Predictive value of intraoperative electrocorticograms in resective epilepsy surgery

Abstract

The preresection and postresection intraoperative electrocorticograms of 76 consecutive patients undergoing resective surgery for intractable epilepsy were analyzed to see if location, configuration, and discharge rate of epileptiform activity correlated with type and location of pathology of the resected specimens and outcome in regard to seizure control. The location of the predominant spike focus did not correlate with either type of location of pathology or with seizure outcome from temporal lobe surgery (n = 58). The presence of spontaneous or activated spikes outside the resected area did not correlate with outcome from any surgery type. Positive spikes recorded from the amygdala and anterior hippocampus (n = 37) were not associated with type or location of pathology, but bursts of fast repetitive spikes on these needle recordings tended to associate with mesiotemporal pathology (p = less than 0.02) and with mesial temporal sclerosis (p = less than 0.04). A preresection spike discharge rate of 1 per 4 minutes or less was associated with a poor outcome in 5 of 6 patients (p = 0.03), whereas a rate of 18 or more per minute was associated with a good outcome in 15 of 18 patients (p less than 0.06). Persistence of 50% or more of the preresection epileptiform activity in the postresection electrocorticogram after temporal lobectomy correlated with poor outcome in 80% (p = less than 0.03), although the absolute amount of epileptiform activity remaining in the postresection electrocorticogram did not correlate with outcome. Further studies are needed to define the role of intraoperative electrocorticograms in resective epilepsy surgery.

Do Reactive Post‐Resection “Injury” Spikes Exist?

“…Most authors agree that low-frequency post-resection spikes, regardless of their cause, are innocuous (1,3,19,35,37,46). Because injury spikes exist in cortex chronically irritated by a mass lesion, we propose that they must also exist in acutely injured cortex that has been chronically irritated by recurrent seizures and must account for some fraction of the spikes recorded on the neocortical margins after standard en bloc resection for temporal lobe epilepsy.…”

“…These reactive spikes correlated with the absence of mesial temporal sclerosis and were attributed to injury of relatively normal tissue. McBride et al (35), however, refuted this claim and showed that hippocampal spikes that resulted from the placement of depth electrodes correlated not with normal pathology but rather with the presence of frequent spiking on subtemporal strips, the placement of which does not injure the cortex.…”

Surgery for focal cortical dysplasia in children using intraoperative mapping

“…Since the diagnosis of FCD was established, electroclinical features will be needed to confirm the relationship between lesion and epilepsy. Clinical features include focal and generalized seizures, and complete resection of the lesion seems to be the most significant fact related to a good postoperative seizure outcome [26,30,32,39]. In children, extratemporal localization of the lesions is the rule, although neocortical temporal lesions may also be found.…”

The Reliability of Intraoperative Electrocorticography in Magnetic Resonance Imaging–Negative Temporal Lobe Epilepsy

“…7 An evaluation of ECoG with a similar number of patients as the present study found no correlations among IED location, pathology, and outcome. 8 However, the authors point out that their highly homogeneous sample with consistent epileptologists and surgeons may have had an advantage over studies with a variety of focal epilepsies 7,8 treated in multicenter consortiums. 7 An important addition to their findings was that most of their patients had ECoG recorded both before and after treatment with intraoperative opioids.…”