Figure 2 The new concept of prodromal RBD Figure 2 | The new concept of prodromal RBD. Neurophysiological and behavioural findings on polysomnography and EMG (electromyography) progress along a continuum over time. From initially normal findings, patients enter a prodromal stage of rapid eye movement (REM) sleep behaviour disorder (RBD) that progresses into isolated RBD, and eventually into RBD with overt α-synucleinopathy. FDS, flexor digitorum superficialis; RBEs, REM sleep behavioural events. Högl, B. et al. (2017) Idiopathic REM sleep behaviour disorder and neurodegeneration — an update Nat. Rev. Neurol. doi:10.1038/nrneurol.2017.157