Spectrum of EEG Findings in Patients with Leptomeningeal Carcinomatosis and Seizures: Correlation with Neurodiagnostic Results and Outcome.

Purpose: Leptomeningeal carcinomatosis (LC) is a devastating condition in patients with systemic malignancies or primary brain tumors. Although much is known about neuro-radiologic investigations, there is very little information about EEG findings in these patients. Whether EEG is correlated with cranial magnetic resonance imaging (MRI) results and survival has not been investigated. Methods: Medical records of 2340 adult patients with the diagnosis of brain tumor, either metastatic (Group 1) or primary (Group 2), between 2000-2021 were reviewed for the presence of LC and seizures. Demographic and clinical features, laboratory results and Karnofsky performance scores of included patients were noted. Available routine EEG recordings were re-evaluated. Any possible correlation between EEG findings-MRI and EEG findings-survival were investigated statistically. Results: Sixty-six patients with LC and seizures were identified. The most common malignancies were lung cancer and glioblastoma multiforme. Twenty-six EEG recordings of 17 patients in Group 1, and 13 EEGs of 9 patients in Group 2 were available for final analysis. The most common EEG characteristic was background slowing (73%). The most frequent findings were rhythmic periodic patterns or spike wave activity (27%). Sporadic epileptiform discharges (8%) or ictal recordings (4%) were very rare. None of the EEG features correlated with MRI results or survival. Conclusion: There are various EEG patterns in patients with LC and seizures. The most common findings are related to background activity, with rhythmic periodic patterns or spike wave activity being observed less commonly. EEG characteristics do not predict MRI findings or survival.