30. A combined ERP and PET study in persistent vegetative state patients

Abstract

In recent years, a number of studies have identified evidence of partially functional cerebral regions in persistent vegetative state (PVS). Nevertheless, the residual cognitive function does not necessarily reflect conscious perception and awakening. In order to most effectively define the degree and extent of preserved cognitive function in persistent vegetative state, a complex approach and the systematic multimodale study of possible residual cognitive function in PVS is required. To investigate the neuro-metabolic integrity in detection of one’s own name in two patients in a PVS with same behavioural features (WHIM 7), same etiology (anoxie) and similar duration (more than 12 months) of PVS. We co-registered a cerebral blood flow by the positron emission tomography (PET) and the auditory evoked potentials to the patient’s own name as a novel stimulus (ERP – novelty P3 component) in a bloc design study. Novelty P3 response was absent in response to the patient’s name in both patients. The positron emission tomography study revealed no diminution of cerebral blood flow to patient’s own name in predicted regions (regions activated in the healthy population) but significant multifocal decrease of cerebral blood flow in the rest of the brain. Each patient’s brain expressed a unique metabolic pattern. This report identifies evidence of alteration of the neuro-metabolic coupling in PVS. In both PVS patients, islands of relatively preserved brain metabolism in predicted regions, if they are associated with a reduction of metabolism in other cerebral regions and no evoked novelty P3 response, cannot produced consciousness. Preliminary results in our small series of PVS patients provide a strong basis for the considerable role of temporal organisation of the modular nature of individual functional networks that underlie conscious brain function.