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National Institutes of Health Stroke Scale (NIHSS) inter-group comparison. Cortico-subcortical lesioned patients (CS), Subcortical lesioned patients (S).
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A brain injury resulting from unilateral stroke critically alters brain functionality and the complex balance within the cortical activity. Such modifications may critically depend on lesion location and cortical involvement. Indeed, recent findings pointed out the necessity of applying a stratification based on lesion location when investigating i...
Citations
... It indicates relaxed wakefulness and disappears when opening the eyes or alerting by thinking or calculating. Beta waves (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) reflect alertness and active concentration, which is generally regarded as normal rhythm in patients who are alert or anxious or have their eyes open. It may be reduced or absent in areas of cortical damage. ...
... In stroke, the increased slow activity and reduced Alpha frequency are always related to worse outcomes [13,14]. An abnormal increase of Delta is usually associated with a primary brain injury, and Alpha relative power below 10 % is highly specific for a poor functional outcome [15]. However, the activation of Alpha indicates the survival of neurons in the stroke area and a good prognosis [16]. ...
Persistent motor deficits are highly prevalent among post-stroke survivors, contributing significantly to disability. Despite the prevalence of these deficits, the precise mechanisms underlying motor recovery after stroke remain largely elusive. The exploration of motor system reorganization using functional neuroimaging techniques represents a compelling yet challenging avenue of research. Quantitative electroencephalography (qEEG) parameters, including the power ratio index, brain symmetry index, and phase synchrony index, have emerged as potential prognostic markers for overall motor recovery post-stroke. Current evidence suggests a correlation between qEEG parameters and functional motor outcomes in stroke recovery. However, accurately identifying the source activity poses a challenge, prompting the integration of EEG with other neuroimaging modalities, such as functional near-infrared spectroscopy (fNIRS). fNIRS is nowadays widely employed to investigate brain function, revealing disruptions in the functional motor network induced by stroke. Combining these two methods, referred to as integrated fNIRS-EEG, neural activity and hemodynamics signals can be pooled out and offer new types of neurovascular coupling-related features, which may be more accurate than the individual modality alone. By harnessing integrated fNIRS-EEG source localization, brain connectivity analysis could be applied to characterize cortical reorganization associated with stroke, providing valuable insights into the assessment and treatment of post-stroke motor recovery.
... In particular, the DAR was found to be one of the most useful qEEG indices for this purpose [16,35], with a minimal number of electrodes required [35]. The Brain Symmetry Index (BSI) measures spectral asymmetry between the two cerebral hemispheres in the presence of lesions, by estimating PSD symmetry between affected and unaffected sides in unilateral lesions [14,37,45]. More severely afflicted stroke survivors generally have a lesioned hemisphere that generates higher power in the delta and theta frequency bands than the non-lesioned hemisphere, thus resulting in higher spectral asymmetry [14]. ...
... The Brain Symmetry Index (BSI) measures spectral asymmetry between the two cerebral hemispheres in the presence of lesions, by estimating PSD symmetry between affected and unaffected sides in unilateral lesions [14,37,45]. More severely afflicted stroke survivors generally have a lesioned hemisphere that generates higher power in the delta and theta frequency bands than the non-lesioned hemisphere, thus resulting in higher spectral asymmetry [14]. ...
... When analyzing pairs of homologous electrodes, the pdBSI was adopted, which assesses the spectral asymmetry between two channels reflected on the y-central axis. It was computed for the following electrodes pair F3-F4; F7-F8; C3-C4; T3-T4; T5-T6; P3-P4; The pdBSI ranges from zero (perfect symmetry) to one (maximal asymmetry) [14,37] and it was calculated as follows: ...
