Continuous MEP monitoring provides reliable monitoring of the motor system, influences the course of operation in some cases, and has to be regarded as the standard for IOM of the motor system. In our series, we found no false-negative MEP results.

T he resection of tumors within or adjacent to language-eloquent brain regions is still a neurosurgical quest, and a profound presurgical workup is crucial to achieving the best functional and oncological result. 6,71 Today, the most precise way to localize individual language-eloquent regions is direct cortical stimulation (DCS) during awake craniotomy. 9,12,26,44,45,54,62,65,74 Using only DCS, however, we cannot provide the longitudinal abbreviatioNs BOLD = blood oxygen level-dependent; CPS = cortical parcellation system; DCS direct cortical stimulation; ER = error rate; ERT error rate threshold; fMRI = functional MRI; IPI = interpicture interval; NPV = negative predictive value; nTMS navigated TMS; PPV = positive predictive value; PTI = picture-to-trigger interval; RMT = resting motor threshold; ROC = receiver operating characteristic; rTMS repetitive navigated TMS; TMS = transcranial magnetic stimulation. obJect Repetitive navigated transcranial magnetic stimulation (rTMS) is now increasingly used for preoperative language mapping in patients with lesions in language-related areas of the brain. Yet its correlation with intraoperative direct cortical stimulation (DCS) has to be improved. To increase rTMS's specificity and positive predictive value, the authors aim to provide thresholds for rTMS's positive language areas. Moreover, they propose a protocol for combining rTMS with functional MRI (fMRI) to combine the strength of both methods. methods The authors performed multimodal language mapping in 35 patients with left-sided perisylvian lesions by using rTMS, fMRI, and DCS. The rTMS mappings were conducted with a picture-to-trigger interval (PTI, time between stimulus presentation and stimulation onset) of either 0 or 300 msec. The error rates (ERs; that is, the number of errors per number of stimulations) were calculated for each region of the cortical parcellation system (CPS). Subsequently, the rTMS mappings were analyzed through different error rate thresholds (ERT; that is, the ER at which a CPS region was defined as language positive in terms of rTMS), and the 2-out-of-3 rule (a stimulation site was defined as language positive in terms of rTMS if at least 2 out of 3 stimulations caused an error). As a second step, the authors combined the results of fMRI and rTMS in a predefined protocol of combined noninvasive mapping. To validate this noninvasive protocol, they correlated its results to DCS during awake surgery. results The analysis by different rTMS ERTs obtained the highest correlation regarding sensitivity and a low rate of false positives for the ERTs of 15%, 20%, 25%, and the 2-out-of-3 rule. However, when comparing the combined fMRI and rTMS results with DCS, the authors observed an overall specificity of 83%, a positive predictive value of 51%, a sensitivity of 98%, and a negative predictive value of 95%. coNclusioNs In comparison with fMRI, rTMS is a more sensitive but less specific tool for preoperative language mapping than DCS. Moreover, rTMS is most reliable when using ERTs of 15%, 20...

Since transcranial magnetic stimulation (TMS) was introduced for stimulating the human motor cortex by Barker et al. in 1985, the method has become more sophisticated and was extensively refined.1 PascualLeone and colleagues introduced the term "virtual lesion" and were already in 1991 able to induce speech arrests and counting errors by the use of rapid-rate TMS. 35,36 In the late 1990s and early 2000s, a combination of TMS with optically tracked stereotactic navigation systems was established, whereby it was possible to visualize the stimulation sites via the 3D reconstructed MRI data of the patient's brain. 31,37 Thus, the door to the operating theater was opened since the recorded and analyzed stimulation sites could be used for presurgical planning and data could be abbreviatioNs BOLD = blood-oxygen-level dependent; CPS = cortical parcellation system; DCS = direct cortical stimulation; DTI-FT = diffusion tensor imaging fiber tracking; fMRI = functional MRI; NPV = negative predictive value; PPV = positive predictive value; PTI = picture-to-trigger interval; RMT = resting motor threshold; ROC = receiver operating characteristic; rTMS = repetitive navigated TMS; TMS = transcranial magnetic stimulation. (rTMS) is increasingly used and has already replaced functional MRI (fMRI) in some institutions for preoperative mapping of neurosurgical patients. Yet some factors affect the concordance of both methods with direct cortical stimulation (DCS), most likely by lesions affecting cortical oxygenation levels. Therefore, the impairment of the accuracy of rTMS and fMRI was analyzed and compared with DCS during awake surgery in patients with intraparenchymal lesions. methods Language mapping was performed by DCS, rTMS, and fMRI using an object-naming task in 27 patients with left-sided perisylvian lesions, and the induced language errors of each method were assigned to the cortical parcellation system. Subsequently, the receiver operating characteristics were calculated for rTMS and fMRI and compared with DCS as ground truth for regions with (w/) and without (w/o) the lesion in the mapped regions. results The w/ subgroup revealed a sensitivity of 100% (w/o 100%), a specificity of 8% (w/o 5%), a positive predictive value of 34% (w/o: 53%), and a negative predictive value (NPV) of 100% (w/o: 100%) for the comparison of rTMS versus DCS. Findings for the comparison of fMRI versus DCS within the w/ subgroup revealed a sensitivity of 32% (w/o: 62%), a specificity of 88% (w/o: 60%), a positive predictive value of 56% (w/o: 62%), and a NPV of 73% (w/o: 60%). coNclusioNs Although strengths and weaknesses exist for both rTMS and fMRI, the results show that rTMS is less affected by a brain lesion than fMRI, especially when performing mapping of language-negative cortical regions based on sensitivity and NPV.

