Fronto-parietal coherence response to tDCS modulation in patients with disorders of consciousness
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Abstract:
A transcranial direct current stimulation (tDCS) protocol (20 min, 2 mA, anodal electrode at the left dorsolateral prefrontal cortex and cathodal electrode at the right supraorbital area) was applied in patients with different degrees of disorders of consciousness (DoC). Although previous research indicates that it could improve patients' coma recovery scale-revised (CRS-R) scores, the brain's electrophysiological responses to tDCS are still unclear. Therefore, the present study was performed to explore the underlying brain responses of patients in a minimally conscious state (MCS) and an unresponsive wakefulness syndrome (UWS) to tDCS modulation.Seventeen patients with DoC were recruited in a sham controlled crossover study receiving real and sham tDCS. EEG coherence was used to measure functional connectivity changes induced by the tDCS modulation.After real tDCS modulation, the fronto-parietal coherence significantly increased in the theta band and decreased in the gamma band in the MCS group. No significant changes were found in the UWS group. The coherence responses significantly correlated with the patients' baseline CRS-R scores. No distinct alteration occurred in the sham session for either the MCS or UWS patients.The coherence responses to the present tDCS protocol may be a tool for diagnosing MCS versus UWS, as they may be a crucial cause of the different clinical effects in the two states.Keywords:
Transcranial Direct Current Stimulation
Persistent vegetative state
Coma (optics)
Crossover study
Brain damage of various aetiologies can lead to different disorders of consciousness (DOC), varying from coma to vegetative, to minimally conscious states. Each state is characterised by a different degree of wakefulness, awareness, pain sensitivity and is differentially handled with respect to treatment, ethical considerations and end-oflife decisions. Thus, its correct identification is crucial while devising or modulating appropriate treatment strategies. Actually, the main coma scales cannot always accurately determine the state of consciousness of an individual, while other tools (e.g. imaging techniques) present a certain degree of uncertainty. A complementary approach may be constituted by a 24-hour observation of patients, for a sufficient period of days, using an ad hoc behavioural scale, further correlated with physiological and pharmacological parameters measured on patients. The method herein described might help recognising the presence of consciousness of the different DOC patients, and thus discerning a vegetative from a minimally conscious state.
Coma (optics)
Persistent vegetative state
Level of consciousness
Consciousness Disorders
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Primary objective: This study investigates (1) the utility of the bispectral index (BIS) to distinguish levels of consciousness in severely brain damaged patients and, particularly, disentangle vegetative state (VS) from minimally conscious state (MCS), as compared to other EEG parameters; (2) the prognostic value of BIS with regards to recovery after 1 year.Research design: Multi-centric prospective study.Method and procedures: Unsedated patients recovering from coma were followed until death or transferal. Automated electrophysiological and standardized behavioural assessments were carried out twice a week. EEG recordings were categorized according to level of consciousness (coma, VS, MCS and Exit MCS). Outcome was assessed at 1 year post-insult.Main outcomes and results: One hundred and fifty-six EEG epochs obtained in 43 patients were included in the analyses. BIS showed a higher correlation with behavioural scales as compared to other EEG parameters. Moreover, BIS values differentiated levels of consciousness and distinguished VS from MCS while other EEG parameters did not. Finally, higher BIS values were found in patients who recovered at 1 year post-insult as compared to patients who did not recover.Conclusion: EEG-BIS recording is an interesting additional method to help in the diagnosis as well as in the prognosis of severely brain injured patients recovering from coma.
Coma (optics)
Persistent vegetative state
Bispectral index
Level of consciousness
Quantitative electroencephalography
Consciousness Disorders
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The minimally conscious state (MCS) results from coma or vegetative state (VS) after acute brain injury, also from degenerative or congenital nervous system disorders. These patients with severe disorders in consciousness do not meet diagnostic criteria for coma or VS. MCS is characterized by inconsistent but discernible behavioral evidence of consciousness. It is important to distinguish the patients in MCS from those in coma or VS because preliminary findings suggest that there are significant differences in outcome. In this article, the authors have summarized the definition, diagnostic criteria and clinical features of disorders of consciousness about the MCS.
