The relationship between slowing EEGs and the progression of Parkinson's disease.

The previous association study confirmed that diffuse slowing of EEGs was present in Parkinson's disease (PD), demonstrated with the use of the quantitative EEG technique. This study was the first to assess the relationship between progression of PD and quantitative EEG. A total of 106 patients with PD with a mean Hoehn-Yahr stage of 2.73 were serially enrolled. Lack of ischemic lesions was confirmed in all patients by magnetic resonance imaging. Absolute power values were measured for four frequency bands from delta to beta. The electrodes were divided among six locations: frontal pole, frontal, central, parietal, temporal, and occipital locations. Spectral ratio was calculated as the sum of power values for the alpha and beta waves divided by the sum values for the slow waves. The relationship between the progression of PD and spectral ratio was assessed by the Jonckheere-Terpstra trend test. At all electrode locations, spectral ratio significantly decreased with progression of Hoehn-Yahr stage (frontal pole, P = 0.007; frontal, P = 0.005; central, P = 0.031; parietal, P = 0.017; temporal, P = 0.005; occipital, P = 0.010). This shows that the slowing of EEGs became more obvious with PD progression.