BackgroundMapping of the motor cortex by navigated transcranial magnetic stimulation (nTMS) can be used for preoperative planning in brain tumor patients. Just recently, it has been proven to actually change outcomes by increasing the rate of gross total resection (GTR) and by reducing the surgery-related rate of paresis significantly in cohorts of patients suffering from different entities of intracranial lesions. Yet, we also need data that shows whether these changes also lead to a changed clinical course, and can also be achieved specifically in high-grade glioma (HGG) patients.MethodsWe prospectively enrolled 70 patients with supratentorial motor eloquently located HGG undergoing preoperative nTMS (2010–2014) and matched these patients with 70 HGG patients who did not undergo preoperative nTMS (2007–2010).ResultsOn average, the overall size of the craniotomy was significantly smaller for nTMS patients when compared to the non-nTMS group (nTMS: 25.3 ± 9.7 cm2; non-nTMS: 30.8 ± 13.2 cm2; p = 0.0058). Furthermore, residual tumor tissue (nTMS: 34.3%; non-nTMS: 54.3%; p = 0.0172) and unexpected tumor residuals (nTMS: 15.7%; non-nTMS: 32.9%; p = 0.0180) were less frequent in nTMS patients. Regarding the further clinical course, median inpatient stay was 12 days for the nTMS and 14 days for the non-nTMS group (nTMS: CI 10.5 – 13.5 days; non-nTMS: CI 11.6 – 16.4 days; p = 0.0446). 60.0% of patients of the nTMS group and 54.3% of patients of the non-nTMS group were eligible for postoperative chemotherapy (OR 1.2630, CI 0.6458 – 2.4710, p = 0.4945), while 67.1% of nTMS patients and 48.6% of non-nTMS patients received radiotherapy (OR 2.1640, CI 1.0910 – 4.2910, p = 0.0261). Moreover, 3, 6, and 9 months survival was significantly better in the nTMS group (p = 0.0298, p = 0.0015, and p = 0.0167).ConclusionsWith the limitations of this study in mind, our data show that HGG patients might benefit from preoperative nTMS mapping.

F or the treatment of cerebral metastases, indication for surgery is currently limited to a subgroup of patients. Although radiosurgery and resection have been shown to be equivalent in terms of survival, some studies have shown that radiosurgery leads to better local control due to its effect on the infiltration zone surrounding the lesion and whole brain radiation therapy is associated with significantly shorter survival.26,27 Nevertheless, in many patients who have focal deficits resulting from metastases, resection is still undertaken in order to achieve rapid improvement in neurological function. Metastases within or close to the motor cortex or subcortical motor tracts may therefore be treated by resection.Intraoperative neuromonitoring is routinely used for resection of gliomas in or adjacent to the motor system. 15,22,33 Cerebral metastases, however, are generally believed to be noninfiltrative, and IOM during resection of these lesions in motor-eloquent regions is still not widely described. 29 As recent studies have shown that cerebral metastases also infiltrate surrounding brain tissue, intraoperative surveillance of the motor systems might be helpful to reduce surgery-related motor deficits. 25,26,28 Motor evoked potential monitoring allows us to identify crucial steps during resection of tumors within the rolandic region or tumors adjacent to the pyramidal tract. 5,19,21,24,33 Furthermore, several studies have shown that MEP moniReliability of intraoperative neurophysiological monitoring using motor evoked potentials during resection of metastases in motor-eloquent brain regions Object. Resection of gliomas in or adjacent to the motor system is widely performed using intraoperative neuromonitoring (IOM). For resection of cerebral metastases in motor-eloquent regions, however, data are sparse and IOM in such cases is not yet widely described. Since recent studies have shown that cerebral metastases infiltrate surrounding brain tissue, this study was undertaken to assess the value and influence of IOM during resection of supratentorial metastases in motor-eloquent regions.Methods. Between 2006 and 2011, the authors resected 206 consecutive supratentorial metastases, including 56 in eloquent motor areas with monitoring of monopolar direct cortically stimulated motor evoked potentials (MEPs). The authors evaluated the relationship between the monitoring data and the course of surgery, clinical data, and postoperative imaging.Results. Motor evoked potential monitoring was successful in 53 cases (93%). Reduction of MEP amplitude correlated better with postoperative outcomes when the threshold for significant amplitude reduction was set at 80% (only > 80% reduction was considered significant decline) than when it was set at 50% (> 50% amplitude reduction was considered significant decline). Evidence of residual tumor was seen on MR images in 28% of the cases with significant MEP reduction. No residual tumor was seen in any case of stable MEP monitoring. Moreover, preoperative motor deficit, recursive parti...

