Objective: To report a case of an 82-year-old man with a long-standing history of REM sleep behavior disorder (RBD) and colonic Lewy pathology without significant neurological abnormalities.

Background: RBD is known as a prodromal symptom of α-synucleinopathies, including Parkinson’s disease, dementia with Lewy bodies and MSA. According to previous report, more than 70% of iRBD convert into α-synucleinopathies in 12 years, while cases with prolonged iRBD are rare. Recently, trials for explaining the clinical course of Parkinson’s disease by the propagating direction of αsynuclein such as  body-first or brain-first, however the mechanism is still unclear.

Method: Case

Results: An 82-year-old man developed dream-enacting behaviors at the age of 64. He visited our hospital at the age of 67. Neurological examination at first visit showed no remarkable abnormality. Polysomnography tests revealed preserved muscle tonus during REM sleeping stage, confirming the diagnosis of RBD. ¹²³I-MIBG scintigraphy test revealed reduced myocardial uptake in early and delayed scan. He was medicated with clonazepam from the age of 64 to 71 to treat RBD symptom. At the age of 81, he complained of constipation and diagnosed of type 2 colon cancer, stage II. He underwent right hemicolectomy for ascending colon. Histopathological examination of the non-tumorous tissue revealed Lewy depositions positive for antiα-synuclein antibodies in the neural plexus of subserosa. Despite long clinical course, he exhibited no neurological abnormalities including parkinsonism, dementia, autonomic dysfunction except constipation. Brain MRI at the age of 80 and the striatal uptakes in ¹²³I-ioflupane DAT-scintigraphy at the age of 82 remained normal.

Conclusion: We experienced an iRBD case with 18 years of clinical course, and considered as indolent α-synucleinopathy. In our case, Lewy pathology was supposed to exist at least in neural plexus of colon serosa, cardiac sympathetic terminal and dorsal part of the brainstem including sublaterodorsal nucleus. These findings suggested that Lewy pathology might stay in the specific peripheral tissue or distinct area of the central nervous system without propagating into other CNS part for 18 years. Autopsy of iRBD case and the surveillance with surgical specimen is necessary to investigate the natural history of iRBD and mechanism of relationship between peripheral and central Lewy pathology.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/case-report-of-an-82-year-old-man-with-an-18-year-history-of-rem-sleep-behavior-disorder-and-colonic-lewy-pathology/