Analysis of EMG signals of patients with essential tremor focusing on the change of tremor frequency

2012 ◽  
Author(s):  
Yuya Matsumoto ◽  
M. Seki ◽  
T. Ando ◽  
Y. Kobayashi ◽  
H. Iijima ◽  
...  
Keyword(s):  
Essential Tremor ◽  
Tremor Frequency

Cortical Involvement in the Generation of Essential Tremor

2007 ◽  
Vol 97 (5) ◽  
pp. 3219-3228 ◽  
Author(s):  
Jan Raethjen ◽  
R. B. Govindan ◽  
Florian Kopper ◽  
M. Muthuraman ◽  
Günther Deuschl
Keyword(s):  
Essential Tremor ◽  
Hot Spot ◽  
Power Spectra ◽  
Emg Activity ◽  
Cortical Circuits ◽  
Coherent Signals ◽  
Cortical Motor ◽  
Tremor Frequency ◽  
Cortical Involvement

Conflicting results on the existence of tremor-related cortical activity in essential tremor (ET) have raised questions on the role of the cortex in tremor generation. Here we attempt to address these issues. We recorded 64 channel surface EEGs and EMGs from forearm muscles in 15 patients with definite ET. EEG and EMG power spectra, relative power of the rhythmic EMG activity, relative EEG power at the tremor frequency, and EEG–EMG and EEG–EEG coherence were calculated and their dynamics over time explored. Corticomuscular delay was studied using a new method for narrow-band coherent signals. Corticomuscular coherence in the contralateral central region at the tremor frequency was present in all patients in recordings with a relative tremor EMG power exceeding a certain level. However, the coherence was lost intermittently even with tremors far above this level. Physiological 15- to 30-Hz coherence was found consistently in 11 patients with significantly weaker EMG activity in this frequency range. A more frontal (mesial) hot spot was also intermittently coupled with the tremor and the central hot spot in five patients. Corticomuscular delays were compatible with transmission in fast corticospinal pathways and feedback of the tremor signal. Thus the tremor rhythm is intermittently relayed only in different cortical motor areas. We hypothesize that tremor oscillations build up in different subcortical and subcortico-cortical circuits only temporarily entraining each other.

Essential tremor frequency decreases with time

Neurology ◽  
2000 ◽  
Vol 55 (10) ◽  
pp. 1547-1551 ◽  
Author(s):  
R. J. Elble
Keyword(s):  
Essential Tremor ◽  
Tremor Frequency

scholarly journals Modeling mechanisms of tremor reduction for essential tremor using symmetric biphasic DBS

2019 ◽  
Author(s):  
Shane Lee ◽  
Wael F Asaad ◽  
Stephanie R Jones
Keyword(s):  
Deep Brain Stimulation ◽  
Side Effects ◽  
Movement Disorder ◽  
Essential Tremor ◽  
Brain Stimulation ◽  
Future Studies ◽  
Tremor Frequency ◽  
Ventral Intermediate Nucleus ◽  
Different Shapes ◽  
Deep Brain

AbstractEssential tremor (ET) is the most common movement disorder, in which the primary symptom is a prominent, involuntary 4–10 Hz movement. For severe, medication refractory cases, deep brain stimulation (DBS) targeting the ventral intermediate nucleus of the thalamus (VIM) can be an effective treatment for cessation of tremor and is thought to work in part by disrupting tremor frequency oscillations (TFOs) in VIM. However, DBS is not universally effective and may be further disrupting cerebellar-mediated activity in the VIM. Here, we applied biophysically detailed computational modeling to investigate whether the efficacy of DBS is affected by the mechanism of generation of TFOs or by the pattern of stimulation. We simulated the effects of DBS using standard, asymmetric pulses as well as biphasic, symmetric pulses to understand biophysical mechanisms of how DBS disrupts TFOs generated either extrinsically or intrinsically. The model results suggested that the efficacy of DBS in the VIM is affected by the mechanism of generation of TFOs. Symmetric biphasic DBS reduced TFOs more than standard DBS in both networks, and these effects were stronger in the intrinsic network. For intrinsic tremor frequency activity, symmetric biphasic DBS was more effective at reducing TFOs. Simulated non-tremor signals were also transmitted during symmetric biphasic DBS, suggesting that this type of DBS may help to reduce side effects caused by disruption of the cerebellothalamocortical pathway. Biophysical details in the model provided a mechanistic interpretation of the cellular and network dynamics contributing to these effects that can be empirically tested in future studies.Significance StatementEssential tremor (ET) is a common movement disorder, whose primary symptom is an involuntary rhythmic movement of the limbs or head. An area of the human tha-lamus demonstrates electrical activity that oscillates at the frequencies of tremor, and deep brain stimulation (DBS) in this area can reduce tremor. It is not fully understood how DBS affects tremor frequency activity in the thalamus, and studying different patterns of DBS stimulation may help to clarify these mechanisms. We created a computational model of different shapes of DBS and studied how they reduce different hypothesized generators of tremor frequency activity. A greater understanding of how DBS affects the thalamus may lead to improved treatments to reduce tremor and alleviate side effects in patients with ET.

