Aurore Thibaut1, Carol Di Perri2, Camille Chatelle3, Marie-Aurélie Bruno2, Mohamed Ali Bahri4, Sarah Wannez2, Andrea Piarulli5, Claire Bernard6, Charlotte Martial2, Lizette Heine2, Roland Hustinx6, Steven Laureys2. 1. Coma Science Group, GIGA Research, Cyclotron Research Centre and Neurology Department, University and University Hospital of Liège, Belgium. Electronic address: athibaut@ulg.ac.be. 2. Coma Science Group, GIGA Research, Cyclotron Research Centre and Neurology Department, University and University Hospital of Liège, Belgium. 3. Neurorehabilitation Lab, Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Harvard Medical School, Boston, MA, USA; Laboratory for NeuroImaging of Coma and Consciousness, Massachusetts General Hospital, Boston, MA, USA. 4. Cyclotron Research Centre, University of Liège, Liège, Belgium. 5. Coma Science Group, GIGA Research, Cyclotron Research Centre and Neurology Department, University and University Hospital of Liège, Belgium; PERCRO Laboratory, Scuola Superiore Sant'Anna, Pisa, Italy. 6. Nuclear Medicine Department, University Hospital of Liège, Belgium.
Abstract
BACKGROUND:Transcranial direct current stimulation (tDCS) was recently shown to promote recovery of voluntary signs of consciousness in some patients in minimally conscious state (MCS). However, it remains unclear why clinical improvement is only observed in a subgroup of patients. OBJECTIVES: In this retrospective study, we investigated the relationship between tDCS responsiveness and neuroimaging data from MCS patients. METHODS:Structural Magnetic Resonance Imaging (MRI), Fluorodeoxyglucose Positron emission tomography (FDG-PET) and clinical electroencephalography (EEG) were acquired in 21 sub-acute and chronic MCS patients (8 tDCS responders) who subsequently (<48 h) received left dorsolateral prefrontal (DLPF) tDCS in a double-blind randomized cross-over trial. The behavioral data have been published elsewhere (Thibaut et al., Neurology, 2014). RESULTS:Grey matter atrophy was observed in non-responders as compared with responders in the left DLPF cortex, the medial-prefrontal cortex, the cingulate cortex, the hippocampi, part of the rolandic regions, and the left thalamus. FDG-PET showed hypometabolism in non-responders as compared with responders in the left DLPF cortex, the medial-prefrontal cortex, the precuneus, and the thalamus. EEG did not show any difference between the two groups. CONCLUSION: Our findings suggest that the transient increase of signs of consciousness following left DLPF tDCS in patients in MCS require grey matter preservation and residual metabolic activity in cortical and subcortical brain areas known to be involved in attention and working memory. These results further underline the critical role of long-range cortico-thalamic connections in consciousness recovery, providing important information for guidelines on the use of tDCS in disorders of consciousness.
RCT Entities:
BACKGROUND: Transcranial direct current stimulation (tDCS) was recently shown to promote recovery of voluntary signs of consciousness in some patients in minimally conscious state (MCS). However, it remains unclear why clinical improvement is only observed in a subgroup of patients. OBJECTIVES: In this retrospective study, we investigated the relationship between tDCS responsiveness and neuroimaging data from MCS patients. METHODS: Structural Magnetic Resonance Imaging (MRI), Fluorodeoxyglucose Positron emission tomography (FDG-PET) and clinical electroencephalography (EEG) were acquired in 21 sub-acute and chronic MCS patients (8 tDCS responders) who subsequently (<48 h) received left dorsolateral prefrontal (DLPF) tDCS in a double-blind randomized cross-over trial. The behavioral data have been published elsewhere (Thibaut et al., Neurology, 2014). RESULTS: Grey matter atrophy was observed in non-responders as compared with responders in the left DLPF cortex, the medial-prefrontal cortex, the cingulate cortex, the hippocampi, part of the rolandic regions, and the left thalamus. FDG-PET showed hypometabolism in non-responders as compared with responders in the left DLPF cortex, the medial-prefrontal cortex, the precuneus, and the thalamus. EEG did not show any difference between the two groups. CONCLUSION: Our findings suggest that the transient increase of signs of consciousness following left DLPF tDCS in patients in MCS require grey matter preservation and residual metabolic activity in cortical and subcortical brain areas known to be involved in attention and working memory. These results further underline the critical role of long-range cortico-thalamic connections in consciousness recovery, providing important information for guidelines on the use of tDCS in disorders of consciousness.
Keywords:
Disorders of consciousness; Magnetic resonance imaging; Minimally conscious state; Positron emission tomography; Transcranial direct current stimulation; Treatment; Voxel-based morphometry
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