Functional DTI tractography in brainstem cavernoma surgery

2020 ◽  
pp. 1-10
Author(s):  
Anna Zdunczyk ◽  
Fabia Roth ◽  
Thomas Picht ◽  
Peter Vajkoczy
Keyword(s):  
Surgical Resection ◽  
Diffusion Tensor ◽  
Motor Evoked Potential ◽  
Fiber Tracking ◽  
Motor Deficit ◽  
Individual Risk ◽  
Resting Motor Threshold ◽  
The Individual ◽  
Dti Fiber Tracking ◽  
Facial Function

OBJECTIVESurgical resection of brainstem cavernomas is associated with high postoperative morbidity due to the density of local vulnerable structures. Classical mapping of pathways by diffusion tensor imaging (DTI) has proven to be unspecific and confusing in many cases. In the current study, the authors aimed to establish a more reliable, specific, and objective method for somatotopic visualization of the descending motor pathways with navigated transcranial magnetic stimulation (nTMS)–based DTI fiber tracking.METHODSTwenty-one patients with brainstem cavernomas were examined with nTMS prior to surgery. The resting motor threshold (RMT) and cortical representation areas of hand, leg, and facial function were determined on both hemispheres. Motor evoked potential (MEP)–positive stimulation spots were then set as seed points for tractography. Somatotopic fiber tracking was performed at a fractional anisotropy (FA) value of 75% of the individual FA threshold.RESULTSMapping of the motor cortex and tract reconstruction for hand, leg, and facial function was successful in all patients. The somatotopy of corticospinal and corticonuclear tracts was also clearly depicted on the brainstem level. Higher preoperative RMT values were associated with a postoperative motor deficit (p < 0.05) and correlated with a lower FA threshold (p < 0.05), revealing structural impairment of the corticospinal tract (CST) prior to surgery. In patients with a new deficit, the distance between the lesion and CST was below 1 mm.CONCLUSIONSnTMS-based fiber tracking enables objective somatotopic tract visualization on the brainstem level and provides a valuable instrument for preoperative planning, intraoperative orientation, and individual risk stratification. nTMS may thus increase the safety of surgical resection of brainstem cavernomas.

Quantifying accuracy and precision of diffusion MR tractography of the corticospinal tract in brain tumors

2014 ◽  
Vol 121 (2) ◽  
pp. 349-358 ◽  
Author(s):  
Maria Luisa Mandelli ◽  
Mitchel S. Berger ◽  
Monica Bucci ◽  
Jeffrey I. Berman ◽  
Bagrat Amirbekian ◽  
...  
Keyword(s):  
Brain Tumors ◽  
Corticospinal Tract ◽  
Diffusion Tensor ◽  
Fiber Tracking ◽  
Subcortical White Matter ◽  
Motor Pathways ◽  
Motor Mapping ◽  
Fiber Tracts ◽  
Accuracy And Precision ◽  
Dti Fiber Tracking

Object The aim of this paper was to validate the diffusion tensor imaging (DTI) model for delineation of the corticospinal tract using cortical and subcortical white matter electrical stimulation for the location of functional motor pathways. Methods The authors compare probabilistic versus deterministic DTI fiber tracking by reconstructing the pyramidal fiber tracts on preoperatively acquired DTI in patients with brain tumors. They determined the accuracy and precision of these 2 methods using subcortical stimulation points and the sensitivity using cortical stimulation points. The authors further explored the reliability of these methods by estimation of the potential that the found connections were due to a random chance using a novel neighborhood permutation method. Results The probabilistic tracking method delineated tracts that were significantly closer to the stimulation points and was more sensitive than deterministic DTI fiber tracking to define the tracts directed to the motor sites. However, both techniques demonstrated poor sensitivity to finding lateral motor regions. Conclusions This study highlights the importance of the validation and quantification of preoperative fiber tracking with the aid of electrophysiological data during the surgery. The poor sensitivity of DTI to delineate lateral motor pathways reported herein suggests that DTI fiber tracking must be used with caution and only as adjunctive data to established methods for motor mapping.

