The objective of this study was to evaluate whether paroxysmal slow wave events (PSWEs) identified in early electroencephalography (EEG) predict posttraumatic epilepsy (PTE) and disability outcomes following severe traumatic brain injury (sTBI).

A retrospective case–control study included 45 patients with sTBI (17 with PTE and 28 without PTE) matched by age and Glasgow coma scale. Clinical and EEG data were analyzed. Logistic regression and leave-one-out cross-validation (LOOCV) assessed PTE risk and disability. The area under the curve (AUC) measured accuracy.

Patients with PTE had longer time in PSWEs (P = 0.04) and lower median power frequency (MPF) of PSWEs (P = 0.02) on initial EEGs, along with increased time in PSWEs between initial and follow-up EEGs (P = 0.03). Lower MPF was associated with increased PTE risk (odds ratio 5.88; P = 0.04). Multivariate regression identified hemicraniectomy, time in PSWEs, and MPF as PTE predictors (AUC 0.87; P < 0.0001), maintaining strong LOOCV performance (AUC 0.83; P < 0.0001, accuracy 80%). Longer time in PSWEs was observed in patients with severe disability at the 3-, 6-, and 12-month follow-ups compared with moderate-to-good recovery (P = 0.012, 0.006, and 0.04, respectively).

PSWEs predict PTE development and are more prevalent among patients with worse disability after sTBI. Quantitative PSWE analysis may guide preventive and therapeutic strategies for PTE.