female mice with or without SCI. METHODS: C57BL/6N mice at 9-10-weeks old were used. SCI mice underwent complete transection of the Th8-9 spinal cord. Six weeks after SCI, cystometrograms (CMGs) and EUS- electromyography (EMG) were performed under an awake condition. Thereafter, L6-S1 dorsal root ganglia (DRG) were harvested to evaluate the transcripts of TRPV1 and Piezo2 using qPCR. RESULTS: In female SI mice, voiding occurred during an EUS relaxation period. Female SCI mice voided urine during notch like reductions in bladder pressure, which corresponded to EMG signal reduction periods during tonic EMG activity (DSD). On the other hand, male SI and SCI mice voided during EUS bursting activity characterized by alternating active and silent phases of EMG activity, with the longer active phase and low voiding efficiency in SCI vs. SI mice (Table and Figure). The mRNA levels of TRPV1 and Piezo2 in L6-S1 DRG were significantly higher in SCI male mice (n=4) and female mice (n=4) vs. SI mice (n=4). CONCLUSIONS: Lower urinary tract function during the voiding phase was different between male and female mice. Female SI mice, in which voiding occurs during EUS relaxation, and female SCI mice, which exhibit DSD with periodic EUS relaxations, seem to be more suitable for the study of SCI-induced EUS dysfunction in humans, compared to SI and SCI male mice that exhibit EUS bursting activity during voiding. Source of Funding: NIH R01DK129194 © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e846 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Mamoru Hashimoto More articles by this author Kang Jun Cho More articles by this author Stephanie L Daugherty More articles by this author PA Pittsburgh More articles by this author Nobutaka Shimizu More articles by this author Pradeep Tyagi More articles by this author Akihide Hirayama More articles by this author Hirotsugu Uemura More articles by this author Jonathan M Beckel More articles by this author Sergei Karnup More articles by this author Naoki Yoshimura More articles by this author Expand All Advertisement PDF downloadLoading ...

Possible predictors of phenoconversion in isolated REM sleep behaviour disorder: a systematic review and meta-analysis

BackgroundA number of promising biomarkers for predicting imminent α-synucleinopathies have been suggested in isolated rapid eye movement sleep behaviour disorder (iRBD). However, existing evidence is conflicting without quantitative evaluation.MethodsPubMed, Web...

Prochlorperazine Withdraws the Delayed Onset Tonic Activity of Unloaded Rat Soleus Muscle: A Pilot Study.

A gradual increase in rat soleus muscle electromyographic (EMG) activity is known to occur after 3–4 days of hindlimb suspension/unloading (HS). The physiological significance and mechanisms of such activity of motoneurons under unloading conditions are currently unclear. Since hyperactivity of motoneurons and muscle spasticity after spinal cord injury are associated with KCC2 downregulation, we hypothesized that a decrease in potassium (K+)/chloride (Cl−) co-transporter 2 (KCC2) in motoneurons would be responsible for an increase in soleus muscle EMG activity during HS. We aimed to investigate the effect of prochlorperazine (KCC2 activator) on the electrical activity of rat soleus muscle under HS. Wistar rats were divided into the following groups: (1) vivarium control (C), (2) 7-day HS group (7HS) and (3) 7-day HS group plus intraperitoneal injections of prochlorperazine (10 mg/kg, daily) (7HS + P). Expression of proteins in the motoneurons of the lumbar spinal cord was determined by Western blotting. An electromyogram of the rat soleus muscle was recorded using intramuscular electrodes. KCC2 content after 7-day HS significantly decreased by 34% relative to the control group. HS-induced decrease in KCC2 protein content was prevented by prochlorperazine administration. HS also induced a significant 80% decrease in KCC2 Ser940 phosphorylation; however prochlorperazine did not affect KCC2 phosphorylation. The treatment of the rats with prochlorperazine prevented a HS-induced increase in Na(+)/K(+)/(Cl−) co-transporter 1 (KCC2 antagonist) protein content. In parallel with the restoration of KCC2 content, prochlorperazine administration during HS partially prevented an increase in the soleus muscle tonic EMG activity. Thus, prochlorperazine administration during 7-day HS prevents a decrease in KCC2 protein expression in motoneurons and significantly reduces the level of HS-induced soleus muscle electrical activity.