scholarly journals Low-Frequency Repetitive Transcranial Magnetic Stimulation for Stroke-Induced Upper Limb Motor Deficit: A Meta-Analysis

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Lan Zhang ◽  
Guoqiang Xing ◽  
Shiquan Shuai ◽  
Zhiwei Guo ◽  
Huaping Chen ◽  
...  
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Upper Limb ◽  
Magnetic Stimulation ◽  
Cortical Excitability ◽  
Repetitive Transcranial Magnetic Stimulation ◽  
Meta Analysis ◽  
Low Frequency ◽  
Motor Evoked Potential ◽  
Motor Deficit ◽  
Resting Motor Threshold

Background and Purpose. This meta-analysis aimed to evaluate the therapeutic potential of low-frequency repetitive transcranial magnetic stimulation (LF-rTMS) over the contralesional hemisphere on upper limb motor recovery and cortex plasticity after stroke.Methods. Databases of PubMed, Medline, ScienceDirect, Cochrane, and Embase were searched for randomized controlled trials published before Jun 31, 2017. The effect size was evaluated by using the standardized mean difference (SMD) and a 95% confidence interval (CI). Resting motor threshold (rMT) and motor-evoked potential (MEP) were also examined.Results. Twenty-two studies of 1 Hz LF-rTMS over the contralesional hemisphere were included. Significant efficacy was found on finger flexibility (SMD = 0.75), hand strength (SMD = 0.49), and activity dexterity (SMD = 0.32), but not on body function (SMD = 0.29). The positive changes of rMT (SMD = 0.38 for the affected hemisphere and SMD = −0.83 for the unaffected hemisphere) and MEP (SMD = −1.00 for the affected hemisphere and SMD = 0.57 for the unaffected hemisphere) were also significant.Conclusions. LF-rTMS as an add-on therapy significantly improved upper limb functional recovery especially the hand after stroke, probably through rebalanced cortical excitability of both hemispheres. Future studies should determine if LF-rTMS alone or in conjunction with practice/training would be more effective.Clinical Trial Registration Information. This trial is registered with unique identifierCRD42016042181.

Individual Fiber Anatomy of the Subthalamic Region Revealed With Diffusion Tensor Imaging: A Concept to Identify the Deep Brain Stimulation Target for Tremor Suppression

Neurosurgery ◽  
2011 ◽  
Vol 68 (4) ◽  
pp. 1069-1076 ◽  
Author(s):  
Volker A. Coenen ◽  
Burkhard Mädler ◽  
Hagen Schiffbauer ◽  
Horst Urbach ◽  
Niels Allert
Keyword(s):  
Diffusion Tensor Imaging ◽  
Deep Brain Stimulation ◽  
Brain Stimulation ◽  
Diffusion Tensor ◽  
Fiber Tracking ◽  
Helical Computed Tomography ◽  
Individual Fiber ◽  
Electrode Contact ◽  
Dti Fiber Tracking ◽  
Deep Brain

Abstract BACKGROUND: Deep brain stimulation (DBS) has been proven to alleviate tremor of various origins. Distinct regions have been targeted. One explanation for good clinical tremor control might be the involvement of the dentatorubrothalamic tract (DRT) as has been suggested in superficial (thalamic) and inferior (posterior subthalamic) target regions. Beyond a correlation with atlas data and the postmortem evaluation of patients treated with lesion surgery, proof for the involvement of DRT in tremor reduction in the living, the scope of this work, is elusive. OBJECTIVE: To report a case of unilateral refractory tremor in tremor-dominant Parkinson disease treated with thalamic DBS. METHODS: Preoperative diffusion tensor imaging (DTI) was performed. Correlation with individual DBS electrode contact locations was obtained through postoperative fusion of helical computed tomography (CT) data with DTI fiber tracking. RESULTS: Tremor was alleviated effectively. An evaluation of the active electrode contact position revealed clear involvement of the DRT in tremor control. A closer evaluation of clinical effects and side effects revealed a highly detailed individual fiber map of the subthalamic region with DTI fiber tracking. CONCLUSION: This is the first time the involvement of the DRT in tremor reduction through DBS has been shown in the living. The combination of DTI with postoperative CT and the evaluation of the electrophysiological environment of distinct electrode contacts led to an individual detailed fiber map and might be extrapolated to refined DTI-based targeting strategies in the future. Data acquisition for a larger study group is the topic of our ongoing research.

