Prediction of later clinical course by a specific glucose metabolic pattern in non-demented patients with probable REM sleep behavior disorder admitted to a memory clinic: A case study

The present study is a follow-up study of 11 non-demented patients with probable rapid eye movement (REM) sleep behavior disorder (RBD) at our memory clinic. During the follow-up period (mean±SD of 46.7±6.4 months), all 11 patients exhibited cognitive decline: four (Group A) exhibited core clinical features of dementia with Lewy bodies (DLB), along with severe cognitive decline, and were subsequently diagnosed as having probable DLB; four (Group B) did not exhibit core clinical features of DLB; and the remaining three (Group C) were diagnosed as having Parkinson's disease with dementia (PDD). Positron emission tomography with fluorodeoxyglucose-F18 at baseline revealed that Groups A and B exhibited glucose hypometabolism in the occipital lobe, especially in the primary visual cortex, and Group A tended to present hypometabolism in the parieto-temporal area as well. Group C tended to present hypometabolism in the medial prefrontal area and anterior cingulate gyrus. Neuropsychological examinations indicated poor performance in verbal memory and visuoperception in all groups. This case study suggests that patterns of hypometabolism and neuropsychological examinations at baseline may be indicators of the later clinical course of probable RBD patients.