Inter-Hemispheric Asymmetry and Intra-Hemispheric Discrepancy of Electroencephalographic Activities in Patients With Idiopathic Rapid Eye Movement Sleep Behavior Disorder: An Exploratory Study

BACKGROUND: In idiopathic rapid eye movement (REM) sleep behavior disorder (iRBD) patients, electroencephalogram (EEG) activities during REM sleep in some cortical regions are different from those in normal controls. This study aimed to examine inter-hemispheric asymmetry and intra-hemispheric EEG discrepancy in iRBD patients and normal controls during REM sleep. METHODS: Polysomnographic recordings were carried out on 15 iRBD patients and 15 normal controls. The inter-hemispheric asymmetry and intra-hemispheric differences of EEG activities in the iRBD patients were compared with those in the normal controls during REM sleep. RESULTS: During REM sleep, most of the powers of theta, alpha, sigma, beta, and gamma waves in the right cerebral hemisphere were significantly greater than those in the left cerebral hemisphere in both the iRBD patients and normal controls. The inter-hemispheric asymmetry was significantly larger in the central and occipital regions and generally smaller in the frontal region in the iRBD patients compared with the normal controls. In the iRBD patients and normal controls, the powers of theta, alpha, beta, and gamma bands during tonic and phasic REM sleep were highest in the frontal cortical region, followed by the central cortical region, and lowest in the occipital cortical region; sigma power during phasic, but not tonic, REM sleep fully followed this rule. CONCLUSION: In iRBD patients EEG activities are unevenly distributed, with an altered inter-hemispheric asymmetry that might be associated with changed bilateral neuronal differences compared with normal controls.