Leclair-Visonneau L, et al. - This cross-sectional study aimed to determine whether REM sleep behavior disorder (RBD) in Parkinson's disease (PD) was associated with lesions and dysfunctions of the autonomic nervous system by evaluating enteric phosphorylated α-synuclein histopathology (PASH) and permeability. In the enteric nervous system, patients with PD and RBD had a greater frequency of synuclein pathology, implying that RBD was correlated with widespread synuclein neuropathology.

• The authors included 45 patients with PD in this study.
• They diagnosed RBD on the basis of a standardized clinical interview and confirmed by polysomnography.
• During the course of a rectosigmoidoscopy, 5 biopsies were taken at the junction between the sigmoid and descending colon for each patient.
• Two colonic biopsies were examined by immunohistochemistry with antibodies against phosphorylated α-synuclein and PGP9.5 in 43 patients (2 patients were excluded because only 1 biopsy was available) for the detection of enteric PASH.
• They evaluated the paracellular permeability and transcellular permeability by measuring sulfonic acid and horseradish peroxidase flux, respectively, in the 3 remaining biopsies mounted in Ussing chambers.

• Compared to patients without RBD, enteric PASH was more frequent in the subgroup of patients with PD with RBD (18 of 28, 64.3%, vs 2 of 15, 13.3%, respectively, p < 0.01).
• The authors observed no differences in intestinal permeability between patients with PD with and without RBD.