Isolated prolonged retrograde amnesia.

We describe a patient who had isolated retrograde amnesia of 1-year duration without anterograde amnesia after recovery from encephalitis. Single photon emission computed tomography using 123I-IMP revealed that left temporal lobe abnormality. We postulate that the learning ability for new information and recalling ability for old information involve different neural structures, and there is a possible relationship between isolated retrograde amnesia and left temporal dysfunction.