The insula was described more than two centuries ago, in 1809, by the anatomist Johann Christian Reil. However, the functional anatomy of the insular cortex and the importance of the insula in psychiatric and neurologic pathological conditions remained obscure for a long period after the initial description of Reil. The location and the complex functional organization of the insula explain, for instance, the difficulty researchers and clinicians had in defining its contribution in temporal lobe epilepsy. This introductory chapter reviews the important steps that led to a better understanding of the role of the insula in human focal epilepsy.

Refractory epilepsy from operculoinsular origin is increasingly recognized because of published descriptions of its clinical presentations, more attention in the interpretation of non-invasive focus localization techniques, and the development of invasive electrode implantation schemes to sample that area. Microsurgical techniques of operculo-insular cortical resection have been refined, taking into consideration the complex and deep anatomy and the high vascularity of the perisylvian area. Selective transsylvian and/or subpial transopercular insulectomies are performed, depending on the definition of the extent of cortectomy needed and the functional areas to preserve. Seizure control results after surgery are similar than those in other brain locations. Neurological complications and neuropsychological consequences are acceptable. It is crucial that these highly selected patients be investigated and operated in epilepsy centers dedicated to this complex type of refractory epilepsy, both to optimize the results of seizure control and keep the complication rate as low as possible.