Retrograde Amnesia Following Anterior Thalamic Infarction

ABSTRACT

BACKGROUND: Retrograde amnesia (RA) refers to the failure to recall events that occurred before a brain injury. RA is known to be associated with brain lesions involving the hippocampus, entorhinal cortex and the frontal lobe. Anterior thalamic lesion often causes anterograde amnesia but rarely causes RA. The aim of the present study is in two parts . First, we discuss the neuroanatomical perspectives of RA based on our case with severe RA after a right anterior thalamic infarction. Second, we introduce a test for RA termed the "Korean Public Events Recall Test (K-PERT)", which was developed based on famous Korean public events from 1966 to 1997. METHODS: A 62-year-old woman with transient RA after a left anterior thalamic infarction 4 years ago presented severe and persistent RA following a right anterior thalamic infarction. We followed up the patient with neuropsychological tests. We also performed the K-PERT on the patient as well as on 14 women of the same age and education. RESULTS: Neuropsychological tests showed severe impairment in autobiographical memory with frontal lobe dysfunction. On K-PERT, the normal controls scored 13.7 +/- 3.7 in recall and 21.2 +/- 3.1 in recognition out of a maximum score of 30, whereas the patient obtained only 3/30 and 4/30, respectively. CONCLUSIONS: In our case, RA might have resulted from damage to the pathway that retrieves old memories, which are stored in the frontal lobe. Thus, anterior thalamus might be viewed as the gate of memory engram. Further studies are needed to elaborate the usefulness of K-PERT as an objective tool for investigating remote memory.