Abstracts

Rationale: Precise localisation of an epileptic focus in the peri-Sylvian/insular area is a major challenge, especially in MRI negative patients. The difficult access and the high density of blood vessels within the Sylvian fissure have lead to poor coverage of intra-Sylvian opercular and insular cortex by available depth and subdural electrodes. Our objective was to design and use in patients a new type of electrode that allows recordings from the insular cortex and the hidden surfaces of the opercula. Methods: The hybrid operculo-insular electrode was fabricated by Ad-Tech Medical Instrument Corporation, Wisconsin, USA. It was use in patients for long term intracranial recordings, combined with regular subdural and depth electrodes. The new electrode is inserted after microsurgical opening of the Sylvian fissure. The depth component that has two contacts is implanted into the insular cortex. The opercular component has one or two double sided recording contacts facing the superior and inferior opercula.Results: The hybrid operculo-insular electrode was used in five patients. It allowed including (two patients) or excluding (three patients) the insula and the opercula as part of the epileptic focus and the surgical resection.Conclusions: The new hybrid operculo-insular electrode can be used for intracranial investigation of peri-Sylvian/insular refractory epilepsy. It can contribute to increase cortical coverage of this complex region. A better definition of the epileptic focus could lead to better success of epilepsy surgery.