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March 1994

Electroencephalography as an Aid in the Exclusion of Alzheimer's Disease

Author Affiliations

From the Department of Research, London (Ontario) Psychiatric Hospital.

Arch Neurol. 1994;51(3):280-284. doi:10.1001/archneur.1994.00540150074020

Objective:  To determine the usefulness or otherwise of the awake electroencephalogram (EEG) in the diagnosis of Alzheimer's disease (AD).

Design:  Prospective collection of one or more awake EEGs in patients diagnosed as having AD or mixed AD and multi-infarct dementia according to current systematic criteria with analysis of those cases confirmed by postmortem examination. Systematized blind interpretation of EEGs.

Setting:  Tertiary care practice with both ambulatory and hospitalized patients, ie, neurological department in general hospital and psychogeriatric unit in psychiatric hospital.

Patients:  A series of 86 subjects with AD and 17 with mixed AD and multi-infarct dementia being those members of a consecutive series on whom postmortem information was available. Awake EEGs in 56 age- and sex-matched control subjects.

Results:  Seventy-five patients with AD (87.2%) and 13 of the mixed group (76.5%) had abnormal EEGs on first testing, giving a sensitivity of 87.2% for uncomplicated AD. Ultimately, 79 (92%) of 86 patients with AD had abnormal EEGs. Twenty (35%) of 56 EEGs for matching control subjects were abnormal. Moderately abnormal or severely abnormal EEGs were found in 10 (50%) of 20 of the patients with AD of less than 4 years' duration compared with two (4.1%) of 49 of the control subjects, giving a specificity of 95.9% for EEGs with this degree of abnormality. The normal EEG had a negative predictive value of 0.825 with respect to the diagnosis of AD in these populations.

Conclusions:  Widespread availability, low cost, and high sensitivity support the use of the awake EEG in the diagnosis of AD.

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