The Diagnostic Value of EEG in Alzheimer Disease

Abstract

The aim of our study was to analyze EEG changes in patients with Alzheimer disease (AD) and to determine how closely EEG reflects the progression of mental impairment in people with AD. Ninety-five patients with probable AD according to National Institute of Neurological and Communicative Disorders and Stroke/Alzheimer's Disease and Related Disorders Association criteria treated in our Clinic for Memory Disorders were selected for this study. Patients were divided into three subgroups with mild, marked, and severe dementia according to the results of psychometric scales. The EEG findings were classified using an eight-degree scale according to the background activity, presence and amount of theta and delta waves, focal changes, lateralization of focal changes, synchronization, and presence of sharp and spike waves. A significant correlation between the degree of EEG abnormalities and cognitive impairment was found. We did not observe any correlation between the presence of delta waves and the results of neuropsychological tests. Our study revealed an important diagnostic value of EEG in the estimation of the severity of dementia parallel to psychometric scales.

EEG Abnormalities Are Associated with Different Cognitive Profiles in Alzheimer’s Disease

“…In our study a substantial proportion of patients with AD (28%) showed no EEG abnormalities, in accordance with previous studies [9,11,12,13,24]. The neuropsychological test scores were relatively least impaired in this group of patients.…”

“…Patients with only diffuse abnormalities were in general most severely impaired on neuropsychological testing and slightly more impaired on global cognition (MMSE = 21 ± 5), in line with former studies [13,15,16]. The present study extends these findings, as we took into account performance on specific neuropsychological tests.…”

“…The sensitivity of visual EEG analyses in differentiating AD from healthy controls or other dementias varies in different studies from 0.45 to 0.88 [7]. These numbers underscore that EEG can also be normal in patients with AD [11,12,13]. …”

“…These studies concluded that severity of EEG abnormalities was associated with severity of cognitive impairment [13,14,15,16]. A few, only small, studies examined relations with impairment in specific cognitive domains.…”

Quantitative EEG Applying the Statistical Recognition Pattern Method: A Useful Tool in Dementia Diagnostic Workup

“…The main EEG abnormalities in AD are slowing of alpha activity and increases in theta and delta activities, and these changes correspond well with the severity of AD [13,14,15]. Quantitative data from EEG recordings are generated by use of computerized analysis [16], and quantitative EEG (qEEG) parameters have repeatedly shown good discriminatory power between different dementia disorders and healthy aging in a number of clinical studies [17,18,19,20,21].…”