Abstracts

Rationale: In patients with refractory mesial temporal lobe epilepsy due to hippocampal sclerosis (MTLE-HS), surgery with anterior temporal lobectomy and amygdalohippocampectomy (ATL-AH) or selective amygdalohippocampectomy (SelAH) has been associated with seizure-freedom in up to 70%. These procedures may not be options for patients with a less favorable risk-benefit ratio due to medical comorbidity or a lower predicted surgical benefit. Recently, MRI-guided stereotaxic laser thermal tissue ablation (Visualase, Inc.) has been FDA-approved and is being applied towards epilepsy surgery. We report our experience with this procedure in two cases of refractory MTLE-HS. Methods: Patient A is a 61 year-old right-handed male with refractory epilepsy from childhood, with monthly clusters of partial complex seizures and annual secondarily generalized convulsions. Routine EEG revealed left fronto-temporal spike-and-wave complexes. Brain MRI revealed left hippocampal sclerosis. Brain PET/CT revealed mild hypometabolism of the left medial temporal region. Video-EEG revealed left temporal interictal spikes and ictal onsets. Wada testing revealed right hemispheric language and memory dominance. Because of numerous medical comorbidities, he was offered laser ablation of the left hippocampus. Patient B is a 26 year-old right-handed female with refractory epilepsy since age 6, with monthly clusters of 2-3 partial complex seizures and secondarily generalized convulsions every few months. Routine EEG was unremarkable. Brain MRI revealed right hippocampal sclerosis. Brain PET/CT revealed right posterior temporal hypometabolism. Video-EEG revealed 24 temporal seizures, 21 from the right, 2 from the left, and one non-localized. Wada testing showed left hemispheric language and memory dominance. Because of the lower chance for seizure-freedom, she was offered laser ablation of the right hippocampus. Results: Laser ablation of the hippocampus was achieved with frameless stereotaxy in both cases. Both patients tolerated the procedure well without postoperative neurological deficits and were discharged on postoperative day 1. Patient A had an Engel Class Ib / ILAE Class II (auras only) outcome 7 months later (last followup). Patient B experienced complex partial seizures with her typical right hemispheric semiology on postoperative days 1 and 4. She experienced recurrent seizures with her typical left hemispheric semiology 2 months after the procedure, though the electrographic lateralization of her seizures remains unknown. Conclusions: Laser thermal ablation of the hippocampus is well-tolerated procedure and warrants consideration for patients with MTLE-HS who may have a less favorable risk-benefit profile for craniotomy. Because a smaller extent of the epileptic network is removed, residual auras and acute postoperative seizures resembling the typical pre-operative seizures may be more common. Though the procedure appears to be associated with less morbidity than ATL-AH and SelAH, it remains to be seen whether the seizure outcome is equivalent in MTLE-HS.