[Prolonged antegrade amnesia due to left anterior thalamic infarct, and SPECT findings]

A 60-year-old right-handed man developed disorientation, antegrade amnesia and transient mild clouding of consciousness. The antegrade amnesia persisted for more than one year after its onset. T2-weighted MR images showed high signal intensity in the left anteromedial thalamus. 99mTc-HM-PAO SPECT revealed decreased uptake in the left frontal and temporal lobes. These SPECT findings were still observed a year later. These findings suggest that functional involvement of the frontal and temporal lobe connections with the dorsomedial nucleus, anterior nucleus, and the mamillothalamic tract in the anteromedial part of thalamus were responsible for the prolonged antegrade amnesia. We think that SPECT findings are important for evaluating the outcome of thalamic amnesia.