REM sleep without atonia and vestibular-evoked myogenic potentials: clinical brainstem dysfunction in early-stage Parkinson's disease and isolated REM sleep behavior disorder

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ObjectiveTo determine whether the onset of rapid eye movement (REM) sleep behavior disorder (RBD) is associated with changes in brainstem neuronal pathway dysfunction as reflected by vestibular-evoked myogenic potentials (VEMPs) and to evaluate associations between VEMPs and REM sleep without atonia (RSWA) in patients with early-stage Parkinson's disease (PD) and isolated RBD (iRBD). MethodsEighty-two early-stage PD patients, 40 iRBD patients, and 41 healthy control individuals underwent one-night video-polysomnography (vPSG) and VEMPs examination. We compared cervical (cVEMP), ocular (oVEMP), and masseter (mVEMP) VEMP parameters among PD with RBD (PD + RBD), PD without RBD (PD-RBD), iRBD, and control groups and analyzed correlations between VEMPs and RSWA in PD and iRBD groups. ResultsThe PD + RBD group showed delays in bilateral cVEMP (Lp13, Ln23, Rn23: all p < 0.05) and oVEMP (Ln10, Rn10, Rp15: all p < 0.05) peak latencies compared with the PD-RBD group. Total cVEMP scores were higher in the PD + RBD group than in the iRBD group (p = 0.033). In PD patients, phasic RSWA was correlated with total cVEMP scores (p = 0.003), and tonic RSWA was correlated with left oVEMP scores (p = 0.013). ConclusionsBrainstem neurophysiology as evidenced by altered VEMPs in patients with PD and iRBD could reflect disease evolvement. Moreover, VEMPs alterations may vary depending on the presence of RBD in PD patients. The associations between altered RSWA and VEMP parameters highlight the meaningfulness of detecting brainstem dysfunction in early-stage PD.