Comparison of navigated transcranial magnetic stimulation and functional magnetic resonance imaging for preoperative mapping in rolandic tumor surgery

Abstract

Navigated transcranial magnetic stimulation (nTMS) is a novel tool for preoperative functional mapping. It detects eloquent cortical areas directly, comparable to intraoperative direct cortical stimulation (DCS). The aim of this study was to evaluate the advantage of nTMS in comparison with functional magnetic resonance imaging (fMRI) in the clinical setting. Special focus was placed on accuracy of motor cortex localization in patients with rolandic lesions. Thirty consecutive patients were enrolled in the study. All patients received an fMRI and nTMS examination preoperatively. Feasibility of the technique and spatial resolution of upper and lower extremity cortical mapping were compared with fMRI. Consistency of preoperative mapping with intraoperative DCS was assessed via the neuronavigation system. nTMS was feasible in all 30 patients. fMRI was impossible in 7 out of 30 patients with special clinical conditions, pediatric patients, central vascular lesions, or compliance issues. The mean accuracy to localize motor cortex of nTMS was higher than in fMRI. In the subgroup of intrinsic tumors, nTMS produced statistically significant higher accuracy scores of the lower extremity localization than fMRI. fMRI failed to localize hand or leg areas in 6 out of 23 cases. Using nTMS, a preoperative localization of the central sulcus was possible in all patients. Verification of nTMS motor cortex localization with DCS was achieved in all cases. The fMRI localization of the hand area proved to be postcentral in one case. nTMS has fewer restrictions for preoperative functional mapping than fMRI and requires only a limited level of compliance. nTMS scores higher on the accuracy scale than fMRI. nTMS represents a highly valuable supplement for the preoperative functional planning in the clinical routine.

Navigated transcranial magnetic stimulation for mapping the motor cortex in patients with rolandic brain tumors

“…Since then 8 more studies have been published (up to October 2012-2 of these studies 3,19 were published online first in 2012 and then appeared in print in 2013). These studies contain larger clinical samples, and all but one 3 were quantitatively evaluated.…”

“…Since then 8 more studies have been published (up to October 2012-2 of these studies 3,19 were published online first in 2012 and then appeared in print in 2013). These studies contain larger clinical samples, and all but one 3 were quantitatively evaluated. The challenge of visualizing the stimulation point at the "correct" (that is, the most likely) anatomical area where the stimulation would be effective, has been addressed differently by different systems.…”

“…This approach assures a high accuracy in matching the virtual stimulation point to the "real" anatomy derived from the anatomical MRI scan. 3,4,8,9,14,21 The first of the 8 studies 14 performed using a secondgeneration TMS system was in 20 patients with rolandic tumors, although only 17 had surgery and thus DES. In this study, DES locations were chosen independently of nTMS, and the distance between nTMS and DES hotspots was quantitatively determined.…”

“…For mapping of the motor cortex, most studies used a biphasic TMS pulse (250-280 μsec pulse length) from a figure-eight coil with an outer diameter of 70 mm applied at 110% of the resting motor threshold and a maximum frequency of 0.25 Hz. [2][3][4][5][7][8][9]12,[14][15][16][17]20,21 For lower-extremity stimulation the intensity was adapted on an individual basis.…”

“…Although TMS was introduced in clinical neurology in 1985, 1 its use in neurosurgery has been sporadic, and only recently an increasing number of reports from neurosurgical institutions on the use of nTMS for brain mapping in patients with rolandic brain tumors have been published. 3,4,6,[8][9][10][11]13,14,21 In the present article, based on a review of previous reports evaluating the spatial accuracy of nTMS in comparison with the gold standard of DES and/or assessing the clinical impact of the method, we address the clinical utility of nTMS in rolandic brain tumor surgery. …”