Presurgical navigated transcranial magnetic brain stimulation for recurrent gliomas in motor eloquent areas

https://doi.org/10.1016/j.clinph.2012.08.011Get rights and content

Abstract

Objective

Navigated transcranial magnetic stimulation (nTMS) has been repeatedly shown to be comparably accurate to direct cortical stimulation (DCS) for rolandic region mapping. However, there are no data on its use for recurrent gliomas in which scarring and radiotherapy can impair nTMS. We therefore evaluated the accuracy of nTMS versus DCS and functional MRI (fMRI) in recurrent gliomas compared to initially operated tumors.

Methods

We examined 8 patients with recurrent gliomas and 23 patients with initially operated lesions in or adjacent to the precentral gyrus by preoperative nTMS.

Results

Preoperative motor mapping correlated well with intraoperative DCS in recurrent gliomas (6.2 ± 6.0 mm), as well as in newly diagnosed tumor patients (5.7 ± 4.6 mm) with no significant difference. Compared to fMRI, the difference was larger for upper (recurrent: 8.5 ± 7.2 mm; new: 9.8 ± 8.6 mm) and lower (recurrent: 17.1 ± 10.6 mm; new: 13.8 ± 13.0 mm) extremities, with no significant differences.

Conclusions

When comparing nTMS with DCS and fMRI, nTMS is as accurate in recurrent gliomas as it is prior to the first operation. It should be considered a helpful modality in recurrent glioma patients as well.

Significance

nTMS is also applicable in recurrent tumors.

Highlights

► Navigated transcranial magnetic stimulation (nTMS) and intraoperative direct cortical stimulation (DCS) results correlate well. ► Recurrent tumor does not affect nTMS accuracy despite scarring, plasticity, and edema. ► fMRI results were significantly different, but independent of recurrent tumor or control group.

Introduction

Resection of gliomas in eloquent motor areas remains a surgical challenge and can only be safely achieved with the aid of intraoperative neuromonitoring. While continuous transcranial, cortical motor evoked potentials (MEP) monitoring and subcortical electrical stimulation are well-established techniques to monitor functional integrity of the motor strip and corticospinal tract, a reliable method that functionally identifies motor cortex prior to surgery is not currently in use. Modalities for non-invasive preoperative brain mapping, such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) are unable to adequately identify motor functional areas because metabolic and electrical activity do not necessarily correlate with neurophysiological pathways. Therefore, its usefulness for functional motor cortex mapping is limited (Rutten and Ramsey, 2010).

Several studies have shown that navigated transcranial magnetic brain stimulation (nTMS) correlates well with intraoperative direct cortical stimulation (DCS) and is a useful tool for surgical planning (Forster et al., 2011, Krieg et al., 2012a, Krieg et al., 2012c, Picht et al., 2009, Picht et al., 2011a). However, it has only been assessed in newly diagnosed tumors. Scar formation and commonly suggested cerebral plasticity in recurrent tumors could potentially impair nTMS applicability (Ius et al., 2011, Robles et al., 2008). Therefore, this study aimed to prospectively evaluate nTMS accuracy in recurrent gliomas with relation to the established mapping methods of intraoperative DCS and preoperative fMRI. We also compared nTMS accuracy in recurrent gliomas and newly diagnosed brain tumors, which served as a control group.

Section snippets

Patients

We performed presurgical nTMS mapping in 8 patients prior to recurrent glioma resection and in 23 patients who underwent resection of newly diagnosed tumors (control group) between May 2010 and September 2011. All tumors were located in or near the precentral gyrus or the CST (Fig. 1). Demographic data and the clinical neurological status of every patient was assessed and documented. Tumor location was determined from imaging data, and tumor histology was acquired.

Magnetic resonance imaging

Pre- and postoperative MRI

Patients

For recurrent gliomas, the mean age was 50.1 ± 11.1 years (median 45.2 years; range 40.5–69.1 years); 5 patients (62.5%) were female and 3 (37.5%) were male. All patients were right-handed and had a history of seizures, and 6 of the 8 (75.0%) were on antiepileptic drugs (AED). Mild preoperative motor deficits were present in 2 cases (25.0%), and two tumors (25.0%) were in the dominant hemisphere. Out of 8 cases, there were 6 glioblastomas (WHO°IV), 1 anaplastic astrocytoma (WHO°III), and 1 diffuse

Discussion

The present study aimed to assess the feasibility and accuracy of nTMS in patients with recurrent gliomas near or in motor eloquent areas. Therefore, motor areas outlined during preoperative non-invasive nTMS were compared to intraoperative DCS. Spatial errors for recurrent gliomas were compared to a series of newly diagnosed gliomas, in which the same comparison between presurgical nTMS and DCS was performed. The central finding of the present study is that nTMS in patients with recurrent

Disclosure

The study was completely financed by institutional grants through the Department of Neurosurgery. SK has been involved in Nexstim Oy workshops but is not a contracted consultant. Therefore, the authors report no conflict of interest concerning the materials or methods used in this study, or the findings specified in this paper.

Acknowledgements

The authors would like to thank Ms. Maria Becker for performing the highly demanding imaging studies in addition to her other duties.

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