Introduction: The management of brain tumors in and around the eloquent areas presents a specific challenge to the neurosurgeon. The goals are for maximal safe resection, preserving the patient’s existing neurological function. Functional information about the cortical and subcortical areas at risk is crucial for the avoidance of neurological deficits after tumor surgery. Although direct cortical stimulation (DCS), remains the gold standard, non-invasive methods of motor mapping are becoming increasingly accurate and useful.

Methods: We describe our initial experience with 11 patients with brain tumors located adjacent to eloquent areas. All cases were performed using navigated transcranial magnetic stimulation (nTMS) and intraoperative direct cortical stimulation (DCS).

Results: Of the 11 patients 63% were High Grade Gliomas, 27% Low Grade Gliomas and 10% metastasis respectively. In 73% of patients a positive response with nTMS (either upper or lower extremity), correlated well with those generated by DCS. However, of these, the correlation in the upper extremity, alone was 91% (n=11) of cases, and 100% (n=5) in the lower extremity. In 3(36%) cases nTMS was superior to DCS in isolating the lower extremity response while in 1(10%) case DCS isolated the upper extremity response when nTMS failed. There were no adverse events to patients during the stimulation. The mean time for generating a preoperative nTMS map was 20 minutes.

Conclusions: Navigated transcranial magnetic stimulation (nTMS) can be safely used in the presurgical mapping of the motor cortex involving both the upper or lower extremity and the results correlate well with intraoperative direct cortical stimulation (DCS).

Patient Care: By functional information about the cortical and subcortical areas at risk is crucial for the avoidance of neurological deficits after tumor surgery.With the goals for maximal safe resection, preserving the patient’s existing neurological function.

Learning Objectives: correlation between brain mapping by navigated transcranial magnetic stimulation and direct cortical stimulation

References: 1. Petrella JR, Shah LM, Harris KM, Friedman AH, George TM,Sampson JH, Pekala JS, Voyvodic JT (2006) Preoperative functional mr imaging localization of language and motor areas: effect on therapeutic decision making in patients with potentially resectable brain tumors1. Radiology 240(3):793–802; 2. Duffau H, Capelle L, Sichez J, Faillot T, abdennour L, Law Koune JD, et al: Intra-operative direct electrical stimulations of the central nervous system: the Salpetriere experience with 60 patients. Acta Neurochir (Wien) 141:1157-1167, 1999; 3. Keles GE, Lundin DA, Lamborn KR, Chang EF, Ojemann G, Berger MS: Intraoperative subcortical stimulation mapping for hemispherical perirolandic gliomas located within or adjacent to the descending motor pathways: evaluation of morbidity and assessment of functional outcome in 294 patients. J Neurosurg 100:369–375, 2004; 4. Sanai N, Berger MS: Intraoperative stimulation techniques for functional pathway preservation and glioma resection. Neurosurg Focus 28(2):E1, 2010; 5. Picht T, Wachter D, Mularski S, et al. Functional magnetic resonance imaging and cortical mapping in motor cortex tumor surgery: complementary methods. Zentralbl Neurochir. 2008;69(1):1-6.; 6. Rutten GJ, Ramsey NF. The role of functional magnetic resonance imaging in brain surgery. Neurosurg Focus. 2010;28(2):E4.