Retrograde amnesia during transient global amnesia

Abstract

Two patients who met Hodges' clinical criteria for transient global amnesia (TGA) were given anterograde and retrograde memory tests during and after the attack. A SPECT scan was performed during TGA in one case, showing a reduced blood flow confined to the bilateral medial temporal lobes, which resolved on the next day. In both cases, the initial period of retrograde amnesia was within several years. In one case, autobiographical and public retrograde memory were assessed separately. These assessments revealed that autobiographical and public retrograde amnesias were impaired to the same extent during TGA. During recovery, almost all the events that had been forgotten gradually recovered according to a temporal gradient, apart from a single exceptional memory which had made a deep impression at the time of memorizing. In addition, both cases during recovery first remembered the existence of the events and second their contents. This finding indicates that the memory of events themselves may be more easily accessible than their contents. Even when the two patients had recovered from the retrograde amnesia almost completely, definite anterograde amnesia still remained. This implies that there exists a time in the recovery phase where anterograde amnesia is still prominent but retrograde amnesia has already almost disappeared, which may account for the previously reported variation in the extent of retrograde amnesia.