Combined noninvasive language mapping by navigated transcranial magnetic stimulation and functional MRI and its comparison with direct cortical stimulation

Abstract

T he resection of tumors within or adjacent to language-eloquent brain regions is still a neurosurgical quest, and a profound presurgical workup is crucial to achieving the best functional and oncological result. 6,71 Today, the most precise way to localize individual language-eloquent regions is direct cortical stimulation (DCS) during awake craniotomy. 9,12,26,44,45,54,62,65,74 Using only DCS, however, we cannot provide the longitudinal abbreviatioNs BOLD = blood oxygen level-dependent; CPS = cortical parcellation system; DCS direct cortical stimulation; ER = error rate; ERT error rate threshold; fMRI = functional MRI; IPI = interpicture interval; NPV = negative predictive value; nTMS navigated TMS; PPV = positive predictive value; PTI = picture-to-trigger interval; RMT = resting motor threshold; ROC = receiver operating characteristic; rTMS repetitive navigated TMS; TMS = transcranial magnetic stimulation. obJect Repetitive navigated transcranial magnetic stimulation (rTMS) is now increasingly used for preoperative language mapping in patients with lesions in language-related areas of the brain. Yet its correlation with intraoperative direct cortical stimulation (DCS) has to be improved. To increase rTMS's specificity and positive predictive value, the authors aim to provide thresholds for rTMS's positive language areas. Moreover, they propose a protocol for combining rTMS with functional MRI (fMRI) to combine the strength of both methods. methods The authors performed multimodal language mapping in 35 patients with left-sided perisylvian lesions by using rTMS, fMRI, and DCS. The rTMS mappings were conducted with a picture-to-trigger interval (PTI, time between stimulus presentation and stimulation onset) of either 0 or 300 msec. The error rates (ERs; that is, the number of errors per number of stimulations) were calculated for each region of the cortical parcellation system (CPS). Subsequently, the rTMS mappings were analyzed through different error rate thresholds (ERT; that is, the ER at which a CPS region was defined as language positive in terms of rTMS), and the 2-out-of-3 rule (a stimulation site was defined as language positive in terms of rTMS if at least 2 out of 3 stimulations caused an error). As a second step, the authors combined the results of fMRI and rTMS in a predefined protocol of combined noninvasive mapping. To validate this noninvasive protocol, they correlated its results to DCS during awake surgery. results The analysis by different rTMS ERTs obtained the highest correlation regarding sensitivity and a low rate of false positives for the ERTs of 15%, 20%, 25%, and the 2-out-of-3 rule. However, when comparing the combined fMRI and rTMS results with DCS, the authors observed an overall specificity of 83%, a positive predictive value of 51%, a sensitivity of 98%, and a negative predictive value of 95%. coNclusioNs In comparison with fMRI, rTMS is a more sensitive but less specific tool for preoperative language mapping than DCS. Moreover, rTMS is most reliable when using ERTs of 15%, 20...

Non-invasive Mapping of Face Processing by Navigated Transcranial Magnetic Stimulation

“…In this context, the combination of rTMS with DTI fiber tracking or fMRI might be a promising modality, as already published for motor function (Krieg et al, 2012a; Frey et al, 2014) and language function (Ille et al, 2015). …”

“…Nonetheless, the exact localization of facial processing remains debatable since it involves a large variety of subfunctions and structures, including visual pathways like the OFA, memory-associated structures like the hippocampus, sensory components like the somatosensory cortex, or emotional aspects, such as those processed in the amygdala (Atkinson and Adolphs, 2011). This study provides two different facts to the scientific community: (1) rTMS could serve as an additional modality for this endeavor, maybe by serving as a seed region for diffusion tensor imaging (DTI) fiber tracking (Frey et al, 2012; Krieg et al, 2012a), and (2) since rTMS is less affected by brain tumors (Ille et al, 2015), we suggest that it could be feasible for cortical delineation of facial-processing-related areas in brain tumor patients as a stand-alone technique.…”

Language mapping with navigated transcranial magnetic stimulation in pediatric and adult patients undergoing epilepsy surgery: Comparison with extraoperative direct cortical stimulation

“…Several studies in such patients have compared language mapping by nTMS to direct cortical stimulation (DCS), the current gold standard of localizing eloquent function in neurosurgery. nTMS has been shown to be highly sensitive but less specific for language mapping . The reported sensitivity values, as well as intra‐ and interindividual replicability, are best for frontal areas.…”

When imaging meets neurophysiology: the value of navigated transcranial magnetic stimulation for preoperative neurophysiological mapping prior to brain tumor surgery

“…In 2 consecutive studies Ille et al reported that rTMS language mapping seems more sensitive but less specific in comparison with fMRI. 25,26 The clinical usefulness of the combination of rTMS cortical language mapping with DTI fiber tracking has been demonstrated by several papers. 41,52,56,72 Thanks to these studies, the nTMS-based reconstruction of the language network has also entered the clinical workflow prior to surgery of language-eloquent brain tumors 71 (Video 2).…”