Objective: The clinical profiles of late-onset psychiatric patients exhibiting incidental REM sleep without atonia (RWA), which is a hallmark of REM sleep behavior disorder (RBD) on polysomnography (PSG), and its relevance to Lewy body disease (LBD) is investigated.

Background: The profoundly high risk of neurodegenerative disease associated with idiopathic RBD is the most potentially accurate prodromal predictor of Parkinson’s disease (PD) and dementia with Lewy bodies (DLB). Thus, the concept of subclinical RBD is attracting attention for early the detection of RBD. The relationship between incidental RWA and clinical characteristics, however, remains unclear.

Methods: Eight late-onset psychiatric patients with incidental RWA, nine patients with idiopathic RBD, and seven patients with PD or DLB who had preceding RBD were included. Radiological findings by cardiac MIBG scintigraphy, imaging for the dopamine transporter (DAT), and brain perfusion SPECT, were compared among three groups. The cingulate island sign (CIS) ratios were investigated based on Imabayashi’s report (Ann Nucl Med 2017;31:536-543). The percentage of RWA in the total REM sleep (%RWA) was calculated to evaluate their severity.

Results: In the incidental RWA group, patients were diagnosed with major depressive disorder (MDD) (n = 6) and somatic symptom disorder (n = 2). Seven patients were receiving antidepressants when PSG was performed. Augmentation pharmacotherapy with aripiprazole, a partial agonist at dopamine D2 and D3, was effective in three patients with MDD. Four patients had a clinical history of drug-induced parkinsonism. Although the cardiac MIBG uptake was significantly higher in the incidental RWA group than in the idiopathic RBD and PD/DLB groups, there were overlaps in the specific binding ratio (SBR) on DAT scan among the three groups. All patients exhibited CIS ratios within a threshold of 0.281, which is the optimal cutoff value for a diagnosis of DLB. The median %RWA was significantly lower in the incidental RWA group than in the idiopathic RBD and PD/DLB groups.

Conclusions: In this series, the late-onset psychiatric patients with incidental RWA partially shared common radiological findings with LBD. As it remains unknown whether these patients with incidental RWA are presenting subclinical RBD, continued follow-up of the patients is needed.

References: Imabayashi E, Soma T, Sone D, Tsukamoto T, Kimura Y, Sato N, Murata M, Matsuda H. Validation of the cingulate island sign with optimized ratios for discriminating dementia with Lewy bodies from Alzheimer’s disease using brain perfusion SPECT Ann Nucl Med 2017;31:536-543. Fujishiro H, Okuda M, Iwamoto K, Miyata S, Otake H, Noda A, Iritani S, Ozaki N. REM sleep without atonia in middle-aged and older psychiatric patients and Lewy body disease: a case series Int J Geriatr Psychiatry 2017;32:397-406.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/clinical-profiles-of-late-onset-psychiatric-patients-with-incidental-rem-sleep-without-atonia/