Neurophysiological characterization of transitory global amnesia syndrome.

A total of 27 patients with transitory global amnesia (TGA) in the acute and late (from 7 days) periods and 31 patients with dyscirculatory encephalopathy and subjective memory impairments (control group) were studied. EEG data and assessment of the P300 cognitive evoked potential wave established differences in the nature of beta1 activity between these groups. The extent of beta1 activity on the EEG showed different relationships with the latent period of the P300 wave: in the control group, there were increases in beta1 activity with increases in the latent period (r = 0.43). while beta1 activity in TGA decreased with increases in latent period (r = -0.23). These changes were most marked in the frontocentral areas. The authors believe that these patterns of changes in EEG and cognitive evoked potentials in the acute period of TGA and at later periods, as well as in the control group, provide evidence of the functional nature of TGA syndrome, which is not related to any damaged brain structure.