Electrocorticographic discharge patterns in glioneuronal tumors and focal cortical dysplasia

Purpose: To determine whether highly epileptiform electrocorticographical discharge patterns occur in patients with glioneuronal tumors (GNTs) and focal cortical dysplasia (FCD) and whether specific histopathological features are related to such patterns. Methods: The series consists of operated patients with pharmacoresistant epilepsy because of FCD or GNT between 1992 and 2003. Electrocorticography was reviewed for presence of continuous spiking, bursts, recruiting discharges, or sporadic spikes. Surgical specimens were reviewed for the presence of balloon cells, (coexisting) cortical dysplasia, and relative frequencies of neurons, glia, and microglia. Results: Continuous spiking was seen in 55% versus 12% of patients with FCD and GNT, respectively (p = 0.005). Bursts and recruiting discharges were seen in a similar proportion of patients with FCD or GNT. Ninety-one percent of patients with continuous spiking showed (coexisting) cortical dysplasia in contrast to 42% of patients without this pattern (p = 0.004). The presence of balloon cells and glia or microglia content were not associated with discharge patterns. Conclusion: Continuous spiking, bursts, and recruiting discharges occur in patients with FCD and GNT. Continuous spiking was seen significantly more often in patients with FCD. When continuous spiking is found with GNT, it is likely to be associated with dysplastic regions with a high neuronal density.