[Multimodal evoked potentials in patients with dementia]

The event-related potential (ERP), somatosensory evoked potential (SEP) and visual evoked potential (VEP) were studied in 15 patients with Alzheimer's disease (AD), 16 patients with Parkinson's disease with dementia (PD), 7 patients with Binswanger's disease (BD) and 15 normal controls. ERP was recorded during auditory discriminative tasks. SEP evoked by median nerve stimulation was recorded from the second cervical vertebra and contralateral primary somatosensory cortex with a midfrontal reference. VEP was recorded during pattern reversal stimulation. All three groups with dementia showed significant prolongation of the N200 and P300 latencies of ERP compared with the normal controls. In addition, patients with AD showed significant prolongation of the P200 latency. There was a significant correlation between the P300 latency of ERP and MMSE scores in AD patients. Patients with AD and PD showed significant prolongation of the interpeak latency between N13 and P40 (N13-P40) and N20-P40 of SEP compared with the normal controls. Patients with BD showed significant prolongation of the N13-N20, N13-N33, N13-P40 and N20-P40. These results suggest that there is impairment of the ascending somatosensory pathway in patients with dementia. Patients with PD showed significant prolongation of the P100 latency of VEP compared with normal controls. There was a significant correlation between the N200 latency of ERP and the P100 latency of VEP in PD patients. The VEP results suggest that dysfunction in the central visual system plays a role in abnormal pattern VEP in PD. In conclusion, the present results show that these three dementing diseases have different electrophysiological features, which may be related to the underlying pathogenic mechanisms. Additionally, the measurement of multimodal evoked potentials may be helpful in the differential diagnosis of patients with dementia.