Search

Objective: Language dominance in the developing brain can vary widely across anatomical and pathological conditions as well as age groups. Repetitive navigated transcranial magnetic stimulation (rnTMS) has been applied to calculate the hemispheric dominance ratio (HDR) in adults. In this study, the authors aimed to assess the feasibility of using rnTMS to identify language lateralization in a pediatric neurosurgical cohort and to correlate the preoperative rnTMS findings with the postoperative language outcome., Methods: A consecutive prospectively collected cohort of 19 children with language-associated lesions underwent bihemispheric rnTMS mapping prior to surgery (100 stimulation sites on each hemisphere). In addition to feasibility and adverse effects, the HDR (ratio of the left hemisphere to right hemisphere error rate) was calculated. The anatomical surgical site and postoperative language outcome at 3 months after surgery were assessed according to clinical documentation., Results: Repetitive nTMS mapping was feasible in all 19 children (mean age 12.5 years, range 4-17 years; 16 left-sided lesions) without any relevant adverse events. Thirteen children (68%) showed left hemispheric dominance (HDR > 1.1), and 2 children (11%) showed right hemispheric dominance (HDR < 0.9). In 4 children (21%), the bihemispheric error rates were nearly the same (HDR ≥ 0.9 and ≤ 1.1). Sixteen children underwent surgery (14 tumor/lesion resections and 2 hemispherotomies) and 3 patients continued conservative therapy. After surgery, 4 patients (25%) showed an improvement in language function, 10 (63%) presented with stable language function, and 2 (12.5%) experienced deterioration in language function. Of the 6 patients with right hemispheric language involvement, 4 (80%) had glial tumors, 1 (20%) had focal cortical dysplasia, and 1 (20%) experienced hypoxic brain injury. Children with right hemispheric language involvement (HDR ≤ 1.1) did not show any language deterioration postoperatively., Conclusions: Bihemispheric rnTMS language mapping as a noninvasive mapping technique to assess lateralization of language function in the pediatric neurosurgical population is safe and feasible. Why relevant right hemispheric language function (HDR ≤ 1.1) was associated with postoperative unaltered language function needs to be validated in future studies. Bihemispheric rnTMS language mapping strengthens risk-benefit considerations prior to pediatric tumor/epilepsy surgery in language-associated areas.

Objective: Given the interindividual variance of functional language anatomy, risk prediction based merely on anatomical data is insufficient in language area-related brain tumor surgery, suggesting the need for direct cortical and subcortical mapping during awake surgery. Reliable, noninvasive preoperative methods of language localization hold the potential for reducing the necessity for awake procedures and may improve patient counseling and surgical planning. Repetitive navigated transcranial magnetic stimulation (rnTMS) is an evolving tool for localizing language-eloquent areas. The aim of this study was to investigate the reliability of rnTMS in locating cortical language sites., Methods: Twenty-five patients with brain tumors in speech-related areas were prospectively evaluated with preoperative rnTMS (5 Hz, train of five, average 105% resting motor threshold) and navigated direct cortical stimulation (DCS; bipolar, 50 Hz, 6-8 mA, 200-μsec pulse width) during awake surgeries employing a picture-naming task. Positive and negative stimulation spots within the craniotomy were documented in the same MRI data set. TMS and DCS language-positive areas were compared with regard to their spatial overlap, their allocation in a cortical parcellation system, and their linguistic qualities., Results: There were over twofold more positive language spots within the exposed area on rnTMS than on DCS. The comparison of positive rnTMS and DCS (ground truth) overlaps revealed low sensitivity (35%) and low positive predictive value (16%) but high specificity (90%) and high negative predictive value (96%). Within the overlaps, there was no correlation in error quality. On DCS, 73% of language-positive spots were located in the pars opercularis and pars triangularis of the frontal operculum and 24% within the supramarginal gyrus and dorsal portion of the superior temporal gyrus, while on rnTMS language positivity was distributed more evenly over a large number of gyri., Conclusions: The current protocol for rnTMS for language mapping identified language-negative sites with good dependability but was unable to reliably detect language-positive spots. Further refinements of the technique will be needed to establish rnTMS language mapping as a useful clinical tool.