S20-2 Thalamic neurons with tremor-frequency activity in patients with essential tremor

2010 ◽  
Vol 121 ◽  
pp. S32
Author(s):  
Y. Katayama ◽  
H. Oshima ◽  
C. Fukaya ◽  
T. Yamamoto
Keyword(s):  
Essential Tremor ◽  
Thalamic Neurons ◽  
Tremor Frequency

Posture-Related Oscillations in Human Cerebellar Thalamus in Essential Tremor Are Enabled by Voluntary Motor Circuits

2005 ◽  
Vol 93 (1) ◽  
pp. 117-127 ◽  
Author(s):  
Sherwin E. Hua ◽  
Frederick A. Lenz
Keyword(s):  
Essential Tremor ◽  
Thalamic Nucleus ◽  
Oscillatory Activity ◽  
Active Movement ◽  
Thalamic Nuclei ◽  
Motor Circuits ◽  
Cross Correlation Analysis ◽  
Tremor Frequency ◽  
Sensory Nucleus ◽  
Proprioceptive Inputs

The mechanism of essential tremor (ET) is unclear. Animal models of tremor and functional imaging studies in ET predict that the cerebellum and a cerebellar recipient thalamic nucleus ( ventral intermediate, Vim) should exhibit oscillatory activity during rest and during tremor due to abnormal olivo-cerebellar activity. Physiologic responses of 152 single neurons were recorded during awake mapping of the ventral thalamus in seven patients with ET prior to thalamotomy. During postural tremor, spectral cross-correlation analysis demonstrated that 51% of the neurons studied exhibited a concentration of power at tremor frequency that was correlated with electromyography, i.e., tremor neurons. During rest, thalamic neurons did not exhibit tremor-frequency activity. Among the three thalamic nuclei surveyed, Vim had a significantly higher proportion of tremor neurons than did the principal somatic sensory nucleus ( ventral caudal, Vc) or a pallidal recipient thalamic nucleus ( ventral oral posterior, Vop). Neurons related to active movement (voluntary neurons) had significantly greater tremor-related activity than did nonvoluntary neurons. These findings are not consistent with a model of continuous olivo-cerebellar driving of the motor cortex through thalamic connections. Instead ET may be facilitated by motor circuits that enable tremor-related thalamic activity during voluntary movement. Additionally, a subgroup of tremor neurons with proprioceptive inputs were identified that may allow sensory feedback to access the central tremor network.

scholarly journals Role of cerebellar GABAergic dysfunctions in the origins of essential tremor

2019 ◽  
Vol 116 (27) ◽  
pp. 13592-13601 ◽  
Author(s):  
Xu Zhang ◽  
Sabato Santaniello
Keyword(s):  
Essential Tremor ◽  
Dentate Nucleus ◽  
Oscillatory Activity ◽  
High Frequency Stimulation ◽  
Inferior Olivary Nucleus ◽  
Functional Changes ◽  
Decay Times ◽  
Tremor Frequency ◽  
Frequency Stimulation ◽  
Inferior Olivary

Essential tremor (ET) is among the most prevalent movement disorders, but its origins are elusive. The inferior olivary nucleus (ION) has been hypothesized as the prime generator of tremor because of the pacemaker properties of ION neurons, but structural and functional changes in ION are unlikely under ET. Abnormalities have instead been reported in the cerebello-thalamo-cortical network, including dysfunctions of the GABAergic projections from the cerebellar cortex to the dentate nucleus. It remains unclear, though, how tremor would relate to a dysfunction of cerebellar connectivity. To address this question, we built a computational model of the cortico-cerebello-thalamo-cortical loop. We simulated the effects of a progressive loss of GABAA α1-receptor subunits and up-regulation of α2/3-receptor subunits in the dentate nucleus, and correspondingly, we studied the evolution of the firing patterns along the loop. The model closely reproduced experimental evidence for each structure in the loop. It showed that an alteration of amplitudes and decay times of the GABAergic currents to the dentate nucleus can facilitate sustained oscillatory activity at tremor frequency throughout the network as well as a robust bursting activity in the thalamus, which is consistent with observations of thalamic tremor cells in ET patients. Tremor-related oscillations initiated in small neural populations and spread to a larger network as the synaptic dysfunction increased, while thalamic high-frequency stimulation suppressed tremor-related activity in thalamus but increased the oscillation frequency in the olivocerebellar loop. These results suggest a mechanism for tremor generation under cerebellar dysfunction, which may explain the origin of ET.

