Changes in the amplitude of the N30 frontal component of SEPs during apomorphine test in parkinsonian patients

Somatosensory evoked potentials (SEPs) to median nerve stimulation have been performed before and after apomorphine-test in 10 parkinsonian patients. Latency and amplitude of the P14-N20 parietal complex and of the P20-N30 frontal complex were evaluated. The N30 amplitude was significantly reduced before apomorphine administration (p < 0.001) with a consequent increase of the N20/N30 amplitude ratio (p < 0.001). Eight patients clinically improved after Apomorphine. Following Apomorphine there was no change in the amplitude of the parietal complex P14-N20. On the other hand the frontal complex P20-N30 showed a significant amplitude potentiation (p < 0.005), with a reduction of the N20/N30 amplitude ratio (ns). This finding was almost constant among the 8 responder patients. These results suggest the utility of combining clinical and neurophysiological data to assess the responsiveness to dopaminergic treatment.