The Utility of NIOM During LITT for Refractory MTLE

Overview

Mesial temporal lobe epilepsy (MTLE) is the most common cause of medication-resistant epilepsy in adults, and MRI-guided laser interstitial thermal therapy is a new approach to its surgical management; however, while LITT demonstrates fewer complications than traditional surgical techniques, it generates lower rates of seizure freedom. During traditional temporal lobectomy for MTLE, neurophysiologic intraoperative monitoring (NIOM) can be used to better identify epileptogenic tissue and guide resection. Our study proposes to investigate the utility of NIOM during LITT for MTLE. Subjects will be drawn from refractory mesial temporal lobe epilepsy patients determined to be candidates for LITT. During their LITT surgery, in addition to the placement of the stereotactic LITT probe, subjects will receive a second smaller stereotactic electrode for intraoperative monitoring of epileptic discharges before and after surgery. After surgery, at regularly scheduled follow-ups, patients will receive the Quality of Life in Epilepsy questionnaire (QOLIE-31-P), in addition to standard post-operative care. Endpoints will be surgical complications, fractional decrement in epileptiform discharges from pre- to post-ablation recordings, and surgical outcome at 6 months and one year. Analysis of severe complications will be expressed as a simple complication rate, for overall complications, severe complications, and hemorrhagic complications in specific. The relationship between fractional discharge decrement and outcome will be assessed by regression analysis. Risks of the study will stem from the placement of the stereotactic electrode for intraoperative monitoring, which represents a small incremental risk beyond typical LITT for MTLE.

Mesial temporal lobe epilepsy (MTLE) is the most common cause of medication-resistant epilepsy in adults. The standard treatment for refractory MTLE is surgical resection by craniotomy. Stereotactic laser interstitial thermal therapy (LITT) is a new surgical technique being used to treat MTLE. Under MRI-guidance, a laser probe is inserted into the seizure focus and heat is used to destroy the tissue. Compared to temporal lobectomy, LITT results in shorter hospital stays, low complication rates, and possibly less cognitive decline; however, seizure freedom rates are potentially lower. During temporal lobectomy, neurophysiologic intraoperative monitoring (NIOM) can be used to better identify epileptogenic tissue and guide resection. This tool has been unavailable during LITT procedures. Recently, the investigators demonstrated in two cases that NIOM with a depth electrode is technically feasible during LITT and can identify epileptiform activity intra-operatively. This is a prospective trial of NIOM during LITT for mesial temporal lobe epilepsy. The investigators will assess the safety of performing NIOM during LITT and whether data from NIOM (frequency and characteristics of epileptiform discharges recorded before and after ablation) are associated with seizure outcomes. If there is an association, NIOM could be used for prognostication and could potentially even be used to guide surgery. Hypotheses: 1. NIOM performed by MRI-guided stereotactic depth electrode placed in the parahippocampal gyrus adjacent to the LITT catheter is safe, as compared to institutional LITT controls without NIOM and published LITT complication rates. 2. Greater magnitude fractional decrements in discharge frequency from pre-ablation to post-ablation recordings will be significantly associated with better seizure outcomes, as measured by International League Against Epilepsy (ILAE) surgical outcome scores. Objectives: The primary project goals are to assess if NIOM by parahippocampal depth electrode is safe during LITT of MTLE and to assess if the fractional decrement of interictal discharges (ID) on NIOM can be significantly correlated with outcome. The study will be powered to address these questions a priori. Post hoc analyses consisting of a multivariate analysis of other patient demographic data, NIOM findings, operative parameters, quality of life scores, and neuropsychiatric outcomes will also be assessed.