A default mode of brain function in altered states of consciousness.
; Vanhaudenhuyse, Audrey ; Boly, Mélanie et al
in Archives Italiennes de Biologie (2012), 150(2-3), 107-21
Using modern brain imaging techniques, new discoveries are being made concerning the spontaneous activity of the brain when it is devoid of attention-demanding tasks. Spatially separated patches of ... [more ▼]
Using modern brain imaging techniques, new discoveries are being made concerning the spontaneous activity of the brain when it is devoid of attention-demanding tasks. Spatially separated patches of neuronal assemblies have been found to show synchronized oscillatory activity behavior and are said to be functionally connected. One of the most robust of these is the default mode network, which is associated with intrinsic processes like mind wandering and self-projection. Furthermore, activity in this network is anticorrelated with activity in a network that is linked to attention to external stimuli. The integrity of both networks is disturbed in altered states of consciousness, like sleep, general anesthesia and hypnosis. In coma and related disorders of consciousness, encompassing the vegetative state (unresponsive wakefulness syndrome) and minimally conscious state, default mode network integrity correlates with the level of remaining consciousness, offering the possibility of using this information for diagnostic and prognostic purposes. Functional brain imaging is currently being validated as a valuable addition to the standardized behavioral assessments that are already in use. [less ▲]Detailed reference viewed: 133 (3 ULg)
Assessment of White Matter Injury and Outcome in Severe Brain Trauma: A Prospective Multicenter Cohort
; ; et al
in Anesthesiology (2012), 117(6), 1300-1310
BACKGROUND:: Existing methods to predict recovery after severe traumatic brain injury lack accuracy. The aim of this study is to determine the prognostic value of quantitative diffusion tensor imaging ... [more ▼]
BACKGROUND:: Existing methods to predict recovery after severe traumatic brain injury lack accuracy. The aim of this study is to determine the prognostic value of quantitative diffusion tensor imaging (DTI). METHODS:: In a multicenter study, the authors prospectively enrolled 105 patients who remained comatose at least 7 days after traumatic brain injury. Patients underwent brain magnetic resonance imaging, including DTI in 20 preselected white matter tracts. Patients were evaluated at 1 yr with a modified Glasgow Outcome Scale. A composite DTI score was constructed for outcome prognostication on this training database and then validated on an independent database (n = 38). DTI score was compared with the International Mission for Prognosis and Analysis of Clinical Trials Score. RESULTS:: Using the DTI score for prediction of unfavorable outcome on the training database, the area under the receiver operating characteristic curve was 0.84 (95% CI: 0.75-0.91). The DTI score had a sensitivity of 64% and a specificity of 95% for the prediction of unfavorable outcome. On the validation-independent database, the area under the receiver operating characteristic curve was 0.80 (95% CI: 0.54-0.94). On the training database, reclassification methods showed significant improvement of classification accuracy (P < 0.05) compared with the International Mission for Prognosis and Analysis of Clinical Trials score. Similar results were observed on the validation database. CONCLUSIONS:: White matter assessment with quantitative DTI increases the accuracy of long-term outcome prediction compared with the available clinical/radiographic prognostic score. [less ▲]Detailed reference viewed: 12 (2 ULg)
Connectivity graph analysis of the auditory resting state network in tinnitus.
MAUDOUX, Audrey ; Lefèbvre, Philippe ; et al
in Brain Research (2012), 1485
Thirteen chronic tinnitus patients and fifteen age-matched healthy controls were studied on a 3T magnetic resonance imaging (MRI) scanner during resting condition (i.e. eyes closed, no task performance ... [more ▼]
Thirteen chronic tinnitus patients and fifteen age-matched healthy controls were studied on a 3T magnetic resonance imaging (MRI) scanner during resting condition (i.e. eyes closed, no task performance). The auditory resting-state component was selected using an automatic component selection approach. Functional connectivity (correlations/anti-correlations) in the extracted network was portrayed by integrating the independent component analysis (ICA) approach with a graph theory method. Tinnitus and control groups showed different graph connectivity patterns. In the control group, the connectivity graph was divided into two distinct anti-correlated networks. The first one encompassed the auditory cortices and the insula. The second one encompassed frontoparietal and anterior cingulate cortices, brainstem, amygdala, basal ganglia/nucleus accumbens and parahippocampal regions. In the tinnitus group, only one of the two previously described networks was observed, encompassing the auditory cortices and the insula. Direct group comparison showed, in the tinnitus group, an increased functional connectivity between auditory cortices and the left parahippocampal region surviving multiple comparisons. We investigated a possible correlation between four tinnitus relevant measures (tinnitus handicap inventory (THI) and tinnitus questionnaire (TQ) scores, tinnitus duration and tinnitus intensity during the scanning session) and the connectivity pattern in the tinnitus population. We observed a significant positive correlation between the beta values of the posterior cingulate/precuneus region and the THI score. Our results show a modified functional connectivity pattern in tinnitus sufferers and highlight the role of the parahippocampal region in tinnitus physiopathology. They also point out the importance of the activity and connectivity pattern of the posterior cingulate cortex/precuneus region to the development of the tinnitus associated distress. This article is part of a Special Issue entitled: Tinnitus Neuroscience. [less ▲]Detailed reference viewed: 20 (9 ULg)
Resting-state EEG study of comatose patients: a connectivity and frequency analysis to find differences between vegetative and minimally conscious states.
