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    Home > Active Ingredient News > Study of Nervous System > Neuromodulation: EEG assessment of electrical spinal cord stimulation-related neuromodulation activity

    Neuromodulation: EEG assessment of electrical spinal cord stimulation-related neuromodulation activity

    • Last Update: 2022-01-23
    • Source: Internet
    • Author: User
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    Little is known about how different modalities of spinal cord stimulation (SCS) suppress pain
    .
    The mechanism of action may exist locally in the spinal cord, but also involves larger networks, including subcortical and cortical brain structures

    .
    Tonic, burst, and high-frequency patterns of the SCS can in principle introduce distinct temporal activity patterns in this network, which must ultimately have specific effects on pain suppression

    .
    This paper employs high-density electroencephalography (EEG) and recently developed spatial filtering techniques to reduce SCS artifacts and enhance EEG signals particularly relevant to SCS neuromodulation

    .
    The article was published in Neuromodulation: Technology at the Neural Interface
    .

    The article was published in Neuromodulation: Technology at the Neural Interface
    .

    Data were collected from samples of four chronic pain patients who received cervical or thoracic epidural spinal cord stimulation for neuropathic pain due to peripheral and spinal cord injury
    .
    The patient had multiple etiologies, including complex regional pain syndrome (CRPS) and central spinal pain due to hemorrhage from a spinal cavernous
    hemangioma
    .
    Three of the four patients were recorded a few days after the final stimulation generator implantation, following a trial period that demonstrated the efficacy of SCS

    .
    One of the four patients was recorded twice, in the first session, two days after the test implant, with the stimulation generator still external, and in the second treatment, one day after the stimulation generator was finally implanted , 14 days later

    .
    Experiments were performed in accordance with the Declaration of Helsinki and were approved by the Ethics Committee of Otto von Gerich University Magdeburg (135/19)

    .

    Blood vessel

    Analysis of the neuromodulation effect of SCS on brain oscillations

    Electroencephalograms (EEGs) were recorded from 61 standard scalp locations using a Brainamp recording system (Brain Products GmbH, Germany) with electrodes AFz grounded and FCz referenced
    .
    Additional skin electrodes were placed on the face, neck, and arms to measure eye movements, ECG, and SCS-related artifacts

    .
    SCS patients sit comfortably in a soundproof, electrically shielded recording studio with constant contact with the experimenter

    .
    Eye-open resting-state EEGs were recorded at 3- to 5-minute intervals for each SCS mode and SCS-off condition

    .
    Between blocks, the experimenter uses the SCS remote to select the stimulation mode for the next recording block

    .
    A tonic stimulation (TONIC mode) was recorded in all five sessions

    .
    In four sessions, the tonic pulse rate was 40 Hz (patients 1, 3, and 4) and one was 80 Hz

    .

    It is important to note that the analysis is not for detailed differences between specific mode parameters, but for general differences between modes
    .
    Actively charged burst stimulation (BURST mode) with a pulse frequency of 200 Hz and a burst frequency of 40 Hz and a high-frequency stimulation block set to a pulse frequency of 1200 Hz (HF mode) were recorded in four sessions of patient 1

    .
    In three sessions (patients 3 and 4), low-frequency stimulation blocks at 2 Hz (LF mode) were recorded to characterize the response to a single SCS pulse

    .
    The stimulus intensity was consistently maintained at 20% below the threshold level for evoking paresthesia for BURST and 30% below the threshold level for HF mode

    .
    For TONIC mode, set the stimulus intensity to a level that the patient is comfortable with at the paresthesia threshold

    .
    In all sessions, we ended up recording the rest block where the SCS was off (off state)

    .
    We compared resting EEG during SCS in different modalities with the corresponding OFF condition in each session

    .
    We did not inform subjects of the SCS mode chosen; although they could not be completely blinded by switching modes

    .
    We used the maximum possible sampling rate of 5000 Hz for EEG recordings to reduce distortion caused by SCS artifacts
    .
    Spatial SCS artifact filters for artifact attenuation and SCS response filters for enhancement of neuromodulation signals were designed using the artifact and average EEG responses in the post-artifact interval as target signals, respectively

    .

    We used the maximum possible sampling rate of 5000 Hz for EEG recordings to reduce distortion caused by SCS artifacts
    .
    Spatial SCS artifact filters for artifact attenuation and SCS response filters for enhancement of neuromodulation signals were designed using the artifact and average EEG responses in the post-artifact interval as target signals, respectively

    .
    We used the maximum possible sampling rate of 5000 Hz for EEG recordings to reduce distortion caused by SCS artifacts
    .
    Spatial SCS artifact filters for artifact attenuation and SCS response filters for enhancement of neuromodulation signals were designed using the artifact and average EEG responses in the post-artifact interval as target signals, respectively

    .

