Comparison of standard and extended 3-hour EEG in older adults with acute confusion

Background: Continuous EEG has been proposed to improve detection of epileptiform activity in older patients presenting with acute confusional state (ACS), but its added value outside critical care and in resource-limited settings remains uncertain. Methods: We conducted a prospective observational pilot study including 40 patients aged ≥65 years admitted with acute confusional state of unknown aetiology after initial clinical, laboratory, and neuroimaging work-up in a resource-limited setting. All patients underwent sequential EEG recordings of 20 min, 30 min, and 3 h using a standard 10–20 electrode system. EEGs were independently reviewed by two EEG-trained neurologists and classified according to established consensus criteria. Potentially clinically significant findings included interictal epileptiform discharges, periodic and rhythmic patterns. Results: Only one patient (2.5 %) demonstrated a new potentially clinically significant EEG finding on 30 min compared to 20 min EEG. Seven of 40 EEGs (17.5 %) revealed additional abnormalities on 3 h EEG compared with the initial 30 min recording. However, only four cases (10 %) were considered potentially clinically significant. The increase in diagnostic yield with prolonged EEG was not statistically significant (p = 0.125), and no clinical, laboratory, or imaging predictors of additional findings were identified. Conclusion: In older patients with acute confusional state of unknown aetiology, extending EEG recording to 3 h resulted in a small, statistically non-significant increase in diagnostic yield. Most clinically relevant EEG abnormalities were detected within the first 30 min, suggesting limited added value of routine prolonged EEG in resource-limited setting.