Objective: There is emerging confidence that quantitative EEG (qEEG) has the potential to inform clinical decision-making and guide individualized rehabilitation after stroke, but consensus on the best EEG biomarkers is needed for translation to clinical practice. This study investigates the spatial qEEG spectral and symmetry distribution in patients with a left/right hemispheric stroke, to evaluate their side-specific prognostic power in post-acute rehabilitation outcome. Methods: Resting-state 19-channel EEG recordings were collected with clinical information on admission to intensive inpatient rehabilitation (within 30 days post stroke), and six months post stroke. After preprocessing, spectral (Delta-to-Alpha Ratio, DAR) and symmetry (pairwise and hemispheric Brain Symmetry Index) features were extracted. Patients were divided into Affected Right and Left (AR/AL) groups, according to the location of their lesion. Within each group, DAR was compared between homologous electrode pairs and the pairwise difference between pairs was compared across pairs in the scalp. Then, the prognostic power of qEEG admission metrics was evaluated by performing correlations between admission metrics and discharge mBI values. Results: Fifty-two patients with hemorrhagic or ischemic stroke (20 females, 38.5 %, median age 76 years [IQR = 22]) were included in the study. DAR was significantly higher in the affected hemisphere for both AR and AL groups, and, a higher frontal (to posterior) asymmetry was found independent of the side of the lesion. DAR was found to be a prognostic marker of 6-months modified Barthel Index (mBI) only for the AL group, while hemi-spheric asymmetry did not correlate with follow-up outcomes in either group. Discussion: While the presence of EEG abnormalities in the affected hemisphere of a stroke is well recognized, we have shown that the extent of DAR abnormalities seen correlates with disability at 6 months post stroke, but only for left hemispheric lesions. Routine prognostic evaluation, in addition to motor and functional scales, can add information concerning neuro-prognostication and reveal neurophysiological abnormalities to be assessed during rehabilitation.
... The copyright holder for this preprint this version posted April 9, 2024. ; https://doi.org/10.1101/2024.04.06.24304834 doi: medRxiv preprint parallel, increased inhibition has been found to arise locally post-stroke [15,61] and blocking increased tonic GABA-mediated inhibition in the peri-infarct tissue facilitated functional recovery at later stages post-stroke [15,59]. A speculative yet very interesting theory is that slow waves post-stroke may not only be an epiphenomenon of mechanisms leading to less successful recovery but might even constitute the direct manifestation of a vast inhibitory tone, potentially blocking functional reorganization and thereby at least in parts leading to a less favorable outcome. ...
Background:
Acute ischemia triggers a number of cellular mechanisms not only leading to excitotoxic cell death but also to enhanced neuroplasticity, facilitating neuronal reorganization and functional recovery.
Objective:
Identifying their critical distinction and transferring these cellular mechanisms to neurophysiological correlates adaptable to patients is crucial to promote recovery post-stroke. The combination of TMS and EEG constitute a promising readout of neuronal network activity in stroke patients.
Methods:
Using this technique, we investigated the development of local signal processing and global network alterations of 40 stroke patients with motor deficits alongside neural reorganization from the acute to the chronic phase.
Results:
We show that the TMS-EEG response reflects information about reorganization and signal alterations associated with persistent motor deficits throughout the entire post-stroke period. Early post-stroke in subgroup of patients with severe motor deficits, TMS applied to the lesioned motor cortex evoked a sleep-like slow wave response associated with a cortical off-period, a manifestion of cortical bistability, as well as a rapid disruption of the TMS-induced formation of causal network effects. Mechanistically, these phenomena were linked to lesions affecting ascending activating brainstem fibers. Of note, sleep-like slow waves invariably vanished in the chronic phase, but were highly indicative of a poor functional outcome.
Conclusion:
In summary, we suggest that transient effects of sleep-like waves and cortical bistability within ipsilesional M1 resulting in excessive inhibition may block functional reorganization leading to a less favorable functional outcome post-stroke, pointing to a new therapeutic target to improve recovery of function.
... This highlights the capability of our approach to distinguish between two important categories of stroke. Stroke with cortical involvement is known to present marked EEG slowing (29), while small subcortical lesions not involving large white matter areas, such as lacunar stroke, do not seem to have a deep impact on EEG rhythms. ...
Introduction
Understanding the residual recovery potential in stroke patients is crucial for tailoring effective neurorehabilitation programs. We propose using EEG and plasmatic Neurofilament light chain (NfL) levels as a model to depict longitudinal patterns of stroke recovery.
Methods
We enrolled 13 patients (4 female, mean age 74.7 ± 8.8) who underwent stroke in the previous month and were hospitalized for 2-months rehabilitation. Patients underwent blood withdrawal, clinical evaluation and high-definition EEG at T1 (first week of rehabilitation) and at T2 (53 ± 10 days after). We assessed the levels of NfL and we analyzed the EEG signal extracting Spectral Exponent (SE) values. We compared our variables between the two timepoint and between cortical and non-cortical strokes.
