Purpose: New post-resection spikes on electrocorticography (ECoG) after lesionectomy in patients with seizures may represent residual epileptogenic tissue or presumed reactive injury spikes. We investigated the existence of post-resection injury spikes by eliminating the possibility of residual epileptogenic tissue.
Methods: Preresection and post-resection ECoG was performed on seven patients with an intra-axial neocortical tumor (glioblastoma multiforme or metastasis) and no history of seizures. All tumors were gross-totally resected.
Results: The mean age of the patients was 59 years. The tumor location was frontal in four patients, parietal in two, and temporal in one. Two patients had preresection spikes with an average rate of 68 spikes/min that disappeared after surgery. Two different patients had new post-resection spikes, with an average firing rate of 4 spikes/min, despite normal preresection ECoG. In one of these patients, the new spikes were superimposed over a burst suppression pattern. Neither patient developed seizures after surgery.
Conclusions: Surgical irritation of the neocortex is sufficient to produce reactive post-resection epileptogenic discharges surrounding an intra-axial neocortical tumor even in the absence of preoperative seizures and spikes. Injury spikes fire at a slow rate and are not predictive of clinical seizures.