scholarly journals Risk Assessment by Presurgical Tractography Using Navigated TMS Maps in Patients with Highly Motor- or Language-Eloquent Brain Tumors

Cancers ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1264 ◽  
Author(s):  
Nico Sollmann ◽  
Haosu Zhang ◽  
Alessia Fratini ◽  
Noémie Wildschuetz ◽  
Sebastian Ille ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Diffusion Tensor ◽  
Functional Decline ◽  
World Health ◽  
Individual Risk ◽  
Language Function ◽  
Patient Counseling ◽  
Who Grade ◽  
Health Organization ◽  
The Individual

Patients with functionally eloquent brain lesions are at risk of functional decline in the course of resection. Given tumor-related plastic reshaping and reallocation of function, individual data are needed for patient counseling and risk assessment prior to surgery. This study evaluates the utility of mapping by navigated transcranial magnetic stimulation (nTMS) and nTMS-based diffusion tensor imaging fiber tracking (DTI FT) for individual risk evaluation of surgery-related decline of motor or language function in the clinical setting. In total, 250 preoperative nTMS mappings (100 language and 150 motor mappings) derived from 216 patients (mean age: 57.0 ± 15.5 years, 58.8% males; glioma World Health Organization (WHO) grade I & II: 4.2%, glioma WHO grade III & IV: 83.4%, arteriovenous malformations: 1.9%, cavernoma: 2.3%, metastasis: 8.2%) were included. Deterministic tractography based on nTMS motor or language maps as seed regions was performed with 25%, 50%, and 75% of the individual fractional anisotropy threshold (FAT). Lesion-to-tract distances (LTDs) were measured between the tumor mass and the corticospinal tract (CST), arcuate fascicle (AF), or other closest language-related tracts. LTDs were compared between patients and correlated to the functional status (no/transient/permanent surgery-related paresis or aphasia). Significant differences were found between patients with no or transient surgery-related deficits and patients with permanent surgery-related deficits regarding LTDs in relation to the CST (p < 0.0001), AF (p ≤ 0.0491), or other closest language-related tracts (p ≤ 0.0435). The cut-off values for surgery-related paresis or aphasia were ≤ 12 mm (LTD—CST) and ≤ 16 mm (LTD—AF) or ≤25 mm (LTD—other closest language-related tract), respectively. Moreover, there were significant associations between the status of surgery-related deficits and the LTD when considering the CST (range r: −0.3994 to −0.3910, p < 0.0001) or AF (range r: −0.2918 to −0.2592, p = 0.0135 and p = 0.0473 for 25% and 50% FAT). In conclusion, this is the largest study evaluating the application of both preoperative functional mapping and function-based tractography for motor and language function for risk stratification in patients with functionally eloquent tumors. The LTD may qualify as a viable marker that can be seamlessly assessed in the clinical neurooncological setup.

Pediatric navigated transcranial magnetic stimulation motor and language mapping combined with diffusion tensor imaging tractography: clinical experience

2020 ◽  
Vol 26 (5) ◽  
pp. 583-593
Author(s):  
Tizian Rosenstock ◽  
Thomas Picht ◽  
Heike Schneider ◽  
Peter Vajkoczy ◽  
Ulrich-Wilhelm Thomale
Keyword(s):  
Diffusion Tensor Imaging ◽  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Surgical Planning ◽  
Diffusion Tensor ◽  
Fiber Tracking ◽  
Navigated Transcranial Magnetic Stimulation ◽  
Language Mapping ◽  
Eloquent Areas ◽  
Dti Fiber Tracking

