Do reactive post-resection "injury" spikes exist?

Purpose: New post-resection spikes on electrocorticography (ECoG) after les ionectomy in patients with seizures may represent residual epileptogenic ti ssue or presumed reactive injury spikes. We investigated the existence of p ostresection injury spikes by eliminating the possibility of residual epile ptogenic tissue. Methods: Preresection and post-resection ECoG was performed on seven patien ts with an intra-axial neocortical tumor (glioblastoma multiforme or metast asis) 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 patient s had preresection spikes with an average rate of 68 spikes/min that disapp eared after surgery. Two different patients had new post-resection spikes, with an average firing rate of 4 spikes/min, despite normal preresection EC oG. 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 seizu res.