BackgroundToday, the treatment of choice for high- and low-grade gliomas requires primarily surgical resection to achieve the best survival and quality of life. Nevertheless, many gliomas within highly eloquent cortical regions, e.g., insula, rolandic, and left perisylvian cortex, still do not undergo surgery because of the impending risk of surgery-related deficits at some centers. However, pre and intraoperative brain mapping, intraoperative neuromonitoring (IOM), and awake surgery increase safety, which allows resection of most of these tumors with a considerably low rate of postoperatively new deficits.MethodsBetween 2006 and 2012, we resected 47 out of 51 supratentorial gliomas (92%), which were primarily evaluated to be non-resectable during previous presentation at another neurosurgical department. Out of these, 25 were glioblastomas WHO grade IV (53%), 14 were anaplastic astrocytomas WHO grade III (30%), 7 were diffuse astrocytomas WHO grade II (15%), and one was a pilocytic astrocytoma WHO grade I (2%). All data, including pre and intraoperative brain mapping and monitoring (IOM) by motor evoked potentials (MEPs) were reviewed and related to the postoperative outcome.ResultsAwake surgery was performed in 8 cases (17%). IOM was required in 38 cases (81%) and was stable in 18 cases (47%), whereas MEPs changed the surgical strategy in 10 cases (26%). Thereby, gross total resection was achieved in 35 cases (74%). Postoperatively, 17 of 47 patients (36%) had a new motor or language deficit, which remained permanent in 8.5% (4 patients). Progression-free follow-up was 11.3 months (range: 2 weeks – 64.5 months) and median survival was 14.8 months (range: 4 weeks – 20.5 months). Median Karnofsky Performance Scale was 85 before and 80 after surgery).ConclusionsIn specialized centers, most highly eloquent gliomas are eligible for surgical resection with an acceptable rate of surgery-related deficits; therefore, they should be referred to specialized centers.

BackgroundRecent data show differences in intraoperative neuromonitoring (IOM) in relation to the operated brain lesion. Due to the recently shown infiltrative nature of cerebral metastases, this work investigates the differences of IOM for cerebral metastases and glioma resection concerning sensitivity, specificity, and predictive values when aiming on preservation of motor function.MethodsBetween 2006 and 2011 we resected 171 eloquently located tumors (56 metastases, 115 gliomas) associated with the rolandic cortex or the pyramidal tract using IOM via direct cortical motor evoked potentials (MEPs). Postoperatively, MEP data were re-analyzed with respect to surgery-related paresis, residual tumor, and postoperative MRI with two different thresholds for MEP decline (50 and 80 % below baseline).ResultsMEP monitoring was successful in 158 cases (92.4 %). MEPs were stable in 54.7 % of all metastases cases and in 65.2 % of all glioma cases (p < 0.0001). After metastases resection, 21.4 % of patients improved and 21.9 % deteriorated in motor function. Glioma patients improved in only 5.4 % and worsened in 31.3 % of cases (p < 0.05). Resection was stopped due to MEP decline in 8.0 % (metastases) and 34.8 % of cases (gliomas) (p < 0.0002).ConclusionThere is significant difference between glioma and metastases resection. Post-hoc, metastases show more stable MEPs but a surprisingly high rate of surgery-related paresis and therefore a higher rate of false negative IOM.

Objective: A considerable number of gliomas require resection via direct electrical stimulation (DES) during awake craniotomy. Likewise, the feasibility of resecting language-eloquent gliomas purely based on navigated repetitive transcranial magnetic stimulation (nrTMS) has been shown. This study analyzes the outcomes after preoperative nrTMS-based and intraoperative DES-based glioma resection in a large cohort. Due to the necessity of making location comparable, a classification for language eloquence for gliomas is introduced. Methods: Between March 2015 and May 2019, we prospectively enrolled 100 consecutive cases that were resected based on preoperative nrTMS language mapping (nrTMS group), and 47 cases via intraoperative DES mapping during awake craniotomy (awake group) following a standardized clinical workflow. Outcome measures were determined preoperatively, 5 days after surgery, and 3 months after surgery. To make functional eloquence comparable, we developed a classification based on prior publications and clinical experience. Groups and classification scores were correlated with clinical outcomes. Results: The functional outcome did not differ between groups. Gross total resection was achieved in more cases in the nrTMS group (87%, vs. 72% in the awake group, p = 0.04). Nonetheless, the awake group showed significantly higher scores for eloquence than the nrTMS group (median 7 points; interquartile range 6–8 vs. 5 points; 3–6.75; p < 0.0001). Conclusion: Resecting language-eloquent gliomas purely based on nrTMS data is feasible in a high percentage of cases if the described clinical workflow is followed. Moreover, the proposed classification for language eloquence makes language-eloquent tumors comparable, as shown by its correlation with functional and radiological outcomes.