Executive dysfunction and memory impairment in idiopathic REM sleep behavior disorder

Background: Idiopathic REM sleep behavior disorder (iRBD) might be a stage in the development of neurodegenerative disorders, especially Parkinson disease and dementia with Lewy bodies. Recent studies showing a slowing of waking EEG in iRBD suggest that iRBD is associated with cognitive impairment. Objective: To compare patients with iRBD on measures of cognitive function and quantitative waking EEG. Methods: Fourteen patients with iRBD and 14 healthy control subjects matched for age and educational level were studied. Subjects underwent an extensive neuropsychological evaluation and waking EEG recordings. Results: Compared to controls, patients with iRBD showed a lower performance on neuropsychological tests measuring attention, executive functions, and verbal memory. Moreover, patients with iRBD showed EEG slowing (higher delta and theta power) during wakefulness in all brain areas compared to controls. However, no correlation was found between performance on cognitive tests and quantitative waking EEG in patients with iRBD. Conclusion: This study shows a co-occurrence of impaired cognitive profile and waking EEG slowing in patients with idiopathic REM sleep behavior disorder similar to that observed in early stages of some synucleinopathies.