Results
We found a significant difference in the symmetry of SE values between cortical and non-cortical stroke at both T1 (p = 0.005) and T2 (p = 0.01). SE in the affected hemisphere showed significantly steeper values at T1 when compared with T2 (p = 0.001). EEG measures were consistently related to clinical scores, while NfL at T1 was related to the volume of ischemic lesions (r = 0.75; p = 0.003). Additionally, the combined use of NfL and SE indicated varying trends in longitudinal clinical recovery.
Conclusion
We present proof of concept of a promising approach for the characterization of different recovery patterns in stroke patients.
... 23 In stroke, the increased Delta oscillation is considered a classic marker of this clinical group. 24 We observed that the motor functionality measure by Fugl-Meyer, negatively predicts Delta oscillation, indicating that the greater the impairment of functionality in these patients, the greater the Delta power activity. Thus, suggesting that Delta oscillations is a marker of disrupted maladaptive plasticity. ...
Objective: Investigate the relationship between resting-state EEG-measured brain oscillations and clinical and demographic measures in Stroke patients. Methods: We performed a cross-sectional analysis of a cohort study (DEFINE cohort), Stroke arm, with 85 patients, considering demographic, clinical, and stroke characteristics. Resting-state EEG relative power from delta, theta, alpha, and beta oscillations were measured from the central region. Multivariate regression models were used for both affected and non-affected hemispheres. Results: Motor function was negatively associated with Delta and Theta oscillations, while positively associated with Alpha oscillations (both hemispheres). Similarly, cognition levels measured were negatively associated with Delta activity. Depression levels were negatively associated with Alpha activity specifically in the affected hemisphere, while positively associated with Beta activity in both hemispheres. Regarding pain measures, no significant association was observed, while CPM measure showed a positive association with Alpha activity in the non-affected hemisphere. Finally, we found that theta/alpha ratio was negatively associated with motor function and CPM scores. Conclusion: The results lead us to propose a framework for brain oscillations in stroke, whereas Delta and Beta would represent disrupted mal-adaptive brain plasticity and Theta and Alpha would represent compensatory and functional brain oscillations for motor and sensory deficits in stroke, respectively.
... The EEG data were referenced to a common average. We defined 26 channels on the left hemisphere (FP1, AF3, F7, F5, F3, F1, FT7, FC5, FC3, FC1, T7, C5, C3, C1, TP7, CP5, CP3, CP1, P7, P5, P3, P1, PO7, PO5, PO3, and O1) and other 26 channels on the right hemisphere (FP2, AF4, F2, F4, F6, F8, FC2, FC4, FC6, FT8, C2, C4, C6, T8, CP2, CP4, CP6, TP8, P2, P4, P6, P8, PO4, PO6, PO8, and O2) to explore the hemispheric effect associated with stroke-induced lesions on cortical EEG rhythms and network features [17]. The data from patients with righthemispheric stroke were flipped for the convenience of visualization and data analysis. ...
... Subsequently, we compared the within-hemisphere differences using paired t-tests for the EEG rhythmic powers over different frequency bands, separately for each group. Following previous practice, regional power was defined as the mean power over adjacent electrodes within the following areas: frontal (left side: FP1, AF3, AF7, F1, F3, F5, and F7; right side: FP2, AF4, AF8, F2, F4, F6, and F8), central (left side: FT7, FC5, FC3, FC1, C5, C3, C1, CP5, CP3, CP1, T7, and TP7; right side: FT8, FC2, FC4, FC6, C2, C4, C6, T8, CP2, CP4, CP6, and TP8), and posterior (left side: P7, P5, P3, P1, PO7, PO5, PO3, and O1; right side: P2, P4, P6, P8, PO4, PO6, PO8, and O2) [17]. Finally, the potential correlation between EEG metrics and upper limb clinical scores was explored using Pearson's correlation in the group of stroke patients. ...
Objective
To investigate the resting-state cortical electroencephalogram (EEG) rhythms and networks in patients with chronic stroke and examine their correlation with motor functions of the hemiplegic upper limb.
