Aim: To describe associations of abnormalities in the electroencephalogram (EEG) with the most prevalent diagnoses in a memory clinic cohort. Methods: Associations between visual EEG findings and diagnoses in 1,116 consecutive patients [382 Alzheimer’s disease (AD), 274 subjective complaints, 190 mild cognitive impairment (MCI), 118 psychiatric disorder, 61 frontotemporal lobar degeneration, 53 vascular dementia (VaD), 38 dementia with Lewy bodies (DLB)] were determined by prevalence ratio (PR). Results: Diagnoses of subjective complaints [PR = 1.6; 95% confidence interval (CI) = 1.4–1.9] and psychiatric disorder (1.4; 95% CI = 1.1–1.9) were associated with a normal EEG, while subjects with both focal and diffuse EEG disturbances were more likely to have DLB (3.5; 95% CI = 2.1–5.6), VaD (2.3; 95% CI = 1.4–3.6) or AD (1.5; 95% CI = 1.3–1.8). Subjects with only diffuse EEG abnormalities were more likely to have AD (PR = 1.5; 95% CI = 1.3–1.9). The prevalence of MCI was higher among those with only focal EEG abnormalities (PR = 1.3; 95% CI = 1.0–1.7). Conclusions: A normal EEG argues for subjective complaints or psychiatric diagnosis. An EEG with only focal abnormalities supports MCI. An EEG with only diffuse abnormalities argues for AD. An EEG with both focal and diffuse abnormalities argues for DLB, VaD or AD.
Background: Although EEG is not considered as standard in memory clinics, evidence indicates that epileptiform discharges are of value in diagnosing cognitive complaints as epilepsy. Objective: To determine prevalence and significance of epileptiform discharges in a memory clinic. Methods: 1,674 consecutive patients underwent routine EEGs [mean age 66 years, diagnoses: Alzheimer disease (AD; n = 510), other dementia (n = 193), mild cognitive impairment (MCI; n = 225), subjective complaints (n = 368), and other disorders (n = 378)]. Database statistics, charts and EEG reports were reviewed. Results:Epileptiform discharges were present in 42 (3%) patients, of which 60% lacked clinical seizures. All discharges were focal and predominantly temporally localized. Epileptiform activity was not associated with a dementia diagnosis (2% in AD and 1% in other dementia vs. 2% in MCI, 2% in subjective complaints and 5% in other disorders, p = 0.07) or with lower Mini-Mental State Examination scores (p = 0.69). Two (diagnoses: AD, vascular dementia) of 20 patients with epileptiform activity without clinical seizures developed first seizures after 2 years. Conclusion: In a memory clinic cohort, epileptiform discharges are rare, nonspecific and indicate a moderate risk of first-ever seizures in demented patients. These findings should be taken into account when routinely evaluating memory clinic patients with EEG.
Objective: Our purpose was to investigate associations between different cognitive profiles and their underlying functional brain changes as measured by electroencephalogram (EEG) in Alzheimer’s disease (AD). Methods: EEG was obtained and neuropsychological performance assessed in 254 patients with AD. The EEGs were visually assessed for the presence of focal and/or diffuse abnormalities. Multivariate analysis of variance for repeated measures was performed with presence of focal and/or diffuse abnormalities as between-subjects factor and neuropsychological tests as within-subject factor. Age, sex and education were entered as covariates. Results: Twenty-eight percent of the patients had a normal EEG, 32% had focal abnormalities, 14% diffuse abnormalities and 26% had both focal and diffuse abnormalities. Patients with a normal EEG presented with a cognitive profile in which memory was mostly impaired. Patients with focal and diffuse EEG abnormalities presented with a nonmemory profile. Conclusion: These results illustrate that specific types of EEG abnormalities are associated with different cognitive profiles in AD, providing biological support in terms of brain functioning for variability in cognitive impairment.
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