scholarly journals Development and Validation of a New Wearable Mobile Device for the Automated Detection of Resting Tremor in Parkinson’s Disease and Essential Tremor

Diagnostics ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 200
Author(s):  
Basilio Vescio ◽  
Rita Nisticò ◽  
Antonio Augimeri ◽  
Andrea Quattrone ◽  
Marianna Crasà ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Essential Tremor ◽  
Mobile Device ◽  
Low Cost ◽  
Digital Signal ◽  
New Device ◽  
Resting Tremor ◽  
Phase Displacement ◽  
Tremor Frequency

Involuntary tremor at rest is observed in patients with Parkinson’s disease (PD) or essential tremor (ET). Electromyography (EMG) studies have shown that phase displacement between antagonistic muscles at prevalent tremor frequency can accurately differentiate resting tremor in PD from that detected in ET. Currently, phase evaluation is qualitative in most cases. The aim of this study is to develop and validate a new mobile tool for the automated and quantitative characterization of phase displacement (resting tremor pattern) in ambulatory clinical settings. A new low-cost, wearable mobile device, called µEMG, is described, based on low-end instrumentation amplifiers and simple digital signal processing (DSP) capabilities. Measurements of resting tremor characteristics from this new device were compared with standard EMG. A good level of agreement was found in a sample of 21 subjects (14 PD patients with alternating resting tremor pattern and 7 ET patients with synchronous resting tremor pattern). Our results demonstrate that tremor analysis using µEMG is easy to perform and it can be used in routine clinical practice for the automated quantification of resting tremor patterns. Moreover, the measurement process is handy and operator-independent.

scholarly journals Voluntary and tremorogenic inputs to motor neuron pools of agonist/antagonist muscles in essential tremor patients

2019 ◽  
Vol 122 (5) ◽  
pp. 2043-2053
Author(s):  
Gonthicha Puttaraksa ◽  
Silvia Muceli ◽  
Juan Álvaro Gallego ◽  
Ales Holobar ◽  
Steven K. Charles ◽  
...  
Keyword(s):  
Essential Tremor ◽  
Frequency Band ◽  
Voluntary Movement ◽  
Motor Units ◽  
Spike Trains ◽  
Frequency Bands ◽  
Synaptic Inputs ◽  
Antagonist Muscles ◽  
Tremor Frequency ◽  
Muscle Groups

Pathological tremor is an oscillation of body parts at 3–10 Hz, determined by the output of spinal motor neurons (MNs), which receive synaptic inputs from supraspinal centers and muscle afferents. The behavior of spinal MNs during tremor is not well understood, especially in relation to the activation of the multiple muscles involved. Recent studies on patients with essential tremor have shown that antagonist MN pools receive shared input at the tremor frequency. In this study, we investigated the synaptic inputs related to tremor and voluntary movement, and their coordination across antagonist muscles. We analyzed the spike trains of motor units (MUs) identified from high-density surface electromyography from the forearm extensor and flexor muscles in 15 patients with essential tremor during postural tremor. The shared synaptic input was quantified by coherence and phase difference analysis of the spike trains. All pairs of spike trains in each muscle showed coherence peaks at the voluntary drive frequency (1–3 Hz, 0.2 ± 0.2, mean ± SD) and tremor frequency (3–10 Hz, 0.6 ± 0.3) and were synchronized with small phase differences (3.3 ± 25.2° and 3.9 ± 22.0° for the voluntary drive and tremor frequencies, respectively). The coherence between MN spike trains of antagonist muscle groups at the tremor frequency was significantly smaller than intramuscular coherence. We predominantly observed in-phase activation of MUs between agonist/antagonist muscles at the voluntary frequency band (0.6 ± 48.8°) and out-of-phase activation at the tremor frequency band (126.9 ± 75.6°). Thus MNs innervating agonist/antagonist muscles concurrently receive synaptic inputs with different phase shifts in the voluntary and tremor frequency bands. NEW & NOTEWORTHY Although the mechanical characteristics of tremor have been widely studied, the activation of the affected muscles is still poorly understood. We analyzed the behavior of motor units of pairs of antagonistic wrist muscle groups in patients with essential tremor and studied their activity at voluntary movement- and tremor-related frequencies. We found that the phase relation between inputs to antagonistic muscles is different at the voluntary and tremor frequency bands.

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