OBJECTIVEIn adults, navigated transcranial magnetic stimulation (nTMS) has been established as a preoperative examination method for brain tumors in motor- and language-eloquent locations. However, the clinical relevance of nTMS in children with brain tumors is still unclear. Here, the authors present their initial experience with nTMS-based surgical planning and family counseling in pediatric cases.METHODSThe authors analyzed the feasibility of nTMS and its influence on counseling and surgical strategy in a prospective study conducted between July 2017 and September 2019. The main inclusion criterion was a potential benefit from functional mapping data derived from nTMS and/or nTMS-enhanced tractography in pediatric patients who presented to the authors’ department prior to surgery for lesions close to motor- and/or speech-eloquent areas. The study was undertaken in 14 patients (median age 7 years, 8 males) who presented with different brain lesions.RESULTSMotor mapping combined with cortical seed area definition could be performed in 10 children (71%) to identify the corticospinal tract by additional diffusion tensor imaging (DTI). All motor mappings could be performed successfully without inducing relevant side effects. In 7 children, nTMS language mapping was performed to detect language-relevant cortical areas and DTI fiber tractography was performed to visualize the individual language network. nTMS examination was not possible in 4 children because of lack of compliance (n = 2), syncope (n = 1), and preexisting implant (n = 1). After successful mapping, the spatial relation between lesion and functional tissue was used for surgical planning in all 10 patients, and 9 children underwent nTMS-DTI integrated neuronavigation. No surgical complications or unexpected neurological deterioration was observed. In all successful nTMS cases, better function-based counseling was offered to the families. In 6 of 10 patients the surgical strategy was adapted according to nTMS data, and in 6 of 10 cases the extent of resection (EOR) was redefined.CONCLUSIONSnTMS and DTI fiber tracking were feasible for the majority of children. Presurgical counseling as well as surgical planning for the approach and EOR were improved by the nTMS examination results. nTMS in combination with DTI fiber tracking can be regarded as beneficial for neurosurgical procedures in eloquent areas in the pediatric population.

Language pathway tracking: comparing nTMS-based DTI fiber tracking with a cubic ROIs-based protocol

2017 ◽  
Vol 126 (3) ◽  
pp. 1006-1014 ◽  
Author(s):  
Chiara Negwer ◽  
Nico Sollmann ◽  
Sebastian Ille ◽  
Theresa Hauck ◽  
Stefanie Maurer ◽  
...  
Keyword(s):  
Diffusion Tensor ◽  
Fiber Tracking ◽  
Subcortical Structures ◽  
Language Mapping ◽  
Glioma Surgery ◽  
Fiber Tracts ◽  
Uncinate Fascicle ◽  
Dti Fiber Tracking ◽  
Language Pathways ◽  
Diffusion Tensor Imaging Dti

OBJECTIVE Diffusion tensor imaging (DTI) fiber tracking (FT) has been widely used in glioma surgery in recent years. It can provide helpful information about subcortical structures, especially in patients with eloquent space-occupying lesions. This study compared the newly developed navigated transcranial magnetic stimulation (nTMS)-based DTI FT of language pathways with the most reproducible protocol for language pathway tractography, using cubic regions of interest (ROIs) for the arcuate fascicle. METHODS Thirty-seven patients with left-sided perisylvian lesions underwent language mapping by repetitive nTMS. DTI FT was performed using the cubic ROIs–based protocol and the authors' nTMS-based DTI FT approach. The same minimal fiber length and fractional anisotropy were chosen (50 mm and 0.2, respectively). Both protocols were performed with standard clinical tractography software. RESULTS Both methods visualized language-related fiber tracts (i.e., corticonuclear tract, arcuate fascicle, uncinate fascicle, superior longitudinal fascicle, inferior longitudinal fascicle, arcuate fibers, commissural fibers, corticothalamic fibers, and frontooccipital fascicle) in all 37 patients. Using the cubic ROIs-based protocol, 39.9% of these language-related fiber tracts were detected in the examined patients, as opposed to 76.0% when performing nTMS-based DTI FT. For specifically tracking the arcuate fascicle, however, the cubic ROIs-based approach showed better results (97.3% vs 75.7% with nTMS-based DTI FT). CONCLUSIONS The cubic ROIs-based protocol was designed for arcuate fascicle tractography, and this study shows that it is still useful for this intention. However, superior results were obtained using the nTMS-based DTI FT for visualization of other language-related fiber tracts.