Global Brain Consortium Open Science Platform

Rapid eye movement (REM) sleep without atonia (RWA) is observed in some patients without a clinical history of REM sleep behavior disorder (RBD). It remains unknown whether these patients meet the refined quantitative electromyographic (EMG) criteria supporting a clinical RBD diagnosis. We quantitatively evaluated EMG activity and investigated its overnight distribution in patients with isolated qualitative RWA.Fifty participants with an incidental polysomnographic finding of RWA (isolated qualitative RWA) were included. Tonic, phasic, and ‘any’ EMG activity during REM sleep on PSG were quantified retrospectively.Referring to the quantitative cut-off values for a polysomnographic diagnosis of RBD, 7/50 (14%) and 6/50 (12%) of the patients showed phasic and ‘any’ EMG activity in the mentalis muscle above the respective cut-off values. No patient was above the cut-off value for tonic EMG activity or phasic EMG activity in the anterior tibialis muscles. Patients with RWA above the cut-off value showed higher amounts of RWA during later REM sleep periods.This is the first study showing that some subjects with incidental RWA meet the refined quantitative EMG criteria for a diagnosis of RBD. Future longitudinal studies must investigate whether this subgroup with isolated qualitative RWA is at an increased risk of developing fully expressed RBD and/or neurodegenerative disease.

Sleep-related head jerks: toward a new movement disorder.

Sleep-related head jerks (SRHJ) are often considered as a physiological motor phenomenon, occurring mainly during rapid eye movement (REM) sleep. Their clinical relevance and links with other sleep parameters are unclear. We characterized the clinical and polysomnographic features of patients with excessive SRHJ and compare them with healthy controls and patients with isolated REM sleep behavior disorder (iRBD). A total of 30 patients (19 males, 27.5 y.o., 16.0-51.0) with a REM-HJ index >30/h were identified over a period of 5 years. All had a video-polysomnographic (PSG) recording to characterize the SRHJ, to assess associations with other sleep parameters and to quantify phasic and tonic electromyographic activity during REM sleep, compared with 30 healthy controls and 30 patients with iRBD. Five among the 30 patients had a primary complaint of involuntary nighttime head movements associated with sleepiness or non-restorative sleep. The mean REM-HJ index was 57.22/h ± 24.42, a nonperiodic pattern, stable across the sleep cycles, and with a low between-test variability (for the nine patients with two PSG assessments in untreated condition). REM-HJs were often associated with arousals (65.2%) and leg movements (38.1%) and less with respiratory events (9.6%), without association with increased phasic and tonic electromyographic activities. SRHJ were also found in 36.7% of controls and 56.7% of iRBD patients, but with a lower index in REM sleep (0.79/h ± 1.59 and 2.76/h ± 4.57). Although SRHJ are frequent in the general population and with uncertain clinical significance, rare severe symptomatic forms should be individualized and eventually be categorized as a new sleep-related movement disorder, distinct from RBD and periodic leg movements.

Electromyography activity level in rapid eye movement sleep predicts neurodegenerative diseases in idiopathic rapid eye movement sleep behavior disorder: a 5-year longitudinal study

