Functional connectivity in electroencephalography of brain tumor patients in status epilepticus: a retrospective evaluation of prognostic value.

Background: There is currently no individualized prognostic tool to predict outcomes in patients with brain tumors following status epilepticus (SE), despite its clinical importance for counseling and therapeutic decision-making. This proof-of-principle, retrospective monocentric study investigated whether electroencephalography (EEG)-derived functional connectivity patterns differ in brain tumor patients after SE with respect to survival and tumor type. Methods: EEG data from 37 brain tumor patients with SE were analyzed. Thirty epochs per frequency band (delta-gamma) were selected using spectral power. Source-space connectivity was measured via weighted Phase Lag Index (wPLI). Permutation tests compared connectivity between survival (>1 vs. <1 year) and tumor subgroups (glioma, meningioma, metastases). Results: The cohort had a mean age of 68.1 years; 67.6% were female. One-year survival was 32.4%, with a mortality rate of 46.0% and 21.6% lost to follow-up. Tumor diagnoses included 11 adult-type diffuse gliomas, 12 meningiomas, 11 brain metastases, and single cases of primary cerebral lymphoma, schwannoma, and pineal tumor. Higher source connectivity in the alpha and beta bands was observed in patients with longer survival, and higher delta band connectivity in patients with brain metastases compared to those with glioblastoma or meningioma. Conclusions: Functional connectivity analysis in source space did not reliably differentiate patients by survival or tumor type following SE. These findings suggest that current connectivity metrics are insufficient as standalone prognostic tools in this context. Larger, more homogeneous cohorts and stratification by clinical and tumor characteristics are needed to clarify the potential prognostic value of EEG connectivity in this population.