Abstracts

Rationale: Controlling seizures produced by insular cortex epilepsy can present a perplexing clinical challenge due to the ambiguity of seizure symptoms and the complex technical requirements for a definitive diagnosis. Insular involvement on subtraction SPECTS are often overshadowed by the cortical element. Failure to accurately isolate the true seizure origin may explain why some epilepsy surgeries fail to resolve seizures. We studied the utility of insular depth placement in better defining insular involvement in ictal onset or evolution. Methods: We retrospectively reviewed our database from 2010 to present to determine which patients had insular depths placed. High resolution MRI was then used post-operatively to confirm accurate electrode placement. Once a seizure focus had been confirmed in the insular cortex after a period of 2-8 days, patients underwent insular removal or partial insular resection. Results: Of the 74 surgical resections performed 15 had longitudinal 8 channel depths placed traversing the anterior-posterior length of the insular on the side of seizure onset using an MRI-stereotactic frame-guided system. Their ages at the time of surgery ranged from 4 years 3 months to 20 years one month. Seizure semiology varied greatly. In 10 of 15 patients the insular was involved at seizure onset and was partially removed (anterior or posterior insular determined by the electrodes involved) or removed in totality from the involved hemisphere. The anterior insular was involved at seizure onset in cases where the seizure involved the anterior to mid-frontal region but those with posterior frontal, parietal or more extensive involvement, the posterior or entire insular was involved at onset. Patients were followed post-operatively for up to 23 weeks for the development of seizures. All of the patients had seizure improvement and 7/10 was seizure free during their follow up period (3-23 weeks). Conclusions: Insular involvement should be entertained in cases where seizure onset is not easily identified. Longitudinal depth placement allows for sampling of the entire length of the insular cortex. This may be instrumental in determining the full extent of involvement of ictal onset, hence allowing for resection of epileptic focus in its entirety.