Navigated Transcranial Magnetic Stimulation and Functional Magnetic Resonance Imaging: Advanced Adjuncts in Preoperative Planning for Central Region Tumors

BACKGROUND: Tumor resection in the vicinity of the motor cortex poses a challenge to all neurosurgeons. For preoperative assessment of eloquent cortical areas, functional magnetic resonance imaging (fMRI) is used, whereas intraoperatively, direct cortical stimulation (DCS) is performed. Navigated transcranial magnetic stimulation (nTMS) is comparable to DCS in activating cortical pyramidal neurons. OBJECTIVE: To evaluate the reliability of nTMS compared with fMRI and DCS for preoperative resection planning of centrally located tumors. METHODS: In a prospective series, 11 patients (ages, 20-63 years; mean, 41.9 +/- 14.9 years, 2 women) with tumors located in or adjacent to the motor cortex were evaluated for surgery. fMRI and nTMS were applied for preoperative assessment of the extent of tumor resection. A 3-dimensional anatomic data set with superimposed fMRI data was integrated in the eXimia Navigated Brain Stimulation station for ensuing motor cortex mapping by nTMS. Responses from nTMS were evaluated by electromyographic response. During surgery, the coordinates of each DCS site were unambiguously defined and integrated into neuronavigation. A post hoc comparison of the coordinates of nTMS, fMRI, and DCS was performed. RESULTS: Distances from nTMS to DCS (10.5 +/- 5.67 mm) were significantly smaller than those from fMRI to DCS (15.0 +/- 7.6 mm). CONCLUSION: nTMS anticipates information usually only enabled by DCS and therefore allows surgical planning in eloquent cortex surgery.