ObjectivesTo investigate whether baseline electromyography (EMG) activity during rapid eye movement (REM) sleep predicts the development of neurodegenerative diseases over time in patients with idiopathic REM sleep behavior disorder (iRBD). MethodsA total of 216 patients with polysomnography-confirmed iRBD were recruited from September 1997 to December 2016 with a mean follow-up duration of 5.0 ± 3.7 years (median: 4.0, range: 0.5–19.0). Neurodegenerative diseases were ascertained according to standard diagnostic criteria during follow-up. Time-dependent receiver operating characteristic (ROC) curves were employed to evaluate the dynamic predictive performance of EMG activity over time. Both tonic and phasic EMG activity were dichotomized into ‘mild’ and ‘severe’ categories by the ROC curves estimated optimal cut-offs. ResultsA total of 58 patients (26.9%) developed neurodegenerative diseases. The predictive performance of tonic EMG activity was stable (area under the curve of approximately 0.68) over time, while the performance of phasic EMG activity was significantly superior to chance only after five years of follow-up. The optimal cut-off for prediction at five years was 15.4% (sensitivity, 0.69; specificity, 0.57) and 7.8% (sensitivity, 0.79; specificity, 0.47) for tonic and phasic EMG activity, respectively. Cox proportional hazards regression analyses further revealed that severe tonic (adjusted HR: 2.76, 95% CI: 1.35–5.62) and phasic EMG activity (adjusted HR: 3.10, 95% CI: 1.10–8.71) were associated with early development of Parkinson's disease (PD) and dementia with Lewy bodies (DLB), respectively. ConclusionsTonic but not phasic EMG activity may serve as a stable biomarkers for predicting the progression of neurodegeneration in iRBD.

Tonic electromyographic activity following bilateral tonic-clonic seizures is associated with periictal respiratory dysfunction and postictal generalized EEG suppression.

No biomarkers reliably predict risk for sudden unexpected death in epilepsy (SUDEP). Postictal generalized electroencephalography (EEG) suppression (PGES) is a possible biomarker for SUDEP risk. However, its utility in predicting SUDEP remains uncertain. We had observed that postictal tonic electromyography (PTEMG) activity follows some generalized convulsive seizures (GCS). PTEMG activity and PGES may have a common pathophysiologic basis. PGES is associated with periictal respiratory distress. There is evidence that tonic EMG occurs with brain hypoxia. Thus PTEMG activity may be related to seizure-associated hypoxemia. Pronounced variation occurs among expert clinicians in identifying PGES, thereby limiting its utility as a biomarker. Characteristics of PTEMG activity and its relationship to preceding GCS have not been explored. We studied PTEMG activity characteristics, its relationship to the preceding seizure and associated respiratory dysfunction. We reviewed 145 GCS in 66 patients undergoing video-EEG telemetry (VET). The presence of PTEMG activity was defined when tonic EMG occurred for at least 3seconds following seizure termination and was identified with filter settings at 5-200Hz. Duration of PTEMG activity, the seizure, PGES, seizure-associated peripheral capillary oxygen saturation (SpO2 ) change, and end-tidal CO2 were analyzed. We compared data from GCS with and without PTEMG activity. Ninety of 145 seizures with GCS had PTEMG activity. The remainder had postictal slowing without PTEMG activity, and cessation of activity was followed by EEG slowing. Duration of the initial PTEMG discharge was 39.1 (mean)±(standard deviation) 17.9seconds. SpO2 nadir was lower (P=0.005) in seizures with PTEMG activity than in those without (72% vs 77%). End-tidal CO2 was higher (P=0.05) in seizures with PTEMG activity than in those without (63 vs 56mm Hg). PGES duration was 35.6±22.2seconds and associated with duration of PTEMG activity (P<0.001). The novel finding is that PTEMG activity occurs following 62% of GCS and that seizures with PTEMG activity have greater severity of respiratory dysfunction than seizures without. PTEMG activity is readily discerned by visual analysis of VET at appropriate filter settings and has the potential of being a complementary or surrogate biomarker of PGES for assessing SUDEP risk.

Vestibular and corticospinal control of human body orientation in the gravitational field.

