title: Measures of metabolism and complexity in the brain of patients with disorders of consciousness.
abstract: Making an accurate diagnosis in patients with disorders of consciousness remains challenging.18F-fluorodeoxyglucose (FDG)-PET has been validated as a diagnostic tool in this population, and allows identifying unresponsive patients with a capacity for consciousness. In parallel, the perturbational complexity index (PCI), a new measure based on the analysis of the electroencephalographic response to transcranial magnetic stimulation, has also been suggested as a tool to distinguish between unconscious and conscious states. The aim of the study was to cross-validate FDG-PET and PCI, and to identify signs of consciousness in otherwise unresponsive patients.
  
  
  
  We jointly applied the Coma Recovery Scale-Revised, FDG-PET and PCI to assess 24 patients with non-acute disorders of consciousness or locked-in syndrome (13 male; 19-54 years old; 12 traumatic; 9 unresponsive wakefulness syndrome, 11 minimally conscious state; 2 emergence from the minimally conscious state, and 2 locked-in syndrome).
  
  
  
  FDG-PET and PCI provided congruent results in 22 patients, regardless of their behavioural diagnosis. Notably, FDG-PET and PCI revealed preserved metabolic rates and high complexity levels in four patients who were behaviourally unresponsive.
  
  
  
  We propose that jointly measuring the metabolic activity and the electrophysiological complexity of cortical circuits is a useful complement to the diagnosis and stratification of patients with disorders of consciousness.
authors.affiliation: Giga-Consciousness, Coma Science Group, and Neurology Department, University and University Hospital of Liege, Belgium.
authors.forename: Olivier
authors.initials: O
authors.lastname: Bodart
authors.affiliation: Giga-Consciousness, Coma Science Group, and Neurology Department, University and University Hospital of Liege, Belgium; Department of Psychiatry, University of Wisconsin, Madison, WI, USA.
authors.forename: Olivia
authors.initials: O
authors.lastname: Gosseries
authors.affiliation: Giga-Consciousness, Coma Science Group, and Neurology Department, University and University Hospital of Liege, Belgium.
authors.forename: Sarah
authors.initials: S
authors.lastname: Wannez
authors.affiliation: Giga-Consciousness, Coma Science Group, and Neurology Department, University and University Hospital of Liege, Belgium.
authors.forename: Aurore
authors.initials: A
authors.lastname: Thibaut
authors.affiliation: Giga-Consciousness, Coma Science Group, and Neurology Department, University and University Hospital of Liege, Belgium.
authors.forename: Jitka
authors.initials: J
authors.lastname: Annen
authors.affiliation: Giga-Consciousness, Coma Science Group, and Neurology Department, University and University Hospital of Liege, Belgium; Department of Psychiatry, University of Wisconsin, Madison, WI, USA.
authors.forename: Melanie
authors.initials: M
authors.lastname: Boly
authors.affiliation: Department of Biomedical and Clinical Sciences "Luigi Sacco", University of Milan, Italy; Fondazione Europea di Ricerca Biomedica, FERB Onlus, Milan, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Rosanova
authors.affiliation: Department of Biomedical and Clinical Sciences "Luigi Sacco", University of Milan, Italy; Institute of Science and Technology, Federal University of São Paolo, São José dos Campos, Brazil.
authors.forename: Adenauer G
authors.initials: AG
authors.lastname: Casali
authors.affiliation: Department of Biomedical and Clinical Sciences "Luigi Sacco", University of Milan, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Casarotto
authors.affiliation: Department of Psychiatry, University of Wisconsin, Madison, WI, USA.
authors.forename: Giulio
authors.initials: G
authors.lastname: Tononi
authors.affiliation: Department of Biomedical and Clinical Sciences "Luigi Sacco", University of Milan, Italy; Istituto Di Ricovero e Cura a Carattere Scientifico, Fondazione Don Carlo Gnocchi, Milan, Italy.
authors.forename: Marcello
authors.initials: M
authors.lastname: Massimini
authors.affiliation: Giga-Consciousness, Coma Science Group, and Neurology Department, University and University Hospital of Liege, Belgium.
authors.forename: Steven
authors.initials: S
authors.lastname: Laureys
mesh_terms: D000328:Adult; D001921:Brain / Q000000981:diagnostic imaging* / Q000378:metabolism*; D001930:Brain Injuries / Q000150:complications; D003244:Consciousness Disorders / Q000000981:diagnostic imaging / Q000209:etiology / Q000473:pathology*; D004569:Electroencephalography; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D049268:Positron-Emission Tomography; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
chemical_list: D019788:Fluorodeoxyglucose F18; D010100:Oxygen
keywords: Brain injury; CRS-R, Coma Recovery Scale-Revised; DOC, disorders of consciousness; Disorders of consciousness; EMCS, emergence from the minimally conscious state; Electroencephalography; FDG, 18F-fluorodeoxyglucose; LIS, locked-in syndrome; MCS*, non-behavioural minimally conscious state; MCS, minimally conscious state; PCI, perturbational complexity index; Positron emission tomography; SPM, statistical parametric mapping; TMS–EEG, transcranial magnetic stimulation coupled with high-density EEG; Transcranial magnetic stimulation; UWS, unresponsive wakefulness syndrome; Unresponsive wakefulness syndrome minimally conscious state; fMRI, functional MRI