Abstracts

Rationale: Small or occult temporal anterior-inferior meningoencephaloceles (MEs), often of the temporal pole, are increasingly recognized on neuroimaging of patients with medication-resistant focal temporal lobe epilepsy. Intracranial recording may help define the extent of seizure networks, and stereoelectroencephalography (SEEG)-guided laser interstitial thermal therapy (LITT) and/or radiofrequency ablation (RFA) may provide completely minimally invasive approaches to both diagnosis and therapy. We report our early experience of 13 patients undergoing thermal ablation for epileptogenic MEs, 12 of whom underwent SEEG first. Methods: We retrospectively reviewed 13 sequential patients with MEs managed with thermal ablation. Preoperative evaluation of patients included ictal video-EEG study, 3T-MRI, interictal PET scan, volumetric CT, neuropsychometry, and multi-disciplinary conference. Imaging and medical records were retrospectively reviewed for electrode/lesion localization, extent of ablation, complications, and seizure control. In general, where SEEG implicated the region of the ME, we performed stereotactic LITT ablation or RFA (along SEEG electrodes) of the anterior-inferior temporal pole, often including the contiguous entorhinal cortex and amygdala (sparing the hippocampus). If SEEG showed simultaneous hippocampal involvement or independent onsets of clinical seizures, the amygdala and hippocampus were also ablated with LITT. Results: Thermal ablation was performed on 13 patients (12 LITT, 1 RFA) with mean age 36.8 (range 22-50) years and mean duration of epilepsy 9.3 years (range 3-38). Patients were predominantly female (n=11), African-American (n=11), and had adult-onset epilepsy (n=11). Mean follow-up was 12 months (range 4-25). One patient preferred to undergo LITT targeting a ME at the temporal pole without preceding SEEG. All 12 SEEG procedures appeared to directly implicate the region of the ME (e.g. temporal pole +/- entorhinal cortex) and 7 of these also implicated the hippocampus. All 12 patients underwent ablation of region of the ME and 6 also underwent ablation of the ipsilateral hippocampus (5 right and 1 left). The 7th did not undergo left hippocampal ablation due to concern for neurocognitive risk. At most recent follow-up after ablation, all 13 patients reported worthwhile improvement in seizure frequency, and 9/13 were free of disabling seizures or had reported a rare seizure from missed medications. These 9 patients with good seizure outcomes included all 6 that had undergone hippocampal ablation. Notably, the one patient whose left hippocampus was implicated but not ablated was not initially seizure free, but has more recently achieved prolonged seizure freedom (>11 months, classified as worthwhile improvement). Complications included one patient with transient partial CN3 and CN5 palsies, and another with persistent partial CN7 palsy (House-Brackmann grade 2). Conclusions: While limited in follow-up, this first series describing SEEG-guided thermal ablation suggests a potentially effective alternative to open surgery for management of epileptogenic temporal lobe MEs. SEEG may be of use in planning the extent of intended laser or radiofrequency ablations, especially with regard to the hippocampus. Care is required to avoid cranial nerve injury when ablating near skull base and cavernous sinus. Maximizing seizure freedom and minimizing neurocognitive risk will require optimization of ablation strategies over larger studies with longer follow-up. Funding: No funding