Exploring Brain Plasticity in Motor Cortex Gliomas: A Novel Approach with nTMS Mapping

Brain tumours can significantly impact the function of the primary motor cortex, leading to deficits in motor performance. However, the brain has a remarkable capacity for plasticity, and the study of this phenomenon in the context of brain tumours is critical to understanding the underlying mechanisms and improving patient outcomes. In this study, the authors evaluated the plasticity of the primary motor cortex in patients with brain tumours using navigated transcranial magnetic stimulation (nTMS).

A week prior to the surgery, patients underwent neuronavigated TMS using a Brainsight TMS system for guidance and registration of TMS stimulated points. 

The authors analysed graphic cortical maps and introduced new quantitative parameters, such as rRMT and ratio values of ΔL, SDpc, and VCpc, to assess brain plasticity. By using normalised ratios, they were able to compare data across patients and mitigate discrepancies in the literature. The study also demonstrated that smaller rΔL values were associated with hemiparesis, which could be explained by slower and more significant changes in cortical representation or recruitment of more distant cortical neurons due to white matter tract migration.

Furthermore, the study found that the rRMT values were associated with the performance status and tumour grade. The authors suggest that preoperative mapping with nTMS might be integrated into a broader prognostic tool, and they propose cutoff values for differentiating WHO grade IV tumours. Although the study has some limitations, such as the evaluation of only hands and upper limbs and the absence of patients with severe motor deficits, it provides valuable insights into brain plasticity in the context of brain tumours.

The study adds to our understanding of brain plasticity in patients with brain tumours involving the primary motor cortex. The use of nTMS mapping and the introduction of new quantitative parameters can aid in operative planning and prognostic assessments. Further studies with larger samples and more comprehensive evaluations are necessary to fully appreciate the role of brain plasticity in patients with brain tumours.

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Reference Study

Almeida, C.C. et al. (2023) “Quantification of tumor induced motor cortical plasticity using navigated transcranial magnetic stimulation in patients with adult-type diffuse gliomas,” Frontiers in Neuroscience, 17. Available at: https://doi.org/10.3389/fnins.2023.1143072.