Continuous Intraoperative Monitoring of Temporal Lobe Epilepsy Surgery

Abstract

Background/Aims: The monitoring of interictal epileptiform discharge rates (IEDRs) all along anterior temporal lobe resections (ATLRs) has never been reported. Here the effect of ATLR on continuous IEDR monitoring is described. Methods: IEDRs computed automatically during entire interventions were recorded in 34 patients (38.2%, 13/34 depth; 61.8%, 21/34 scalp electrodes only). Monitorings were invalidated when burst suppression occurred or if initial IEDRs were <5. Results: Monitoring was successful for 69.2% (9/13) of the patients with depth recordings and for 4.8% (1/21) of the patients with scalp recordings. Burst suppressions precluded it in 30.8% (4/13) of the depth and in 57.1% (12/21) of the scalp recordings. Initial IEDRs were <5 for 38.1% (8/21) of the scalp recordings. Significant IEDR decreases were observed in 8/10 patients with successful monitoring. These decreases started with resection of the superior temporal gyrus. IEDRs decreased further with amygdalohippocampectomy in 3/5 patients. At the 12-month follow-up, all patients with IEDR decreases remained seizure free; both patients without did not. Conclusion: IEDR monitoring was possible with depth, but not with scalp electrodes. IEDR decreases started with resection of the superior temporal gyrus. A larger patient cohort is necessary to confirm the high predictive values of IEDR monitoring that could become a tool for surgery customization.

The role of the piriform cortex in temporal lobe epilepsy: A current literature review

“…Several studies that utilized EEG-fMRI to study brain activity in patients with TLE consistently observed abnormal activity in an area corresponding with the PC ( 12 , 78 – 81 ). Additionally, various studies have reported excellent rates of seizure freedom following surgical resection of the PC ( 5 , 8 , 83 ). Laser interstitial thermal therapy is an alternative therapeutic option that has demonstrated good efficacy in the treatment of patients with medically refractory TLE ( 84 – 86 ); however, future studies should aim to define specific inclusion parameters for the PC within the distribution of LITT ablation.…”

“…Tyrand et al found that patients with treatment resistant TLE had significant decreases in interictal epileptic discharge rates (IEDR) following anterior temporal lobe resection, specifically with resection of the superior temporal gyrus. Additionally, 100% of patients who underwent concomitant mesial resection remained seizure free at 12-month follow up ( 83 ); such findings strongly advocate for inclusion of both anterior and mesial temporal lobe structures in the parameters for surgical management of TLE patients.…”

Second surgery after vertical paramedian hemispherotomy for epilepsy recurrence

“…Neuronavigation must be used in a standard fashion for the first surgery and especially for the second surgery as the neuroanatomical landmarks may be greatly distorted. Intraoperative scalp EEG on the contralateral hemisphere is used by some teams to detect interictal spikes [ 1 , 24 , 25 ]. A large prospective observational study published in 2019 showed similar efficacy of endoscopic hemispherotomy compared with open hemispherotomy, with lower levels of blood loss and shorter postoperative hospital stay [ 26 ].…”

High frequency oscillations in relation to interictal spikes in predicting postsurgical seizure freedom

“…More recent contributions have highlighted the importance of delineating the spike onset and propagation path 30 , 31 and that the resection of the source of spike propagation is associated with good outcome 32 . During real time intraoperative monitoring of spikes in anterior temporal lobe resections, a gradual decrease of spikes was reported following superior temporal gyrus resection with continued decrease following en bloc removal of the lateral temporal pole 7 . Moreover, this immediate decrease in spikes was observed in ipsilateral and contralateral destinations of spike propagation from the resected epileptic foci.…”

“…Epileptiform potentials have served as the main interictal biomarker of reference for the EZ during preoperative assessment 6 . Intraoperative interictal spike frequency has been shown to drastically decrease in real time following the resection of epileptic foci 7 . Although these epileptic spikes confer a high sensitivity for identification of the true EZ, they are limited by low specificity.…”