Sleep in the unresponsive wakefulness syndrome and minimally conscious state

in Journal of Neurotrauma (2013), 30(5), 339-346

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 ... [more ▼]

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). 24h polysomnography was performed in 20 patients in a UWS (n=10) or in a MCS (n=10) due to brain injury. The data were first tested for the presence of a sleep-wake cycle and the observed sleep patterns were compared to standard scoring criteria. Sleep spindles, slow waves 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 5 MCS and 3 VS/UWS patients. Sleep stages did not always match the standard scoring criteria which therefore needed to be adapted. Sleep spindles were more present in patients who clinically improved within 6 months. Slow wave sleep was present in 8 MCS and 3 VS/UWS patients but never in the ischemic etiology. Rapid eye movement sleep, and therefore dreaming which is a form of consciousness, was present in all MCS and 3 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. [less ▲]

Our rapidly changing understanding of acute and chronic disorders of consciousness: challenges for neurologists

in Future Neurology (2013), 8(1), 43-54

A number of recent studies suggest that some ‘vegetative state’ patients have been misdiagnosed, judging by their ability to follow commands and in some cases even communicate through brain activity. Such ... [more ▼]

A number of recent studies suggest that some ‘vegetative state’ patients have been misdiagnosed, judging by their ability to follow commands and in some cases even communicate through brain activity. Such studies highlight the difficulty in forming a diagnosis based only on behavioral assessments. We think that neuroimaging and electrophysiology methods will be used more frequently in clinical settings, integrated with existing behavioral assessments. Such efforts are expected to lead to a more accurate understanding of individual patients’ cognitive abilities or even provide prognostic indicators. In terms of treatment planning (i.e., pain management and end-of-life decision-making), patients with disorders of consciousness are now offered the possibility of expressing their preferences by means of brain–computer interfaces. What remains to be clarified is the degree to which such indirect responses can be considered reliable and of legal representation. [less ▲]

The neuroscience of tinnitus: Perspectives from human neuroimaging studies

Conference (2012, November)

Memories of Near-Death experiences are they memories of imagined events?

Poster (2012, October 27)

Background: The phenomenon of Near-Death Experiences (NDEs) has always intrigued but is still not fully explained despite numerous theories and studies. Since reports of NDEs are proposed to be imagined ... [more ▼]

Background: The phenomenon of Near-Death Experiences (NDEs) has always intrigued but is still not fully explained despite numerous theories and studies. Since reports of NDEs are proposed to be imagined events (French, 2001), and since memories of imagined events have, on average, fewer phenomenological characteristics than real event memories (e.g. Johnson et al., 1988), we here compared phenomenological characteristics of NDEs reports with memories of imagined and real events. Methods: We included 3 groups of coma survivors (8 patients with NDE as defined by the Greyson NDE scale – the “NDE memory group”- , 6 patients without NDE but with memory of their coma – the “coma memory group” – and 7 patients without memories of their coma – the “no memory group”) and a group of 18 age-matched healthy volunteers. Five memories were assessed using Memory Characteristics Questionnaire (MCQ – Johnson et al., 1988): target memory (NDE for NDE memory group, coma memory for coma memory group, and first childhood memory for no memory and control groups), old and recent real event memories and old and recent imagined event memories. Results: In NDE group, NDE memories showd more characteristics than memories of imagined and real events (p<0.02). These memories contain more self-referential and emotional information and have better clarity than memories of coma (all p<0.02). Conclusion: The present study showed that NDE memories contain more characteristics than real event memories and coma memories. Thus, they cannot be considered as classic imagined event memories. On the contrary, their physiological origins could lead them to be really perceived although not lived in the reality. Further work is needed to better understand this phenomenon [less ▲]

Investigating the tinnitus brain using resting-state fMRI

Conference (2012, June)

Auditory Resting-State Network Connectivity in Tinnitus: a Functionnal MRI Study.

in PLoS ONE (2012)

The underlying functional neuroanatomy of tinnitus remains poorly understood. Few studies have focused on functional cerebral connectivity changes in tinnitus patients. The aim of this study was to test ... [more ▼]

The underlying functional neuroanatomy of tinnitus remains poorly understood. Few studies have focused on functional cerebral connectivity changes in tinnitus patients. The aim of this study was to test if functional MRI ‘‘resting-state’’ connectivity patterns in auditory network differ between tinnitus patients and normal controls. Thirteen chronic tinnitus subjects and fifteen age-matched healthy controls were studied on a 3 tesla MRI. Connectivity was investigated using independent component analysis and an automated component selection approach taking into account the spatial and temporal properties of each component. Connectivity in extra-auditory regions such as brainstem, basal ganglia/NAc, cerebellum, parahippocampal, right prefrontal, parietal, and sensorimotor areas was found to be increased in tinnitus subjects. The right primary auditory cortex, left prefrontal, left fusiform gyrus, and bilateral occipital regions showed a decreased connectivity in tinnitus. These results show that there is a modification of cortical and subcortical functional connectivity in tinnitus encompassing attentional, mnemonic, and emotional networks. Our data corroborate the hypothesized implication of non-auditory regions in tinnitus physiopathology and suggest that various regions of the brain seem involved in the persistent awareness of the phenomenon as well as in the development of the associated distress. leading to disabling chronic tinnitus. [less ▲]