Body orientation with respect to the direction of gravity changes when we lean forward from upright standing. We tested the hypothesis that during upright standing, the nervous system specifies the referent body orientation that defines spatial thresholds for activation of multiple muscles across the body. To intentionally lean the body forward, the system is postulated to transfer balance and stability to the leaned position by monotonically tilting the referent orientation, thus increasing the activation thresholds of ankle extensors and decreasing their activity. Consequently, the unbalanced gravitational torque would start to lean the body forward. With restretching, ankle extensors would be reactivated and generate increasing electromyographic (EMG) activity until the enhanced gravitational torque would be balanced at a new posture. As predicted, vestibular influences on motoneurons of ankle extensors evaluated by galvanic vestibular stimulation were smaller in the leaned compared with the upright position, despite higher tonic EMG activity. Defacilitation of vestibular influences was also observed during forward leaning when the EMG levels in the upright and leaned position were equalized by compensating the gravitational torque with a load. The vestibular system is involved in the active control of body orientation without directly specifying the motor outcome. Corticospinal influences originating from the primary motor cortex evaluated by transcranial magnetic stimulation remained similar at the two body postures. Thus, in contrast to the vestibular system, the corticospinal system maintains a similar descending facilitation of motoneurons of leg muscles at different body orientations. The study advances the understanding of how body orientation is controlled. NEW & NOTEWORTHY The brain changes the referent body orientation with respect to gravity to lean the body forward. Physiologically, this is achieved by shifts in spatial thresholds for activation of ankle muscles, which involves the vestibular system. Results advance the understanding of how the brain controls body orientation in the gravitational field. The study also extends previous evidence of empirical control of motor function, i.e., without the reliance on model-based computations and direct specification of motor outcome.

The REM sleep circuit and how its impairment leads to REM sleep behavior disorder.

REM sleep is characterized by rapid eye movements, desynchronized electroencephalographic activity, dreams and muscle paralysis that preclude the individual from acting out the action of dreams. REM sleep is generated and modulated by a complex and still poorly understood, neuronal network that involves multiple nuclei and neurotransmission systems. The key structures that generate REM sleep muscle paralysis are the subcoeruleus nucleus in the mesopontine tegmentum and the reticular formation of the ventral medial medulla. Using glutamatergic, GABAergic and glycinergic inputs, direct and indirect projections from these two areas inhibit the motoneurons of the spinal cord resulting in skeletal paralysis in REM sleep. Experimental studies in cats and rodents where the subcoeruleus nucleus and ventral medial medulla were impaired by electrolytic, pharmacological and genetic manipulations have repeatedly produced increased electromyography activity during REM sleep associated with abnormal motor behaviors (e.g., prominent twitching, attack-like behaviors). These animal models represent the pathophysiological substrate of REM sleep behavior disorder, a parasomnia in humans characterized by nightmares and abnormal vigorous behaviors (e.g., prominent jerking, shouting, kicking) linked to excessive phasic and/or tonic electromyographic activity in REM sleep. The extraordinary observation that a sleep disorder is often the first manifestation of a devastating neurodegenerative disease such as Parkinson disease carries important diagnostic implications and opens a window for neuroprotection. This review addresses the neuronal substrates of REM sleep generation and modulation and how its impairment may lead to REM sleep behavior disorder.

Inter-rater agreement for visual discrimination of phasic and tonic electromyographic activity in sleep.

The objective of this study was to determine the confidence of expert raters in discriminating phasic and tonic electromyographic (EMG) activity. We undertook this study because we suspected that even expert scorers may disagree on whether a given EMG segment contained phasic activity, tonic activity, or both. Six individuals holding either Fellowship status in the American Academy of Sleep Medicine or Board Certification in Sleep Medicine with at least 5 years experience in interpreting polysomnography visually examined 60 segments containing EMG activity. Raters determined their relative confidence that each segment contained phasic and tonic activity by noting whether they were highly certain or somewhat certain that the segment contained such activity or somewhat certain or highly certain that each segment did not contain such activity. Every segment was rated by every rater twice, once for phasic and once for tonic activity. Substantial differences among raters existed in certainty regarding presence/absence of both phasic and tonic activity, although raters agreed on segments far above chance. Consensus was higher on certainty regarding presence of phasic, relative to tonic, activity. These findings indicate the limitations of visual analyses for discriminating abnormal muscle activity during sleep. Conversely, when expert judgments are combined with digitized measurements of EMG activity in sleep (e.g. REM atonia index), some allowance must be made for the unique contribution of visual analyses to such judgments, most notably for short duration EMG signals. These results may have relevance for polysomnographic interpretation in suspected synucleinopathies.

