Reassessing the impact of intraoperative electrocorticography on postoperative outcome of patients undergoing standard temporal lobectomy for MRI-negative temporal lobe epilepsy

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OBJECTIVE

Almost 30% of the patients with suspected temporal lobe epilepsy (TLE) have normal results on MRI. Success rates for resection of MRI-negative TLE are less favorable, ranging from 36% to 76%. Herein the authors describe the impact of intraoperative electrocorticography (ECoG) augmented by opioid activation and its effect on postoperative seizure outcome.

METHODS

Adult and pediatric patients with medically resistant MRI-negative TLE who underwent standardized ECoG at the time of their elective anterior temporal lobectomy (ATL) with amygdalohippocampectomy between 1990 and 2016 were included in this study. Seizure recurrence comprised the primary outcome of interest and was assessed using Kaplan-Meier and multivariable Cox regression analysis plots based on distribution of interictal epileptiform discharges (IEDs) recorded on scalp electroencephalography, baseline and opioid-induced IEDs on ECoG, and extent of resection.

RESULTS

Of the 1144 ATLs performed at the authors’ institution between 1990 and 2016, 127 (11.1%) patients (81 females) with MRI-negative TLE were eligible for this study. Patients with complete resection of tissue generating IED recorded on intraoperative ECoG were less likely to have seizure recurrence compared to those with incomplete resection on univariate analysis (p < 0.05). No difference was found in seizure recurrence between patients with bilateral independent IEDs and unilateral IEDs (p = 0.15), presence or absence of opioid-induced epileptiform activation (p = 0.61), or completeness of resection of tissue with opioid-induced IEDs on intraoperative ECoG (p = 0.41).

CONCLUSIONS

The authors found that incomplete resection of IED-generating tissue on intraoperative ECoG was associated with an increased chance of seizure recurrence. However, they found that induction of epileptiform activity with intraoperative opioid activation did not provide useful intraoperative data predictive of improving operative results for temporal lobectomy in MRI-negative epilepsy.

ABBREVIATIONS ATL = anterior temporal lobectomy; ECoG = electrocorticography; EEG = electroencephalography; IED = interictal epileptiform discharge; iEEG = intracranial EEG; IFG = inferior frontal gyrus; ITG = inferior temporal gyrus; LITT = laser interstitial thermal therapy; MTS = mesial temporal sclerosis; sdEEG = subdural EEG; sEEG = stereo-EEG; STG = superior temporal gyrus; TLE = temporal lobe epilepsy.

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Article Information

Correspondence Jamie J. Van Gompel: Mayo Clinic, Rochester, MN. vangompel.jamie@mayo.edu.

INCLUDE WHEN CITING Published online February 22, 2019; DOI: 10.3171/2018.11.JNS182124.

Disclosures Dr. Worrell is a patent holder with the Mayo Clinic.

© AANS, except where prohibited by US copyright law.

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    Upper: Schematic of standardized electrode configuration for intraoperative ECoG in patients undergoing ATL. Dashed lines indicate cortical resections at 30 mm (line A), 40 mm (line B), and 50 mm (line C). Lower: Schematics of standard ATL performed in all patients. The extent of lateral neocortical resection for the dominant and nondominant temporal lobe is shown (lower left). The mesial temporal structures, amygdala, hippocampus, and parahippocampus are also resected (lower right). IFS = IFG strip; ITS = ITG strip; STS = STG strip; 1, 2, 3 = locations of 1-contact depth electrodes. Copyright Rosemary Perry. Published with permission. Figure is available in color online only.

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    Graphs showing results of Kaplan-Meier analysis of seizure-free probability. A: Comparison of survival between patients with complete resection on baseline ECoG and those with incomplete resection. B: Comparison of survival between patients with unilateral IEDs on scalp EEG and those with bilateral IEDs on scalp EEG. C: Comparison of survival between patients with and without opioid-induced seizure activation. D: Comparison of survival between patients with complete resection on opioid-induced seizure activation and those with incomplete resection on opioid-induced seizure activation. E: Comparison of survival between patients with and without agreement between opioid-induced seizure activation and baseline ECoG. b/w = between. Figure is available in color online only.

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    Graph showing results of Kaplan-Meier analysis of seizure-free probability. Comparison of survival between patients with left-sided pathology and those with right-sided pathology. Figure is available in color online only.

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    Graph showing results of Kaplan-Meier analysis of seizure-free probability. Comparison of survival between patients with gliosis and those with MTS. Figure is available in color online only.

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    Chart showing results of Cox regression of factors associated with risk of recurrence of seizures after surgery. AIC = Akaike information criterion.

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    The Rochester algorithm for invasive monitoring protocol and resection among patients with TLE. fMRI = functional MRI; MR-g = MR-guided.

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