Evaluation of cholinergic treatment in demented patients by P300 evoked related potentials

Centrally acting cholinesterase inhibitors (ChEls) improve cognitive functions in Alzheimer's disease (AD) and other forms of dementia. Evaluation of treatment efficacy is based mainly on subjective assessment tools which includes standardized neuropsychological tests. Therefore, an additional objective tool for the evaluation of drug response is necessary. Thirty two patients were treated with ChEls for dementia (tacrine 19, donepezil 5, rivastigmine 8). Cognitive response was assessed before ChEls (baseline) and after 26 weeks, as optimal tolerated doses were achieved and maintained (endpoint). Evaluation included repeated measurements of Mini Mental State Examination (MMSE), ADAS-cog and P300. For statistical analysis we used ANOVA with repeated measures and Pearson correlation coefficient. Results demonstrated improvement of mean ADAS-cog by 2.0 points (from 29.4 to 27.4 p = 0.08) while MMSE remained almost unchanged (20.1 to 19.8). Mean P300 latency reduced significantly by 24 msec (from 383 msec to 359 msec, p = 0.0001) thus reflecting the clinical improvement. However mean amplitudes did not change from baseline to endpoint (13 microvolts). Significant correlation was found between mean ADAS-cog and mean P300 latency at baseline and end-point (R = 0.452 p = 0.014, R = 0.567 p = 0.001 respectively). Strong correlation was found between mean MMSE and P300 latency at Baseline (R = -0.335 p = 0.07), and significant correlation was found at endpoint (R = -0.613 p < 0.001). Our data suggests that P300 is a reliable instrument for assessment of cognitive response to ChEls in demented patients.