Navigated Brain Stimulation (NBS) by Nexstim is the only CE marked and FDA cleared noninvasive solution to presurgical mapping of the motor cortex. The NBS System 5 adds navigation to transcranial magnetic stimulation (nTMS), creating a precise map of the eloquent cortex superimposed on a patient specific MRI. NBS accurately locates the stimulating electric field (E-field) in the cortex, with the proven accuracy of direct cortical stimulation (DCS)1.
The patient’s motor responses are clearly marked as pegs color coded as a heat scale. Each mapping session can be stored to precisely replicate any session at a later date. The NBS 5’s mapping results can be exported via DICOM to planning systems or directly into the neuronavigator. In the OR, NBS maps help optimal placement of DCS electrodes and facilitates surgical guidance.
In a recent study of 250 consecutive patients, presurgical mapping with NBS enabled a more aggressive surgical strategy in more the 75% of the cases. The same study using navigated TMS (nTMS) disproved suspected involvement of the primary motor cortex in over 25% of the cases, expanding surgical indication by 14.8%. The study concluded that the integration of nTMS into the surgical workflow crucially improves pre-operative planning, patient counseling, and surgical procedures, leading to longer progression-free survival rates and better neurological outcomes by expanding the indications and extent of resection.3
Introduction: Language mapping by repetitive navigated transcranial magnetic stimulation (rTMS) is used for resection planning in patients suffering from brain lesions within regions known to be involved in language.
Methods: We enrolled 25 patients with language eloquently located brain lesions undergoing preoperative rTMS language mapping (GROUP 1, 2011–2013), with the mapping results not being available for the surgeon, and we matched these patients with 25 subjects who also underwent preoperative rTMS (GROUP 2, 2013–2014), but the mapping results were taken into account during tumor resection. Additionally, cortical language maps were generated by analyzing preoperative rTMS and intraoperative direct cortical stimulation (DCS) data.
Results: Group 1 patients had significantly more post-operative language deficits than did Group 2 patients (p=0.00153) even though there was no significant difference in pre-operative language deficits. Group 2 patients surgical procedures were completed with significantly smaller craniotomies than those in Group 1. Trends toward fewer unexpected residual tumors, shorter surgical times, shorter length of stay, and higher Karnofsky scores for patients in Group 2.
Conclusion: The present study provides a first hint that the clinical course of patients suffering from brain tumors might be improved by preoperative rTMS language mapping. However, a significant difference between both groups was only found for craniotomy extents and postoperative deficits, but not for other clinical parameters, which only showed a trend toward better results in GROUP 2. Therefore, multicenter trials with higher sample sizes are needed to further investigate the distinct impact of rTMS language mapping on the clinical course of brain tumor patients.
Publication: BMC Cancer (2015) 15:261 DOI 10.1186/s12885-015-1299-5
Introduction: The integration of state-of-the-art neuroimaging into treatment planning may increase the therapeutic potential of stereotactic radiosurgery. Functional neuroimaging, including functional MRI, navigated brain stimulation, and diffusion tensor imaging-based tractography, may guide the orientation of radiation beams to decrease the dose to critical cortical and subcortical areas. The authors describe their method of integrating functional neuroimaging technology into radiosurgical treatment planning using the CyberKnife radiosurgery system.
Methods: The records of all patients who had undergone radiosurgery for brain lesions at the CyberKnife Center of the University of Messina, Italy, between July 2010 and July 2012 were analyzed. Among patients with brain lesions in critical areas, treatment planning with the integration of functional neuroimaging was performed in 25 patients. Morphological and functional imaging data sets were coregistered using the Multiplan dedicated treatment planning system. Treatment planning was initially based on morphological data; radiation dose distribution was then corrected in relation to the functionally relevant cortical and subcortical areas. The change in radiation dose distribution was then calculated.
Results: The data sets could be easily and reliably integrated into the CyberKnife treatment planning. Using an inverse planning algorithm, the authors achieved an average 17% reduction in the radiation dose to functional areas. Further gain in terms of dose sparing compromised other important treatment parameters, including target coverage, conformality index, and number of monitor units. No neurological deficit due to radiation was recorded at the short-term follow-up.
