The ERD Of ? Rhythm And The Slow Cortial Potential From ECoG Are New Parameters In Intraoperative Mapping Of Motor Related Cortices

?Background?The goals of surgery of lesions(esp.Gliomas or epileptic foci)in motor-related cortices are maximal lesion resection and minimal functional areas impairments.As a result of the interindividual variabilities in the anatomic location of motor areas,mapping of the sensorimotor(SM)cortices before the resection of lesions is important in reducing the risk of post-surgical deficits.The current gold standard for intraoperative mapping of eloquent areas is direct electrical stimulation(DES).There are,however,several limitations to this approach.Intraoperative DES can induce seizures attack and inappropriate using it can result in sham positive and sham negative mapping.Furthermore,DES is time-consuming and requires patients cooperation intraoperatively that makes functional mapping in young and uncooperative patients quite challenging.Somatosensory evoked potentials(SSEPs)is another method in intraoperative mapping of sensorimotor(SM)cortices.This technique can be used to identify the transition between motor and sensory cortex in patients under general anesthesia and is generally safe,fast,and easy to apply in the operating room.SSEPs appear to be influenced by certain anesthetic agents.So the sensitivity is low in fact.Given the limitations of DES and SSEPs,other functional mapping approaches have been developed,including ECoG.More recently,ECoG changes in activity associated with a given stimulus or cognitive task.So they havebeen explored to use in intraoperative mapping of eloquent areas.Functional mapping through ECoG has several advantages over DES,most notably lower seizures during passive ECoG recordings and a reduction of the duration required for functional mapping.Relatively low frequencies in the ? ranges are thought to be produced by thalamocortical circuits that decrease in amplitude in association with actual or imagined movements.It is recognized as characteristics of SM cortex activation.He et al.studied ECoG frequencies ranging from 0.5 to 200 Hz and demonstrated that the rhythms that were most closely correlated SM network were the SCPs.However,complex wave of EEG is impossible to analyze and study the single rhythm.These resting-state SCP networks and ? rhythm have never been evaluated for their reliability in intraopative mapping of eloquent cortiece.Therefore,based on the principle of ECoG specificity,we performed wavelet transform with feature extraction and classification of ECoG to explore the sensitivity and specificity of ECoG in intraoperative mapping motor cortices with the ERD of ? rhythm or slow cortical potential.Part 1:The ERD of ? rhythm from ECoG in intraoperative mapping of motor related cortices?Objective? To explore the efficacy of ? rhythm from ECoG in intraoperative mapping of motor related cortices.?Methods? Eight patients with brain lesions near eloquent areas were underwent awake craniotomy.The motor-related cortices were detected by intraoperative direct electrical stimulation.The ECoGs were collected both hand-move state(grasp and extension motion).The ECoG signals were decomposed into four types of rhythm(?,?,?,?),the ERD of each rhythm was analyzed before and after motion.The sensitivity and specificity of each rhythm in mapping of motor cortices were evaluated.?Results? Motor cortices were identified by DES in all patients when the intensity reached certain threshold,usually 3mA-4mA.The ERD of ? rhythm was significant and regarded as the specific rhythm of motor cortex.When the threshold of ERD of ? rhythm was chosen as 40%,this method showed the optimal sensitivity(81.0%)and specificity(91.7%)compared with the other thresholds.?Conclusion? The ERD of ? rhythm extracted from ECoG can be used to map motor areas intraoperatively.It is expected as a new method for intraoperative mapping of motor cortex.Part 2:The energy value of slow cortical potential from ECoG in intraoperative mapping of motor related cortices during resting state?Objective? To explore the efficacy of slow cortical potential from ECoG in intraoperative mapping of motor related cortices during resting state.?Methods? Thirteen patients with brain lesions near eloquent areas were treated under awake craniotomy.The motor-related cortices were determined by DES.The ECoGs from all patients were collected in resting-state.The energy value of each rhythm in resting-state was analyzed.The sensitivity and specificity of them in mapping of motor cortices were evaluated.?Results? Motor areas were identified by DES in all patients.The energy value of slow cortical potential in resting-state was significant and regarded as the specific rhythm of motor cortex.When the threshold of energy value of the specific rhythm was chosen as 1.6,this method showed the optimal sensitivity(90.6%)and modest specificity(59.2%)compared with the other thresholds.?Conclusion? The energy value of slow cortical potential in resting state extracted from ECoG can be used for mapping motor areas intraoperatively.It is expected as a new adjunct to DES in the intraoperative mapping.