Clinical Biomarkers of Neurodegeneration in REM Sleep Behavior Disorder

Address for correspondence Yun Kwok Wing, FRCPsych Department of Psychiatry, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong SAR Tel: +852-26367748 Fax: +852-26475321 E-mail: ykwing@cuhk.edu.hk Rapid eye movement sleep behavior disorder (RBD) is currently considered as a prodromal stage of α-synucleinopathies neurodegeneration. The update data suggested that over 80% patients with idiopathic RBD eventually developed neurodegenerative disease after a mean of 14 years interval from the onset of RBD. A series of potential biomarkers have been identified to predict the development of neurodegeneration in idiopathic RBD, including olfactory loss, color vision deficit, depression, mild cognitive impairment, excessive daytime sleepiness, dopamine dysfunction, and tonic electromyographic activity. Early recognition of the predictive markers of neurodegeneration in idiopathic RBD is essential for development of intervention or prevention strategies at the presymptomatic stage. Nonetheless, the current literature is lacking biomarkers that might reflect the α-synuclein neuropathology at the earliest stages. Future studies with large samples and systematic follow-up are needed to confirm more potential markers of neurodegeneration at its early stages. J Sleep Med 2015;12(2):27-33

Loss of REM sleep features across nighttime in REM sleep behavior disorder

ObjectivesMelatonin is a chronobiotic treatment which also alleviates rapid eye movement (REM) sleep behavior disorder (RBD). Because the mechanisms of this benefit are unclear, we evaluated the clock-dependent REM sleep characteristics in patients with RBD, whether idiopathic (iRBD) or associated with Parkinson's Disease (PD), and we compared findings with PD patients without RBD and with healthy subjects. MethodsAn overnight videopolysomnography was performed in ten iRBD patients, ten PD patients with RBD (PD + RBD+), ten PD patients without RBD (PD + RBD−), and ten controls. The rapid eye movement frequency per minute (REMs index), the tonic and phasic electromyographic (EMG) activity of the levator menti muscle, and the duration of each REM sleep episode were evaluated. A generalized linear model was applied in each group, with the REM sleep cycle (four ordinal levels) as the dependent variable, as a function of REMs index, REM sleep duration, and tonic and phasic EMG activity. ResultsFrom the first to the fourth sleep cycle, REM sleep duration progressively increased in controls only, REMs index increased in subjects without RBD but not in patients with RBD, whether idiopathic or associated with PD, whereas tonic and phasic EMG activity did not change. ConclusionsPatients with PD or iRBD lost the physiologic nocturnal increase in REM sleep duration, and patients with RBD (either with or without PD) lost the increase of REMs frequency across the night, suggesting an alteration in the circadian system in RBD. This supports the hypothesis of a direct effect of melatonin on RBD symptoms by its chronobiotic activity.

Rapid Eye Movement Sleep Behavior Disorder During Childhood.

Rapid eye movement (REM) sleep behavior disorder (RBD) is a type of parasomnia that arises out of REM sleep and is characterized by aggressive or violent motor dream enactment in conjunction with preservation of tonic electromyographic activity (ie, REM sleep without atonia). RBD occurs at all ages and in both sexes, although it remains relatively infrequent during childhood. The literature pertaining to RBD in childhood is scant, and composed only of single case reports or small case series. RBD etiologies include Parkinson disease, multisystem atrophy, and dementia with Lewy body disease. This article presents an updated review of childhood RBD.

Effect of tongue position on masseter and temporalis electromyographic activity during swallowing and maximal voluntary clenching: a cross-sectional study.

