Incidence of epilepsy as a symptom of brain tumor

Tumors that cause chronic intractable epilepsy are usually low-grade benign gliomas. Whether epilepsy is a specific property of the tumor or the brain's reaction to the tumor remains to be explored. Benign gliomas can masquerade as static cicatricial lesions and may not come to the surgeon's attention for long periods of time due to the misdiagnosis. Low-grade gliomas account for 60–90% of the tumors in most series.

Epilepsy is frequently the only presenting symptom of a tumor, and in the past, the diagnosis was frequently missed due to poor imaging or a lack of imaging. Advances in cerebral imaging have made early diagnosis more likely to be achieved today. In several surgical series, the incidence of tumors associated with epilepsy ranged between 10% and 15%. In a study from the MNI, Rasmussen reported 184 patients operated on between 1929 and 1971 with chronic epilepsy secondary to slow-growing gliomas. It is interesting to note in this study that prior to the era of computed tomography, 10% of the tumors were not suspected until disclosed at surgery. In another MNI series, 20% of the patients operated on for focal cerebral seizures were found to have a space-occupying lesion (a tumor in the majority of cases) with a small number of non-neoplastic vascular lesions.