Cortical neuroplasticity has been demonstrated in eloquent motor and language regions of the brain due to tumor growth. This has substantial implications for the neurosurgical intervention of brain tumors, as the cortical function may not reside where anatomical magnetic resonance imaging suggests it to be. Therefore, preoperative localization of eloquent areas may demonstrate unexpected organization that can influence the neurosurgical approach to the lesion.
Leveraging knowledge of an individual’s functional anatomy may be key to minimize the risk of functional worsening and to better counsel patients prior to tumor resection.
In May, a neurosurgery team at the Technical University of Munich (TUM) in Germany published an important article in Cancers which offers neurosurgeons a standardized, science-based tool to assess pre-procedural risk using nTMS-guided diffusion tensor imaging (DTI). The study included 250 preoperative nTMS mappings (100 language, 150 motor) from 216 patients undergoing surgical resection for glioma, AVM, cavernoma, or metastasis.
The article by Sollmann and colleagues investigated the utility of preoperative functional mapping and function-based tractography to develop a personalized preoperative risk assessment in patients with highly motor- or language-eloquent brain tumors using Nexstim’s NBS System and nTMS-based diffusion tensor imaging fiber tracking (DTI FT).
This risk stratification was based off of the comparisons of the lesion-to-tract distance (LTD) between patients and correlated to post-surgical functional status. The authors suggest that the closer a tract (motor or language) is in relation to the site of surgery, the higher the risk for potential damage due to both the surgical procedure and potential vascular affection. The authors found that LTDs were highly different between patients with no or only transient surgery-related deficits and patients with permanent surgery-related deficits. While future research is necessary, the correlations to functional outcome may enable the LTD to become a viable preoperative marker in the clinical neurooncological realm.
Sollmann, N.; Zhang, H.; Fratini, A.; Wildschuetz, N.; Ille, S.; Schröder, A.; Zimmer, C.; Meyer, B.; Krieg, S.M. Risk Assessment by Presurgical Tractography Using Navigated TMS Maps in Patients with Highly Motor- or Language-Eloquent Brain Tumors. Cancers 2020, 12, 1264.
https://www.mdpi.com/2072-6694/12/5/1264
Nexstim NBS System: Indications or Use
The Nexstim Navigated Brain Stimulation (NBS) System 5 is indicated for non-invasive mapping of the primary motor cortex of the brain to its cortical gyrus. The Nexstim NBS System 5 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 5, is indicated for non-invasive 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. Intra-operatively, the localization information provided by NexSpeech® is intended to be verified by direct cortical stimulation.
The Nexstim NBS System 5 and NBS System 5 with NexSpeech® are not intended to be used during a surgical procedure.
The Nexstim NBS System 5 and NBS System 5 with NexSpeech® are intended to be used by trained clinical professionals.