EEG variability in inflammatory encephalopathy: Dissemination in time and space

To assess the diagnostic value of repeated EEG in differentiating autoimmune encephalitis (AE) from herpes simplex virus-associated viral encephalitis (HSVE).

This observational case-control study analyzed 269 EEGs from 35 AE, 26 HSVE patients and two control groups with temporal lobe epilepsy (TLE) and acute non-inflammatory encephalopathy (ENC). We examined time- and space-related EEG changes in focal slowing (FS), epileptiform discharges (ED), and seizures. A five-item EEG variability score was calculated for each patient.

Patients with AE showed greater spatial variability in FS (46.4 % vs. 28.9 %, p < 0.001) and higher variability in FS severity (44.3 % vs. 34.6 %, p < 0.05) than patients with HSVE. Bilateral FS was more frequent in AE (67.7 % vs. 41.7 %, p = 0.05). AE demonstrated also higher ED location variability (37.5 % vs. 29.87 %, p = 0.058), and more bilateral ED (40 % vs. 23.5 %, p = 0.73). The EEG variability score was higher in patients with AE (2.34) than HSVE (1.43, p < 0.05) or in patients with TLE (1.17, p < 0.005) and acute encephalopathy (0.63, p < 0.001).

AE is characterized by greater temporal and spatial EEG variability than HSVE.

EEG variability is a consistent feature mainly seen in AE and may offer additional insights for differential diagnosis.