Objective: Navigated transcranial magnetic stimulation (nTMS) has been increasingly used for presurgical cortical mapping of the primary motor cortex (M1) but remains controversial for the evaluation of non-primary motor areas (NPMA). This study investigates clinical and neurophysiological parameters in brain tumour patients and healthy volunteers to decide whether single-pulse biphasic nTMS allows to reliably elicite MEP outside from M1 or not., Materials and Methods: Twelve brain tumour patients and six healthy volunteers underwent M1 nTMS mapping. NPMA nTMS mapping followed using 120% and 150% M1 resting motor threshold (RMT) stimulation intensity. Spearman's correlation analysis tested the association of clinical and neurophysiological parameters between M1 and NPMA mapping., Results: A total of 88.81% of nTMS stimulations in NPMA in patients/83.87% in healthy volunteers in patients/83.87% in healthy volunteers did not result in MEPs ≥ 50 μV. Positive nTMS mapping in NPMA correlated with higher stimulation intensity and larger M1 areas in patients (120% M1 RMT SI p = 0.005/150% M1 RMT SI p = 0.198)., Conclusion: Our findings indicate that in case of positive nTMS mapping in NPMA, MEPs originate mostly from M1. For future studies, MEP parameters and TMS coil rotation should be studied closely to assess the risk for postoperative motor deterioration.

Introduction: Navigated transcranial magnetic stimulation (nTMS) is increasingly used for preoperative mapping of motor function, and clinical evidence for its benefit for brain tumor patients is accumulating. In respect to language mapping with repetitive nTMS, literature reports have yielded variable results, and it is currently not routinely performed for presurgical language localization. The aim of this project is to define a common protocol for nTMS motor and language mapping to standardize its neurosurgical application and increase its clinical value., Methods: The nTMS workshop group, consisting of highly experienced nTMS users with experience of more than 1500 preoperative nTMS examinations, met in Helsinki in January 2016 for thorough discussions of current evidence and personal experiences with the goal to recommend a standardized protocol for neurosurgical applications., Results: nTMS motor mapping is a reliable and clinically validated tool to identify functional areas belonging to both normal and lesioned primary motor cortex. In contrast, this is less clear for language-eloquent cortical areas identified by nTMS. The user group agreed on a core protocol, which enables comparison of results between centers and has an excellent safety profile. Recommendations for nTMS motor and language mapping protocols and their optimal clinical integration are presented here., Conclusion: At present, the expert panel recommends nTMS motor mapping in routine neurosurgical practice, as it has a sufficient level of evidence supporting its reliability. The panel recommends that nTMS language mapping be used in the framework of clinical studies to continue refinement of its protocol and increase reliability.

The surgical removal of brain tumours in so-called eloquent regions is frequently associated with a high risk of causing disabling postoperative deficits. Among the preoperative techniques proposed to help neurosurgical planning and procedure, navigated transcranial magnetic stimulation (nTMS) is increasingly performed. A high level of evidence is now available in the literature regarding the anatomical and functional accuracy of this mapping technique. This article presents the principles and facts demonstrating the value of using nTMS in clinical practice to preserve motor or language functions from deleterious lesions secondary to brain tumour resection or epilepsy surgery., (Copyright © 2016 Elsevier Masson SAS. All rights reserved.)

