Is long-term electroencephalogram more appropriate than standard electroencephalogram in the elderly?

Objective: To compare the diagnostic accuracy of standard (st) and long-term video (lt) EEG in elderly patients with suspected non-convulsive seizures.

Methods: Over a 12-month period, we prospectively included all elderly (over-65) hospitalized patients having undergone lt-EEG for suspected non-convulsive seizures (n=43). st-EEG was defined as the first 20min of each lt-EEG. We recorded the patients' clinical and imaging characteristics and final diagnosis and assessed the respective diagnostic values of st-EEG and lt-EEG.

Results: Epileptiform discharges were detected on standard EEG in only 7% of patients and in 28% of patients on Lt-EEG (p=0.004). Non-convulsive seizures were recorded in 1 case vs. 4, respectively. Nine of 40 negative standard EEG showed later epileptiform activities. The median time to occurrence of the first epileptiform activities was 46.5min (interquartile range: 36.5-239.75min). Epileptiform activity occurred during sleep only in 33% patients with a negative st-EEG. Dementia was associated with a positive lt-EEG (p:0.047).

Conclusion: Lt-EEG was clearly superior to standard EEG for detecting epileptiform activity in elderly when suspecting non convulsive seizures.

Significance: St-EEG has a low diagnostic yield in elderly patients with suspected non-convulsive seizures and so lt-EEG is preferable in this situation.