ELECTROENCEPHALOGRAPHY AS AN AID IN THE EXCLUSION OF ALZHEIMERS-DISEASE

Objective: To determine the usefulness or otherwise of the awake elect roencephalogram (EEG) in the diagnosis of Alzheimer's disease (AD). De sign: Prospective collection of one or more awake EEGs in patients dia gnosed as having AD or mixed AD and multiinfarct dementia according to current systematic criteria with analysis of those cases confirmed by postmortem examination. Systematized blind interpretation of EEGs. Se tting: Tertiary care practice with both ambulatory and hospitalized pa tients, ie, neurological department in general hospital and psychogeri atric unit in psychiatric hospital. Patients: A series of 86 subjects with AD and 17 with mixed AD and multi-infarct dementia being those me mbers of a consecutive series on whom postmortem information was avail able. 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% f or uncomplicated AD. Ultimately, 79 (92%) of 86 patients with AD had a bnormal EEGs. Twenty (35%) of 56 EEGs for matching control subjects we re abnormal. Moderately abnormal or severely abnormal EEGs were found in 10 (50%) of 20 of the patients with AD of less than 4 years' durati on compared with two (4.1%) of 49 of the control subjects, giving a sp ecificity of 95.9% for EEGs with this degree of abnormality. The norma l EEG had a negative predictive value of 0.825 with respect to the dia gnosis of AD in these populations. Conclusions: Widespread availabilit y, low cost, and high sensitivity support the use of the awake EEG in the diagnosis of AD.