Combination Of Co-SEP, MEP And ECoG Used In Monitoring Surgical Therapy Of Secondary Epilepsy Of Central Area Lesions

Objective To explore the combination of cortical somatosensory evoked potentials (Co-SEP), cortical electrical stimulation motor evoked potential (MEP) and electroencephalogram (EEG) monitoring technology used in the secondary epilepsy surgery on the central area of the cortex.Methods In 19 cases with secondary epilepsy on the central area,6 of these, epileptogenic lesion were located in right frontal lobe,7 in left frontal lobe,3 in left parietal lobe and 2 in right parietal lobe. All cases experienced ambulatory electroencephalography monitoring (AEEG) or video electroencephalography monitoring (VEEG) for 32 to 80 hours, as well as magnetic resonance imaging (MRI) scan and strengthening, positron emission computerized tomography (PET-CT), functional magnetic resonance imaging (fMRI) in order to localize eloquent cortex.All cases undergo total intravenous anesthesia (TIVA). Four contact strip electrode were across central sulcus theoretically. Co-SEP was evoked with the 4-channel intraoperative evoked potential monitor (Viking Quest). We judged central sulcus by phase inversion between N20-P25 and P22-N33. Afterwards, strip electrodes were adjusted on precentral gyrus. We stimulated the gyrus with strip electrode. Stimulus intensity began with 2mA, by 1 mA increments, to 25 mA, until well-differentiated MEP. MEP was recorded from contralateral orbicularis oris, orbicularis oculi, masticatory muscles, muscles of thenar or hypothenar, flexor digitorum brevis and tibialis anterior. We marked the area where MEP was evoked. Before resection of epileptic focus, the appropriate grid electrode was chosen to determine the epileptic focus. We avoided eloquent area and removed lesions and epileptic focus. If not, we can choose multiple subpial transection (MST) or bipolar coagulation technique. The process was repeated until the spikes disappeared or significantly decreased.The results were observed for 6～12 months after surgery. Observation including reservations of neurological function, the improvement in seizures, completeness of tumor resection and tumor recurrence.Results In 19 cases, Co-SEP were evoked to define the location of the central sulcus intraoperatively. In one case with malacia, strip electrode was across the central sulcus that was defined by anatomic landmark, but all display were P22-N33. So we moved strip electrode towards occipitalis lobe, terminally phase inversion of Co-SEP was recorded. On these grounds, the central sulcus was backwards than normal localization. All cases could be recorded MEP from different muscles. Among these,13 was from muscle of thenar,9 from muscle of hypothenar,10 from orbicularis oris,2 from flexor digitorum brevis and 6 from tibialis anterior. The stimulus intensiy was from 5.8 to 21.6 mA. After surgery, MEP still could be evoked. During follow-up period, seizures disappeared or reduced significantly.18 cases has reached Angel III level or above. No cases appeared permanent motor dysfunction. Only one case with astrocytoma suffered from transient Broca aphasia incompletely and one with oligodendroglioma was undergone transient hemiparesis. The remaining were well. Three cases of glioma patients achieved total or subtotal resection, and were followed up for 8-9 months, no recurrence was found.Conclusion With the guidance of intraoperative Co-SEP, MEP and ECoG monitoring, all cases has achieved the maximum extent of epileptic focus and epileptogenic zone, but did not cause significant neurological dysfunction.It help to improve the quality of life in epilepsy patients. So intraoperative neurophysiologic monitoring is a safe and effective technique, and should be promoted and developed.