Electroencephalographic Phase Synchrony Index as a Biomarker of Poststroke Motor Impairment and Recovery

I can see zero usefulness for this. Survivors don't fucking care about biomarkers that point to failure to recover. They want protocols that deliver recovery results. GET THERE! This is the crapola we get when survivors are not in charge.

Electroencephalographic Phase Synchrony Index as a Biomarker of Poststroke Motor Impairment and Recovery

Show all authors

Teiji Kawano, MD, Noriaki Hattori, MD, PhD, Yutaka Uno, PhD, ...

First Published July 21, 2020 Research Article

https://doi.org/10.1177/1545968320935820

Article information

Abstract

Background.
Motor recovery after stroke is of great clinical interest. Besides magnetic resonance imaging functional connectivity, electroencephalographic synchrony is also an available biomarker. However, the clinical relevance of electroencephalographic synchrony in hemiparesis has not been fully understood.  
Objective.
We aimed to demonstrate the usefulness of the phase synchrony index (PSI) by showing associations between the PSI and poststroke outcome in patients with hemiparesis.  
Methods.
This observational study included 40 participants with cortical ischemic stroke (aged 69.8 ± 13.8 years) and 22 healthy controls (aged 66.9 ± 6.5 years). Nineteen-channel electroencephalography was recorded at 36.9 ± 11.8 days poststroke. Upper extremity Fugl-Meyer scores were assessed at the time of admission/before discharge (FM-UE1/FM-UE2; 32.6 ± 12.3/121.0 ± 44.7 days poststroke). Then, correlations between the PSIs and FM-UE1 as well as impairment reduction after rehabilitation (FM-UEgain) were analyzed.  
Results.
The interhemispheric PSI (alpha band) between the primary motor areas (M1s) was lower in patients than in controls and was selectively correlated with FM-UE1 (P = .001). In contrast, the PSI (theta band) centered on the contralesional M1 was higher in patients than in controls and was selectively correlated with FM-UEgain (P = .003). These correlations remained significant after adjusting for confounding factors (age, time poststroke, National Institute of Health Stroke Scale, and lesion volume). Furthermore, the latter correlation was significant in severely impaired patients (FM-UE1 ≤ 10).  
Conclusions.
This study showed that the PSIs were selectively correlated with motor impairment and recovery. Therefore, the PSIs may be potential biomarkers in persons with a hemispheric infarction.

Keywords biomarkers, electroencephalography, prognosis, rehabilitation, stroke, upper extremity

Introduction

Hemiparesis is a common poststroke impairment, and the prediction of motor recovery has been of great interest to researchers and clinicians.^1,2 According to the consensus-based core recommendation from the Stroke Recovery and Rehabilitation Roundtable,² corticospinal tract (CST) injury biomarkers indexed by diffusion tensor imaging, lesion overlap, or transcranial magnetic stimulation are recommended for use in clinical trials.^3-5 In addition, functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) markers may be promising biomarkers.² Quinlan et al demonstrated that it is best to predict motor recovery using both CST injury (lesion overlap) and functional connectivity (FC) between the primary motor areas (M1).⁶ Although lesion overlap can be quantified based on routine MRI,⁷ fMRI^8,9 is not available at all medical facilities. Notably, neural network status can also be evaluated using EEG synchrony because FC is defined as the temporal correlation of physiological events.^10,11 In fact, the blood oxygen level–dependent signal has been shown to temporally correlate with the EEG signal.^12-14 Thus, abnormalities in large-scale EEG synchrony have been observed in various brain disorders, such as schizophrenia, autism spectrum disorders,^15,16 and stroke.^17,18 Moreover, EEG is sensitive to the balance of cortical excitatory/inhibitory (glutaminergic/GABAergic) activity that associates with neural plasticity.^2,19,20 However, the clinical relevance of EEG synchrony in poststroke motor impairment and recovery^21-23 is not fully understood.^2,4
The association between interhemispheric FC of the M1 and the motor score is commonly demonstrated in fMRI studies,^9,24,25 but only one study has found a correlation between interhemispheric EEG synchrony of the M1 and motor score.¹⁷ In contrast, longitudinal studies indicate that EEG synchrony related to the ipsilesional M1 is significantly correlated with the motor recovery.^22,23 Interestingly, EEG synchrony related to the contralesional M1 only shows a trend toward a correlation with recovery,²² although neurophysiological studies have demonstrated correlations between contralesional M1 activity and poststroke outcome.^26-28 Thus, the role of interhemispheric EEG synchrony of the M1 in motor impairment as well as the contralesional M1 in recovery have not been fully elucidated. Furthermore, correlation analyses have been performed by assessing the coherence computed from signals with high-density electrodes (128- or 256-channel) in previous studies. However, EEG recordings with the widespread international 10-20 system are more clinically feasible. Our recent study found that the large-scale interhemispheric phase synchrony index (PSI)²⁹ from a 19-channel EEG was associated with the scores of Functional Independence Measure (FIM), which evaluates the activities of daily living,²⁶ and National Institutes of Health Stroke Scale (NIHSS), which assesses general neurological deficits,³⁰ in poststroke patients.¹⁷ Theoretically, the PSI is free from amplitude changes and can be used to evaluate phase synchrony robustly.^31-33
This observational study examined whether a novel method that combines the PSI with a 19-channel EEG could be used to assess patients with hemiparesis. We investigated the associations between the various interhemispheric/intrahemispheric PSIs and motor impairment (upper extremity Fugl-Meyer Assessment score at the time of admission [FM-UE1]) cross-sectionally, as well as motor recovery (impairment reduction after rehabilitation [FM-UEgain]) longitudinally.