scholarly journals Benefit of Action Naming Over Object Naming for Visualization of Subcortical Language Pathways in Navigated Transcranial Magnetic Stimulation-Based Diffusion Tensor Imaging-Fiber Tracking

2021 ◽  
Vol 15 ◽  
Author(s):  
Ann-Katrin Ohlerth ◽  
Roelien Bastiaanse ◽  
Chiara Negwer ◽  
Nico Sollmann ◽  
Severin Schramm ◽  
...  
Keyword(s):  
Diffusion Tensor Imaging ◽  
Magnetic Stimulation ◽  
Diffusion Tensor ◽  
Fiber Tracking ◽  
Object Naming ◽  
Navigated Transcranial Magnetic Stimulation ◽  
Language Mapping ◽  
Action Naming ◽  
Dti Fiber Tracking ◽  
Language Pathways

Visualization of functionally significant subcortical white matter fibers is needed in neurosurgical procedures in order to avoid damage to the language network during resection. In an effort to achieve this, positive cortical points revealed during preoperative language mapping with navigated transcranial magnetic stimulation (nTMS) can be employed as regions of interest (ROIs) for diffusion tensor imaging (DTI) fiber tracking. However, the effect that the use of different language tasks has on nTMS mapping and subsequent DTI-fiber tracking remains unexplored. The visualization of ventral stream tracts with an assumed lexico-semantic role may especially benefit from ROIs delivered by the lexico-semantically demanding verb task, Action Naming. In a first step, bihemispheric nTMS language mapping was administered in 18 healthy participants using the standard task Object Naming and the novel task Action Naming to trigger verbs in a small sentence context. Cortical areas in which nTMS induced language errors were identified as language-positive cortical sites. In a second step, nTMS-based DTI-fiber tracking was conducted using solely these language-positive points as ROIs. The ability of the two tasks’ ROIs to visualize the dorsal tracts Arcuate Fascicle and Superior Longitudinal Fascicle, the ventral tracts Inferior Longitudinal Fascicle, Uncinate Fascicle, and Inferior Fronto-Occipital Fascicle, the speech-articulatory Cortico-Nuclear Tract, and interhemispheric commissural fibers was compared in both hemispheres. In the left hemisphere, ROIs of Action Naming led to a significantly higher fraction of overall visualized tracts, specifically in the ventral stream’s Inferior Fronto-Occipital and Inferior Longitudinal Fascicle. No difference was found between tracking with Action Naming vs. Object Naming seeds for dorsal stream tracts, neither for the speech-articulatory tract nor the inter-hemispheric connections. While the two tasks appeared equally demanding for phonological-articulatory processes, ROI seeding through the task Action Naming seemed to better visualize lexico-semantic tracts in the ventral stream. This distinction was not evident in the right hemisphere. However, the distribution of tracts exposed was, overall, mirrored relative to those in the left hemisphere network. In presurgical practice, mapping and tracking of language pathways may profit from these findings and should consider inclusion of the Action Naming task, particularly for lesions in ventral subcortical regions.

