NCMP-12. GLIOMA RELATED EPILEPSY: CLINICAL AND PATHOLOGICAL CORRELATES

Abstract

INTRODUCTION: The overall incidence of brain tumor related epilepsy among all causes of epilepsies ranges from 4-8%. Epileptic seizures are associated with brain tumor in approximately 30-50% of patients. Glioma is the most common cause of primary brain tumors, contributing nearly 50% of all cases. In high grade glioma seizure frequency is 20-50%, but in low grade it can be up to 90%. There have been multiple publications describing epilepsy frequency in low grade and high-grade glioma but few have described the relationship between seizures and IDH1 R132H mutation. METHOD: This is an observational retrospective clinical study. Medical records and neuroimaging data were reviewed for all newly diagnosed patients with brain tumor and pathology consisting of oligodendroglioma and astrocytoma WHO grade II and III at the Montreal Neurological Institute and Hospital between 2011 and 2015. IDH1 R132H status was obtained in all tumors and 1p/19q co-deletion was analyzed in all oligodendrogliomas. The details about related seizures were collected, including seizure semiology, timing in relation to surgery, frequency, and antiepileptic medications used. Tumor location was determined by preoperative MRI. RESULT: There were a total of 103 subjects included in the study. Preoperative seizure frequency was 66% (n=68). There was no association between single or multi-lobe location of tumor and preoperative seizure frequency (n=103, p=0.186). Tumors with mutated IDH1 had a higher rate of preoperative seizure at presentation (74%, n=62 vs 49%, n=37, p=0.007). Seizure freedom at 1 year was increased by gross total resection compared to subtotal resection or biopsy (90%, n= 20 vs 67%, n=55, p=0.049). CONCLUSION: Presence of an IDH1 mutation, but not tumor location, is associated with higher risk of pre-operative seizure in low and intermediate grade glioma. Extent of surgical resection may influence seizure control at 1 year in patients with low and intermediate grade glioma.