Objective: Navigated transcranial magnetic stimulation (nTMS) is a non-invasive technique for pre-surgical motor and language mapping in patients with brain lesions. This study examines the safety and tolerability of nTMS in a large, multi-center cohort of neurosurgical patients., Methods: Functional mapping with monopulse and repetitive nTMS was performed in 733 patients. In this cohort, 57% of patients had left-sided tumors, 50% had frontal tumors, and 50% had seizures secondary to the lesion. Side effects and pain intensity related to the procedure were documented., Results: Patients undergoing monopulse stimulation underwent an average of 490 pulses while those undergoing repetitive stimulation received an average of 2268 pulses. During monopulse stimulation, 5.1% reported discomfort (VAS 1-3), and 0.4% reported pain (VAS>3). During repetitive stimulation, 23.4% reported discomfort and 69.5% reported pain. No seizures or other adverse events were observed., Conclusions: nTMS is safe and well-tolerated in neurosurgical patients. Clinicians should consider expanding nTMS to patients with frequent seizures, but more evaluation is necessary to evaluate this risk fully., Significance: nTMS is safe and well-tolerated, even in neurosurgical patients with persistent occasional seizure secondary to a lesion. It should be considered in any patient with a lesion in a presumed peri-eloquent or eloquent brain region., (Copyright © 2015 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.)

The authors report on an observational study designed to isolate the impact of navigated transcranial magnetic stimulation (nTMS) on surgical outcome in glioblastoma treatment. We undertook a controlled observational study to identify the additive impact of presurgical nTMS in patients scheduled for surgical treatment of glioblastoma in or near motor eloquent locations. The trial data is derived from a large university hospital with a differential availability of its nTMS mapping service at its two campuses, both equally served by a single neurosurgical department. When available, the nTMS cortical mapping data and nTMS-based fiber tractography are used for surgical planning and patient counseling as well as intraoperative identification of the primary motor cortex and guidance in subcortical motor mapping. The addition of preoperative nTMS mapping data to a clinical routine already incorporating preoperative fiber tractography and intraoperative neuronavigation and electrophysiology was shown to improve surgical outcomes by increasing the extent of resection, without compromising patient safety or long-term functional outcomes in comparison to the concurrent non-TMS control group. This study is the first to prove that the improved surgical outcomes observed in previous studies after the implementation of nTMS to presurgical work-up are not caused by any overall improvement in patient care or a paradigm shift toward more aggressive resection but by the additional functional data provided by nTMS.

Background: Brain tumor surgery in functionally relevant areas is particularly challenging. Preoperative functional mapping with navigated transcranial magnetic stimulation (TMS) was introduced into the clinical routine in 2009 and since then has seen widespread adoption., Objectives: Accuracy and consistency of TMS motor and language mapping and its clinical relevance., Methods: Analysis of published scientific papers and discussion of the findings., Results: Positive (i.e. motor responses are elicited) and negative cortical points for TMS motor mapping can be used for treatment planning and intraoperative decision making. Language mapping points (disruption of language function) positive in TMS can support treatment planning but should be confirmed intraoperatively with direct electrical stimulation. Negative TMS language mapping (language functions are not disrupted) correlates well with the gold standard of intraoperative testing. Recent studies reported improved treatment outcome after preoperative TMS mapping., Conclusion: Patients suffering from brain tumors in eloquent locations should be counseled based on individual functional mapping data before surgery and TMS is a valid non-invasive methodology which can provide such functional mapping.

