Pure progressive amnesia: An atypical amnestic syndrome?

We report on M.S., an 83-year-old patient with isolated pure progressive amnesia. This rare, recently identified, form of amnesia has been described in elderly patients. Neuropathological studies suggest that this syndrome is an atypical clinical presentation of Alzheimer's disease. The aim of our study was to characterize the neuropsychological pattern of pure progressive amnesia in comparison with other amnestic syndromes and memory dissociations reported in the literature. Our results indicate that pure progressive amnesia is characterized by a highly unusual dissociation in the realm of memory, with severe deficits on tests based on recognition and recall of verbal and visual single items, contrasting with relatively preserved anterograde autobiographical and spatial memory and normal recall of complex material such as stories. These findings suggest that memory for single items could depend on an independent system. One hypothesis is that M.S.'s unusual memory profile results from relative dysfunction of the ventral medial temporal lobe pathway. An alternative explanation implicates cognitive reserve. Further studies are required in order to progress on this matter. In any case, pure progressive amnesia is a clinical syndrome that may provide further insight into the organization of declarative memory.