NBS in planning radiotherapy

NBS mapping for safer radiotherapy

For patients undergoing radiotherapy for brain metastases, it is important to preserve quality of life after a course of therapy. For the first time, radiotherapists now have the ability to accurately and reliably modify dosing to help preserve motor function and potentially the quality of life of their patients.

Ionizing radiation is effective in treating tumor tissue because it damages the cells, slowing growth of the tumor—and at high doses can cause the cancerous cells to die. However, the radiation beams can also cause undesirable toxicity to other, healthy areas of the brain. Unlike in surgical resection, which can be guided by direct electrocortical stimulation (DES), with radiotherapy there is no way to be sure of the location of the individual patient’s motor areas, unless brain mapping is used.

On the left, isodose plan made with nTMS and on the right side isodose plan without nTMS. (Image courtesy of Maximilian Schwendner/ TU Munich)

Valuable new tool for radiotherapists

Brain mapping with Nexstim’s nTMS technology NBS® accurately defines the areas in the brain responsible for motor function—non-invasively. nTMS differs from fMRI by being a direct, causal method and there is wealth of clinical data showing good concordance of nTMS mapping with DES.1)

The NBS functional maps allow the radiotherapist to modify the dose plan in order to minimize undesired dosing of eloquent motor areas which need to be preserved. High doses of radiation are associated with cell death and high doses of radiation to motor areas are associated with a deterioration in patient’s motor function post-therapy.

Studies have shown that using nTMS to guide the orientation of the applied radiation beam allows for significantly reduced dosing to motor areas (-18.1%). Importantly, this reduction is achieved without compromising treatment of the tumors.2)

As a non-invasive method, NBS mapping is a valuable new tool for radiotherapists. NBS complements the use of non-surgical (non-invasive) treatment approaches. DICOM tools allow for direct export of NBS results into dose planning software for visualization.

1) Tarapore P, et al. Preoperative multimodal motor mapping: a comparison of magnetoencephalography imaging, navigated transcranial magnetic stimulation, and direct cortical stimulation. J Neurosurg. 2012 Aug; 117(2)

2)Schwendner, MJ. et al. The Role of Navigated Transcranial Magnetic Stimulation Motor Mapping in Adjuvant Radiotherapy Planning in Patients With Supratentorial Brain Metastases. Front Oncol. 2018 Oct 2;8:424.


Indications for 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.