Microstructural and Sodium 7 Tesla Brain MRI in Idiopathic REM Sleep Behaviour Disorder (SODISLEEP)

Inclusion Criteria for patients with REM Sleep Behaviour Disorder : Patient aged between 40 and 80 years old Patient fulfilling the diagnostic criteria for RBD (International Classification of Sleep Disorders version 3, American Academy of Sleep Medicine, 2014) with polysomnographic confirmation (which will be carried out as part of the routine work-up); UPDRS Part III score under or equal to 5 The patient is enrolled in the French social security system The patient understood and signed the consent to participate in the study. Inclusion Criteria for control group : Patient aged between 40 and 80 years old Score under or equal 4 for the RBD screening questionnaire UPDRS Part III score under or equal 5 The patient is enrolled in the French social security system The patient understood and signed the consent to participate in the study. Exclusion Criteria : Patient / Subject with a history of central nervous system disease (e.g. PD, Alzheimer's disease, stroke, brain tumour, multiple sclerosis, amyotrophic lateral sclerosis, etc.). If a doubt exist, this criterion will be left to the judgement of the principal investigator, who is a neurologist. Contraindications to 7T MRI: presence of a metal in the body or in the eye, patient with a pacemaker or neurostimulator, cochlear implants or any implanted electronic medical equipment in general, metallic heart valve, aneurysm clips. Claustrophobia. Montreal Cognitive Assessment Test (MOCA) < 25/30 Pregnant or breast-feeding woman or protected person (under guardianship, curatorship, deprived of liberty).