Object: Within the primary motor cortex, navigated transcranial magnetic stimulation (nTMS) has been shown to yield maps strongly correlated with those generated by direct cortical stimulation (DCS). However, the stimulation parameters for repetitive nTMS (rTMS)-based language mapping are still being refined. For this purpose, the present study compares two rTMS protocols, which differ in the timing of pulse train onset relative to picture presentation onset during object naming. Results were the correlated with DCS language mapping during awake surgery., Methods: Thirty-two patients with left-sided perisylvian tumors were examined by rTMS prior to awake surgery. Twenty patients underwent rTMS pulse trains starting at 300 ms after picture presentation onset (delayed TMS), whereas another 12 patients received rTMS pulse trains starting at the picture presentation onset (ONSET TMS). These rTMS results were then evaluated for correlation with intraoperative DCS results as gold standard in terms of differential consistencies in receiver operating characteristics (ROC) statistics. Logistic regression analysis by protocols and brain regions were conducted., Results: Within and around Broca's area, there was no difference in sensitivity (onset TMS: 100%, delayed TMS: 100%), negative predictive value (NPV) (onset TMS: 100%, delayed TMS: 100%), and positive predictive value (PPV) (onset TMS: 55%, delayed TMS: 54%) between the two protocols compared to DCS. However, specificity differed significantly (onset TMS: 67%, delayed TMS: 28%). In contrast, for posterior language regions, such as supramarginal gyrus, angular gyrus, and posterior superior temporal gyrus, early pulse train onset stimulation showed greater specificity (onset TMS: 92%, delayed TMS: 20%), NPV (onset TMS: 92%, delayed TMS: 57%) and PPV (onset TMS: 75%, delayed TMS: 30%) with comparable sensitivity (onset TMS: 75%, delayed TMS: 70%). Logistic regression analysis also confirmed the greater fit of the predictions by rTMS that had the pulse train onset coincident with the picture presentation onset when compared to the delayed stimulation. Analyses of differential disruption patterns of mapped cortical regions were further able to distinguish clusters of cortical regions standardly associated with semantic and pre-vocalization phonological networks proposed in various models of word production. Repetitive nTMS predictions by both protocols correlate well with DCS outcomes especially in Broca's region, particularly with regard to TMS negative predictions., Conclusions: With this study, we have demonstrated that rTMS stimulation onset coincident with picture presentation onset improves the accuracy of preoperative language maps, particularly within posterior language areas. Moreover, immediate and delayed pulse train onsets may have complementary disruption patterns that could differentially capture cortical regions causally necessary for semantic and pre-vocalization phonological networks., (Published by Elsevier Inc.)

Background: Neurological and oncological outcomes of motor eloquent brain-tumor patients depend upon the ability to localize functional areas and the respective proposed therapy. We set out to determine whether the use of navigated transcranial magnetic stimulation (nTMS) had an impact on treatment and outcome in patients with brain tumors in motor eloquent locations., Methods: We enrolled 250 consecutive patients and compared their functional and oncological outcomes to a matched pre-nTMS control group (n = 115)., Results: nTMS mapping results disproved suspected involvement of primary motor cortex in 25.1% of cases, expanded surgical indication in 14.8%, and led to planning of more extensive resection in 35.2% of cases and more restrictive resection in 3.5%. In comparison with the control group, the rate of gross total resections increased significantly from 42% to 59% (P < .05). Progression-free-survival for low grade glioma was significantly better in the nTMS group at 22.4 months than in control group at 15.4 months (P < .05). Integration of nTMS led to a nonsignificant change of postoperative deficits from 8.5% in the control group to 6.1% in the nTMS group., Conclusions: nTMS provides crucial data for preoperative planning and surgical resection of tumors involving essential motor areas. Expanding surgical indications and extent of resection based on nTMS enables more patients to undergo surgery and might lead to better neurological outcomes and higher survival rates in brain tumor patients. The impact of this study should go far beyond the neurosurgical community because it could fundamentally improve treatment and outcome, and its results will likely change clinical practice., (© The Author(s) 2014. Published by Oxford University Press on behalf of the Society for Neuro-Oncology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background: Intracranial arteriovenous malformations (AVM) are known to be potent inductors of functional plasticity, and their vasculature makes standard functional imaging difficult. Here we conducted functional mapping of both primary motor cortex and speech related areas in patients with AVM using navigated transcranial magnetic stimulation (nTMS), which has been recently proven as a reliable noninvasive modality of preoperative functional brain mapping., Method: nTMS mapping was performed in ten patients with unruptured intracranial AVMs located in or near eloquent areas. Motor mapping was conducted for six patients with AVMs near the rolandic region, and speech mapping was performed for four patients with left perisylvian AVMs. After the examination, all patients were treated with surgery, radiosurgery or observed with best medical treatment on case-by-case basis., Results: Motor mapping allowed for delineation of the primary motor cortex, even if the anatomy was severely obscured by the AVM in all cases with rolandic AVMs. No plastic relocation of the primary motor cortex was observed. Repetitive stimulation of the left ventral precentral gyrus led to speech impairments in all four cases that underwent speech mapping. Right hemispheric involvement was observed in one out of four cases and potentially indicated plastic changes. No side effects were observed., Conclusion: nTMS allowed for detailed delineation of eloquent areas even within hypervascularized cortical areas. Our observations indicate that nTMS functional mapping is feasible not only in tumorous brain lesions, but also in AVMs.

