Abstracts

Rationale:
Magnetic resonance thermometry-guided stereotactic laser amygdalohippocampotomy (SLAH) is a minimally invasive surgical approach used to treat drug-resistant epilepsy. Although SLAH results in seizure freedom in over half of patients1, ~40% of patients experience persistent seizures.  Failure of an initial SLAH procedure may be due to 1) technically insufficient ablation including residual medial temporal tissue2 2) extra-medial temporal or extra-temporal epileptogenic foci or 3) multifocal disease.  This retrospective review explores patient outcomes after initial SLAH procedure and the impact of additional procedures on seizure control. 
Method:
Between 2011 and 2019, 108 subjects (51 male, 57 female ages 15-67) underwent SLAH at Emory University and were included in this study.  When deemed appropriate by our multidisciplinary epilepsy team, either with or without intracranial monitoring, SLAH was performed by one of two surgeons (REG and JTW) using the Visualase® system (Medtronic, Inc.) and magnetic resonance thermal imaging.  Demographic information, semiology, imaging data, intracranial monitoring results, subsequent surgical interventions, and seizure outcomes were analyzed.
Results:
Of the 108 subjects studied, 71 patients underwent SLAH with phase I presurgical EEG and imaging data alone, while 37 patients underwent intracranial monitoring (ICM, including foramen ovale, strips/grids, or depth electrodes) prior to SLAH. In total, 52% (57) of patients experienced seizure freedom (Engel class I, including 42 who were skipped to SLAH without initial ICM and 15 who underwent initial ICM prior to SLAH).   Of the remaining 51 patients who continued to have seizures following SLAH, 19 patients underwent a secondary intervention while 32 patients had no further intervention.  In many cases (19/32), the patient’s decision to not pursue an additional intervention was due to significant improvement in the frequency and severity of seizures (Engel IIa-IIIa), despite not being entirely seizure free.  Of the 19 patients undergoing a secondary procedure, nine underwent repeat SLAH of residual medial temporal structures, three underwent anterior temporal lobectomy and five underwent intracranial monitoring.  One patient underwent corpus callosotomy (CC, mesial temporal sclerosis in the setting of a genetic generalized epilepsy) and one had a vagal nerve stimulator placed.  Following a secondary procedure, an additional 9/19 (47%) of patients became seizure free (repeat SLAH- 4, ATL- 2, SEEG- 2, CC- 1).  Of the patients undergoing intracranial monitoring following SLAH failure, onsets were determined to be ipsilateral in 4 patients (1 temporal pole, 1 parahippocampal gyrus, 1 hippocampal remnant, 1 posterior cingulate) and contralateral medial temporal in one patient.  Eventually, 3/5 underwent stereotactic laser ablation of the identified seizure onset zone (Engel Ia, IIb, IIa), 1 underwent ATL (Engel Ia) and 1 deferred further surgery (no change). 
Conclusion:
This study demonstrates that, while SLAH is often effective in achieving seizure freedom in many patients with medial temporal lobe epilepsy, patients with continued seizures may benefit from a secondary intervention.  Intracranial monitoring can be helpful in localizing ictal onset zones outside of the medial temporal structures when seizures persist following SLAH.
Funding:
:None