Piriform Cortex Ablation Volume Is Associated With Seizure Outcome in Mesial Temporal Lobe Epilepsy

Abstract

BACKGROUND: Growing evidence suggests that piriform cortex resection during anterior temporal lobectomy is important for achieving good seizure outcome in mesial temporal lobe epilepsy (mTLE). However, the relationship between seizure outcome and piriform cortex ablation during MR-guided laser interstitial thermal therapy (MRgLITT) remains unclear. OBJECTIVE: To determine whether ablation of piriform cortex was associated with seizure outcome in patients with mTLE undergoing MRgLITT. METHODS: We performed preablation and postablation volumetric analyses of hippocampus, amygdala, piriform cortex, and ablation volumes in patients with mTLE who underwent MRgLITT at our institution from 2014 to 2019. RESULTS: Thirty nine patients with mTLE were analyzed. In univariate logistic regression, percent piriform cortex ablation was associated with International League Against Epilepsy (ILAE) class 1 at 6 months (odds ratio [OR] 1.051, 95% CI [1.001-1.117], P = .045), whereas ablation volume, percent amygdala ablation, and percent hippocampus ablation were not (P > .05). At 1 year, ablation volume was associated with ILAE class 1 (OR 1.608, 95% CI [1.071-2.571], P = .021) while percent piriform cortex ablation became a trend (OR 1.050, 95% CI [0.994-1.109], P = .054), and both percent hippocampus ablation and percent amygdala ablation were not significantly associated with ILAE class 1 (P > .05). In multivariable logistic regression, only percent piriform cortex ablation was a significant predictor of seizure freedom at 6 months (OR 1.085,], P = .019) and at 1 year (OR 1.074, 95% CI [1.003-1.178], P = .041). CONCLUSION: Piriform cortex ablation volume is associated with seizure outcome in patients with mTLE undergoing MRgLITT. The piriform cortex should be considered a high yield ablation target to achieve good seizure outcome.

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

“…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.…”

“…Hwang et al conducted a pre- and post-ablation volumetric analysis on patients with mTLE who underwent magnetic resonance guided LITT of the hippocampus, amygdala, and piriform cortex to determine the relationship between ablation volume and seizure outcomes. Following multivariate logistic regression analysis, they determined that in patients with mTLE, percent PC ablation volume was a significant predictor of seizure freedom at both 6 months (95% CI = 1.012–1.193; p = 0.019) and 1 year (95% CI = 1.003–1.178; p = 0.041) ( 86 ). Although these studies suggest that the PC may be an important target to include in ablation volumetric parameters, no studies have explicitly defined such margins.…”

Ablation of apparent diffusion coefficient hyperintensity clusters in mesial temporal lobe epilepsy improves seizure outcomes after laser interstitial thermal therapy

“…Compared to open-resection anterior amygdalohippocampectomy, seizure-freedom rates after LiTT are relatively lower, 8 presumably due to inadequate ablation of extra-amygdalohippocampal regions in LiTT. This is reflected in cases reporting improved seizure outcomes for mTLE after ablation of piriform cortex 51,52 and parahippocampal cortex, 53 as well as after adopting two-laser trajectories to fully ablate mesial temporal lobe structures. 54 Because our ADC-based clustering approach was implemented only within the amygdalohippocampal complex, further investigations are required to fully extend its clinical utility by evaluating the clustering approach on other extra-amygdalohippocampal regions.…”

Quelling the Area Tempesta: Removal of the Piriform Cortex Improves the Outcomes of Surgery for Temporal Lobe Epilepsy

“…Hwang et al performed preablation and postablation volumetric analyses of hippocampus, amygdala, PC, and ablation volumes in 39 patients with mTLE who underwent LITT and found that with multivariable logistic regression only percent PC ablation was a significant predictor of seizure freedom at 6 months (Odds Ratio (OR) 1.085, 95% Confidence Interval (CI) [1.012-1.193], P = .019) and at 1 year (OR 1.074, 95% CI [1.003-1.178], P = .041). 13 In the future, electrical stimulation of the PC could potentially be offered for treatment of epilepsy. 14…”

“…Hwang et al performed preablation and postablation volumetric analyses of hippocampus, amygdala, PC, and ablation volumes in 39 patients with mTLE who underwent LITT and found that with multivariable logistic regression only percent PC ablation was a significant predictor of seizure freedom at 6 months (Odds Ratio (OR) 1.085, 95% Confidence Interval (CI) [1.012-1.193], P ¼ .019) and at 1 year (OR 1.074, 95% CI [1.003-1.178], P ¼ .041). 13 In the future, electrical stimulation of the PC could potentially be offered for treatment of epilepsy. 14 The recently renewed attention on the role of the PC in epilepsy and the technological advances allowing for successful removal, ablation, and potential neuromodulation may be important in our goal of quelling the area tempesta and creating "la quiete dopo la tempesta" (quiet after the storm, ie, seizure freedom).…”