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

• 20min, 30min, and 3h EEG was compared in older patients with acute confusion. • Most abnormalities appeared within 30 minutes; a 3-hour EEG added only a 10% gain. • No clinical or laboratory predictors of findings on prolonged EEG were identified. 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. 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 minutes, 30 minutes, and 3 hours 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. Only one patient (2.5%) demonstrated a new potentially clinically significant EEG finding on 30-minute compared to 20-minute EEG. Seven of 40 EEGs (17.5%) revealed additional abnormalities on 3-hour EEG compared with the initial 30-minute 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. In older patients with acute confusional state of unknown aetiology, extending EEG recording to 3 hours resulted in a small, statistically non-significant increase in diagnostic yield. Most clinically relevant EEG abnormalities were detected within the first 30 minutes, suggesting limited added value of routine prolonged EEG in resource-limited setting.