• José Pedro Lavrador, Ifigeneia Gioti, Szymon Hoppe, Josephine Jung, Sabina Patel, Richard Gullan, Keyoumars Ashkan, Ranjeev Bhangoo, and Francesco Vergani.
• Neurosurgical Department, King's College Hospital Foundation Trust, London, United Kingdom.
• Neurosurgery. 2020 Dec 15; 88 (1): 183-192.

BackgroundDiffuse gliomas have an increased biological aggressiveness across the World Health Organization (WHO) grading system. The implications of glioma grading on the primary motor cortex (M1)-corticospinal tract (CST) excitability is unknown.ObjectiveTo assess the excitability of the motor pathway with navigated transcranial magnetic stimulation (nTMS).MethodsRetrospective cohort study of patients admitted for surgery with diffuse gliomas within motor eloquent areas. Demographic, clinical, and nTMS-related variables were collected. The Cortical Excitability Score (CES 0 to 2 according to the number of abnormal interhemispheric resting motor threshold (RMT) ratios) was calculated for patients where bilateral upper and lower limb mapping was performed.ResultsA total of 45 patients were included: 9 patients had a low-grade glioma and 36 patients had a high-grade glioma. The unadjusted analysis revealed an increase in the latency of the motor evoked potential of the lower limb with an increase of the WHO grade (P = .038). The adjusted analysis confirmed this finding (P = .013) and showed a relation between the increase in the WHO and a decreased RMT (P = .037) of the motor evoked responses in the lower limb. When CES was calculated, an increase in the score was related with an increase in the WHO grade (unadjusted analysis-P = .0001; adjusted analysis-P = .001) and in isocitrate dehydrogenase (IDH) wild-type tumors (unadjusted analysis-P = .020).ConclusionAn increase in the WHO grading system and IDH wild-type tumors are associated with an abnormal excitability of the motor eloquent areas in patients with diffuse gliomas.Copyright © 2020 by the Congress of Neurological Surgeons.

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