Residual cerebral functioning in the vegetative state

Cyclotron Research Center, Department of Neurology, Anesthesiology and Intensive Care Medicine and Internal Medicine, CHU Sart Tilman, University of Liege, Liege; Department of Neurology, AZ-VUB, Brussels; PET/Biomedical Cyclotron Unit and Department of Intensive Care and Neurology, ULB Erasme, Brussels, Belgium LIFE-SUSTAINING TREATMENTS AND VEGETATIVE STATE: Scientific advances and ethical dilemmas 17-18-19-20 March, 2004 Rome, Italy Summary Cerebral metabolism is massively reduced in the vegetative state. However, recovery of consciousness from vegetative state is not always associated with substantial changes in global metabolism. This led us to hypothesize that some vegetative patients are unconscious not just because of a global loss of neuronal function, but rather due to an altered activity in some critical brain regions and to the abolished functional connections between them. We could show that the most dysfunctional brain regions in vegetative patients are bilateral frontal and parieto-temporal associative cortices. Yet, despite the metabolic impairment, external stimulation still induces a significant neuronal activation in vegetative patients as shown by both auditory and noxious stimuli. However, this activation is limited to primary cortices and dissociated from higher-order associative cortices, thought to be necessary for conscious perception. Finally, we could show that vegetative patients have impaired functional connections between distant cortical areas and between the thalami and the cortex and, more importantly, that recovery of consciousness is paralleled by a restoration of this cortico-thalamo-cortical interaction.