Methods
Resting-state EEG data from 22 chronic stroke patients were compared to EEG data from 19 age-matched and 16 younger-age healthy controls. The EEG rhythmic powers and network metrics were analyzed. Upper limb motor functions were evaluated using the Fugl–Meyer assessment-upper extremity scores and action research arm test.
Results
Compared with healthy controls, patients with chronic stroke showed hemispheric asymmetry, with increased low-frequency activity and decreased high-frequency activity. The ipsilesional hemisphere of stroke patients exhibited reduced alpha and low beta band node strength and clustering coefficient compared to the contralesional side. Low beta power and node strength in the delta band correlated with motor functions of the hemiplegic arm.
Conclusion
The stroke-affected hemisphere showed low-frequency oscillations and decreased influence and functional segregation in the brain network. Low beta activity and redistribution of delta band network between hemispheres were correlated with motor functions of hemiplegic upper limb, suggesting a compensatory mechanism involving both hemispheres post-stroke.
... 21,22 However, it is a well-established clinical finding that focal high-amplitude, low-frequency rhythmic brain activity, as observed on scalp electroencephalography (EEG), is indicative of a lesion. [23][24][25][26] To date, no study has investigated the Current Biology 33, 1-12, November 20, 2023 ª 2023 Elsevier Inc. 1 ll effects of frontoparietal lesions on the fine-grained temporal dynamics of attention at the behavioral and electrophysiological level. Furthermore, it remains unclear whether the lesioninduced focal slowing of brain activity has immediate functional consequences. ...
... (1) Given that the patients performed the task with high accuracy, we hypothesized that indices of sensory processing, i.e., early evoked responses, remain largely intact. (2) High-amplitude, low-frequency EEG activity is indicative of an underlying cortical lesion, 24,25 which might predict the enhanced amplitude in rhythmic behavioral sampling. (3) We observed a clear distinction into best and worst phases in both patients and controls, implying that phase-behavior relationships are maintained following a lesion. ...
... As in spatial neglect, our results demonstrate that deficits emerge after lesions to multiple network nodes, hence, conceptualizing periodic attention deficit as a network disorder. ll Brain lesions and EEG slowing Focal EEG slowing is a well-established clinical hallmark of underlying brain lesions, [23][24][25][26] but the neural mechanisms responsible for this phenomenon remain unclear. Traditionally regarded as physical distortions caused by the damaged tissue, 70 more recent evidence suggests that low-frequency activity may reflect functional reorganization after stroke. ...
... In our study, we observed an increase in the activity of another group of CA3 interneurons (type II) confirming the functional heterogeneity of hippocampal interneurons. Previous studies have shown that the delta band power of hippocampal network oscillation increases during ischemic hypoxia in both rats and human subjects (Fanciullacci et al., 2017;Ferreira et al., 2021). In the present study, we observed a pronounced low-frequency activity (2.18 Hz) in the delta wave that increased with normobaric hypoxia under urethane anaesthesia in the hippocampus. ...
... Pyramidal neurons found in the cortical III, V, and VI layers are especially sensitive to decreased blood flow (Jordan, 2004). Based on this observation, an increase in delta activity may represent the sustained hyperpolarization and inhibition of the cortical neurons, which influence the activity of the hippocampus via the entorhinal cortex (Sirota et al., 2003;John and Prichep, 2006;Fanciullacci et al., 2017). In our case, the decrease in blood flow is unlikely, as it is known that the reduced oxygen supply to the brain results in several compensatory mechanisms, for example, increased cerebral blood flow (Kety and Schmidt, 1948;Kuwahira et al., 1993;Xu et al., 2012;Ogoh et al., 2014). ...
