When tumors speak: Understanding EEG periodic discharges in primary brain tumors and their clinical relevance

Background. Periodic discharges (PDs) are electroencephalogram (EEG) patterns commonly associated with focal cerebral lesions, particularly brain tumors (BTs). The clinical interpretation of PDs and their pathophysiological origins are controversial. This retrospective study describes the prevalence and characteristics of PDs in patients with BT, focusing on their association with BT-related epilepsy (BTRE) and status epilepticus (SE) diagnosis. Methods.Adult patients with BT who underwent a video-EEG recording were retrospectively selected from the Neurology Institute of "G. d'Annunzio" University of Chieti-Pescara from January 2016 to January 2024. Demographics, clinical features, tumor characteristics, and radiological findings were collected. Video-EEG data were reviewed to identify PDs. Results.One hundred and forty patients with BT (mean age: 60.6 +/- 17.6 years; 61 females) were enrolled. Fifteen patients (10.7%) exhibited PDs on video-EEG (PD+ group). In the PD+ group, lateralized PDs (LPDs) were most observed (93.3%). Periodic discharges were concordant with the side of the tumor lesion in 73.3% of cases. Compared to the PD- group, patients in the PD+ group more frequently showed a parietal (P = .0019) and occipital BT localization (P < .0001), a high-grade tumor histology (P = .048) and a previous BTRE diagnosis (P = .014). SE was observed in 4 patients (26.7%), in association with a significantly higher PDs frequency (SE patients: 1.6 Hz, non-SE patients: 0.8 Hz; P = .003). Conclusions.PDs are more commonly observed in patients with high-grade primary BT, particularly those with parietal or occipital localization. They are predominantly reported in individuals with a prior diagnosis of BTRE and may indicate SE, especially when their frequency exceeds 1.6 Hz.