Seizure Freedom Despite Piriform Cortex Sparing: Structural Connectivity Remodeling After SEEG-Guided Mesial Temporal RFTC

Abstract

Objective

To investigate whether selective radiofrequency thermocoagulation (RFTC) targeting mesiotemporal structures, while sparing the piriform cortex (PC), can achieve seizure freedom in drug-resistant mesial temporal lobe epilepsy (MTLE), and to assess whether said seizure freedom is associated with an indirect disconnection of the PC within the epileptogenic network.

Methods

A retrospective analysis was performed on 32 patients (mean age 27.81 ± 13.37 years) with drug-resistant MTLE who underwent stereoelectroencephalography (SEEG)-guided RFTC. Volumetric and structural connectivity (SC) analyses were conducted using pre- and postoperative T1-weighted (T1W) and diffusion-weighted imaging (DWI). The regions of interest (ROIs) targeted included the hippocampus, amygdala, rhinal cortex, and parahippocampal cortex, while the PC was spared. Network metrics assessed pre- and postoperative SC changes.

Results

At a mean follow-up of 40.63 ± 16.36 months, 25 patients (78.1%) became seizure free (SF). SF patients had significantly greater ablation volumes in the amygdala (p = 0.026) and rhinal cortex (p = 0.023) compared to non-seizure-free (NSF) patients. SF patients showed significant postoperative reductions in SC across all mesiotemporal ROIs, including the spared PC (p ≤ 0.020). NSF patients exhibited no significant SC changes.

Conclusions

Seizure freedom following SEEG-guided RFTC is associated with widespread disruption of SC in mesiotemporal networks, including the spared PC. These findings support the hypothesis that seizure freedom following the ablation of key mesiotemporal ROIs can induce an indirect disconnection of the PC through its connected nodes, offering a safer therapeutic option for MTLE.