Associations between clinical outcome and navigated transcranial magnetic stimulation characteristics in patients with motor-eloquent brain lesions: a combined navigated transcranial magnetic stimulation–diffusion tensor imaging fiber tracking approach

Abstract

OBJECTIVE Navigated transcranial magnetic stimulation (nTMS) and diffusion tensor imaging fiber tracking (DTI FT) based on nTMS data are increasingly used for preoperative planning and resection guidance in patients suffering from motor-eloquent brain tumors. The present study explores whether nTMS-based DTI FT can also be used for individual preoperative risk assessment regarding surgery-related motor impairment. METHODS Data derived from preoperative nTMS motor mapping and subsequent nTMS-based tractography in 86 patients were analyzed. All patients suffered from high-grade glioma (HGG), low-grade glioma (LGG), or intracranial metastasis (MET). In this context, nTMS-based DTI FT of the corticospinal tract (CST) was performed at a range of fractional anisotropy (FA) levels based on an individualized FA threshold ([FAT]; tracking with 50%, 75%, and 100% FAT), which was defined as the highest FA value allowing for visualization of fibers (100% FAT). Minimum lesion-to-CST distances were measured, and fiber numbers of the reconstructed CST were assessed. These data were then correlated with the preoperative, postoperative, and follow-up status of motor function and the resting motor threshold (rMT). RESULTS At certain FA levels, a statistically significant difference in lesion-to-CST distances was observed between patients with HGG who had no impairment and those who developed surgery-related transient or permanent motor deficits (75% FAT: p = 0.0149; 100% FAT: p = 0.0233). In this context, no patient with a lesion-to-CST distance ≥ 12 mm suffered from any new surgery-related permanent paresis (50% FAT and 75% FAT). Furthermore, comparatively strong negative correlations were observed between the rMT and lesion-to-CST distances of patients with surgery-related transient paresis (Spearman correlation coefficient [r]; 50% FAT: r = -0.8660; 75% FAT: r = -0.8660) or surgery-related permanent paresis (50% FAT: r = -0.7656; 75% FAT: r = -0.6763). CONCLUSIONS This is one of the first studies to show a direct correlation between imaging, clinical status, and neurophysiological markers for the integrity of the motor system in patients with brain tumors. The findings suggest that nTMS-based DTI FT might be suitable for individual risk assessment in patients with HGG, in addition to being a surgery-planning tool. Importantly, necessary data for risk assessment were obtained without significant additional efforts, making this approach potentially valuable for direct clinical use.

Clinical Uses of Diffusion Tensor Imaging Fiber Tracking Merged Neuronavigation with Lesions Adjacent to Corticospinal Tract : A Retrospective Cohort Study

“…We concluded that a distance of 10 mm between tumor border and CST was sufficient to preserve motor function. Comparable results were also cited in some prior studies 33,35,37) . The tumor-CST distance may well be regarded as presumptive predictor of outcome, attributable in part to tumor edema.…”

Invasive versus non‐invasive mapping of the motor cortex

“…The increasing use of non‐invasive mapping techniques for preoperative diagnostics has been accompanied by a change in the tumour resection strategy towards a more quality‐of‐life‐oriented, function‐preserving surgical approach over the last decades. As compared with historical cohorts from the 1980s to early 2000s with rates of surgery‐related deterioration of motor function in the range of 60% (transient; 26–38% permanent) (Magill, Han, Li, & Berger, 2018; Raffa et al, 2018), resection of motor‐eloquent brain tumours has become safer since more effort has been made to assess the functional limits of MC areas for surgery using non‐invasive methods: with 35% transient and 5% permanent surgery‐related motor deficits, the outcome results of the glioma patients in our cohort agree relatively well with the recent literature reporting new postoperative motor deficits in the range of 23–29% (transient) versus 8–22% (permanent) after nTMS‐ and DCS‐guided resection of motor‐eloquent gliomas (Hendrix et al, 2016; Rosenstock et al, 2017; Sollmann et al, 2018). However, the relatively high percentage of transient motor deficits in our cohort might be a consequence of considering (even mild) isolated face muscle impairments as surgery‐related motor deficit ( n = 4, that is, 20% of all patients).…”

Global and Targeted Pathway Impact of Gliomas on White Matter Integrity Based on Lobar Localization

“…However, a non-invasive method of determining tumor-related neural degradation would be advantageous. In the context of intracranial tumor resection, DTI has mainly been used for preoperative surgical planning [ 18 ], but increasingly is being explored for use as an anatomical/pathophysiological tool for brain tumor prognosis and analysis. However, information derived from fiber tract analysis must be interpreted with caution due to the difficulty in differentiating tumor from edema, particularly with respect to glioma.…”