The Minimal Energetic Requirement of Sustained Awareness after Brain Injury

• Published in: Current biology Vol. 26; no. 11; pp. 1494 - 1499
• Main Authors: Stender, Johan, Mortensen, Kristian Nygaard, Thibaut, Aurore, Darkner, Sune, Laureys, Steven, Gjedde, Albert, Kupers, Ron
• Format: Journal Article Web Resource
• Language: English
• Published: England Elsevier Ltd 06.06.2016; Cell Press
• Subjects: Adolescent; Adult; Aged; Awareness; Brain - metabolism; Brain Injuries - diagnostic imaging; Brain injury; Consciousness; Consciousness Disorders - diagnostic imaging; FDG-PET; Female; Fluorodeoxyglucose F18 - chemistry; Glucose - metabolism; Human health sciences; Humans; Male; Middle Aged; minimally conscious state; Neurologie; Neurology; Persistent Vegetative State - diagnostic imaging; Positron-Emission Tomography - methods; Sciences de la santé humaine; unresponsive wakefulness syndrome; vegetative state; Young Adult; FDG-PET; brain injury; consciousness; unresponsive wakefulness syndrome; glucose metabolism; minimally conscious state; vegetative state
• ISSN: 0960-9822; 1879-0445; 1879-0445
• DOI: 10.1016/j.cub.2016.04.024

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. •Quantitative FDG-PET allows fine diagnosis and prognosis in disorders of consciousness•Level of consciousness after brain injury correlates with whole-brain energetic state•Emergence of awareness occurs above a sharply defined brain energy metabolic boundary 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.