Coma (optics)
Persistent vegetative state
Consciousness Disorders
Level of consciousness
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Clinical experience suggests that patients with severe disorders of consciousness (DOC) due to brain injury, i.e. vegetative state (PVS) or minimally conscious state (MCS) do not have constant performance levels but show large variations in their behavioral abilities. Novel diagnostic approaches using fMRI or ERPs attempt to detect traces of consciousness even if clinical ratings imply unresponsive wakefulness. It is especially important for such sensitive methods to be aware of possible consciousness fluctuations in DOC patients in order not to measure at the wrong time.
Persistent vegetative state
Consciousness Disorders
Level of consciousness
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Recent studies revealed differences in signal distribution inDOC-patients, depending on the diagnosis. We investigated systematic differences in transcallosal coherence. Greater coherence in healthy than in DOC-Patients and greater coherence in patients in a minimally conscious state (MCS) than patients with unresponsible wakefulness syndrome (UWS) was expected.
Persistent vegetative state
Consciousness Disorders
Coma (optics)
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Coma (optics)
Persistent vegetative state
Brain damage
Consciousness Disorders
Brain Function
Level of consciousness
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Abstract Understanding the neuronal basis of disorders of consciousness can help improve the accuracy of their diagnosis, indicate potential targets for therapeutic interventions, and provide insights into the organization of normal conscious information processing. Measurements of brain activity have been used to find associations of the levels of consciousness with brain complexity, topological features of functional connectomes, and disruption of resting‐state networks. However, obtainment of a detailed picture of activity patterns underlying the vegetative state/unresponsive wakefulness syndrome and the minimally conscious state remains a work in progress. We here aimed at finding the aspects of fMRI‐based functional connectivity that differentiate these states from each other and from the normal condition. A group of 22 patients was studied (9 minimally conscious state and 13 vegetative state/unresponsive wakefulness syndrome). Patients were shown to have reduced connectivity in most resting‐state networks and disrupted patterns of relative connection strengths as compared to healthy subjects. Differences between the unresponsive wakefulness syndrome and the minimally conscious state were found in the patterns formed by a relatively small number of strongest positive correlations selected by thresholding. These differences were captured by measures of functional connectivity disruption that integrate area‐specific abnormalities over the whole brain. The results suggest that the strong positive correlations between the functional activities of specific brain areas observed in healthy individuals may be critical for consciousness and be an important target of disruption in disorders of consciousness.
Persistent vegetative state
Abnormality
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Coma (optics)
Persistent vegetative state
Consciousness Disorders
Locked-in syndrome
Gold standard (test)
Brain Function
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Objective: To establish consensus recommendations among health care specialties for defining and establishing diagnostic criteria for the minimally conscious state (MCS). Background: There is a subgroup of patients with severe alteration in consciousness who do not meet diagnostic criteria for coma or the vegetative state (VS). These patients demonstrate inconsistent but discernible evidence of consciousness. It is important to distinguish patients in MCS from those in coma and VS because preliminary findings suggest that there are meaningful differences in outcome. Methods: An evidence-based literature review of disorders of consciousness was completed to define MCS, develop diagnostic criteria for entry into MCS, and identify markers for emergence to higher levels of cognitive function. Results: There were insufficient data to establish evidence-based guidelines for diagnosis, prognosis, and management of MCS. Therefore, a consensus-based case definition with behaviorally referenced diagnostic criteria was formulated to facilitate future empirical investigation. Conclusions: MCS is characterized by inconsistent but clearly discernible behavioral evidence of consciousness and can be distinguished from coma and VS by documenting the presence of specific behavioral features not found in either of these conditions. Patients may evolve to MCS from coma or VS after acute brain injury. MCS may also result from degenerative or congenital nervous system disorders. This condition is often transient but may also exist as a permanent outcome. Defining MCS should promote further research on its epidemiology, neuropathology, natural history, and management.
Coma (optics)
Persistent vegetative state
Neuropathology
Consciousness Disorders
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Persistent vegetative state
Consciousness Disorders
Level of consciousness
Neurophysiology
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