title: Clinical Response to tDCS Depends on Residual Brain Metabolism and Grey Matter Integrity in Patients With Minimally Conscious State.
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.
  
  
  OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Coma Science Group, GIGA Research, Cyclotron Research Centre and Neurology Department, University and University Hospital of Liège, Belgium. Electronic address: athibaut@ulg.ac.be.
authors.forename: Aurore
authors.initials: A
authors.lastname: Thibaut
authors.affiliation: Coma Science Group, GIGA Research, Cyclotron Research Centre and Neurology Department, University and University Hospital of Liège, Belgium.
authors.forename: Carol
authors.initials: C
authors.lastname: Di Perri
authors.affiliation: 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.
authors.forename: Camille
authors.initials: C
authors.lastname: Chatelle
authors.affiliation: Coma Science Group, GIGA Research, Cyclotron Research Centre and Neurology Department, University and University Hospital of Liège, Belgium.
authors.forename: Marie-Aurélie
authors.initials: MA
authors.lastname: Bruno
authors.affiliation: Cyclotron Research Centre, University of Liège, Liège, Belgium.
authors.forename: Mohamed Ali
authors.initials: MA
authors.lastname: Bahri
authors.affiliation: Coma Science Group, GIGA Research, Cyclotron Research Centre and Neurology Department, University and University Hospital of Liège, Belgium.
authors.forename: Sarah
authors.initials: S
authors.lastname: Wannez
authors.affiliation: 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.
authors.forename: Andrea
authors.initials: A
authors.lastname: Piarulli
authors.affiliation: Nuclear Medicine Department, University Hospital of Liège, Belgium.
authors.forename: Claire
authors.initials: C
authors.lastname: Bernard
authors.affiliation: Coma Science Group, GIGA Research, Cyclotron Research Centre and Neurology Department, University and University Hospital of Liège, Belgium.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Martial
authors.affiliation: Coma Science Group, GIGA Research, Cyclotron Research Centre and Neurology Department, University and University Hospital of Liège, Belgium.
authors.forename: Lizette
authors.initials: L
authors.lastname: Heine
authors.affiliation: Nuclear Medicine Department, University Hospital of Liège, Belgium.
authors.forename: Roland
authors.initials: R
authors.lastname: Hustinx
authors.affiliation: Coma Science Group, GIGA Research, Cyclotron Research Centre and Neurology Department, University and University Hospital of Liège, Belgium.
authors.forename: Steven
authors.initials: S
authors.lastname: Laureys
mesh_terms: D001284:Atrophy / Q000473:pathology; D001921:Brain / Q000378:metabolism* / Q000473:pathology* / Q000502:physiology; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004569:Electroencephalography; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism; D066128:Gray Matter / Q000378:metabolism* / Q000473:pathology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D059906:Neuroimaging; D018458:Persistent Vegetative State / Q000378:metabolism* / Q000628:therapy*; D049268:Positron-Emission Tomography; D017397:Prefrontal Cortex / Q000502:physiology; D012189:Retrospective Studies; D065908:Transcranial Direct Current Stimulation; D016896:Treatment Outcome
chemical_list: D019788:Fluorodeoxyglucose F18
keywords: Disorders of consciousness; Magnetic resonance imaging; Minimally conscious state; Positron emission tomography; Transcranial direct current stimulation; Treatment; Voxel-based morphometry