Background: Resection is recommended for low-grade gliomas, but often it is not performed if the tumor is suspected of invading the primary motor cortex. The study aim is to assess what influence preoperative navigated transcranial magnetic stimulation (nTMS) has on the treatment strategy and clinical outcome for suspected low-grade gliomas in presumed motor eloquent location., Methods: This paper reports on all our patients with gliomas in the primary motor cortex that were non-enhancing on MRI, since we began using nTMS (n = 11). For the comparison group, we identified the 11 most recent such patients just before we started using nTMS., Results: Exact delineation of motor functional versus non-functional cortical tissue was provided by nTMS in all cases, also within the area of altered FLAIR signal. In 6 out of 11 cases, the nTMS mapping result changed the treatment plan towards early and more extensive resection. Only one nTMS patient had another seizure within the follow-up period, whereas four patients in the comparison group had further seizures. In the nTMS group, 1 of 4 patients with pre-op neurological deficits improved by one year; whereas the comparison group had increased neurological deficits in 3 of the 8 patients not having surgery. The median (range) change of tumor volume from baseline to 1 year was -83 % (-67 % to -100 %) in the nTMS group, but +12 % (+40 % to -56 %) in the comparison group (p < 0.001)., Conclusions: nTMS provides accurate motor mapping results also in infiltrative gliomas and enables more frequent and more extensive surgical resection of non-enhancing gliomas in or near the primary motor cortex. The substantial differences observed here in neurological and oncological outcomes suggest that further comparative research is warranted.

Background: Navigated transcranial magnetic stimulation (nTMS) is increasingly being used for preoperative mapping of the motor cortex. Any new technology should undergo rigorous validation before being widely adopted in routine clinical practice. The aim of this experimental study was to assess the intraexaminer and interexaminer reliability of topographic mapping with nTMS., Methods: nTMS mapping of the motor cortex for the first dorsal interosseous (FDI) muscle was performed by an expert and a novice examiner, twice in ten healthy volunteers and once in ten tumor patients. The distances between the centers-of-gravity and hotspots were calculated, as were coefficients of variation. This study also compared orthogonal versus variable orientation of the stimulation coil., Results: The mean (range) distance between centers-of-gravity for the expert examiner in the test-retest protocol with healthy volunteers was 4.40 (1.86-7.68) mm. The mean (range) distance between centers-of-gravity for the expert vs. novice examiner was 4.89 (2.39-9.22) mm. There were no significant differences in this result between healthy volunteers and tumor patients., Conclusions: nTMS is sufficiently reliable for clinical use, but examiners should make efforts to minimize sources of error. The reliability of nTMS in tumor patients appears comparable to healthy subjects.

