The value of quantitative EEG in differential diagnosis of Alzheimer's disease and subcortical vascular dementia

Objective: To investigate whether quantitative EEG may be useful in differential diagnosis of AD and SVD and to determine the correlation between dementia and abnormalities in EEG. Materials and methods: The group under study was consisted of 62 patients with AD (mean age: 73.6 yrs; M 51%), 31 with SVD (mean age: 75.2 yrs, M 43%) and a control group of 14 healthy subjects (mean age: 69.5 yrs, M 43%). The patients were divided into subgroups of those with mild, moderate and marked dementia. EEG findings were classified using eight-degree scale according to the presence of slow waves, and then quantitative analysis was carried out by calculating the alpha/slow wave power ratios and the mean frequencies in all and some selected derivations. Results: A significant difference between visual EEGs and QEEGs in AD and SVD was found. Only QEEG parameters differed in AD and SVD subgroups with the same degree of cognitive impairment: the mean wave frequencies of waves in temporal derivations in subgroups with mild and moderate dementia and alphal delta waves power ratio in subgroups with moderate dementia. Conclusions: Visual EEGs and QEEGs could be used in addition to the differential diagnosis between AD and SVD, but only selected parameters of QEEG could be useful in differentiating between AD and SVD subgroups with the same degree of dementia. (C) 2009 Elsevier B.V. All rights reserved.