Conclusions: Radiosurgery treatments rely on the quality of neuroimaging. The integration of functional data allows a reduction in radiation doses to functional organs at risk, including critical cortical areas, subcortical tracts, and vascular structures. The relative simplicity of integrating functional neuroimaging into radiosurgery warrants further research to implement, standardize, and identify the limits of this procedure.
Publication: Neurosurg Focus. 2013 Apr;34(4):E5. doi: 10.3171/2013.2.FOCUS12414. http://www.ncbi.nlm.nih.gov/pubmed/23544411
Background: Stereotactic radiosurgery (SRS) is an established method for treating focal intracranial tumors with good results. However, SRS close to eloquent cortex carries the risk of new neurological deficits. Incidences of new motor deficits of up to 26% have been reported for radiosurgery of metastatic brain tumors in the motor cortex (1). To prevent complications, planning of radiosurgery is performed with the aim of minimizing the exposure of functionally critical cortex to radiation. In practice, this is done based on the approximate neuroanatomic locations of the cortical functions. However, this method neither allows for patient-specific variation, nor fully reflects the functional anatomy of the individual patient.
Navigated Brain Stimulation (NBS) is a non-invasive transcranial magnetic stimulation (TMS) technique. In NBS mapping, the patient’s MRI dataset is used to link the location of the TMS-generated stimulating electric field to the individual patient’s cortical anatomy. Using familiar stereotactic navigation techniques, movement of the TMS coil guides the calculated e-field location through the intracranial structures. DICOM-export of the motor response maps from the NBS System (Nexstim Oy, Helsinki, Finland) permits direct integration of the functional mapping data into other DICOM-compatible software applications, allowing the NBS mapping results to be viewed also during intervention planning. In clinical studies in brain tumor surgery, the NBS System localized the motor cortex in all patients to the same gyrus as intraoperative direct cortical stimulation (DCS). According to the operating neurosurgeons, the results of preoperative mapping of the motor cortex with NBS are as accurate as mapping with DCS (2,
Conclusion: This case demonstrates that accurate, patient-specific NBS motor mapping data can be successfully integrated into the GammaPlan® software, provide information useful for clinical decision-making and can be used for planning optimal SRS delivery.
Publication: White paper 05.03.2011
Background: Stereotactic radiosurgery close to eloquent cortex carries the risk of new neurological deficits. Incidences of new motor deficits of up to 26% have been reported for radiosurgery of metastatic brain tumors in the motor cortex. To prevent complications, planning of radiosurgery is performed with the aim of minimizing the exposure of functionally critical cortex to radiation. In practice, planning software utilize standardized anatomy-based probabilistic maps of approximate locations of cortical functions. However, the maps do not allow for patient-specific variations and do not fully reflect the functional anatomy of the patient.
A non-invasive integrated navigated transcranial magnetic stimulation system (NBS) has received marketing authorization from FDA for localization and assessment of primary motor cortex for pre-procedural planning. In clinical studies in brain tumor surgery, the system localized the motor cortex in all patients to the same gyrus as intraoperative direct cortical stimulation (DCS). According to the neurosurgeons, the results of preoperative mapping of the motor cortex with NBS were as accurate as DCS.
Results: NBS mapping of the hand motor cortex was successfully performed. The obtained information on the location of the functional motor cortex was successfully exported in DICOM format from the NBS software and upload to the BrainLab iPlan radiosurgery planning software.
Conclusions: The study demonstrates that accurate patient-specific noninvasive motor mapping data can be easily and successfully incorporated into planning software for stereotactic radiosurgery. Use of the combined data in radiation planning may provide an additional tool to decrease the likelihood for complications affecting the motor system.
Publication: Abstract presented at the International Stereotactic Radiosurgery Society Annual Meeting in Paris, 2010 ISRS-Poster-2012.pdf
Introduction: In recent years, the neurosurgical operating microscope has undergone rapid development, increasingly becoming the neurosurgeon’s workstation for open microneurosurgery. Integration of the surgical planning data, image-guided orientation, and automatic laser-guided optical focusing are significant developments which support more precise delineation between the normal and pathological brain tissue. Brain tumours as well as vascular malformations may significantly alter the pathological brain tissue. Brain tumours as well as vascular malformations may significantly alter the normal function neuroanatomy which makes the delineation of safe resection by anatomical landmarks challenging especially when the lesions lie close to the eloquent cortical or white matter areas. The integration of accurate and reliable functional localization data into the neurosurgeon’s visual field would allow safer and more complete resections.
