A follow up study of non-demented patients with primary visual cortical hypometabolism: prodromal dementia with Lewy bodies.

We previously reported non-demented patients with glucose hypometabolism in the primary visual cortex (PVC), which is the preferentially affected region in patients with dementia with Lewy bodies (DLB). It remains unknown, however, whether these patients represent a prodromal DLB state. Eleven non-demented patients who attended our memory clinic for more than three years (mean follow-up period: 44 ± 5 months) were examined. All the patients had glucose hypometabolism in the PVC on [(18)F]-fluoro-d-glucose (FDG) positron emission tomography (PET) scans at baseline. Four patients, including one with a clinical history of occipital bleeding, exhibited no core or suggestive features of DLB. Seven patients reported recurrent nocturnal dream-enactment behavior, which is consistent with probable rapid eye movement (REM) sleep behavior disorder (RBD). The condition of the patient with occipital bleeding was stable, which is consistent with an underlying non-neurodegenerative disorder. Of the remaining 10 patients, 5 had stable cognitive conditions (non-converters) and 5 exhibited progression to dementia (converters). The clinical diagnoses of 4 patients with probable RBD were changed to probable DLB. Despite no differences in psychological profiles at baseline between non-converters and converters, the initial pattern of cortical metabolism differed: converters had lower glucose hypometabolism in the parietal and the lateral occipital cortex compared to non-converters. The metabolic reduction in the PVC is present in patients with prodromal DLB. Moreover, the spatial profiles of reduced glucose metabolism at baseline could help to define the distinct prognostic subgroup that has a greater risk of conversion to DLB.