New hope for patients with brain tumors in eloquent cortex

Clinicians report on use of NBS mapping to confirm brain plasticity following neurosurgery

HELSINKI, Finland – Sept. 20, 2012 -- In a newly published paper, neurosurgeons report on a patient case where multi-stage operations on a brain tumor preceded by NBS motor mapping allowed for complete resection of a low grade glioma (LGG) brain tumor which had invaded highly eloquent cortex, without neurological damage to the patient.

In adults, LGGs represent as many as 15% of all primary brain tumours. Surgical resection offers LGG patients the best outcome and the extent of tumour resection is known to be a positive prognostic factor for survival. However, when tumors in or near eloquent areas, the extent of resection can be limited by the need to preserve the patient´s neuropsychological function. This case report offers hope to patients with LGGs in eloquent locations since recent findings suggest that eloquent area relocation following surgeries may not be a rare event. Until recently, the reliable measurement and identification of brain plasticity has only been possible with invasive cortical stimulation. Now, with the Nexstim NBS System, brain plasticity can be assessed non-invasively following surgery in order to help identify those patients who may benefit from multi-stage surgical treatment.

In their paper Plastic relocation of motor cortex in a patient with LGG (low grade glioma) confirmed by NBS (navigated brain stimulation) Takahashi et al. describe the case of a 20-year-old male patient with an LGG in the precentral gyrus. When comparing the NBS mapping results at 18 months after the first surgery with the initial NBS mapping results, they observed that the primary motor cortex representation had shifted from the precentral to the postcentral gyrus. The plastic changes in the primary motor cortex localization permitted complete tumor removal without neurological sequela. In their conclusion, the clinicians state that it is important to routinely perform follow-up, non-invasive brain mapping in patients with LGG in an eloquent location in order to capture eloquent area relocation and offer the possibility of complete tumour removal.

In a published comment to the paper, Professor Hugues Duffau wrote, "This is a very exciting paper. It demonstrates the existence of mechanisms of brain plasticity, thanks to the use of NBS combined with intrasurgical direct stimulation." He added that, "… cerebral plastic potential has been underestimated by neurosurgeons during many decades, and that it should be used to increase surgical indications within areas for a long time considered as inoperable."