Parkinson's dementia and Alzheimer's dementia: an evoked potential comparison.

Auditory endogenous event-related potentials (ERPs) and flash visual evoked potentials (VEPs) were recorded in 26 elderly patients with idiopathic Parkinson's disease (PD), 14 with dementia and 12 non-demented, 16 elderly patients with Alzheimer dementia (AD) and 15 cognitively intact controls. ERP P3 and flash-VEP N2, P2 and delta (P2-P1) latency measures were significantly increased in the demented PD group compared with controls. The ERP P3 latency was also significantly delayed in the AD group compared with controls, but the differences in the flash-VEP measures from controls were not significant. No significant differences were noted between the PD groups, except for a significantly shorter flash-VEP N1 latency in the demented PD group; this was also the only significant evoked potential difference between the AD and PD dementia groups, which were otherwise electrophysiologically similar.