The purpose of this study was to measure and compare the tonic electromyographic (EMG) activity of the temporalis and masseter muscles following placement of the tongue either on the palate or in the floor of the mouth during swallowing and maximal voluntary clenching (MVC). Thirty healthy dental students with natural dentition and bilateral molar support, between the ages of 18 and 22, with no prior history of oro-facial injury, or current or past pain in the jaw, mouth or tongue participated in the study. Tonic masseter and temporalis EMG activities were recorded using surface electrodes. Subjects were instructed to passively place the tongue either on the anterior hard palate or in the floor of the mouth during swallowing and MVC. At each tongue position, the resulting EMG was recorded. During swallowing, no significant difference in EMG activity was found either for the masseter (P-value = 0.1592) or the temporalis (P-value = 0.0546) muscles, regardless of the tongue position. During MVC, there was a statistically significant difference for both the masseter (P-value = 0.0016) and the temporalis (P-value = 0.0277) muscles with lower levels recorded with the tongue in the floor of the mouth. This study found that in normal, pain-free subjects, placing the tongue in the floor of the mouth significantly reduces masticatory muscle activity during MVC. Thus, it may be considered as a possible therapeutic option to decrease masticatory muscle activity; however, further research is needed in patients with oro-facial pain.

Quantitative assessment of isolated rapid eye movement (REM) sleep without atonia without clinical REM sleep behavior disorder: clinical and research implications

BackgroundRapid eye movement (REM) sleep without atonia (RWA) is observed in some patients without a clinical history of REM sleep behavior disorder (RBD). It remains unknown whether these patients meet the refined quantitative electromyographic (EMG) criteria supporting a clinical RBD diagnosis. We quantitatively evaluated EMG activity and investigated its overnight distribution in patients with isolated qualitative RWA. MethodsFifty participants with an incidental polysomnographic finding of RWA (isolated qualitative RWA) were included. Tonic, phasic, and ‘any’ EMG activity during REM sleep on PSG were quantified retrospectively. ResultsReferring to the quantitative cut-off values for a polysomnographic diagnosis of RBD, 7/50 (14%) and 6/50 (12%) of the patients showed phasic and ‘any’ EMG activity in the mentalis muscle above the respective cut-off values. No patient was above the cut-off value for tonic EMG activity or phasic EMG activity in the anterior tibialis muscles. Patients with RWA above the cut-off value showed higher amounts of RWA during later REM sleep periods. ConclusionsThis is the first study showing that some subjects with incidental RWA meet the refined quantitative EMG criteria for a diagnosis of RBD. Future longitudinal studies must investigate whether this subgroup with isolated qualitative RWA is at an increased risk of developing fully expressed RBD and/or neurodegenerative disease.

Motor Events during Healthy Sleep: A Quantitative Polysomnographic Study

Many sleep disorders are characterized by increased motor activity during sleep. In contrast, studies on motor activity during physiological sleep are largely lacking. We quantitatively investigated a large range of motor phenomena during polysomnography in physiological sleep. Prospective polysomnographic investigation. Academic referral sleep laboratory. One hundred healthy sleepers age 19-77 y were strictly selected from a representative population sample by a two-step screening procedure. N/A. Polysomnography according to American Academy of Sleep Medicine (AASM) standards was performed, and quantitative normative values were established for periodic limb movements in sleep (PLMS), high frequency leg movements (HFLM), fragmentary myoclonus (FM), neck myoclonus (NM), and rapid eye movement (REM)-related electromyographic (EMG) activity. Thirty-six subjects had a PLMS index > 5/h, 18 had a PLMS index > 15/h (90th percentile: 24.8/h). Thirty-three subjects had HFLM (90th percentile: four sequences/night). All subjects had FM (90th percentile 143.7/h sleep). Nine subjects fulfilled AASM criteria for excessive FM. Thirty-five subjects had NM (90th percentile: 8.8/h REM sleep). For REM sleep, different EMG activity measures for the mentalis and flexor digitorum superficialis muscles were calculated: the 90th percentile for phasic mentalis EMG activity for 30-sec epochs according to AASM recommendation was 15.6%, and for tonic mentalis EMG activity 2.6%. Twenty-five subjects exceeded the recently proposed phasic mentalis cutoff of 11%. None of the subjects exceeded the tonic mentalis cutoff of 9.6%. Quantification of motor phenomena is a basic prerequisite to develop normative values, and is a first step toward a more precise description of the various motor phenomena present during sleep. Because rates of motor events were unexpectedly high even in physiological sleep, the future use of normative values for both research and clinical routine is essential.

