Relevance of positron emission tomography as to diagnosis and prognosis ofpostanoxic cerebral dysfunctions

Clinical signs, laboratory tests, EEG or evoked potentials only permit an i ndirect estimation of the extent of structural brain damage following sever e global brain anoxia. Positron emission tomography (PET) permits additiona l insights into the extent of neuronal damage in acute and persistent posta noxic vegetative states (VS). PET documents a severe and irreversible damag e of supratentorial cortical structures in postanoxic VS and allows its dif ferential diagnosis from related disorders, e.g. the locked-in-syndrome. PE T 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 informati on concerning the possible recovery of consciousness and neuronal function in VS. In combination with clinical, laboratory and neurophysiological find ings, PET may be helpful to establish the individual prognosis in acute VS.