    Spatial Filters for Artifact Attenuation (SFA) and Response Enhancement (SFR)

    In EEG regions responsive to SCS, neuromodulation greatly reduced activity in theta and low alpha range (6-10 Hz) in all SCS modalities
    .
    The results were consistent across all patients and consistent with the thalamocortical arrhythmia hypothesis of pain

    .
    SCS also persistently and strongly reduced hypergamma activity (>84 Hz) only in tonic mode with paresthesia as a side effect

    .
    Although SCS has been a clinically effective treatment for neuropathic pain for decades, its mechanism of action, especially its effect on supraspinal neuronal processing, is still not fully understood
    .
    Due to its rhythmic nature, SCS may interact with ongoing neural synchronization rhythms

    .

    Although SCS has been a clinically effective treatment for neuropathic pain for decades, its mechanism of action, especially its effect on supraspinal neuronal processing, is still not fully understood
    .
    Due to its rhythmic nature, SCS may interact with ongoing neural synchronization rhythms

    .

    However, gaining a deep understanding of this interaction is difficult
    .
    A major problem with SCS electrophysiological analysis is that SCS-evoked brain responses and SCS-related changes in ongoing brain activity are difficult to separate from stimulation artifacts and nonspecific vigilance effects

    .
    However, by spatial filtering, we greatly reduced SCS artifacts and specifically enhanced SCS-modulated EEG activity, revealing distinct and common changes in brain oscillations across different SCS modalities

    .
    Although our first spatial filter optimized for removing SCS artifact signals was very effective in removing SCS artifacts from ongoing EEG, sometimes small residuals of spectral peaks at SCS correlation frequencies and their harmonics still exists

    .
    Since they persisted after spatial filtering, these peaks were less correlated with the reconstructed artifact signal

    .
    They may arise from hidden artifact sources unrelated to our artifact signals, or by SCS-evoked brain reaction times and phase-locking to the SCS cycle, but not entirely related to the SCS artifact itself
    .
    Notably, spatial filtering attenuated early SCS artifacts without affecting SCS-evoked responses, suggesting the presence of artifact-independent late responses

    .
    Compared to other methods of reducing electrical stimulation artifacts during neuromodulation, the analysis pipeline of

    .

    They may arise from hidden artifact sources unrelated to our artifact signals, or by SCS-evoked brain reaction times and phase-locking to the SCS cycle, but not entirely related to the SCS artifact itself
    .
    Notably, spatial filtering attenuated early SCS artifacts without affecting SCS-evoked responses, suggesting the presence of artifact-independent late responses

    .
    Compared to other methods of reducing electrical stimulation artifacts during neuromodulation, the analysis pipeline of

    .
    They may arise from hidden artifact sources unrelated to our artifact signals, or by SCS-evoked brain reaction times and phase-locking to the SCS cycle, but not entirely related to the SCS artifact itself
    .
    Notably, spatial filtering attenuated early SCS artifacts without affecting SCS-evoked responses, suggesting the presence of artifact-independent late responses

    .
    Compared to other methods of reducing electrical stimulation artifacts during neuromodulation, the analysis pipeline of

    .

    EEG spectral analysis combined with spatial filtering allows for spatially and temporally specific assessment of neuromodulatory EEG activity associated with SCS, helping to unravel the mechanisms of treatment and side effects of SCS
    .

    Buentjen, L.
    , Vicheva, P.
    , Chander, B.
    , Beccard, S.
    -A.
    , Coutts, C.
    , Azañón, E.
    , Stenner, M.
    -P.
    and Deliano, M.
    (2021),
    Spatial Filtering of Electroencephalography Reduces Artifacts and Enhances Signals Related to Spinal Cord Stimulation (SCS).
    Neuromodulation: Technology at the Neural Interface, 24: 1317-1326.
     
    https://doi.
    org/10.
    1111/ner.
    13266

    Buentjen, L.
    , Vicheva, P.
    , Chander, B.
    , Beccard, S.
    -A.
    , Coutts, C.
    , Azañón, E.
    , Stenner, M.
    -P.
    and Deliano, M.
    (2021),
    Spatial Filtering of Electroencephalography Reduces Artifacts and Enhances Signals Related to Spinal Cord Stimulation (SCS).
    Neuromodulation: Technology at the Neural Interface, 24: 1317-1326.
     
    Spatial Filtering of Electroencephalography Reduces Artifacts and Enhances Signals Related to Spinal Cord Stimulation (SCS).
    https ://doi.
    org/10.
    1111/ner.
    13266

     



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