Clinical, neuropsychiatric, and ioflupane SPECT imaging findings in REM sleep behavior disorder

      Background: There is little data regarding which features among those with REM sleep behavior disorder (RBD) predict the eventual phenoconversion to dementia with Lewy bodies (DLB) or Parkinson's disease (PD).
      Methods: We analyzed findings among subjects with RBD (n = 14) who did not have mild cognitive impairment (MCI), DLB or PD. The Neuropsychiatric Inventory was used to measure neuropsychiatric (NP) burden (sleep domain was excluded). The UPDRS was used to measure parkinsonism. Values ≤2.2 for the mean putamen to occipital ratio on ioflupane SPECT imaging were categorized as abnormal (DaT+).
      Results: The sample included 13 (93%) men with a mean age of 62.3 ± 8.2 years, mean Mini-Mental State Examination score of 29 ± 1 and mean UPDRS score of 0.625 ± 1. Nine subjects had ≥3 NP features with irritability (n = 8) and apathy (n = 6) being most frequent across all subjects. Six had subjective cognitive complaints (SCC), 6 had UPDRS >0, and 7 were DaT+. Among the 9 subjects with ≥3 NP features, 6 had SCC, 4 had UPDRS >0, and 5 were DaT+. Of the 6 with SCC, all 6 had ≥3 NP features, 2 had UPDRS >0, and 3 were DaT+. Among the 6 subjects with UPDRS >0, 4 had ≥3 NP features, 2 had SCC, and 4 were DaT+. Among the 7 subjects who were DaT+, 5 had ≥3 NP features, 3 had SCC, and 4 were DaT+. Only 2 subjects had no NP features plus no SCC plus UPDRS = 0, 1 of whom was DaT+.
      Conclusions: Varying degrees of cognitive complaints, NP burden, parkinsonism and ioflupane SPECT findings were present among RBD subjects. Longitudinal assessment of RBD subjects using clinical and imaging measures may predict subsequent phenoconversion of RBD to MCI/DLB versus PD.