Seizure prognosis of patients with low-grade tumors.

Purpose: Seizures frequently impact the quality of life of patients with low grade tumors. Management is often based on best clinical judgment. We examined factors that correlate with seizure outcome to optimize seizure management.

Methods: Patients with supratentorial low-grade tumors evaluated at a single institution were retrospectively reviewed. Using multiple regression analysis the patient characteristics and treatments were correlated with seizure outcome using Engel's classification.

Results: Of the 73 patients with low grade tumors and median follow up of 3.8 years (range 1-20 years), 54 (74%) patients had a seizure ever and 46 (63%) had at least one seizure before tumor surgery. The only factor significantly associated with pre-surgical seizures was tumor histology. Of the 54 patients with seizures ever, 25 (46.3%) had a class I outcome at last follow up. There was no difference in seizure outcome between grade II gliomas (astrocytoma grade II, oligodendroglioma grade II, mixed oligo-astrocytoma grade II) and other pathologies (pilocytic astrocytoma, ependymomas, DNET, gangliocytoma and ganglioglioma). Once seizures were established seizure prognosis was similar between different pathologies. Chemotherapy (p=0.03) and radiation therapy (p=0.02) had a positive effect on seizure outcome. No other parameter including significant tumor growth during the follow up period predicted seizure outcome. Only three patients developed new-onset seizures after tumor surgery that were non-perioperative. Anticonvulsant medication was tapered in 14 patients with seizures and 10 had no further seizures. Five patients underwent additional epilepsy surgery with a class I outcome in four. Two patients received a vagal nerve stimulator with >50% seizure reduction.

Discussion: Seizures at presentation are the most important factor associated with continued seizures after tumor surgery. Pathology does not influence seizure outcome. Use of long term prophylactic anticonvulsants is unwarranted. Chemotherapy and radiation therapy have a favorable impact on seizure outcome. Additional epilepsy surgery is effective.