Wakefulness and loss of awareness

Silva, S.; Alacoque, Xavier; Fourcade, Olivier; Samii, K.; Marqué, P.; Woods, Roger P.; Mazziotta, John C.; Chollet, François; Loubinoux, Isabelle

doi:10.1212/wnl.0b013e3181cbcd96

Cited by 77 publications

(50 citation statements)

References 47 publications

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“…26,29,31,32,35,36,38,41,42 In several studies, when compared with subjects in the MCS, patients in VS had proportionally greater reductions in activity in the precuneus and in the posterior cingulate cortex (PCC). 26,35,39 This reduction in activity in the precuneus was coupled with increased activity in brainstem arousal centers in one study. 39 In patients with VS, widespread reductions in activity were noted within exteroceptive (left and right lateral parietal and lateral prefrontal cortices) and interoceptive systems (midline precuneus/posterior cingulate and mesiofrontal/anterior cingulate cortices), while in MCS, reduced activity was observed in interoceptive systems only, and in EMCS, reduced activity was noted only in the PCC.…”

Section: Systematic Review Population Characteristicsmentioning

confidence: 94%

“…26,35,39 This reduction in activity in the precuneus was coupled with increased activity in brainstem arousal centers in one study. 39 In patients with VS, widespread reductions in activity were noted within exteroceptive (left and right lateral parietal and lateral prefrontal cortices) and interoceptive systems (midline precuneus/posterior cingulate and mesiofrontal/anterior cingulate cortices), while in MCS, reduced activity was observed in interoceptive systems only, and in EMCS, reduced activity was noted only in the PCC. 29 Two SPECT and 4 PET studies evaluated patients with TBI separately (table e-2).…”

Section: Systematic Review Population Characteristicsmentioning

confidence: 94%

“…57 A small number of studies reported increased activity or increased functional connectivity in patients with DOC when compared with HCs. Patients in VS had higher activity in the brainstem, 39 cerebellum, supramarginal cortex, 26 and externally oriented networks, such as the insula and premotor area, 16 in addition to increased connectivity of the DMN to structures within the limbic system. 23 The significance of such increases in connectivity or activity is unknown, but they might represent compensatory/ adaptive or maladaptive mechanisms.…”

Section: Systematic Review Population Characteristicsmentioning

confidence: 99%

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Resting brain activity in disorders of consciousness

et al. 2015

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Objective: To quantitatively synthesize results from neuroimaging studies that evaluated patterns of resting functional activity in patients with disorders of consciousness (DOC).Methods: We performed a systematic review and coordinate-based meta-analysis of studies published up to May 2014. Studies were included if they compared resting-state functional neuroimaging data acquired in patients with DOC (coma, minimally conscious state, emergence from minimally conscious state, or vegetative state) with a group of healthy controls. Coordinate-based meta-analysis was performed in studies that included voxel-based comparisons at the whole-brain level and if analysis was accomplished with data-driven approaches.Results: A total of 36 studies (687 patients, 637 healthy controls) were included in the systematic review. Reported DOC were vegetative state (43.2%), coma (23.4%), minimally conscious state (22.8%), and emergence from minimally conscious state (1.6%); the most common etiologies of DOC were traumatic brain injury (37.7%) and anoxic brain injury (36.9%). Functional neuroimaging was accomplished using fMRI (16 studies), PET (15 studies), SPECT (4 studies), and both PET and SPECT in one study. Meta-analysis in 13 studies (272 patients, 259 healthy controls) revealed consistently reduced activity in patients with DOC in bilateral medial dorsal nucleus of the thalamus, left cingulate, posterior cingulate, precuneus, and middle frontal and medial temporal gyri. Conclusions:In patients with DOC evaluated in the resting state, functional neuroimaging indicates markedly reduced activity within midline cortical and subcortical sites, anatomical structures that have been linked to the default-mode network. Studies are needed to determine the relation between activation (and coherence) within these structures and the emergence of conscious awareness. Neurology ® 2015;84:1272-1280 GLOSSARY ALE 5 activation likelihood estimate; ALFF 5 amplitude of low-frequency fluctuations; BOLD 5 blood oxygen level-dependent; CRS-R 5 Coma Recovery Scale-Revised; DMN 5 default mode network; DOC 5 disorders of consciousness; EMCS 5 emergence from minimally conscious state; FDG 5 fluorodeoxyglucose; HC 5 healthy control; ICA 5 independent component analysis; MCS 5 minimally conscious state; MNI 5 Montreal Neurological Institute; PCC 5 posterior cingulate cortex; ReHo 5 regional homogeneity; ROI 5 region of interest; TBI 5 traumatic brain injury; VS 5 vegetative state.Coma is a cardinal sign of brain injury resulting from trauma, stroke, cardiac arrest, infection, or metabolic causes. While coma is a transient state from which the majority of subjects awaken, a subset of patients develop a more prolonged impairment in consciousness, such as the vegetative state (VS) or minimally conscious state (MCS). Despite considerable research, states such as coma, VS, and MCS-collectively termed disorders of consciousness (DOC)-remain poorly understood regarding their neural basis, clinical recognition, and long-term outcome.1,2 Neurophysiologic...

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Section: Systematic Review Population Characteristicsmentioning

confidence: 94%

Section: Systematic Review Population Characteristicsmentioning

confidence: 94%

Section: Systematic Review Population Characteristicsmentioning

confidence: 99%

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Resting brain activity in disorders of consciousness

et al. 2015

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“…8,9 Contrary to what several definitions state, the presence of rest periods does not always imply preserved electrophysiological sleep-wake cycles nor sleep stages that should no longer be taken as a distinguishing feature for the definition of UWS or MCS. 24,25 The waking state and sleep stages do not fit the elder standard scoring criteria, which therefore needs to be adapted for polysomnography in DOC.…”

Section: Discussionmentioning

confidence: 99%

Sleep in the Unresponsive Wakefulness Syndrome and Minimally Conscious State

Cologan

Drouot

Parapatics

et al. 2013

Journal of Neurotrauma

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The goal of our study was to investigate different aspects of sleep, namely the sleep-wake cycle and sleep stages, in the vegetative state/unresponsive wakefulness syndrome (VS/UWS), and minimally conscious state (MCS). A 24-h polysomnography was performed in 20 patients who were in a UWS (n = 10) or in a MCS (n = 10) because of brain injury. The data were first tested for the presence of a sleep-wake cycle, and the observed sleep patterns were compared with standard scoring criteria. Sleep spindles, slow wave sleep, and rapid eye movement sleep were quantified and their clinical value was investigated. According to our results, an electrophysiological sleep-wake cycle was identified in five MCS and three VS/UWS patients. Sleep stages did not always match the standard scoring criteria, which therefore needed to be adapted. Sleep spindles were present more in patients who clinically improved within 6 months. Slow wave sleep was present in eight MCS and three VS/UWS patients but never in the ischemic etiology. Rapid eye movement sleep, and therefore dreaming that is a form of consciousness, was present in all MCS and three VS/UWS patients. In conclusion, the presence of alternating periods of eyes-open/eyes-closed cycles does not necessarily imply preserved electrophysiological sleep architecture in the UWS and MCS, contrary to previous definition. The investigation of sleep is a little studied yet simple and informative way to evaluate the integrity of residual brain function in patients with disorders of consciousness with possible clinical diagnostic and prognostic implications.

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“…in general anesthesia [52 ]) and pathological alterations of consciousness (e.g. [53,54,55 ,56 ]) provide evidence in favor of this hypothesis. For most neuroscientists, you are your brain.…”

Section: Resultsmentioning

confidence: 99%