The Minimal Energetic Requirement of Sustained Awareness after Brain Injury

Johan Stender, Kristian Nygaard Mortensen, Aurore Thibaut, Sune Darkner, Steven Laureys, Albert Gjedde, Ron Kupers

Research output: Contribution to journalArticle

Abstract

Differentiation of the minimally conscious state (MCS) and the unresponsive wakefulness syndrome (UWS) is a persistent clinical challenge [1]. Based on positron emission tomography (PET) studies with [18F]-fluorodeoxyglucose (FDG) during sleep and anesthesia, the global cerebral metabolic rate of glucose has been proposed as an indicator of consciousness [2, 3]. Likewise, FDG-PET may contribute to the clinical diagnosis of disorders of consciousness (DOCs) [4, 5]. However, current methods are non-quantitative and have important drawbacks deriving from visually guided assessment of relative changes in brain metabolism [4]. We here used FDG-PET to measure resting state brain glucose metabolism in 131 DOC patients to identify objective quantitative metabolic indicators and predictors of awareness. Quantitation of images was performed by normalizing to extracerebral tissue. We show that 42% of normal cortical activity represents the minimal energetic requirement for the presence of conscious awareness. Overall, the cerebral metabolic rate accounted for the current level, or imminent return, of awareness in 94% of the patient population, suggesting a global energetic threshold effect, associated with the reemergence of consciousness after brain injury. Our data further revealed that regional variations relative to the global resting metabolic level reflect preservation of specific cognitive or sensory modules, such as vision and language comprehension. These findings provide a simple and objective metabolic marker of consciousness, which can readily be implemented clinically. The direct correlation between brain metabolism and behavior further suggests that DOCs can fundamentally be understood as pathological neuroenergetic conditions and provide a unifying physiological basis for these syndromes. Stender et al. show that positron emission tomography measurement of whole-brain glucose metabolic state allows accurate diagnosis and prediction of disorders of consciousness. Recovery from the unresponsive wakefulness condition occurs above a sharply defined brain metabolic limit, reflecting the minimal energetic requirements of consciousness.

Original languageEnglish (US)
JournalCurrent Biology
DOIs
StateAccepted/In press - Feb 24 2016
Externally publishedYes

Keywords

  • Brain injury
  • Consciousness
  • FDG-PET
  • Glucose metabolism
  • Minimally conscious state
  • Unresponsive wakefulness syndrome
  • Vegetative state

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Biochemistry, Genetics and Molecular Biology(all)

Fingerprint Dive into the research topics of 'The Minimal Energetic Requirement of Sustained Awareness after Brain Injury'. Together they form a unique fingerprint.

  • Cite this

    Stender, J., Mortensen, K. N., Thibaut, A., Darkner, S., Laureys, S., Gjedde, A., & Kupers, R. (Accepted/In press). The Minimal Energetic Requirement of Sustained Awareness after Brain Injury. Current Biology. https://doi.org/10.1016/j.cub.2016.04.024