Tracking a changing paradigm and the modern face of epilepsy surgery: A comprehensive and critical review on the hunt for the optimal extent of resection in mesial temporal lobe epilepsy

Surgical management of medically intractable epilepsy was historically based on the premise of excising the presumed substrate of disease, that is, the epileptogenic zone. There was early interest in establishing the extent of resection of the temporal lobe that optimized postoperative reduction in seizure burden while preserving neurocognitive function. Studies approaching this question used varied methods of defining and measuring extent, complicating the task of distilling evidence-based recommendations for surgical practice. A palpable shift in the paradigm of surgical epilepsy has gained traction and greatly altered not only the kind of studies being undertaken but the focus of inquiry itself. Key to this paradigm shift has been the increasingly well-held notion that epilepsy, far from being a disease of a single problem focus, is rather a disease of a problem network. Where a former generation of investigators labored to find an optimal extent of resection, concentrating on magnetic resonance imaging-visible lesions and on standardization of the extent of resection (ie, standard temporal lobectomy), the modern strategy is more concerned with understanding network activation and its concordance with presurgical clinical and electrophysiological features and the organization of epileptic activity over time. The vital lessons of the early literature investigating optimal extent of resection, however, remain informative to the field, and it is worthwhile to contextualize them within the modern network-focused paradigm. In this comprehensive review of the literature, we aim to recapitulate the major findings of the optimal extent of resection literature (focusing on both seizure control and neuropsychological outcomes) and distill wherever possible the consensus findings that may guide surgical approach to epileptic disease of the temporal lobe. We also review the particular implications of modern laser ablation techniques on the question of optimal extent of resection in temporal lobe epilepsy, and contextualize them as a marker of a shifting paradigm.