Is Edema a Matter of Concern After Laser Ablation of Epileptogenic Focus?

Abstract

A stereotactically placed laser fiber can deliver thermal energy to an epileptogenic focus in the brain. This procedure is done under intraoperative (thermography) magnetic resonance imaging (MRI) guidance. Thermoablation can lead to edema in the surrounding area and can cause a secondary insult. In this report of 3 cases, we have quantified the edema produced after laser ablation by sequential MRI in the immediate postoperative period. Three patients with intractable epilepsy underwent a detailed neurologic and neuroradiologic workup to localize the site of epileptogenic foci. Two of the patients had mesial temporal lobe sclerosis, and the other patient had hypothalamic hamartoma. A laser fiber was placed stereotactically in the epileptogenic zone, and MRI-guided thermoablation was done. Postoperatively, T1-weighted and fluid-attenuated inversion recovery (FLAIR)-based volumetric MRI sequences were performed on postoperative days 1, 3, and 5 to quantify the edema. I-Plan software was used for volumetric analysis. Targeted volumes were 0.22, 4.2, and 3.5 mL, and lesions were 0.3, 6.5, and 6 mL, respectively. FLAIR hyperintensity was 2.3, 11.8, and 8.4 mL on the first postoperative day and 1.5, 12.6, and 6.3 mL on postoperative day 8. All patients remained seizure-free during the postoperative period. No complications were observed. Laser ablation of epileptic focus is safe. FLAIR hyperintensity in the postoperative period is 3-5 times the targeted volume. However, no significant increase occurs during the first 8 days, and thus steroids can be stopped within 5 days of surgery.