OBJECTIVE: Isolated rapid eye movement (REM) sleep behavior disorder (iRBD) frequently represents the prodromal stage of alpha-synucleinopathies, and similar to these pathologies, iRBD patients show neuropsychological deficits, particularly in the domain of visuospatial abilities and executive functions. We hypothesized that the qualitative scoring of the Mini-Mental State Examination pentagon test (QSPT) may detect subtle visuospatial deficits in these subjects, and we evaluated its relationship with indexes of sleep quality, as measured by polysomnography.