Qualitative Scoring of the Pentagon Test: A Tool for the Identification of Subtle Cognitive Deficits in Isolated REM Sleep Behavior Disorder Patients

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. Methods: A total of 80 polysomnography-confirmed iRBD patients and 40 healthy controls (HCs) were retrospectively recruited. Global and specific qualitative performances were evaluated according to QSPT procedure. Comparisons between iRBD and HC regarding all QSPT parameters, neuropsychological tests, and polysomnographic recordings were performed. Results: Patients displayed significantly lower scores in both "closing-in" and total score parameters in comparison to HC. The QSPT total score exhibited significant positive correlations with verbal comprehension, fluency, visuospatial abilities, and executive functions. Notably, iRBD patients with impaired performance at QSPT showed decreased neuropsychological performances and higher percentages of slow wave sleep (SWS). In addition, SWS percentages negatively correlated with verbal comprehension, fluency, visuospatial abilities, executive functions, and QSPT total score. Conclusion: QSPT may represent a brief and easy to administer tool for the detection of subtle visuospatial changes in iRBD patients. Furthermore, polysomnographic findings suggest a possible slowdown of electroencephalographic pattern during non- REM sleep in iRBD patients in line with the presence of cognitive decline.