UTILITY OF ACUTE INTRAOPERATIVE ELECTROCORTICOGRAPHY IN PREDICTING INTRAOPERATIVE SEIZURES: A PEDIATRIC STUDY

Objectives: Acute Intraoperative Electrocorticography (ECOG) is used during functional cortical mapping to detect epileptiform afterdischarges (EADs). EADs serve as a warning that convulsive threshold is being reached during functional mapping with cortical stimulation. This report presents the data on the utility of ECOG in predicting Intraoperative seizures (IOS), in a cohort of pediatric patients.

Methods: Thirty three patients (age 6 years to 18 years) underwent direct intraoperative cortical motor and language mapping during craniotomies, utilizing somatosensory evoked potentials (SEPs), intracortical stimulation (ECS) and ECOG. Ninteen patients had history of preoperative seizures (POS) and were taking anticonvulsants. SEPs and ECOG recordings were made using an 8 channel Viking IV intraoperative monitoring apparatus. A referential montage was used to record ECOG. Direct cortical stimulation was performed with Ojemann bipolar stimulator (1 second trains of 1msec pulses at 60Hz and 4–20 mA peak to peak amplitude).

Results: Eighteen patiens had baseline epileptiform potentials (BEPs; spikes, and sharp waves). Of these, 12 patients had intraoperative seizures. Of the 15 patients without BEPs, 12 patients had no IOS (Chi-square p<0.004). After ECS epileptiform afterdischarges (EAD) occurred in 13 patients, of these 9 patients had IOS. Of the 20 patients without EADs, 16 had no IOS (Chi-square p<0.007). After ECS electrographic or clinical IOS occurred in 14 patients. Of these 6 patients had POS. Of the 19 patients without POS, 9 patients had no IOS (Chi-square p=0.7).

Conclusion: Presence of Baseline epileptiform potentials (BEPs) and epileptiform afterdischarges (EADs) are strong predictors of intraoperative seizures with intracortical stimulation (ECS) in the pediatric population.