Functional mapping of the insular and opercular cortex: A study using SEEG electrical stimulation in epileptic patients

Abstract

Insular and opercular cortex is involved in complicated physiological function.Insular seizures involve extensive epileptic network, which results in the complex and diverse semiology.Electrical cortical stimulation(ECS) can explore the functional mapping and symptomatogenic zone. The clinical presurgical evaluation and ECS data of 20 patients whose electrode contacts were located in the insular and opercular were analyzed retrospectively.CT scan/3D MRI data fusion was performed in order to accurately identify and locate each contact and check the electrode trajectory by the MRI images performed after the electrodes were removed.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.The classification of the insular were anterior short gyrus, middle short gyrus, precentral gyrus, postcentral gyrus, posterior long gyrus and insular pole.The classification of the opercular were orbital, frontal, precentral, central, parietal and temporal opercular. One hundred and six contacts were located in the insular and 51 responses were evoked (48.11%). Four hundred eighteen contacts were located in the insular and 132 responses were evoked (31.58%). We classified the principal responses as somatosensory, pain, auditory, oropharyngeal, speech disturbances and neurovegetative response.Somatosensory responses were mainly evoked in parietal opercular and postcentral gyrus, while pain response distributed sporadically.Auditory were only evoked in temporal opercular(transverse temporal gyri) and posterior long gyrus.Oropharyngeal symptoms were only evoked in central opercular.Speech disturbances were located in precentral and central opercular and neurovegetative responses were mainly evoked in insular pole and middle short gyrus. These findings may indicate a functional specificity for the insular gyrus and opercular, which contribute to the understanding of anatomo-functional organization and the role in insular and opercular epileptic network.Moreover, it could optimize the implantation strategy for exploring these structures.