Abstracts

Rationale: Laser interstitial thermal therapy / stereotactic laser ablation (SLA) has gained acceptance as a minimally-invasive alternative to open mesial temporal lobe epilepsy surgery. The efficacy of SLA in extra-temporal lobe epilepsy (ETLE), however, has yet to be evaluated. Here we report the largest series of SLA for ETLE to date. Methods: Retrospective chart review was performed for all patients that underwent SLA outside the anterior and medial temporal lobe for the surgical treatment of epilepsy between 2012 and 2019. Targets were determined by presence of concordant lesion on MRI or by stereoelectroencephalography (SEEG), as well as other clinical data. Stereotactic catheter insertions were performed using a headframe (CRW, Integra), robot (ROSA, Zimmer-Biomet), or by direct MRI-guidance (ClearPoint, MRI Interventions). Ablations were performed using the Visualase laser thermal therapy system (Medtronic) with real-time MR thermal imaging. Contrast-enhanced T1 MRI confirmed extent of ablations and volumes were post-processed using ITK-SNAP (itksnap.org). Engel classifications are reported at 12 m follow-up. Demographics are reported as mean ± standard deviation. Results: 37 patients (24 female) underwent SLA for ETLE at age 36.4±12.4 y following epilepsy duration of 21.5±12.4 y. All patients had focal semiology: 36 with dyscognitive seizures, 1 with focal motor seizures, and 4 patients with multiple seizure types for which targeting a particular seizure type was considered palliative. Ablation locations were classified as frontal (17), parietal (5), occipital (2), cingulate (6), insula (5), or hypothalamus (2). Mean ablation volume was 10.4±10.3cc (range 1.0-25.0cc). 28 patients had structural lesions (prior failed open epilepsy surgery without other primary pathology, n=6; cavernous malformation, n=6; focal cortical dysplasia [FCD], n=5; tuberous sclerosis [TS], n=3; epileptogenic tumor, n=2; developmental/migration abnormalities, n=2; post-traumatic, n=1; multiple sclerosis, n=1; mucocele, n=1, hypothalamic hamartoma, n=1). Of 31/37 patients with at least 1-y follow-up, 13 (42%) were Engel I, 4 (13%) were Engel II, 8 (26%) were Engel III, 6 (19%) were Engel IV. When palliative (n=4) and non-compliant (n=1) patients were excluded, then of 26 patients, 12 (46.2%) were Engel I, 4 (15.4%) were Engel II, 6 (23%) were Engel III and 4 (15.4%) were Engel IV. Adverse events included transient weakness (3 patients with an expected supplementary motor area syndrome that completely recovered) and one patient who had complete seizure control but experienced a surgical abscess that required stereotactic drainage and intravenous antibiotics. We observed 3 deaths remote to SLA: 1 patient with multiple seizure types underwent successful SLA of a hypothalamic glioma for focal status epilepticus, but continued to have other seizures and suffered sudden unexplained death (SUDEP) 15 m later. Another patient failed adequate seizure control following SEEG-guided SLA, underwent a second SEEG 7 m later, but suffered SUDEP awaiting additional epilepsy surgery. A third patient who failed prior open surgery for FCD underwent SEEG-guided SLA, recurred at 1 y, refused further surgery, and later committed suicide. Conclusions: We report a large consecutive series of SLE for ETLE, in which many patients had already failed open epilepsy surgery or were considered palliative. Nevertheless, 55% of patients had good outcomes (Engel I+II) at 1 y. While there were no procedure related deaths or disabling neurological deficits, observations of SUDEP and suicide highlight the risks of not achieving long-term seizure freedom in ETLE.  Funding: No funding