The oxymoron of image-guided resection in 3 T MRI-negative extratemporal epilepsy: Technique and postoperative...

We share our experience with extratemporal MRI-negative epilepsies that received "image-guided" resection with the use of neuronavigation after invasive presurgical video-EEG monitoring. We describe and discuss our technique of image generation, navigation system registration, and surgical resection. In addition, we evaluate seizure outcome with respect to the preoperatively planned versus achieved resection.

Seven patients with 3 T MRI-negative extratemporal epilepsy received navigation-guided resective surgery. The resection plan was based on electrophysiological data from intracranial EEG recordings. For each case a resection segment was created in the neuronavigation device in a systematic manner. We compared the preoperatively planned segment to the achieved resection and looked for correlation with postoperative seizure outcome according to Engel classification, at last follow-up (mean 2.4 years, range 1-4 years).

Mean volume of planned resections was 23.8 ± 15.3 cm³ and of achieved resections 17 ± 10.4 cm³. There was complete overlap with planned resection in 4 patients and partial overlap in 3. Postoperative seizure outcome was class I in 4 patients (57%), IIIA in 1 patient and IVB in 2 patients. Three patients reached seizure-freedom (Engel IA). Volume of planned resection, volume difference of planned versus achieved resection and level of overlap (complete versus partial) did not significantly correlate to seizure outcome.

The use of neuronavigation for planning and executing a tailored resection in MRI-negative extratemporal epilepsy is elaborate but can be an effective procedure.