Neurosurgery resident University of Chicago Chicago, Illinois
Rationale: Stereotactic laser amygdalohippocampotomy (SLAH) has emerged as a minimally invasive alternative to selective amygdalohippocampectomy and anterior temporal lobectomy in the treatment of mesial temporal lobe epilepsy (MTLE). The parahippocampal gyrus (PHG) and its subregions are known to be involved in seizure generation and propagation in MTLE. Methods: Seizure outcomes and pre- and postoperative imaging were retrospectively reviewed in patients with MTLE who underwent SLAH at a single institution. Mesial temporal subregions were manually segmented on preoperative MRI, and the contrast-enhancing ablation volume was segmented on immediate post-ablation MRI. Pre- and postoperative MRIs were co-registered to assess anatomic ablation. Postoperative MRI and ablation volumes were also spatially normalized, enabling assessment of seizure outcome with heat maps. Results: Twenty-eight patients with MTLE underwent SLAH; 15 had mesial temporal sclerosis (MTS). The rate of Engel I outcome at one year after SLAH was 42% overall, 60% in patients with MTS, and 18% in patients without MTS. Among six patients with persistent seizures who underwent a second SLAH, 50% had Engel I outcome at one year after reoperation. Percent of PHG ablated was higher in patients with Engel I outcome (39% vs. 24%, p=0.04). Subregion analysis revealed that extent of ablation in the parahippocampal cortex (34% vs. 19%, p=0.04) and angular bundle (62% vs. 41%, p=0.03) was positively associated with Engel I outcome. Degree of amygdalohippocampal complex (AHC) ablated was not associated with seizure outcome (p=0.26). Repeat ablation procedures primarily targeted residual amygdala and hippocampal head. Conclusions: Though AHC is the described target of SLAH, seizure outcome in this cohort was associated with degree of ablation in PHG but not AHC. Complete coverage of both AHC and PHG is technically challenging, and more work is needed to optimize seizure outcome after SLAH. Funding: Please list any funding that was received in support of this abstract.: No funding was received in support of this abstract.