Background: Navigated transcranial magnetic stimulation (nTMS) is increasingly used in presurgical brain mapping. Preoperative nTMS results correlate well with direct cortical stimulation (DCS) data in the identification of the primary motor cortex. Repetitive nTMS can also be used for mapping of speech-sensitive cortical areas., Objective: The current cohort study compares the safety and effectiveness of preoperative nTMS with DCS mapping during awake surgery for the identification of language areas in patients with left-sided cerebral lesions., Methods: Twenty patients with tumors in or close to left-sided language eloquent regions were examined by repetitive nTMS before surgery. During awake surgery, language-eloquent cortex was identified by DCS. nTMS results were compared for accuracy and reliability with regard to DCS by projecting both results into the cortical parcellation system., Results: Presurgical nTMS maps showed an overall sensitivity of 90.2%, specificity of 23.8%, positive predictive value of 35.6%, and negative predictive value of 83.9% compared with DCS. For the anatomic Broca's area, the corresponding values were a sensitivity of 100%, specificity of 13.0%, positive predictive value of 56.5%, and negative predictive value of 100%, respectively., Conclusion: Good overall correlation between repetitive nTMS and DCS was observed, particularly with regard to negatively mapped regions. Noninvasive inhibition mapping with nTMS is evolving as a valuable tool for preoperative mapping of language areas. Yet its low specificity in posterior language areas in the current study necessitates further research to refine the methodology.

Object: Navigated transcranial magnetic stimulation (nTMS) is a novel technology in the field of neurosurgery for noninvasive delineation of cortical functional topography. This study addresses the spatial accuracy and clinical usefulness of nTMS in brain tumor surgery in or near the motor cortex based on a systematic review of observational studies., Methods: A systematic search retrieved 11 reports published up to October 2012 in which adult patients were examined with nTMS prior to surgery. Quality criteria consisted of documentation of the influence of nTMS brain mapping on clinical decision making in a standardized prospective manner and/or performance of intraoperative direct electrical stimulation (DES) and comparison with nTMS results. Cross-observational assessment of nTMS accuracy was established by calculating a weighted mean distance between nTMS and DES., Results: All studies reviewed in this article concluded that nTMS correlated well with the "gold standard" of DES. The mean distance between motor cortex identified on nTMS and DES by using the mean distance in 81 patients described in 6 quantitatively evaluated studies was 6.18 mm. The nTMS results changed the surgical strategy based on anatomical imaging alone in 25.3% of all patients, based on the data obtained in 87 patients in 2 studies., Conclusions: The nTMS technique spatially correlates well with the gold standard of DES. Its functional information benefits surgical decision making and changes the treatment strategy in one-fourth of cases.

Up to now, navigated transcranial magnetic stimulation (nTMS) has been used for motor mapping in the vicinity of rolandic brain lesions. Recently, nTMS has also been suggested to be useful in mapping human language areas. The authors describe the case of a left-handed patient with a left-side glioblastoma within the opercular inferior frontal gyrus who presented with severe motor aphasia. Preoperative functional MRI (fMRI) indicated speech dominance of the right hemisphere and did not show any language-related activation in the vicinity of the tumor. Navigated TMS, however, showed a significantly higher rate of induced speech arrests for the left than for the right. Left-side direct cortical stimulation induced clear speech arrests during awake surgery. This case suggests that nTMS may be useful for preoperative speech mapping in tumors affecting the anatomy, vasculature, and brain oxygen levels and therefore impairing fMRI reliability.

