The Spectrum of Long‐term Epilepsy–associated Tumors: Long‐term Seizure and Tumor Outcome and Neurosurgical Aspects

Abstract

Summary: Purpose: To describe the histologic spectrum and clinical characteristics of patients with neuroepithelial tumors and drug‐resistant epilepsy and to analyze clinical data and treatment related to seizure outcome and survival. Methods: Data were analyzed from 207 consecutive patients with intractable epilepsy (aged 2–54 years), who between 1988 and 1999 had ≥50% resection of supratentorial, neuroepithelial tumors. Extent of resection was assessed on postoperative magnetic resonance imaging (MRI); seizure outcome was classified according to Engel's outcome scale; and follow‐up data were prospectively updated. Results: Median follow‐up was eight years (range, 2–14 years). Histologic examination revealed 154 classic epilepsy‐associated tumors (ganglioglioma, dysembryoplastic neuroepithelial tumor, pleomorphic xanthoastrocytoma, and pilocytic astrocytomas) and 53 others (astrocytomas and oligodendrogliomas). Four World Health Organization (WHO) grade III tumors were found (astrocytoma, n = 3; ganglioglioma, n = 1). After surgery, 82% of the patients were seizure free (class I). The following factors were associated with improved seizure outcome: Short duration of epilepsy before surgery, single EEG focus, absence of additional hippocampal sclerosis or cortical dysplasia, transsylvian approach, other than astrocytomas, and complete tumor resection. After 5 years, only nine (4%) patients had tumor recurrence, four (2%) with malignant transformation and death. None of the four patients with anaplastic tumors died. Even patients with astrocytomas of WHO grade II or III showed 10‐year recurrence of only 25% and 10‐year survival of 90%. Conclusions: Tumors associated with long‐term epilepsy should be removed early for two different reasons: high rate of seizure freedom and rare but potential risk of malignant tumor progression. The unexpected long survival of these astrocytomas should be investigated by using immunohistochemistry and molecular biology.