Continuous dynamic mapping of the corticospinal tract during surgery of motor eloquent brain tumors: evaluation of a new method

2014 ◽  
Vol 120 (5) ◽  
pp. 1015-1024 ◽  
Author(s):  
Andreas Raabe ◽  
Jürgen Beck ◽  
Philippe Schucht ◽  
Kathleen Seidel
Keyword(s):  
Corticospinal Tract ◽  
Diffusion Tensor ◽  
Motor Evoked Potential ◽  
Motor Deficit ◽  
Mapping Technique ◽  
Tumor Surgery ◽  
Motor Mapping ◽  
Dynamic Mapping ◽  
Spatial Coverage ◽  
Continuous Dynamic

Object The authors developed a new mapping technique to overcome the temporal and spatial limitations of classic subcortical mapping of the corticospinal tract (CST). The feasibility and safety of continuous (0.4–2 Hz) and dynamic (at the site of and synchronized with tissue resection) subcortical motor mapping was evaluated. Methods The authors prospectively studied 69 patients who underwent tumor surgery adjacent to the CST (< 1 cm using diffusion tensor imaging and fiber tracking) with simultaneous subcortical monopolar motor mapping (short train, interstimulus interval 4 msec, pulse duration 500 μsec) and a new acoustic motor evoked potential alarm. Continuous (temporal coverage) and dynamic (spatial coverage) mapping was technically realized by integrating the mapping probe at the tip of a new suction device, with the concept that this device will be in contact with the tissue where the resection is performed. Motor function was assessed 1 day after surgery, at discharge, and at 3 months. Results All procedures were technically successful. There was a 1:1 correlation of motor thresholds for stimulation sites simultaneously mapped with the new suction mapping device and the classic fingerstick probe (24 patients, 74 stimulation points; r2 = 0.98, p < 0.001). The lowest individual motor thresholds were as follows: > 20 mA, 7 patients; 11–20 mA, 13 patients; 6–10 mA, 8 patients; 4–5 mA, 17 patients; and 1–3 mA, 24 patients. At 3 months, 2 patients (3%) had a persistent postoperative motor deficit, both of which were caused by a vascular injury. No patient had a permanent motor deficit caused by a mechanical injury of the CST. Conclusions Continuous dynamic mapping was found to be a feasible and ergonomic technique for localizing the exact site of the CST and distance to the motor fibers. The acoustic feedback and the ability to stimulate the tissue continuously and exactly at the site of tissue removal improves the accuracy of mapping, especially at low (< 5 mA) stimulation intensities. This new technique may increase the safety of motor eloquent tumor surgery.

Bicentric validation of the navigated transcranial magnetic stimulation motor risk stratification model

2021 ◽  
pp. 1-13
Author(s):  
Tizian Rosenstock ◽  
Levin Häni ◽  
Ulrike Grittner ◽  
Nicolas Schlinkmann ◽  
Meltem Ivren ◽  
...  
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Risk Stratification ◽  
Magnetic Stimulation ◽  
Corticospinal Tract ◽  
Fiber Tracking ◽  
Motor Deficit ◽  
Navigated Transcranial Magnetic Stimulation ◽  
Risk Stratification Model ◽  
Motor Outcome ◽  
Dti Fiber Tracking

OBJECTIVE The authors sought to validate the navigated transcranial magnetic stimulation (nTMS)–based risk stratification model. The postoperative motor outcome in glioma surgery may be preoperatively predicted based on data derived by nTMS. The tumor-to-tract distance (TTD) and the interhemispheric resting motor threshold (RMT) ratio (as a surrogate parameter for cortical excitability) emerged as major factors related to a new postoperative deficit. METHODS In this bicentric study, a consecutive prospectively collected cohort underwent nTMS mapping with diffusion tensor imaging (DTI) fiber tracking of the corticospinal tract prior to surgery of motor eloquent gliomas. The authors analyzed whether the following items were associated with the patient’s outcome: patient characteristics, TTD, RMT value, and diffusivity parameters (fractional anisotropy [FA] and apparent diffusion coefficient [ADC]). The authors assessed the validity of the published risk stratification model and derived a new model. RESULTS A new postoperative motor deficit occurred in 36 of 165 patients (22%), of whom 20 patients still had a deficit after 3 months (13%; n3 months = 152). nTMS-verified infiltration of the motor cortex as well as a TTD ≤ 8 mm were confirmed as risk factors. No new postoperative motor deficit occurred in patients with TTD > 8 mm. In contrast to the previous risk stratification, the RMT ratio was not substantially correlated with the motor outcome, but high RMT values of both the tumorous and healthy hemisphere were associated with worse motor outcome. The FA value was negatively associated with worsening of motor outcome. Accuracy analysis of the final model showed a high negative predictive value (NPV), so the preoperative application may accurately predict the preservation of motor function in particular (day of discharge: sensitivity 47.2%, specificity 90.7%, positive predictive value [PPV] 58.6%, NPV 86.0%; 3 months: sensitivity 85.0%, specificity 78.8%, PPV 37.8%, NPV 97.2%). CONCLUSIONS This bicentric validation analysis further improved the model by adding the FA value of the corticospinal tract, demonstrating the relevance of nTMS/nTMS-based DTI fiber tracking for clinical decision making.