Lehembre, Remy ; Bruno, Marie-Aurélie ; Vanhaudenhuyse, Audrey et al
in Functional Neurology (2012), 27(1), 41-47
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 ... [more ▼]
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. [less ▲]Detailed reference viewed: 177 (30 ULg)
Diffusion Tensor Imaging to Predict Long-term Outcome after Cardiac Arrest. A Bicentric Pilot Study
; ; et al
in Anesthesiology (2012), 117(6), 1311-1321Detailed reference viewed: 9 (0 ULg)
Metabolic activity in external and internal awareness networks in severely brain-damaged patients.
Thibaut, Aurore ; Bruno, Marie-Aurélie ; Chatelle, Camille et al
in Journal of Rehabilitation Medicine (2012), 44(6), 487-94
OBJECTIVE: An extrinsic cerebral network (encompassing lateral frontoparietal cortices) related to external/sensory awareness and an intrinsic midline network related to internal/self-awareness have been ... [more ▼]
OBJECTIVE: An extrinsic cerebral network (encompassing lateral frontoparietal cortices) related to external/sensory awareness and an intrinsic midline network related to internal/self-awareness have been identified recently. This study measured brain metabolism in both networks in patients with severe brain damage. DESIGN: Prospective [18F]-fluorodeoxyglucose-positron emission tomography and Coma Recovery Scale-Revised assessments in a university hospital setting. SUBJECTS: Healthy volunteers and patients in vegetative state/unresponsive wakefulness syndrome (VS/UWS), minimally conscious state (MCS), emergence from MCS (EMCS), and locked-in syndrome (LIS). RESULTS: A total of 70 patients were included in the study: 24 VS/UWS, 28 MCS, 10 EMCS, 8 LIS and 39 age-matched controls. VS/UWS showed metabolic dysfunction in extrinsic and intrinsic networks and thalami. MCS showed dysfunction mostly in intrinsic network and thalami. EMCS showed impairment in posterior cingulate/retrosplenial cortices. LIS showed dysfunction only in infratentorial regions. Coma Recovery Scale-Revised total scores correlated with metabolic activity in both extrinsic and part of the intrinsic network and thalami. CONCLUSION: Progressive recovery of extrinsic and intrinsic awareness network activity was observed in severely brain-damaged patients, ranging from VS/UWS, MCS, EMCS to LIS. The predominance of intrinsic network impairment in MCS could reflect altered internal/self-awareness in these patients, which is difficult to quantify at the bedside. [less ▲]Detailed reference viewed: 189 (51 ULg)
Prognosis of patients with altered states of consciousness
Bruno, Marie-Aurélie ; ; Vanhaudenhuyse, Audrey et al
in Schnakers, Caroline; Laureys, Steven (Eds.) Coma and disorders of consciousness (2012)Detailed reference viewed: 92 (2 ULg)
Diagnostic, pronostic et traitement de patients sévèrement cérébro-lésés
Scientific conference (2012)Detailed reference viewed: 14 (0 ULg)
Disorders of consciousness: Belgium Federal Project
Conference (2012)Detailed reference viewed: 12 (0 ULg)
The neural correlates of conscious awareness revealed by the study of coma and related states
Conference (2012)Detailed reference viewed: 12 (0 ULg)
How to detect consciousness in severely brain injured patients?
Conference (2012)Detailed reference viewed: 10 (0 ULg)
Does the self-referential stimuli percpetion decrease with diminished level of consciousness?
in Vanhaudenhuyse, Audrey; BOVEROUX, Pierre; Bruno, Marie-Aurélie (Eds.) et al Journal of Neurology (2012)Detailed reference viewed: 22 (0 ULg)
Auditory resting-state network connectivity in tinnitus: a functional MRI study.
