Resting-state EEG study of comatose patients: A connectivity and frequency analysis to find differences between vegetative and minimally conscious states

Cyclotron Research Centre and Neurology Department, University Hospital of Liege, Belgium.
Functional neurology (Impact Factor: 1.86). 06/2012; 27(1):41-7.
Source: PubMed


The aim of this study was to look for differences in the power spectra and in EEG connectivity measures between patients in the vegetative state (VS/UWS) and patients in the minimally conscious state (MCS). The EEG of 31 patients was recorded and analyzed. Power spectra were obtained using modern multitaper methods. Three connectivity measures (coherence, the imaginary part of coherency and the phase lag index) were computed. Of the 31 patients, 21 were diagnosed as MCS and 10 as VS/UWS using the Coma Recovery Scale-Revised (CRS-R). EEG power spectra revealed differences between the two conditions. The VS/UWS patients showed increased delta power but decreased alpha power compared with the MCS patients. Connectivity measures were correlated with the CRS-R diagnosis; patients in the VS/UWS had significantly lower connectivity than MCS patients in the theta and alpha bands. Standard EEG recorded in clinical conditions could be used as a tool to help the clinician in the diagnosis of disorders of consciousness.

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Available from: Quentin Noirhomme, Jan 17, 2014
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    • "Interestingly, the proportion of nonsignificant results markedly differed between countries (Italy: 67%, Germany: 55%, United Kingdom: 33%, Belgium: 17%, France: 50%, Austria: 100%, China: 43%), possibly indicating high variability in the application of standardized diagnostic criteria across countries. The interpretation of these percentages, however, is complicated not only by the difference in the number of studies, but mostly by the fact that multiple measurements were sometimes performed by the same research group, as in the case of the studies performed in Germany (Kotchoubey et al., 2005, 2013, 2014), often presenting non-significant differences between diagnostic groups, and in Belgium (Boly et al., 2004, 2008; Perrin et al., 2006; Schnakers et al., 2008; Lehembre et al., 2012; Cruse et al., 2013), where on the contrary, such differences generally emerged. Measurements in Italy, on the other hand, were performed by four independent research groups (Cavinato et al., 2011; Trojano et al., 2012; Bonfiglio et al., 2013, 2014; Ragazzoni et al., 2013; de Biase et al., 2014), and the occurrence of non-significant differences was common in all the groups, with only one exception (Trojano et al., 2012). "
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    ABSTRACT: Given the enormous consequences that the diagnosis of vegetative state (VS) vs. minimally conscious state (MCS) may have for the treatment of patients with disorders of consciousness, it is particularly important to empirically legitimate the distinction between these two discrete levels of consciousness. Therefore, the aim of this contribution is to review all the articles reporting statistical evidence concerning the performance of patients in VS vs. patients in MCS, on behavioral or neurophysiological measures. Twenty-three articles matched these inclusion criteria, and comprised behavioral, electroencephalographic (EEG), positron emission tomography (PET) and magnetic resonance imaging (MRI) measures. The analysis of these articles yielded 47 different statistical findings. More than half of these findings (n = 24) did not reveal any statistically significant difference between VS and MCS. Overall, there was no combination of variables that allowed reliably discriminating between VS and MCS. This pattern of results casts doubt on the empirical validity of the distinction between VS and MCS.
    Full-text · Article · Oct 2014 · Frontiers in Human Neuroscience
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    • "To meet this needs, different research groups tried to validate the use of EEG in the exploration and interpretation of resting state activity. One attempt was made by Lehembre and colleagues [23] who recorded 15 minutes resting EEG on different comatose patients and were able to show that VS/UWS and MCS patients differ in the amount of delta and alpha power with VS/UWS patients having more delta and less alpha power and in addition significantly lower connectivity in the theta and alpha bands compared to MCS. A similar approach was used to determine whether different frequency bands and spectral EEG can predict the behavioral outcome of DOC patients [24]. "
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    ABSTRACT: With the advent of neuroimaging techniques the level of consciousness in patients with disorders of consciousness (DOC) is better assessable today. What we know so far, is that presence or absence of certain brain responses to stimulation, circadian rhythms or sleep patterns as well as certain forms of resting state activity can serve in the diagnostic and prognostic evaluation process. Despite the considerable progress in this field we still lack a comprehensive understanding of DOC which enables us to reliably differentiate DOC states in clinical routine. We here review current literature and discuss how classical neuroimaging methods (fMRI, PET) and in particular EEG can shed light on the level of preserved cognition or even the degree of conscious awareness.
    Full-text · Article · Oct 2014
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    • "cortico-thalamic coupling have been applied to resting EEG signals in an attempt to enhance their ability to classify the severity of brain damage or assess its prognosis (see for example Gosseries et al., 2011; Lehembre et al., 2012; Fingelkurts et al., 2012, 2013a,b; Holler et al., 2013). It has also been shown that brief latency EPs and cognitive responses to simple or complex stimuli (Kaplan, 2006; Estraneo et al., 2013) can be used to detect and measure residual brain function. "
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    ABSTRACT: Objective The aim of this study was to verify the value of multiple neurophysiological tests in classifying disorders of consciousness (DOCs) in patients in a chronic vegetative or minimal consciousness state categorised on the basis of the Coma Recovery Scale (CRS). Methods The study included 142 patients, all of whom underwent long (18-hour) EEG-polygraphic recordings including one night. The EEG was scored using the Synek scale and sleep patterns using an arbitrary scale. Absolute total power and relative EEG power were evaluated in different frequency bands. Multimodal evoked potentials (EPs), including auditory event-related potentials, were also evaluated and scored. Results The most information came from the combined multimodal EPs and sleep EEG scores. A two-step cluster analysis based on the collected information allowed a satisfactory evaluation of DOC severity. Spectral EEG properties seemed to be significantly related to DOC classes and CRS scores, but did not seem to make any significant additional contribution to DOC classification. Conclusions Multiple electrophysiological evaluations based on EEG, sleep polygraphic recordings and multimodal EPs are helpful in assessing DOC severity and residual functioning in patients with chronic DOCs. Significance Simple electrophysiological measures that can be easily applied at patients’ bedsides can significantly contribute to the recognition of DOC severity in chronic patients surviving a severe brain injury.
    Full-text · Article · Jul 2014 · Clinical Neurophysiology
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