Amplitude normalization reduces cervical vestibular evoked myogenic potential (cVEMP) amplitude asymmetries in normal subjects: proof of concept.

The cervical vestibular evoked myogenic potential (cVEMP) is an acoustically synchronized, signal averaged, brief inhibitory response of a contracted muscle usually resulting from an acoustic stimulus. The cVEMP is recorded from the tonically contracted sternocleidomastoid muscle (SCM). The presence and amplitude of the cVEMP is related to both the integrity of the sacculo-collic pathway and magnitude of electromyographic (EMG) activity at the time of recording. Measurement variables include the absolute latency of the primary positive going component (referred to as P13) and interaural (i.e., left versus right) latency differences. Also measured is the peak-to-peak interaural amplitude asymmetry (IAA; percent difference in amplitude, left versus right). It is known that the amplitude of the cVEMP is positively correlated with the magnitude of tonic EMG from which the evoked potential is extracted. Thus, if EMG amplitude is uncontrolled, one cannot determine whether cVEMP asymmetries are occurring due to unilateral end organ disease or asymmetric tonic EMG activity. Two methods have been suggested to control for tonic EMG activity. These include (1) patient self-monitoring of EMG activity with biofeedback and (2) mathematical correction (i.e., amplitude normalization) of the left and right cVEMP waveforms. Currently, it is unknown how effective amplitude normalization techniques are at reducing cVEMP amplitude asymmetry in the presence of varying levels of EMG. The purpose of this investigation was to determine whether the use of amplitude correction techniques would reduce significantly the P13-N23 IAA data in otologically and neurologically intact adults when the level of EMG was varied between right and left sides. A prospective, repeated measures design was used for three different investigations in which cVEMPs were recorded and then processed using amplitude correction. Subjects were 20 otologically and neurologically health young adults between 21 and 29 yr of age. cVEMPs were recorded at four different EMG target levels ranging from 100 to 400 μV. The absolute peak-to-peak amplitude of P13-N23, absolute latency of P13, and the left/right amplitude asymmetry of P13-N23 were measured both with and without the use of EMG amplitude correction techniques. IAAs were calculated using 10 different conditions of varying EMG asymmetry with and without amplitude correction. Data were analyzed using repeated measures analysis of variance (ANOVA) to detect tonic EMG level-dependent differences separately for P13 latency, P13-N23 peak-to-peak amplitude, and mean root mean square (RMS) amplitude cVEMP responses. The amplitude of cVEMP responses from the left and right side were used to calculate IAA for subsequent analyses. Linear regression analyses compared level of tonic EMG with cVEMP amplitude. A one-way multivariate analysis of variance (MANOVA) was used to determine if IAAs were significantly reduced following amplitude correction. Any differences found were investigated using unplanned linear contrasts. The uncorrected cVEMP amplitude and RMS EMG all increased significantly with increases in the EMG target levels. With amplitude correction, cVEMP amplitude did not change significantly with changes in RMS EMG or EMG target levels. These findings suggest that the use of amplitude correction techniques represent an effective method of neutralizing the factor of variability in tonic EMG level on the cVEMP that would be otherwise uncontrolled. Indeed when correction is employed in cases of extreme tonic EMG asymmetry, the upper limit of percent IAA is roughly half of that when EMG correction techniques are not used. Our findings are also in agreement with those of Bogle et al (2013) showing that the input/output growth function for P13/N23 amplitude is not linear but, in fact, saturates at supra-maximal stimulation levels. Accordingly, and contrary to what has been published previously, achieving maximum muscle activation may produce a paradoxically inferior signal-to-noise ratio and in some cases result in an artificially small (or undetectable) corrected cVEMP amplitude. cVEMP amplitude either asymptotes (if maximum EMG amplitude saturation occurs at the same stimulus intensity as yields the maximum cVEMP amplitude), or the cVEMP can become smaller if EMG amplitude can increase further beyond the stimulus intensity that yields that largest P1-N1 amplitude. In the latter case the noise increases further to reach maximum and creates a disadvantageous signal (cVEMP) to noise (tonic EMG) ratio.

