Sleep EEG Detects Epileptiform Activity in Alzheimer's Disease with High Sensitivity.

BACKGROUND: The reported prevalence of epilepsy in Alzheimer's disease (AD) is variable, probably due to the different methodological approaches.

OBJECTIVE: We aimed to define the optimal electroencephalogram (EEG) settings for reliable detection of epileptiform discharges in AD patients.

METHODS: We analyzed 24-h EEGs of 5 patients living with AD and epilepsy. The sensitivity of various length EEGs in detecting epileptiform discharges in different periods of the day, the diurnal distribution of the discharges, and their relation to sleep-stages were calculated.

RESULTS: Significant high correlation was identified between the sensitivity of EEG and the length of recordings (r = 0.972, p = 0.005). The sensitivity of a 30-min EEG-epoch recorded between 8:00 and 16:00 was 0.0375 compared to 0.7 between 0:00 and 8:00 (p = 0.005). The average sensitivity of an 8-h EEG-epoch was≥0.8. 82% of epileptiform discharges occurred during sleep, mainly related to non-REM sleep (p < 0.001).

CONCLUSION: 8-h awake-, or 1-h sleep-EEG provide sufficient sensitivity in detecting epileptiform activity in AD. This needs to be considered in studies on AD-related epilepsy. Recognizing epilepsy in AD patients is essential because it might compromise cognitive functions and accelerate the progression of the disease.