Functional Mapping Of The Insular Cortex In Epileptic Patients Using SEEG Electrical Stimulation

Objective:The insula is the fifth lobe of the brain and it is hidden in the Sylvian fissure.The insular cortex is involved in a large number of functions and there is an abundance of connections with other structure.Therefore insular seizures present the complex and diverse semiology.There are many methods to study its structure,function and network so far.In this paper,the functional anatomy of the insular cortex and the relationship with other brain tissues were studied by direct electrical stimulation based on stereoelectroencephalography.Methods:A retrospective analysis was made on 2014.4~2016.5 patients with drug-refractory focal epilepsy by stereotactically implanting at least one electrode into the insular cortex at the epilepsy center of Yuquan Hospital of Tsinghua University.CT scan/ 3D MRI data fusion was performed in order to accurately identify and locate each contact.ECS was applied between two contiguous contacts.Stimulation usually lasted for 5 s at 50 Hz(pulse width = 0.3 ms).Depending on the area of stimulated cortex,the stimulation intensities ranged from 0.2 to 3.0 mA.We classified these responses according to the nature and location.Results:220 contacts were located in the insular and 106 responses were evoked(48.2%).We classified the principal responses as somatosensory,auditory,pain,neurovegetative phenomena,gustatory,oropharyngeal and so on.somesthetic responses were mainly evoked in postcentral insular gyrus.auditory were evoked in posterior long gyrus and postcentral insular gyrus.pain response distributed sporadically.neurovegetative phenomena were mainly evoked in insular pole.oropharyngeal symptoms were only evoked in precentral insular gyrus.Conclusion:These findings contribute to understanding the anatomy and functional mapping of the insular,and it is helpful to the evaluation of each insular gyrus to produce or related epileptogenic networks in epilepsy.At the same time,it also shows the important role of intrainsular electrode implantation in the assessment of patients with suspected insular involvement.