[P300 in mild cognitive impairment and in dementia]

The late component of the event-related potential (ERP), P300 is a marker for cognitive brain functions. The objective of this study was to examine P300 parameters in dementia and in mild cognitive impairment (MCI), to examine whether there is a correlation between the changes in P300 parameters and the type and severity of dementia, and to determine P300 abnormalities in MCI in relation to the presence/absence of CT/MRI abnormalities.

Auditory event-related potentials, P300 were recorded in 28 MCI patients (14 of them with normal CT/MRI findings and 10 subjects with mild ventricular enlargement). In another group of patients, 31 demented patients were examined, of whom 17 patients were diagnosed with Alzheimer's dementia (AD), and 14 patients with vascular dementia (VD). Forty healthy volunteers served as the control group.

Mean P300 latency was significantly increased for both demented patient-groups. We found that prolongation of P300 latency was correlated with the severity of dementia. Mean P300 amplitude was significantly decreased in both groups of demented patients. In MCI, the mean latency of P300 was significantly longer among patients with mild cerebral atrophy compared to control volunteers and no significant changes were found for MCI patients with normal CT/MRI findings. Mean P300 amplitude was decreased only in demented patients.

The prolongation of P300 latency was significant among patients with both vascular and Alzheimer's dementia, and also among MCI patients with mild cerebral atrophy. The severity of dementia is positively correlated with P300 latency; however, this prolongation is independent of the type of dementia. The structural brain changes in MCI are related to P300 latency prolongation and thus may indicate an increased risk for developing dementia in MCI patients.