Abstract
PurposeDirect subcortical motor mapping is the golden criterion to detect and monitor the motor pathway during glioma surgery. Minimal subcortical monopolar threshold (MSCMT) means the minimal distance away from the motor pathway and is critical to decide to continue or interrupt glioma resection. However, the optimal cutoff value of MSCMT for glioma resection in non-awake patients has not been reported discreetly. In this study, we try to establish the safe cutoff value of MSCMT for glioma resection and analyzed its relationship with postoperative motor deficit and long-term survivals.MethodsWe designed this prospective study with high-frequency electronic stimulus method. The cutoff MSCMT of postoperative motor deficits was statistically calculated by receiver operating characteristic (ROC) curve, and its relationship with motor deficit and survivals was analyzed by logistic and Cox regression, respectively.ResultsThe cutoff MSCMT to predict motor deficit after surgery was 3.9 mA on day 1, 3.7 mA on day 7, 5.2 mA at 3 months, and 5.2 mA at 6 months. MSCMT ≤3.9 mA and MSCMT ≤5.2 mA independently predicted postoperative motor deficits at four times after surgery (P < 0.05) but had no effect on the removal degree of tumor (P > 0.05). In high-grade gliomas, MSCMT ≤3.9 mA independently predicted shorter progression-free survival [odds ratio (OR) = 3.381 (1.416–8.076), P = 0.006] and overall survival [OR = 3.651 (1.336–9.977), P = 0.012]. Power model has the best fitness for paired monopolar and bipolar high-frequency thresholds.ConclusionsThis study showed strong cause–effect relation between MSCMT and postoperative motor deficit and prognoses. The cutoff MSCMT was dug out to avoid postoperative motor deficit. Further studies are needed to establish the results above.
Highlights
Using electrophysiological techniques to monitor the motor pathway has gradually become the golden criterion for functional localization [1] and facilitated the maximal safe resection of gliomas
For direct electrical stimulation in search of the motor pathway, two techniques have been developed: the low-frequency (50 or 60 Hz) bipolar stimulation first described by Penfield in 1937 [12] and the high-frequency multipulse train stimulation technique first described by Taniguchi in 1993 [13]
We discovered the relationship of minimal subcortical monopolar threshold (MSCMT) cutoff value with motor deficit and further analyzed the relationship between MSCMT and clinical prognoses
Summary
Using electrophysiological techniques to monitor the motor pathway has gradually become the golden criterion for functional localization [1] and facilitated the maximal safe resection of gliomas. The traditional technique of bipolar stimulation at a low frequency, 50 or 60 Hz, has been used for decades and has been reported as an accurate and reliable technique for detecting the motor pathway [2]. A new motor mapping method with high-frequency stimulation has been reported and is increasingly being used widely because of the low probability of seizure [3–8]. It has been stressed that highfrequency monopolar stimulation should be theoretically appropriate for monitoring the motor pathway located in deep cerebral tissue [9]. As the great importance of accurate neuro-location, the subcortical electronic stimulation threshold is usually used as a pivotal reference to decide whether the glioma resection should be continued or not. That value of minimal subcortical monopolar threshold (MSCMT) means the minimal distance away from the motor pathway. To explore the optimal range of tumor resection guided by subcortical stimulus in nonawakened patients, we designed this study with high-frequency
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