Purpose: To establish a novel approach for fiber tracking based on navigated transcranial magnetic stimulation (nTMS) mapping of the primary motor cortex and to propose a new algorithm for determination of an individualized fractional anisotropy value for reliable and objective fiber tracking., Methods: 50 patients (22 females, 28 males, median age 58 years (20-80)) with brain tumors compromising the primary motor cortex and the corticospinal tract underwent preoperative MR imaging and nTMS mapping. Stimulation spots evoking muscle potentials (MEP) closest to the tumor were imported into the fiber tracking software and set as seed points for tractography. Next the individual FA threshold, i.e. the highest FA value leading to visualization of tracts at a predefined minimum fiber length of 110 mm, was determined. Fiber tracking was then performed at a fractional anisotropy value of 75% and 50% of the individual FA threshold. In addition, fiber tracking according to the conventional knowledge-based approach was performed. Results of tractography of either method were presented to the surgeon for preoperative planning and integrated into the navigation system and its impact was rated using a questionnaire., Results: Mapping of the motor cortex was successful in all patients. A fractional anisotropy threshold for corticospinal tract reconstruction could be obtained in every case. TMS-based results changed or modified surgical strategy in 23 of 50 patients (46%), whereas knowledge-based results would have changed surgical strategy in 11 of 50 patients (22%). Tractography results facilitated intraoperative orientation and electrical stimulation in 28 of 50 (56%) patients. Tracking at 75% of the individual FA thresholds was considered most beneficial by the respective surgeons., Conclusions: Fiber tracking based on nTMS by the proposed standardized algorithm represents an objective visualization method based on functional data and provides a valuable instrument for preoperative planning and intraoperative orientation and monitoring., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Background: Transcranial magnetic stimulation (TMS) is the only noninvasive method for presurgical stimulation mapping of cortical function. Recent technical advancements have significantly increased the focality and usability of the method., Objective: To compare the accuracy of a 3-dimensional magnetic resonance imaging-navigated TMS system (nTMS) with the gold standard of direct cortical stimulation (DCS)., Methods: The primary motor areas of 20 patients with rolandic tumors were mapped preoperatively with nTMS at 110% of the individual resting motor threshold. Intraoperative DCS was available from 17 patients. The stimulus locations eliciting the largest electromyographic response in the target muscles ("hotspots") were determined for both methods., Results: The nTMS and DCS hotspots were located on the same gyrus in all cases. The mean ± SEM distance between the nTMS and DCS hotspots was 7.83 ± 1.18 mm for the abductor pollicis brevis (APB) muscle (n = 15) and 7.07 ± 0.88 mm for the tibialis anterior muscle (n = 8). When a low number of DCS stimulations was performed, the distance between the nTMS and DCS hotspots increased substantially (r = -0.86 for APB). After the exclusion of the cases with < 15 DCS APB responses, the mean ± SEM distance between the hotspots was only 4.70 ± 1.09 mm for APB (n = 8)., Conclusion: Peritumoral mapping of the motor cortex by nTMS agreed well with the gold standard of DCS. Thus, nTMS is a reliable tool for preoperative mapping of motor function.

Background and Importance: Navigated brain stimulation (NBS) is an emerging technology that can be used for preoperative mapping of the motor cortex. It combines conventional transcranial magnetic stimulation with neuronavigation and achieves high precision by taking into account all relevant physical factors. In contrast to functional imaging technologies, NBS does not rely on voluntary patient movements for cortical mapping. Thus, NBS can be used even on patients with severe motor impairment., Clinical Presentation: This article presents the case of a hemiplegic elderly woman with a brain tumor in the motor cortex. Preoperative NBS surprisingly demonstrated intact corticospinal tracts in the hemiplegic patient. The results modified the surgical strategy. Direct cortical stimulation was performed intraoperatively. The direct cortical stimulation results were in agreement with the preoperative NBS findings, and the clinical success of the surgery exceeded expectations., Conclusion: NBS can be used for preoperative mapping in plegic patients. Even more important, this case report discusses why tumor resection surgery based on NBS may sometimes lead to substantially better clinical outcomes than surgery planned according to functional imaging technologies.

Objective: Transcranial magnetic stimulation (TMS) is a noninvasive method for analyzing cortical function. To utilize TMS for presurgical functional diagnostics, the magnetic impulse must be precisely targeted by stereotactically positioning the coil. The aim of this study was to evaluate the usefulness of TMS for operation planning when combined with a sensor-based electromagnetic navigation system (nTMS)., Methods: Preoperative functional mapping with nTMS was performed in 10 patients with rolandic tumors. Intraoperative mapping was performed with the "gold standard" of direct cortical stimulation. Stimulation was performed in the same predefined 5-mm raster for both modalities, and the results were compared., Results: In regard to the 5-mm mapping raster, the centers of gravity of nTMS and direct cortical stimulation were located at the same spot in 4 cases and at neighboring spots in the remaining 6 cases. The mean distance between the tumor and the nearest motor response ("safety margin") was 7.9 mm (range, 5-15 mm; standard deviation, 3.2 mm) for nTMS and 6.6 mm (range, 0-12 mm; standard deviation, 3.4 mm) for direct cortical stimulation., Conclusion: nTMS allowed for reliable, precise application of the magnetic impulse, and the peritumoral somatotopy corresponded well between the 2 modalities in all 10 cases. nTMS is a promising method for preoperative functional mapping in motor cortex tumor surgery.

