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Seizures are a common symptom in glioma patients. Approximately 20-40% of adults with primary brain tumors experience one seizure prior to the tumor diagnosis, and another 20-45% will suffer from seizures during the course of the illness [1]. This incidence rate varies depending on the tumor type, the grade of histological malignization and the tumor location. Subsequently, tumors with a dysplastic neuron composition (e.g., dysembrioplastic neuroepithelial tumors and gangliogliomas) have a very high incidence rate -nearly 100%. Slow-growing glial tumors are more frequently associated with epilepsy than high-grade glioma tumors, and intra-axial tumors with cortical involvement are more epileptogenic than extra-axial and deep glial tumors, with insular, frontal and temporal locations more likely to present seizures at presentation or during the course of the disease [2-4]. Specifically, the overall incidence of seizures in glioblastoma multiforme (GBM) patients, without considering the location, has been reported to be between 25-50% at presentation and another 20-30% during the course of the disease, although in large population studies, these figures are restrained to approximately 25% at initiation [2,5-10].
Despite the high frequency of this symptom, retrospective studies have shown suboptimal seizure control in 9-46% of GBM patients, with these treatment-refractory patients presenting with more than one seizure per month [2,6,7,11]. This fact highlights the importance of adequate integration of epilepsy treatment in the complete therapeutic management of GBM patients.
Brain tumor-related seizures are focal in nature, although secondary generalization is not uncommon and may happen quickly. Moreover, the risk of developing status epilepticus is not negligible; patients with brain tumors comprise 4-12% of the total patients emerging with this epileptic complication [10,12,13].
An appropriate approach to the treatment of tumor-related epilepsy becomes important for many reasons such as to decrease the morbidity associated with seizures [14], to reduce the risk of pharmacoresistent epilepsy [15] and to avoid any impairment in the patients'quality of life [16]. Moreover, GBM patients and, in general, brain tumor patients have special considerations, over and above the general non-neoplastic epileptic population, which need to be taken into account in order to not only select the best treatment option for the tumor but also to reduce the therapeutic failures.
Distinctive characteristics of GBM patients with epilepsy
Several specific reasons have been identified that explain the...