Abstract
Clinical signs, laboratory tests, EEG or evoked potentials only permit an indirect estimation of the extent of structural brain damage following severe global brain anoxia. Positron emission tomography (PET) permits additional insights into the extent of neuronal damage in acute and persistent postanoxic vegetative states (VS). PET documents a severe and irreversible damage of supratentorial cortical structures in postanoxic VS and allows its differential diagnosis from related disorders, e.g. the locked-in-syndrome. PET clearly distinguishes functional alterations in VS from those in non-REM sleep and documents that patients in VS are not in a sleep-like condition, but in a state closely related to deep anesthesia. Furthermore, the extent of impairment of the residual cortical glucose consumption yields information concerning the possible recovery of consciousness and neuronal function in VS. In combination with clinical, laboratory and neurophysiological findings, PET may be helpful to establish the individual prognosis in acute VS.