Epilepsy in diffuse low-grade gliomas

Abstract

Epileptic seizures occur in the majority of patients with diffuse low-grade glioma (DLGG) as initial symptoms leading to tumor diagnosis. The temporal relationship between seizures and diagnosis in DLGG is, however, not always easily defined; minor focal seizures may go unnoticed for many years, seizures may occur first after radiological diagnosis in previously asymptomatic patients, and, in rare cases, seizures can precede the diagnosis of brain tumor. The risk of developing tumor-related seizures is inversely correlated with the growth rate of the tumor, being highest for patients with slowly growing tumors. The specific location of the tumor and its proximity to the cortex are other important factors affecting seizure risk in patients with DLGG. About half of all patients with DLGG continue to have seizures before operation, in spite of adequate antiepileptic drug treatment. Poor seizure control has a strong negative impact on the health-related quality of life in this patient group. Improved seizure control in patients with medically refractory epilepsy can be achieved by tumor resection including removal of seizure foci, either as single treatment or in combination with radiotherapy and chemotherapy. When studying the relationship between seizure control and clinical outcome of DLGG, the natural evolution of these tumors has to be considered. The presence of seizures as initial and exclusive symptom at diagnosis is a strong favorable prognostic factor. There is some evidence that preoperative seizure freedom in DLGG is an additional prognostic factor for longer survival. Recurrent seizures after an initial seizure-free period or late-onset seizures are frequently associated with malignant progression, but the exact temporal relationship between seizures and tumor progression in DLGG remains unclear.