Objective: Intraoperative speech mapping has evolved into the "gold standard" for neurosurgical removal of lesions near the language cortex. The integration of neuronavigation into a multimodal protocol can improve the reliability of this type of operation, but most systems require rigid fixation of the patient's head throughout the operation. This article describes and evaluates a new noninvasively attached sensor-based reference tool, which can replace rigid pin fixation of the patient's head during awake craniotomies., Methods: The attachment technique and the resulting application accuracy were investigated under clinical conditions in 13 patients undergoing awake craniotomy with intraoperative mapping of cortical language sites., Results: Spatial information was used for updating the image guidance by continuously adjusting the image planes relative to the position of the patient's head. The mean registration error achieved with this technique was 1.53 +/- 0.51 mm (fiducial registration error +/- standard deviation). The system's median application accuracy between dura opening and closure ranged from 0.83 to 1.85 mm (position error)., Conclusion: The use of a reference sensor can replace uncomfortable pin fixation of the patient's head during navigation-supported awake craniotomies. Application accuracy is not affected by repositioning of the patient or by unavoidable head movements. Thus, this technique enables full exploitation of the benefits of navigation in a multimodal operative protocol without the need to rigidly fix the patient's head.

Objective: In the spine, navigation techniques serve mainly to control and accurately target insertion of implants. The main source of error is that the spine is not a rigid organ, but rather a chain of semiflexible movement segments. Any intraoperative manipulation of the patient alters the geometry and volumetry as compared to the 3D volume model created from the image data. Thus, the objective of the study was to implement the theoretical principle of microsensor referencing in a model experiment and to clarify which anatomical structures are suitable for intermittent implantation of positional sensors, as illustrated with cervical vertebral bodies., Materials and Methods: Laboratory tests were conducted using 70 models of human cervical vertebral bodies. The first experiment investigated whether arbitrary movements of vertebral bodies can be tracked with the positional information from the implanted microsensors. The accuracy of this movement monitoring was determined quantitatively on the basis of positional error measurement. In the second experiment, different ventral and dorsal surgical operations were simulated on five models of the cervical spine. Quantifiable measurement values such as the spatial extension of the intervertebral space and the relative positions of the planes of the upper plates were determined., Results: With respect to the differing anatomy of the individual vertebral bodies of the cervical spine, the sensors could be placed securely with a 5x2 mm drill. The registration error (RE) was determined as a root mean square error. The mean value was 0.9425 mm (range: 0.57-1.2 mm; median: 0.9400 mm; SD: 0.1903 mm). The precision of the movement monitoring of the vertebral body was investigated along its three main axes. The error tolerance between post-interventional 3D reconstruction and direct measurement on the model did not exceed 1.3 mm in the distance measurements or 2.5 degrees in the angular measurements. The tomograms on the system monitor could be updated in close to real time on the basis of the positional information from the reference sensor., Conclusions: Motion sensors implanted into the vertebral bodies communicated any change in position to the navigation system in close to real time, thus enabling the preoperative image data set to be updated. The experiments described could ultimately show that continuous real-time visualization of individual vertebral body movements along the movement axes (flexion-extension, tilting and rotation) is possible with high accuracy using implantable microsensors. A future application of such microsensors might be the integration of robot systems into spinal microsurgery.