The effect of tongue position and resulting vertical dimension on masticatory muscle activity. A cross-sectional study

The purpose of this study was to: (a) compare the tonic electromyographic (EMG) activity of the temporalis and masseter muscles between two tongue positions, (b) compare the vertical dimension (VD) resulting from each tongue position and (c) determine the influence of the VD on the tonic EMG activity for each tongue position. Thirty-three healthy dental students with natural dentition and bilateral molar support, between the ages of 18 and 22 years, with no prior history of oro-facial injury, or current or past pain in the jaw, mouth, or tongue participated in the study. Tonic masseteric and temporalis EMG activities were recorded using surface electrodes. Subjects were instructed to passively place the tongue either on the anterior hard palate or in the floor of the mouth. At each tongue position, the resulting EMG and VD were recorded. No significant difference in EMG activity was found for either the masseter (P-value = 0·5376) or temporalis muscle (P-value = 0·7410), between the two tongue positions. However, there was a significant difference in the VD resulting from the two different tongue positions, being greater with the tongue placed in the floor of the mouth. There was no statistically significant correlation between VD and EMG activity for both tongue positions. In spite of the lack of difference in the effect of both tongue positions on the masseteric and temporalis EMG activity, an increment of the VD was registered for the floor of mouth-tongue position. However, VD was not correlated with EMG activity for both tongue positions.

The Effects of Amplitude Normalization and EMG Targets on cVEMP Interaural Amplitude Asymmetry

The purpose of this investigation was to determine whether the use of visual feedback of tonic electromyographic (EMG) activity, or the use of amplitude normalization techniques would reduce significantly the variability in cervical vestibular evoked myogenic potential (cVEMP) P13-N23 interaural amplitude asymmetry data in otologically and neurologically intact children and adults. There were 97 subjects, both pediatric and adult, from whom the authors recorded cVEMPs with and without the use of an EMG target and amplitude normalization techniques. The four conditions were: (1) conventional recording (condition 1), (2) conventional recording with an EMG target (condition 2), (3) same as condition 1, with the addition of postacquisition amplitude normalization techniques, and (4) same as condition 2, with the addition of postacquisition amplitude normalization techniques. The absolute peak to peak amplitude of positive-negative response (P13-N23), absolute latency of P13, and the left or right amplitude asymmetry of P13-N23 were measured. Neither P13-N23 amplitudes nor latencies, neither mean root mean square (RMS) of the full wave rectified EMG activity, nor the standard deviation of the RMS EMG activity differed significantly when subjects were, and were not, asked to ensure their tonic EMG activity exceeded a visual target (i.e., representing >50 µV RMS EMG). Amplitude normalization of the cVEMP waveforms failed to reduce significantly the variability in the amplitude asymmetry data. Activating the sternocleidomastoid muscle with the patient in a semirecumbent position, with head turned away from the stimulated ear and head elevated (i.e., an optimal activation technique) was sufficient to produce the highest amplitude cVEMPs with an acceptable amount of variability in subjects of all ages. Group data suggested that the use of visual targets and amplitude normalization routines did not reduce significantly the variability in cVEMP interaural amplitude asymmetry measures. However, in isolated cases amplitude normalization converted an "abnormal" cVEMP into a "normal" cVEMP although the reverse occurred as well, suggesting that these techniques may be beneficial for a subset of patients receiving a less than perfectly administered test procedure.