Etude des capacités langagières résiduelles chez les patients en état de conscience altérée

Language impairment such as receptive aphasia might lead to an underestimation of the level of consciousness in post-comatose patients (Schnakers et al., 2014). Yet, only a few studies focused on the behavioral assessment of residual language function, as based on the Coma Recovery Scale-Revised (CRS-R) and other tools, in line with their neural correlates. As previously recommended by Majerus et al. (2009), we here combined such behavioral and neuroimaging assessments to better explore language functions in patients with disorders of consciousness. In the Experimental part I, we investigated the neural correlates of the clinical sub-categorization of minimally conscious state (MCS), based on the presence (i.e., MCS+) or absence (i.e., MCS-) of language-related signs of consciousness. As expected, language areas were shown to be more activated in MCS+ compared to MCS-, either using resting state FDG-PET or fMRI. These areas mainly encompassed the left-sided temporal lobule, angular gyrus, inferior/middle frontal cortex, caudate and temporo-occipital fusiform cortex. We also observed increased connectivity in the left frontoparietal network in MCS+ compared to MCS- patients, which was previously associated to language function. This result was particularly consistent across studies, either according to FDG-PET or fMRI measurements. Hence, MCS patients and healthy subjects could be placed along a continuum, from severe left frontoparietal network dysfunction, possibly associated to severely impaired language processing in MCS- patients, to preserved network connectivity in healthy subjects, with MCS+ patients being situated between these two groups. By contrast, increase of grey matter volume as assessed by voxel-based morphometry analyses was not significantly associated to the recovery of command-following, intelligible verbalization and/or intentional communication, unless at the individual-level. Finally, with regard to consciousness areas, a lower impairment of default mode network areas in MCS+ compared to MCS- was only revealed at the single subject-level. The MCS sub-categorization would thus reflect distinct levels of language impairments more than different levels of consciousness The Experimental part II presents new bedside language assessments to complement the CRS-R and neuroimaging examinations. The Cognitive Assessment by Visual Election (CAVE) comprises tasks involving semantic and reading abilities (i.e., recognition of objects, pictures, letters, numbers, written words and colors), whereas the Brief Evaluation of Receptive Aphasia (BERA) is composed of three subscales examining different domains of language: phonology, semantics and morphosyntax. Good psychometric properties (reliability, validity and sensitivity) were shown using the BERA in aphasic conscious patients.The use of both tools in addition to the CRS-R in patients with disorders of consciousness allowed refining their behavioral language profiles, which were in line with FDG-PET and structural MRI results

Consciousness and language in disorders of consciousness after a coma

peer reviewe

Caractérisation de l'état de conscience minimale moins et plus selon la connectivité fonctionnelle au repos

The minimally conscious state (MCS) has been sub-categorized in MCS plus and MCS minus, i.e. respectively with and without command following capacity. Here we aimed at characterizing differences in MCS plus as compared to MCS minus by means of functional connectivity (FC). Resting state functional magnetic resonance imagery (fMRI) was acquired in 292 MCS patients and a seed-based analysis was conducted on a convenience sample of 19 MCS patients (10 MCS plus and 9 MCS minus) and 35 healthy controls. We investigated the left and right frontoparietal networks (FPN), the auditory network and the default mode network (DMN). We employed a ROI-to-ROI analysis and a voxel-based morphometry in order to investigate the inter-hemispheric connectivity and the grey and white matter volume, respectively. A significantly higher FC was found in MCS plus as compared to MCS minus in the left FPN, specifically between the left dorso-lateral prefrontal cortex and the left temporo-occipital fusiform cortex (TOFC). The FC of auditory network, right FPN and DMN, inter-hemispheric connectivity and structure of grey and white matter did not show differences between patients groups. The clinical sub-categorization of MCS is therefore sustained by FC differences in a language-related executive control network. These patient groups are not differentiated by networks involved in auditory processing, perception of surroundings and internal thoughts, nor by differences in inter-hemispheric connectivity and in morphology

Time-Delay Latency of Resting-State Blood Oxygen Level-Dependent Signal Related to the Level of Consciousness in Patients with Severe Consciousness Impairment

Recent evidence on resting-state functional magnetic resonance imaging (rs-fMRI) suggests that healthy human brains have a temporal organization represented in a widely complex time-delay structure. This structure seems to underlie brain communication flow, integration/propagation of brain activity, as well as information processing. Therefore, it is probably linked to the emergence of highly coordinated complex brain phenomena, such as consciousness. Nevertheless, possible changes in this structure during an altered state of consciousness remain poorly investigated. In this work, we hypothesized that due to a disruption in high-order functions and alterations of the brain communication flow, patients with disorders of consciousness (DOC) might exhibit changes in their time-delay structure of spontaneous brain activity. We explored this hypothesis by comparing the time-delay projections from fMRI resting-state data acquired in resting state from 48 patients with DOC and 27 healthy controls (HC) subjects. Results suggest that time-delay structure modifies for patients with DOC conditions when compared with HC. Specifically, the average value and the directionality of latency inside the midcingulate cortex (mCC) shift with the level of consciousness. In particular, positive values of latency inside the mCC relate to preserved states of consciousness, whereas negative values change proportionally with the level of consciousness in patients with DOC. These results suggest that the mCC may play a critical role as an integrator of brain activity in HC subjects, but this role vanishes in an altered state of consciousness

Needs and quality of life in caregivers of patients with prolonged disorders of consciousness

peer reviewe

SUpporting well-being through PEeR-Befriending (SUPERB) trial: an exploration of fidelity in peer-befriending for people with aphasia

Assessing the evolution of severely brain-injured patients with disorders of consciousness (DOC) with current tools like the Glasgow Outcome Scale-Extended (GOS-E) remains a challenge. At the bedside, the most reliable diagnostic tool is currently the Coma Recovery Scale-Revised. The CRS-R distinguishes patients with unresponsive wakefulness syndrome (UWS) from patients in minimally conscious state (MCS) and patients who have emerged from MCS (EMCS). This international multi-centric study aims to validate a phone outcome questionnaire (POQ) based on the CRS-R and compare it to the CRS-R performed at the bedside and to the GOS-E which evaluates the level of disability and assigns patient’s in outcomes categories. The POQ will allow clinicians to probe the evolution of patient’s state of consciousness based on caregivers feedback. This research project is part of the International Brain Injury Association, Disorders of Consciousness-Special Interest Group (DOCSIG) and DOCMA consortium