From the epilepsy registry at KFSH&RC, 100 patients who underwent surgery for tumor-related epilepsy were included in this study. Our finding is consistent with other reports in the literature, were male patients found to be at a higher risk of developing brain tumors and have poor response to therapy than female patients.[25, 29-33]
Varying associations between different brain tumor types and epilepsy have been reported. Most studies showed gangliogliomas to be the most common tumor type associated with epilepsy, followed by DNET, oligodendrogliomas, and astrocytomas.[29, 34-36] These findings support our results, that is, most of our patients had low-grade G/GNT (93.0%), most of which were gangliogliomas (40%) followed by DNET (29%). Furthermore, Babini et al. reported that gangliogliomas (66.7% vs. 40%)[37] were the most frequent tumors among their patients; however, their sample size was smaller (30 cases) than that of our study. Contrary to our findings, Kahlenberg et al. reported that mixed oligo-astrocytomas were the most prevalent tumors followed by astrocytomas of grade II and oligodendrogliomas of grade II.[25] Incidence of high-grade gliomas was lower (5%) in our study than in a study by Michelucci et al. in Italy (77.0%), which can be attributed to a significantly high prevalence of high-grade gliomas in that area.[15]
Seizures and their management have a great impact on the quality of life of patients with brain tumors and weighs heavily on public health expenses . Epilepsy surgery, in many recent studies, was considered to relieve tumor-related epilepsy and achieve favorable outcome.[15, 38, 39] However, tumor related epilepsy in some cases is drug resistant by nature and it may persist even after resecting the primary focus.[25, 40] All of our patients underwent well-planned epilepsy surgery, which is defined as the resection of the tumor and peritumoral tissues.[23] Consequently, our patients showed varying degrees of improvement during the first year post surgery depending on the type of brain tumor (low-grade G/GNT vs. high-grade gliomas- a difference not statistically significant, P = 0.864). It was reported in the some studies that, postoperative seizure outcome was independent of underlying pathology, although there was a trend in favor of better results with low‐grade tumors, for example, patients with low-grade tumors, which were the most common type of tumors in our study (93 cases), showed favorable outcome during the first-year post epilepsy surgery with approximately 71% seizure freedom (class 1 and 2). Michelucci et al. reported findings that were similar to those of our study, that is, better outcomes were observed in patients with low-grade gliomas (76%).[15] On the contrary, Kahlenberg et al. showed that about half of their patients (30 out of 54; 55.6%) with brain tumor-related epilepsy showed a good outcome (seizure-free period > 12 months at the last follow-up) post epilepsy surgery.[25] Their proportions were lower than those observed in our study (55.6% vs. 71%).
In our opinion, the ILAE classification of the outcome of epilepsy surgery should be simplified, with only 4 categories rather than 6, to facilitate its application. Hence, whenever patients have four or more seizures (outcome 4, 5, and 6), they should be gathered under one category (to be called category 4). The currently used ILAE Commission on Neurosurgery in 2001,[28] still has some elements that make the use of category 4, 5, and 6 difficult to be measured and implemented in daily practice, particularly when include parameters related to quality of life. This suggested new modified classification could be easily implemented by other researchers in their ongoing studies.
Furthermore, few patients in our study had high-grade gliomas (5) and meningiomas (2). These patients showed favorable outcome during the first-year post epilepsy surgery (60% and 100%, respectively). Michelucci et al. reported similar results; 58% of their patients with high-grade glioma who became seizure free after tumor removal.[15]
Pediatric and adult groups showed no significant differences regarding seizure outcome during the first-year post surgery (P = 0.559), and thus, we cannot claim that surgery is more beneficial in pediatric patients. These findings were similar to those of other studies.[23]
Our study has three main limitations: Firstly, the sample size was small and included only 5 patients with high-grade gliomas and 2 patients with meningothelial tumors (2 cases); this makes comparison with low-grade G/GNT insufficient although our sample size (100 cases) is comparable to that of other studies. Secondly, this series of tumor-related epilepsy does not represent the population with epilepsy in Saudi Arabia, because not all patients with tumor-related epilepsy are eligible to be admitted to our institution, and thus, they are treated elsewhere. Finally, this is a retrospective study and it is associated with the possibility of bias occurring during data collection. Despite the above-mentioned limitations, we hope that our study provides valuable information on one of the most debatable topics in epilepsy surgery in the country and in the Middle East.