Hypoxia causes structural and functional changes in several brain regions, including the oxygen-concentration-sensitive hippocampus. We investigated the consequences of mild short-term hypoxia on rat hippocampus in vivo . The hypoxic group was treated with 16% O 2 for 1 h, and the control group with 21% O 2 . Using a combination of Gallyas silver impregnation histochemistry revealing damaged neurons and interneuron-specific immunohistochemistry, we found that somatostatin-expressing inhibitory neurons in the hilus were injured. We used 32-channel silicon probe arrays to record network oscillations and unit activity from the hippocampal layers under anaesthesia. There were no changes in the frequency power of slow, theta, beta, or gamma bands, but we found a significant increase in the frequency of slow oscillation (2.1–2.2 Hz) at 16% O 2 compared to 21% O 2 . In the hilus region, the firing frequency of unidentified interneurons decreased. In the CA3 region, the firing frequency of some unidentified interneurons decreased while the activity of other interneurons increased. The activity of pyramidal cells increased both in the CA1 and CA3 regions. In addition, the regularity of CA1, CA3 pyramidal cells’ and CA3 type II and hilar interneuron activity has significantly changed in hypoxic conditions. In summary, a low O 2 environment caused profound changes in the state of hippocampal excitatory and inhibitory neurons and network activity, indicating potential changes in information processing caused by mild short-term hypoxia.
... We also observed distinct patterns in the distribution of the delta wave activity between the 2 ischemic groups (MCAO and MCAO þ G1). It is interesting to note that some authors believe that the delta waves originate from thalamic connections in the deep CLs, and that lesions in these regions can compromise wave activity (29,30). The findings of the present study corroborate these studies, given that the corticalsubcortical lesions in the animals of the MCAO group provoked a significant reduction in delta wave activity, which was compatible with a stroke. ...
Stroke is one of the principal cerebrovascular diseases in human populations and contributes to a majority of the functional impairments in the elderly. Recent discoveries have led to the inclusion of electroencephalography (EEG) in the complementary prognostic evaluation of patients. The present study describes the EEG, behavioral, and histological changes that occur following cerebral ischemia associated with treatment by G1, a potent and selective G protein-coupled estrogen receptor 1 (GPER1) agonist in a rat model. Treatment with G1 attenuated the neurological deficits induced by ischemic stroke from the second day onward, and reduced areas of infarction. Treatment with G1 also improved the total brainwave power, as well as the theta and alpha wave activity, specifically, and restored the delta band power to levels similar to those observed in the controls. Treatment with G1 also attenuated the peaks of harmful activity observed in the EEG indices. These improvements in brainwave activity indicate that GPER1 plays a fundamental role in the mediation of cerebral injury and in the behavioral outcome of ischemic brain injuries, which points to treatment with G1 as a potential pharmacological strategy for the therapy of stroke.
... The NIHSS [21] is probably the most popular item for measuring the clinical impact of acute stroke and has been extensively related to qEEG features. NIHSS is related to broadband (1-25 Hz) BSI, as more significant asymmetry relates to worse NIHSS scores [30][31][32]. Spectral activity, in particular measures that account for slow oscillation, has been often shown to be closely related to the severity of stroke indexed by NIHSS: delta [33,34], DAR [25,[35][36][37][38][39], DTABR [19,23,35,37]. Noticeably, a study reported a significant clinical correlation of delta power in the UH with NIHSS scores [40], highlighting the importance of the non-lesioned hemisphere. ...
... Spectral measures seem to be particularly effective in large strokes with cortical involvement (i.e. middle cerebral artery) [30]. ...
ObjectQuantitative electroencephalography (qEEG) has shown promising results as a predictor of clinical impairment in stroke. We systematically reviewed published papers that focus on qEEG metrics in the resting EEG of patients with mono-hemispheric stroke, to summarize current knowledge and pave the way for future research.Methods
Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we systematically searched the literature for papers that fitted our inclusion criteria. Rayyan QCRR was used to allow deduplication and collaborative blinded paper review. Due to multiple outcomes and non-homogeneous literature, a scoping review approach was used to address the topic.ResultsOr initial search (PubMed, Embase, Google scholar) yielded 3200 papers. After proper screening, we selected 71 papers that fitted our inclusion criteria and we developed a scoping review thar describes the current state of the art of qEEG in stroke. Notably, among selected papers 53 (74.3%) focused on spectral power; 11 (15.7%) focused on symmetry indexes, 17 (24.3%) on connectivity metrics, while 5 (7.1%) were about other metrics (e.g. detrended fluctuation analysis). Moreover, 42 (58.6%) studies were performed with standard 19 electrodes EEG caps and only a minority used high-definition EEG.Conclusions
We systematically assessed major findings on qEEG and stroke, evidencing strengths and potential pitfalls of this promising branch of research.
