title: Neurodegenerative disease status and post-mortem pathology in idiopathic rapid-eye-movement sleep behaviour disorder: an observational cohort study.
abstract: BACKGROUND
  We postulated that idiopathic rapid-eye-movement (REM) sleep behaviour disorder (IRBD) represents the prodromal phase of a Lewy body disorder and that, with sufficient follow-up, most cases would eventually be diagnosed with a clinical defined Lewy body disorder, such as Parkinson's disease (PD) or dementia with Lewy bodies (DLB).
  
  
  METHODS
  Patients from an IRBD cohort recruited between 1991 and 2003, and previously assessed in 2005, were followed up during an additional period of 7 years. In this original cohort, we sought to identify the nature and frequency of emerging defined neurodegenerative syndromes diagnosed by standard clinical criteria. We estimated rates of survival free from defined neurodegenerative disease by means of the Kaplan-Meier method. We further characterised individuals who remained diagnosed as having only IRBD, through dopamine transporter (DAT) imaging, transcranial sonography (TCS), and olfactory testing. We did a neuropathological assessment in three patients who died during follow-up and who had the antemortem diagnosis of PD or DLB.
  
  
  RESULTS
  Of the 44 participants from the original cohort, 36 (82%) had developed a defined neurodegenerative syndrome by the 2012 assessment (16 patients were diagnosed with PD, 14 with DLB, one with multiple system atrophy, and five with mild cognitive impairment). The rates of neurological-disease-free survival from time of IRBD diagnosis were 65·2% (95% CI 50·9 to 79·5) at 5 years, 26·6% (12·7 to 40·5) at 10 years, and 7·5% (-1·9 to 16·9) at 14 years. Of the four remaining neurological-disease-free individuals who underwent neuroimaging and olfactory tests, all four had decreased striatal DAT uptake, one had substantia nigra hyperechogenicity on TCS, and two had impaired olfaction. In three patients, the antemortem diagnoses of PD and DLB were confirmed by neuropathological examination showing widespread Lewy bodies in the brain, and α-synuclein aggregates in the peripheral autonomic nervous system in one case. In these three patients, neuronal loss and Lewy pathology (α-synuclein-containing Lewy bodies and Lewy neurites) were found in the brainstem nuclei that regulate REM sleep atonia.
  
  
  CONCLUSIONS
  Most IRBD individuals from our cohort developed a Lewy body disorder with time. Patients who remained disease-free at follow-up showed markers of increased short-term risk for developing PD and DLB in IRBD, such as decreased striatal DAT binding. Our findings indicate that in most patients diagnosed with IRBD this parasomnia represents the prodromal phase of a Lewy body disorder. IRBD is a candidate for the study of early events and progression of this prodromal phase, and to test disease-modifying strategies to slow or stop the neurodegenerative process.
  
  
  BACKGROUND
  None.
authors.affiliation: Neurology Service, Hospital Clínic de Barcelona, IDIBAPS, Barcelona, Spain; Centro de Investigación Biomédica en Red Enfermedades Neurodegenerativas CIBERNED, Barcelona 08036, Spain. airanzo@clinic.ub.es
authors.forename: Alex
authors.initials: A
authors.lastname: Iranzo
authors.forename: Eduard
authors.initials: E
authors.lastname: Tolosa
authors.forename: Ellen
authors.initials: E
authors.lastname: Gelpi
authors.forename: José Luis
authors.initials: JL
authors.lastname: Molinuevo
authors.forename: Francesc
authors.initials: F
authors.lastname: Valldeoriola
authors.forename: Mónica
authors.initials: M
authors.lastname: Serradell
authors.forename: Raquel
authors.initials: R
authors.lastname: Sanchez-Valle
authors.forename: Isabel
authors.initials: I
authors.lastname: Vilaseca
authors.forename: Francisco
authors.initials: F
authors.lastname: Lomeña
authors.forename: Dolores
authors.initials: D
authors.lastname: Vilas
authors.forename: Albert
authors.initials: A
authors.lastname: Lladó
authors.forename: Carles
authors.initials: C
authors.lastname: Gaig
authors.forename: Joan
authors.initials: J
authors.lastname: Santamaria
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000378:metabolism / Q000473:pathology*; D015331:Cohort Studies; D018450:Disease Progression; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D020961:Lewy Body Disease / Q000378:metabolism / Q000473:pathology*; D008297:Male; D009410:Nerve Degeneration / Q000378:metabolism / Q000473:pathology; D062706:Prodromal Symptoms; D020187:REM Sleep Behavior Disorder / Q000378:metabolism / Q000473:pathology*; D051844:alpha-Synuclein / Q000378:metabolism
chemical_list: D051844:alpha-Synuclein