title: Long-Term Follow-up Investigation of Isolated Rapid Eye Movement Sleep Without Atonia Without Rapid Eye Movement Sleep Behavior Disorder: A Pilot Study.
abstract: OBJECTIVE
  Idiopathic rapid eye movement (REM) sleep behavior disorder (RBD) is a harbinger of synuclein-mediated neurodegenerative diseases. It is unknown if this also applies to isolated REM sleep without atonia (RWA). We performed a long-term follow-up investigation of subjects with isolated RWA.
  
  
  METHODS
  Participants were recruited from 50 subjects with isolated RWA who were identified at the sleep laboratory of the Department of Neurology at the Medical University of Innsbruck between 2003 and 2005. Eligible subjects underwent follow-up clinical examination, polysomnography, and assessment of neurodegenerative biomarkers (cognitive impairment, finger speed deficit, impaired color vision, olfactory dysfunction, orthostatic hypotension, and substantia nigra hyperechogenicity).
  
  
  RESULTS
  After a mean of 8.6 ± 0.9 y, 1 of 14 participating subjects (7.3%) progressed to RBD. Ten of 14 RWA subjects (71.4%) were positive for at least one neurodegenerative biomarker. Substantia nigra hyperechogenicity and presence of mild cognitive impairment were both present in 4 of 14 subjects with isolated RWA. Electromyographic activity measures increased significantly from baseline to follow-up polysomnography ("any" mentalis and both anterior tibialis muscles: 32.5 ± 9.4 versus 52.2 ± 16.6%; p = 0.004).
  
  
  CONCLUSIONS
  This study provides first evidence that isolated RWA is an early biomarker of synuclein-mediated neurodegeneration. These results will have to be replicated in larger studies with longer observational periods. If confirmed, these disease findings have implications for defining at-risk cohorts for Parkinson disease.
authors.affiliation: Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: Ambra
authors.initials: A
authors.lastname: Stefani
authors.affiliation: Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: David
authors.initials: D
authors.lastname: Gabelia
authors.affiliation: Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: Birgit
authors.initials: B
authors.lastname: Högl
authors.affiliation: Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Mitterling
authors.affiliation: Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: Philipp
authors.initials: P
authors.lastname: Mahlknecht
authors.affiliation: Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: Heike
authors.initials: H
authors.lastname: Stockner
authors.affiliation: Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: Werner
authors.initials: W
authors.lastname: Poewe
authors.affiliation: Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: Birgit
authors.initials: B
authors.lastname: Frauscher
mesh_terms: D004576:Electromyography; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009123:Muscle Hypotonia / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology; D018482:Muscle, Skeletal / Q000503:physiopathology*; D019636:Neurodegenerative Diseases / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D009483:Neuropsychological Tests; D010865:Pilot Projects; D017286:Polysomnography; D020187:REM Sleep Behavior Disorder / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D012895:Sleep, REM / Q000502:physiology*
keywords: EMG activity; REM sleep behavior disorder; SINBAR; biomarker; polysomnography