Recording of cognitive evoked potentials during and after transient globalamnesia: report of three cases.

It is of interest to record event-related potentials in the course of trans ient global amnesia (TGA) because the hippocampus and diencephalon, general ly considered to be the sites of the dysfunction responsible for the amnesi c episodes are also considered as two possible generators of the P300 wave, However, the only four cases reported so far in the literature showed an i ntact auditive P300 in three cases and an intact auditive P300 with reducti on of visual P300 in one case. Here are reported four new cases. The P300 w ave was readily indentifiable in all four cases, without any amplitude redu ction, thus suggesting that the condition did not entail inactivation or fu nctional depression of P300 generators. Concerning P300 latency, in one cas e it was delayed but became normal after the ictus. In the second case, the latency, although within normal limits, shortened after the ictus. In the third and the fourth cases, the latency, initially within normal limits, re mained unchanged. These apparently disparate results should be analysed in the light of the results of isotope measurement of cerebral blood flaw duri ng the amnesia, which are also inconsistent but most frequently indicate bi lateral temporal or thalamic flow reduction. It remains to be determined in the future whether the stability or change in the P300 will make it possib le to predict the brain region involved in transient global amnesia, which could perhaps Vary from one patient to another. (C) 2001 Editions scientifi ques et medicales Elsevier SAS.