Middle Latency Somatosensory Evoked Potentials in Hemiparkinsonism

The reports in the literature regarding the effect of Parkinson's disease (PD) on the frontal N30 components of the somatosensory evoked potentials (SEPs) are contraversial. In order to assess whether frontal, central and parietal components of SEPs are influenced in PD, we studied middle latency SEPs in 19 patients (15 males, 4 females) with hemiparkinsonism (HP) and in 9 (3 males, 6 females) healthy controls. Frontal P14, P20, N30 latencies and P20/N30 amplitudes; central N18, P22, N32, P40 latencies and N18/P22, N32/P40 amplitüdes; parietal N20, P27, N34, P40 latencies and N20/P27, N34/P40 amplitudes were evaluated. There was no significant difference in latencies and amplitudes between the affected and unaffected sides of patients. Compared with the controls, HP patients exhibited lower frontal N18/P22 amplitudes, longer parietal P14 latencies and longer parietal P40 latencies. There was a positive correlation between the Unified Parkinson's Disease Rating Scale (UPDRS) motor score and N18/P22, N20/P27 and N32/P40 amplitudes; while a negative correlation was found between the duration of the disease and N18/P22 as well as N20/P27 amplitudes. Our results suggest that the pathways between the midbrain and both the motor and premotor cortex are affected in PD.