Navigated Brain Stimulation (NBS) is a non-invasive transcranial magnetic stimulation (TMS) technique for the accurate localization of cortical muscle representation areas displayed in detailed cortical anatomy of individual MR images. The functional cortical mapping data obtained by the NBS System (Nexstim Oy, Helsinki, Finland) can be transferred to the neuronavigation system for display during surgery (Figure 1).
Results: In this patient case study, NBS data and the DCS data of the M1 were found to be well overlapping. Brain shift was minimal as the DCS mapping was performed immediately after the dura was opened.
This study illustrated that the integration of preoperative functional localizing data of eloquent motor areas into the OPMI® Pentero® surgical microscopes was straightforward and very practical. The data projected into the visual surgical field supported safer and optimal resection of a lesion in a critical functional location. DICOM compatibility enabled the mapping data from the Nexstim NBS system to be introduced via a StealthStation® neuronavigation system into the operation room workflow reliably, with minimal additional time and workload required from the supporting personnel.
Conclusion: Integration of functional mapping data from the Nexstim NBS System via the Medtronic Stealth Station® neuronavigation system into the surgical visual field of the neuronavigated Zeiss OPMI® Pentero® surgical microscope is a clinically practical concept and supports safer and optimal resection of lesions near critical functional locations.
Publication: White Paper 2010, October 6
History: A 50 year old female, right-handed patient presented with weakness and acroataxia of the right hand. She was admitted to the neurological Department and after an MRI scan showed a single lesion within the left precentral gyrus which was suggestive to be a metastasis of her colon cancer. For further treatment, she was transferred to our neurosurgical department.
Mapping: The MRI scan shows this space occupying lesion to be within the center of the supposed rolandic region. However, due to tumor and edema, the hand knob was not identifiable. Thus, non-invasive cortical motor mapping was performed. Due to edema, motor threshold was extraordinary high, but after determining motor threshold motor mapping of the left motor cortex was performed without any further problem with the Nexstim eXimia NBS system. Transcranial magnetic stimulation (TMS) of the tumor surrounding cortex was done. Motor evoked potentials (MEP) were recorded at the dorsal and medial borders of the metastasis. These positive NBS stimulation points were exported via DICOM and fused with BrainLab neuronavigation data using iPlanet® and transferred to BrainLAB Vector Vision®.
Conclusion: Especially for metastatic lesions complete resection is of crucial importance. However, motor function has to be preserved anyhow. We noticed that NBS simplifies locating of the central region. In some cases, craniotomy might even become smaller Furthermore combination of NBS with navigated direct cortical mapping serves as a link between imaging and electrophysiological intraoperative neuromonitoring.
Publication: Case Report from Technishe Universitat Munchen (TUM), Department of Neurosurgery 2010.07.31
The Nexstim NBS System is indicated for noninvasive mapping of the primary motor cortex of the brain to its cortical gyrus. The NBS System provides information that may be used in the assessment of the primary motor cortex for pre-procedural planning.
Nexstim NexSpeech®, when used together with the NBS System, is indicated for noninvasive localization of cortical areas that do not contain essential speech function. NexSpeech® provides information that may be used in pre-surgical planning in patients undergoing brain surgery. Intraoperatively, the localization information provided by NexSpeech® is intended to be verified by direct cortical stimulation.
The Nexstim NBS System and NBS System with NexSpeech® are not intended to be used during a surgical procedure. The NBS System and NBS System with NexSpeech are intended to be used by trained clinical professionals.
1 Preoperative multimodal motor mapping: a comparison of magnetoencephalography imaging,navigated transcranial magnetic stimulation, and direct cortical stimulation By: Phiroz E. Tarapore, M.D., Mitchel S. Berger, M.D., et. al Journal of Neurosurgery. 2012 Aug;117(2):354-62. doi: 10.3171/2012.5.JNS112124
2 Preoperative motor mapping by navigated transcranial magnetic brain stimulation improves outcome for motor eloquent lesions By: Krieg SM, Ringel F, el. al Neuro-Oncology. 2014 Feb 9.
3 Navigated transcranial magnetic stimulation improves the treatment outcome in patients with brain tumors in motor eloquent locations By: Frey D, P Vajkoczy, T Picht, et. al Neuro-Oncology. 2014 Jun 12. pii: nou110.