Pain perception in disorders of consciousness: Neuroscience, clinical care, and ethics in dialogue

in Neuroethics (2012)

Pain, suffering and positive emotions in patients in vegetative state/unresponsive wakefulness syndrome (VS/UWS) and minimally conscious states (MCS) pose clinical and ethical challenges. Clinically, we ... [more ▼]

Pain, suffering and positive emotions in patients in vegetative state/unresponsive wakefulness syndrome (VS/UWS) and minimally conscious states (MCS) pose clinical and ethical challenges. Clinically, we evaluate behavioural responses after painful stimulation and also emotionally-contingent behaviours (e.g., smiling). Using stimuli with emotional valence, neuroimaging and electrophysiology technologies can detect subclinical remnants of preserved capacities for pain which might influence decisions about treatment limitation. To date, no data exist as to how healthcare providers think about end-of-life options (e.g., withdrawal of artificial nutrition and hydration) in the presence or absence of pain in non-communicative patients. Here, we aimed to better clarify this issue by re-analyzing previously published data on pain perception (Prog Brain Res 2009 177, 329–38) and end-of-life decisions (J Neurol 2010 258, 1058–65) in patients with disorders of consciousness. In a sample of 2259 European healthcare professionals we found that, for VS/UWS more respondents agreed with treatment withdrawal when they considered that VS/UWS patients did not feel pain (77%) as compared to those who thought VS/UWS did feel pain (59%). This interaction was influenced by religiosity and professional background. For MCS, end-of-life attitudes were not influenced by opinions on pain perception. Within a contemporary ethical context we discuss (1) the evolving scientific understandings of pain perception and their relationship to existing clinical and ethical guidelines; (2) the discrepancies of attitudes within (and between) healthcare providers and their consequences for treatment approaches, and (3) the implicit but complex relationship between pain perception and attitudes toward life-sustaining treatments. [less ▲]

A sensitive scale to assess nociceptive pain in patients with disorders of consciousness.

in Journal of Neurology, Neurosurgery & Psychiatry (2012), 83(12), 1233-7

OBJECTIVE: To determine the sensitivity of the Nociception Coma Scale (NCS), the first scale developed to assess nociceptive pain in vegetative state and minimally conscious state patients, in comparing ... [more ▼]

OBJECTIVE: To determine the sensitivity of the Nociception Coma Scale (NCS), the first scale developed to assess nociceptive pain in vegetative state and minimally conscious state patients, in comparing behavioural changes in response to noxious versus non-noxious stimulation. METHODS: The NCS was administered to assess patients' responses in three conditions: (1) baseline (observation of spontaneous behaviours), (2) non-noxious/tactile stimulation (taps on the patient's shoulder), and (3) noxious stimulation (pressure on the nail bed). RESULTS: We included 64 patients (27 vegetative state and 37 minimally conscious state; age range 20-82 years; 22 traumatic brain injury; 21 in the acute stage). The NCS total scores and subscores (motor, verbal and facial) were higher for the noxious versus the non-noxious stimulation conditions. We did not observe a difference between the non-noxious and the noxious stimulation conditions for the visual subscale. We also found a NCS cut-off value of 4 differentiating the patients receiving a noxious stimulation from patients receiving a non-noxious stimulation. The exclusion of the visual subscale increased the cut-off sensitivity (from 46% to 73%; specificity of 97% and accuracy of 85%). CONCLUSION: We propose a new version of the NCS excluding the visual subscale, the NCS-R, which constitutes a highly sensitive tool to assess responses to nociceptive pain in severely brain injured patients. [less ▲]

A default mode of brain function in altered states of consciousness

in Archives Italiennes de Biologie (2012), 150(2-3), 107-121

Granger causality analysis of steady-state electroencephalographic signals during propofol-induced anaesthesia.

in PLoS ONE (2012), 7(1), 29072

Changes in conscious level have been associated with changes in dynamical integration and segregation among distributed brain regions. Recent theoretical developments emphasize changes in directed ... [more ▼]

Changes in conscious level have been associated with changes in dynamical integration and segregation among distributed brain regions. Recent theoretical developments emphasize changes in directed functional (i.e., causal) connectivity as reflected in quantities such as 'integrated information' and 'causal density'. Here we develop and illustrate a rigorous methodology for assessing causal connectivity from electroencephalographic (EEG) signals using Granger causality (GC). Our method addresses the challenges of non-stationarity and bias by dividing data into short segments and applying permutation analysis. We apply the method to EEG data obtained from subjects undergoing propofol-induced anaesthesia, with signals source-localized to the anterior and posterior cingulate cortices. We found significant increases in bidirectional GC in most subjects during loss-of-consciousness, especially in the beta and gamma frequency ranges. Corroborating a previous analysis we also found increases in synchrony in these ranges; importantly, the Granger causality analysis showed higher inter-subject consistency than the synchrony analysis. Finally, we validate our method using simulated data generated from a model for which GC values can be analytically derived. In summary, our findings advance the methodology of Granger causality analysis of EEG data and carry implications for integrated information and causal density theories of consciousness. [less ▲]