[The value of quantitative electroencephalogram analysis in the study of dementias].

INTRODUCTION The question as to whether an electroencephalogram (EEG) needs to be carried out as a preliminary study in patients with dementia is currently the subject of some controversy. AIMS Our aim was to determine the value of conventional and quantitative analysis of EEG recordings in the treatment of dementia. PATIENTS AND METHODS The EEG recordings of patients diagnosed with a syndrome of dementia were analysed both visually and quantitatively (comparing them with patients with major depressive disorder). RESULTS A total of 45 EEG traces were analysed -25 from patients with dementia and 20 with major depressive disorder-. The most significant finding was the number of abnormal recordings in each group, which was higher in the dementia group, with 19 abnormal recordings (76%) versus five in the depression group (25%). The difference was statistically significant (p = 0.001). The slow base rhythm and low voltage also differed notably between the two groups. The two groups displayed significant differences in both the frontal d and the temporal q rhythms (relative power), although the percentage was higher in patients with dementia. The posterior a rhythm was the variable with the greatest difference, and the percentage was higher in patients with depression. In absolute power, only the posterior a rhythm displayed a significant difference between the two groups, and was greater in the patients with depression. CONCLUSIONS Performing an EEG in the initial treatment of patients with dementia is useful to distinguish it from other pathological conditions, and its quantitative analysis helps in the search for the focus.