Detection of subclinical epileptiform discharges in Alzheimer’s disease using long‐term out‐patient EEG monitoring

Abstract

AbstractBackgroundIn patients with Alzheimer’s disease (AD) without clinical seizures, up to half have epileptiform discharges in long‐term in‐patient electroencephalography (EEG) recordings. Long‐term in‐patient monitoring is obtrusive, and expensive as compared to out‐patient monitoring. No studies have so far investigated if long‐term out‐patient EEG monitoring is able to identify epileptiform discharges in AD. To investigate if epileptiform discharges as measured with ear‐EEG are more common in patients with AD compared to healthy elderly controls (HC). To understand the association with AD, we investigated the variability across multiple recordings.MethodIn this longitudinal observational study, 24 patients with mild to moderate AD and 15 age‐matched HC were included in the analysis. Patients with AD underwent up to three ear‐EEG recordings, each lasting up to two days, within 6 months. The first recording was defined as the baseline recording.ResultAt baseline, epileptiform discharges were detected in 75.0% of patients with AD and in 46.7% of HC (p‐value = 0.073). The spike frequency (spikes or sharp waves/24 hours) was significantly higher in patients with AD as compared to HC with a risk ratio of 2.90 (CI: 1.77‐5.01, p<0.001). Most patients with AD (91.7%) showed epileptiform discharges when combining all ear‐EEG recordings.ConclusionLong‐term ear‐EEG monitoring detects epileptiform discharges in most patients with AD with a three‐fold increased spike frequency compared to HC, which most likely originates from the temporal lobes. Since most patients showed epileptiform discharges with multiple recordings, elevated spike frequency should be considered a marker of hyperexcitability in AD.