COMPARISON OF CHOLINERGIC STATUS EVALUATED VIA QUANTITATIVE EEG PARAMETERS IN NORMAL SUBJECTS AND PATIENTS SUSPECTED OF DEMENTIA

Abstract

This study evaluated quantitative electroencephalography (QEEG) variables to distinguish normal subjects from patients who were being investigated for dementia and followed-up with or without acetylcholinesterase inhibitor (AChEI) treatment. Means from 4 EEG epochs obtained with eyes closed (E.Cl.) 80 sec. per epoch or eyes open (E.O.) 25 sec. per epoch, the peak frequency with eyes closed and the vigilance index (ratio of E.O./E.Cl. mean power) were calculated. A normal group and a group suspected of having primary dementia were followed after 10±4 with or 11±4 months without AChEI treatment. Student's t tests compared the means and standard deviations and the extent of changes between the baseline and follow-up assessments. Based on earlier studies when cholinergic and anticholinergic drugs tested in humans, demonstrates the anticholinergic effect on EEG by reducing power of basic rhythm (Alfa-rhythm) and increase power when eyes are open, why vigilance index reflects the anticholinergic effect on the EEG. When the normal group were compared with those of the suspected dementia group at baseline, all variables were significantly altered. The vigilance index and power of the E.O. increased, the peak frequency and E.Cl. power was reduced (Fig 1). At follow-up, the vigilance index and E.O. power of the untreated group increased (p = 0.06, respectively 0.07) compared to AChEI treated group (p = 0.46 respectively 0.43). The ratio of the change compared to baseline was unchanged for the vigilance-index (1.0) for the AchEI treated, while increased (1.15) in the untreated group. For E.O power reduced (0.69) for the treated and increased (1.43) for the treated group. The treated group exhibited a higher proportion of patients with a decreased or unchanged vigilance index and fewer patients with an increased vigilance index than the untreated patients (Fig. 2). The examined variables. A (left) Normal EEG with four epochs superimposed n the graphs. B (right) shows an examination of a patient at baseline (above) under E.CI. and E.O. conditions and follow-up (tower) in B. The patient did not receive AChEI treatment. Thus, the power ratio value of the E.O./E.CI. (vigilance index) increased at follow-up. Comparison of the vigilance index at the follow-up EEG of patients who were treated with or without AChEI after the baseline EEG. The treated group exhibited a higher proportion of patients with a decreased or unchanged vigilance index and fewer patients with an increased vigilance index compared to untreated patients. These data support the hypothesis that acetylcholine levels further reduction halts or even increases in patients treated with AChEI. The increased vigilance index in AChEI treated group suggests that these patients did not respond to the treatment at this follow-up visit (non-responders). The vigilance index reflects the cholinergic status, and it was clearly increased in the early dementia group and at follow-up for those not treated with AChEI, but was not changed in the treated patients. The vigilance index may be used to assess cholinergic deficits in patients with dementia and evaluate the effects of AChEI treatment.