Microsurgery of epileptic foci in the insular region

Clinical article

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The insular region has long been neglected in the investigation and treatment of refractory epilepsy. Surgery in the insular region is rarely performed because of the risk of injury to the opercula, the arteries transiting on the surface of the insula, and the deep structures such as the basal ganglia and the internal capsule. This study was undertaken to report the results of insular surgery using modern microsurgical techniques in patients with epilepsy.


The authors performed a retrospective study of cases involving patients who underwent surgery for insular lesions associated with epilepsy over the last 10 years. In the majority of patients, intracranial electrodes were implanted with neuronavigation guidance to confirm the localization of the epileptic foci.


Nine patients underwent insular surgery: 7 for refractory epilepsy with no tumor and 2 for tumors associated with seizures. Four of the resections were performed in the left hemisphere. After an average follow-up of 54 months (range 14–122 months), Engel Class IA outcome had been achieved in 6 of 7 cases in the Epilepsy Surgery Group. The remaining patient had an Engel Class III outcome after partial insular resection but later became seizurefree (Engel Class IA) following insular Gamma Knife surgery.

Postoperatively, the majority of patients suffered from minor reversible hemipareses that disappeared completely within a few months. There was no surgical mortality.


Insular surgery is both safe and beneficial when it is well planned and performed with modern microsurgical techniques and good anatomical knowledge. Insulectomy is associated with little permanent morbidity and a high rate of seizure control. To the authors' knowledge, this is the first series of insulectomies predominantly performed for refractory epilepsy since those performed by Penfield.

Abbreviation used in this paper: SISCOM = subtraction ictal SPECT coregistered to MR imaging.

Article Information

Address correspondence to: Alain Bouthillier, M.D., Service de neurochirurgie, Centre Hospitalier de l'Université de Montréal, Notre-Dame Hospital, 1560, rue Sherbrooke Est, Montréal, Québec, Canada H2L 4M1. email: alain.bouthillier@umontreal.ca.

Please include this information when citing this paper: published online February 27, 2009; DOI: 10.3171/2009.1.JNS08807.

© AANS, except where prohibited by US copyright law.



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    Case 2. A: Ictal SPECT showing activation of the posterior left insula. B: Intraoperative photograph obtained after placement of subdural and depth electrodes. C: Axial MR image obtained after electrode placement, confirming the position of the depth electrode in the posterior left insula (arrow). D: Intraoperative photograph obtained during insular cortex resection after opening the sylvian fissure. E: Postoperative sagittal MR image showing the posterior left insulectomy.

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    Case 7. A: Preoperative coronal MR image showing cortical dysplasia involving the right insula and frontoparietal operculum (arrows). B and C: Intraoperative images obtained before and after resection of the cortical dysplasia. The opercular cortex was removed first by subpial resection between the branches of the sylvian artery. The subpial resection was then continued to include the insula. D: Postoperative MR images showing complete resection of the insuloopercular cortical dysplasia. The insula was completely resected.

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    Operculoinsulectomy. A and B: Case 4. Coronal MR images obtained before (A) and after (B) subpial resection of cortical dysplasia involving the right insula and frontoparietotemporal opercula. C and D: Case 5. Coronal MR images obtained before (C) and after (D) subpial resection of cortical dysplasia involving the right insula and frontal operculum. The parietal and temporal opercula are not affected. Complete insular resection is shown in B and D.

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    Schematic drawing of depth electrode insertion in the insula under direct vision after opening of the sylvian fissure.



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