scholarly journals Preoperative nTMS and Intraoperative Neurophysiology - A Comparative Analysis in Patients With Motor-Eloquent Glioma

2021 ◽  
Vol 11 ◽  
Author(s):  
Tizian Rosenstock ◽  
Mehmet Salih Tuncer ◽  
Max Richard Münch ◽  
Peter Vajkoczy ◽  
Thomas Picht ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Risk Stratification ◽  
Right Hemisphere ◽  
Diffusion Tensor ◽  
Motor Deficit ◽  
Partial Recovery ◽  
Resting Motor Threshold ◽  
Common Diagnosis ◽  
Motor Outcome ◽  
Amplitude Decrease

BackgroundThe resection of a motor-eloquent glioma should be guided by intraoperative neurophysiological monitoring (IOM) but its interpretation is often difficult and may (unnecessarily) lead to subtotal resection. Navigated transcranial magnetic stimulation (nTMS) combined with diffusion-tensor-imaging (DTI) is able to stratify patients with motor-eloquent lesion preoperatively into high- and low-risk cases with respect to a new motor deficit.ObjectiveTo analyze to what extent preoperative nTMS motor risk stratification can improve the interpretation of IOM phenomena.MethodsIn this monocentric observational study, nTMS motor mapping with DTI fiber tracking of the corticospinal tract was performed before IOM-guided surgery for motor-eloquent gliomas in a prospectively collected cohort from January 2017 to October 2020. Descriptive analyses were performed considering nTMS data (motor cortex infiltration, resting motor threshold (RMT), motor evoked potential (MEP) amplitude, latency) and IOM data (transcranial MEP monitoring, intensity of monopolar subcortical stimulation (SCS), somatosensory evoked potentials) to examine the association with the postoperative motor outcome (assessed at day of discharge and at 3 months).ResultsThirty-seven (56.1%) of 66 patients (27 female) with a median age of 48 years had tumors located in the right hemisphere, with glioblastoma being the most common diagnosis with 39 cases (59.1%). Three patients (4.9%) had a new motor deficit that recovered partially within 3 months and 6 patients had a persistent deterioration (9.8%). The more risk factors of the nTMS risk stratification model (motor cortex infiltration, tumor-tract distance (TTD) ≤8mm, RMTratio &lt;90%/&gt;110%) were detected, the higher was the risk for developing a new postoperative motor deficit, whereas no patient with a TTD &gt;8mm deteriorated. Irreversible MEP amplitude decrease &gt;50% was associated with worse motor outcome in all patients, while a MEP amplitude decrease ≤50% or lower SCS intensities ≤4mA were particularly correlated with a postoperative worsened motor status in nTMS-stratified high-risk cases. No patient had postoperative deterioration of motor function (except one with partial recovery) when intraoperative MEPs remained stable or showed only reversible alterations.ConclusionsThe preoperative nTMS-based risk assessment can help to interpret ambiguous IOM phenomena (such as irreversible MEP amplitude decrease ≤50%) and adjustment of SCS stimulation intensity.

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