Electrophysiological profile after a first unprovoked seizure - a prospective high-density EEG study

Retrospective low-density EEG studies have shown distinct functional connectivity (FC) and power in patients after a first unprovoked seizure, but have methodological limitations. In this prospective observational study, we addressed these limitations and evaluated power and FC in unmedicated, non-lesional patients after a first unprovoked seizure. We further compared patients who developed epilepsy to those who did not after one year of follow-up, and evaluated network differences relative to patients with chronic idiopathic generalized epilepsy (IGE), non-lesional focal epilepsy, and healthy controls.

Resting-state high-density electroencephalography (HD-EEG) recordings (256 channels) were obtained from 51 patients in total: 19 first-seizure, 18 IGE and 14 non-lesional focal epilepsy patients. 23 healthy controls were included. Source-reconstructed FC (imaginary part of coherency) and power were computed across five frequency bands (1-29 Hz). Whole-brain and vertex-wise group differences were assessed using permutation analysis of linear models.

During one year follow-up, 8 patients of the first-seizure group developed epilepsy (early-epilepsy group) while 11 remained seizure-free (single-seizure group). Overall, first-seizure patients showed increased theta and beta-2 FC against controls. The early-epilepsy group had decreased alpha FC compared to single-seizure patients and controls. In comparison to IGE patients, first-seizure patients displayed lower delta FC, and higher beta-1 FC against non-lesional focal epilepsy patients.

Unmedicated, non-lesional, IEDs-free first-seizure patients show differences in FC compared to healthy controls and from established epilepsies. Further, the patients who developed epilepsy after a first unprovoked seizure exhibit distinct theta and alpha FC patterns compared to seizure-free patients.