We report, in a cohort of 16 patients presenting with epilepsy arising from the insulo-opercular cortex solely, the outcome following SEEG-guided radiofrequency thermocoagulation (RFTC). Good outcomes (Engel class 1) are reported in 88% at 2 months and 67% at 18 months among the 9 of the 16 cases who had electrodes implanted following parasagittal trajectories. No one had an Engel class 1 outcome at 1 year in the group of 7 patients who had electrodes inserted solely orthogonally. No complications occurred. The benefit-risk ratio of the SEEG-guided RFTC procedure proved to be particularly favorable for patients presenting an epileptogenic focus located in the insula or in the medial aspect of the operculum, especially when using parasagittally, rather than orthogonally, implanted electrodes to coagulate. Therefore, this technique could be used, in selected cases, as the first-line therapeutic option procedure related to insular epilepsy, providing, in many cases, complete control over epileptic disease.

We provide here a functional mapping of the insular cortex obtained by electrical stimulation carried out during stereo-electro-encephalography (SEEG). Somatosensory sensations and visceral responses were the most frequent responses to insular stimulation, followed in decreasing order of frequency by auditory sensations, vestibular illusions, speech impairment, gustato-olfactory sensations, and motor reactions. The posterior part of the insula seems more implicated in somatosensory functions, notably in pain perception, whereas the anterior part seems more implicated in visceral functions. Although some degree of spatial segregation could be evidenced, there was a clear spatial overlap between the representations of the different types of responses. Electrical stimulations permit to evidence a singularly multi-modal representation in the insula that may support its integrative functions of polymodal inputs. They also provide a better understanding of physiological insular functions and the semiology of insular seizures.

Painful epileptic seizures are scarce and can be a diagnostic challenge, as they may occur as the sole manifestation of seizures. Three categories are distinguished: (1) ictal epileptic headache; (2) ictal abdominal pain; and (3) painful somatosensory seizures, during which patients complain of acute and intense pain affecting part of the body. According to the intracranial EEG recordings, the insulo-opercular cortex and the mesial temporal lobe are implicated in the occurrence of ictal epileptic headache. Such is the case for ictal abdominal pain with the addition of the anterior cingulate gyrus. Stereo-electroencephalography data strongly suggest that painful somatosensory seizures originate in the posterior insula and the secondary sensory area. While ictal epileptic headache and painful abdominal seizures may correspond to an autonomic response resulting from the activation of a central autonomic network, painful somatosensory seizures result from the activation of a central pain network (i.e., the Pain Matrix or Salient Matrix).

Insular epilepsy has come into focus quite late in the field of epileptology. This entity was forgotten between the 1960s and 1980s by the last generation of epileptologists who were busy leading the fight for a localization approach and anatomo-electro-clinical correlations. This lengthy period is well documented in the first chapter of this work. This drift may be attributed to various restrictions, mostly technical: the insular cortex does not appear on the surface of the brain but is the seat of a plethoric vascularization that supplies blood to motor fibers in the centrum ovale through its network of perforating arteries. Therefore, it could not be operated without exposing the patient to unreasonable risks for the goal intended. It could not also be explored invasively without the risk of causing a hemorrhage due to the necessity of crossing a triple curtain of pial arteries. The condemnation was heard: “exploring the insula, at best, is useless, and at worst, dangerous.”

Insular lobe seizures (ILS) may present with several subjective and objective symptoms. Somatosensory and viscerosensory symptoms, notably paresthesia and laryngeal constriction, are symptoms frequently encountered with ILS. Other manifestations may become only evident after the ictal discharge spreads to extra-insular structures. Depending on propagation pathways, ILS exhibit two main clinical patterns: (1) a perisylvian /temporo-perisylvian pattern and (2) a frontal-like pattern. Other miscellaneous clinical presentations include epileptic spasms, ecstatic, gelastic, reflex, and autonomic seizures.