Stereotactic amygdalohippocampotomy for the treatment of medial temporal lobe epilepsy

Purpose: This study was carried out to assess the safety and efficacy of st ereotactic ablation of the amygdala and hippocampus for the treatment of me dial temporal lobe epilepsy. Methods: Twenty-two stereotactic amygdalohippocampotomies were performed in 19 patients with unilateral temporal lobe seizures by using magnetic reson ance imaging (MRI) localization for target planning and radiofrequency tech niques for lesion production. Seizure frequency was assessed at 3-monthly f ollow-up visits. Two lesion groups were defined. In group I, four to 11 (me an, 6.4) discrete lesions were made, encompassing the amygdala and anterior 13-21 mm (mean, 16.8 mm) of the hippocampus. In group II, a large number o f confluent lesions were made (mean, 26.0: range, 12-54) encompassing the a mygdala and anterior 15-34 mm (mean, 21.5 mm) of the hippocampus. MRI scann ing was carried out 24 h and 6-9 months after surgery. Results: In five group I patients, one (20%) experienced a favorable seizur e outcome. Of 15 group II patients, one of whom had previously undergone li mited lesioning and was also analyzed as part of group I, nine (60%) experi enced a favorable seizure outcome, with two seizure free. MRI scans at 6- t o 9-months' follow-up disclosed discrete areas of atrophy in the amygdala a nd hippocampus, interspersed with preserved brain in the group I patients. More uniform and complete destruction of amygdala and hippocampus was evide nt in group II patients. All lesions were confined to thr amygdala and hipp ocampus, sparing the parahippocampal gyrus (PHG). Conclusions: The extensive amygdalohippocampal ablation in group II patient s improved seizure outcome compared with more limited ablation in group I, but these results were not so good as those from temporal lobectomy in a si milar patient group. When considered together with the results of selective amygdalohippocampectomy, and temporal resections that spare hippocampus or amygdala tall producing similar outcomes, and all involving resection of t he entorhinal cortex), this study suggests a pivotal role of the entorhinal cortex in temporal epileptogenesis,