; Lefèbvre, Philippe ; et al
in PLoS ONE (2012), 7(5), 36222
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 ▲]Detailed reference viewed: 18 (0 ULg)
Diffusion Tensor Imaging to Predict Long-term Outcome after Cardiac Arrest: A Bicentric Pilot Study.
; ; et al
in Anesthesiology (2012), 117(6), 1311-1321
BACKGROUND:: Prognostication in comatose survivors of cardiac arrest is a major clinical challenge. The authors' objective was to determine whether an assessment with diffusion tensor imaging, a brain ... [more ▼]
BACKGROUND:: Prognostication in comatose survivors of cardiac arrest is a major clinical challenge. The authors' objective was to determine whether an assessment with diffusion tensor imaging, a brain magnetic resonance imaging sequence, increases the accuracy of 1 yr functional outcome prediction in cardiac arrest survivors. METHODS:: Prospective, observational study in two intensive care units. Fifty-seven comatose survivors of cardiac arrest underwent brain magnetic resonance imaging. Fractional anisotropy (FA), a diffusion tensor imaging value, was measured in predefined white matter regions, and apparent diffusion coefficient was assessed in predefined grey matter regions. Prediction of unfavorable outcome at 1 yr was compared using four prognostic models: FA global, FA selected, apparent diffusion coefficient, and clinical classifiers. RESULTS:: Of the 57 patients included in the study, 49 had an unfavorable outcome at 12 months. Areas under the receiver operating characteristic curve (95% CI) to predict unfavorable outcome for the FA global, FA selected, clinical, and apparent diffusion coefficient models were 0.92 (0.82-0.98), 0.96 (0.87-0.99), 0.78 (0.65-0.88), and 0.86 (0.74-0.94), respectively. The FA selected model had the best overall accuracy for predicting outcome, with a score above 0.44 having 94% (95% CI, 83-99%) sensitivity and 100% (95% CI, 63-100%) specificity for the prediction of unfavorable outcome. CONCLUSION:: Quantitative diffusion tensor imaging indicates that white matter damage is widespread after cardiac arrest. A prognostic model based on FA values in selected white matter tracts seems to predict accurately 1 yr functional outcome. These preliminary results need to be confirmed in a larger population. [less ▲]Detailed reference viewed: 10 (0 ULg)
Reduction in inter-hemispheric connectivity in disorders of consciousness.
; ; Soddu, Andrea et al
in PLoS ONE (2012), 7(5), 37238
Clinical diagnosis of disorders of consciousness (DOC) caused by brain injury poses great challenges since patients are often behaviorally unresponsive. A promising new approach towards objective DOC ... [more ▼]
Clinical diagnosis of disorders of consciousness (DOC) caused by brain injury poses great challenges since patients are often behaviorally unresponsive. A promising new approach towards objective DOC diagnosis may be offered by the analysis of ultra-slow (<0.1 Hz) spontaneous brain activity fluctuations measured with functional magnetic resonance imaging (fMRI) during the resting-state. Previous work has shown reduced functional connectivity within the "default network", a subset of regions known to be deactivated during engaging tasks, which correlated with the degree of consciousness impairment. However, it remains unclear whether the breakdown of connectivity is restricted to the "default network", and to what degree changes in functional connectivity can be observed at the single subject level. Here, we analyzed resting-state inter-hemispheric connectivity in three homotopic regions of interest, which could reliably be identified based on distinct anatomical landmarks, and were part of the "Extrinsic" (externally oriented, task positive) network (pre- and postcentral gyrus, and intraparietal sulcus). Resting-state fMRI data were acquired for a group of 11 healthy subjects and 8 DOC patients. At the group level, our results indicate decreased inter-hemispheric functional connectivity in subjects with impaired awareness as compared to subjects with intact awareness. Individual connectivity scores significantly correlated with the degree of consciousness. Furthermore, a single-case statistic indicated a significant deviation from the healthy sample in 5/8 patients. Importantly, of the three patients whose connectivity indices were comparable to the healthy sample, one was diagnosed as locked-in. Taken together, our results further highlight the clinical potential of resting-state connectivity analysis and might guide the way towards a connectivity measure complementing existing DOC diagnosis. [less ▲]Detailed reference viewed: 18 (2 ULg)