Language mapping with navigated repetitive TMS: Proof of technique and validation

Abstract

Objective Lesion-based mapping of speech pathways has been possible only during invasive neurosurgical procedures using direct cortical stimulation (DCS). However, navigated transcranial magnetic stimulation (nTMS) may allow for lesion-based interrogation of language pathways noninvasively. Although not lesion-based, magnetoencephalographic imaging (MEGI) is another noninvasive modality for language mapping. In this study, we compare the accuracy of nTMS and MEGI with DCS. Methods Subjects with lesions around cortical language areas underwent preoperative nTMS and MEGI for language mapping. nTMS maps were generated using a repetitive TMS protocol to deliver trains of stimulations during a picture naming task. MEGI activation maps were derived from adaptive spatial filtering of beta-band power decreases prior to overt speech during picture naming and verb generation tasks. The subjects subsequently underwent awake language mapping via intraoperative DCS. The language maps obtained from each of the 3 modalities were recorded and compared. Results nTMS and MEGI were performed on 12 subjects. nTMS yielded 21 positive language disruption sites (11 speech arrest, 5 anomia, and 5 other) while DCS yielded 10 positive sites (2 speech arrest, 5 anomia, and 3 other). MEGI isolated 32 sites of peak activation with language tasks. Positive language sites were most commonly found in the pars opercularis for all three modalities. In 9 instances the positive DCS site corresponded to a positive nTMS site, while in 1 instance it did not. In 4 instances, a positive nTMS site corresponded to a negative DCS site, while 169 instances of negative nTMS and DCS were recorded. The sensitivity of nTMS was therefore 90%, specificity was 98%, the positive predictive value was 69% and the negative predictive value was 99% as compared with intraoperative DCS. MEGI language sites for verb generation and object naming correlated with nTMS sites in 5 subjects, and with DCS sites in 2 subjects. Conclusion Maps of language function generated with nTMS correlate well with those generated by DCS. Negative nTMS mapping also correlates with negative DCS mapping. In our study, MEGI lacks the same level of correlation with intraoperative mapping; nevertheless it provides useful adjunct information in some cases. nTMS may offer a lesion-based method for noninvasively interrogating language pathways and be valuable in managing patients with peri-eloquent lesions.

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

“…37,51,75 Most importantly, when regarding current protocols for DCS language mapping during awake surgery, some authors also rely only on negative language mapping intraoperatively. 64,75 In this respect, the absence of false-negative results, as revealed for rTMS language mapping performed with a PTI of 0 msec and analyzed with an ERT of 0%, is of paramount importance (Table 4). 15 Thus, the high sensitivity and NPV of our presented protocol seem already applicable in the daily clinical routine.…”

“…51,68,75 First, the 3D T1-weighted MRI scan of each patient and the patient's head were coregistered. The stimulated brain area during the examination was visualized using a stereotactic camera and reflectors fastened to the patient's head with an elastic strap to track the coil position.…”

“…18,19,40,48,69,80 Its clinical applicability and correlation to DCS during awake surgery have repeatedly been shown as well. 36,37,51,68,75 Although rTMS language mapping has already experienced some improvement, 40 the standard for preoperative, noninvasive language mapping remains functional MRI (fMRI). 21 Yet this technique, though well established, has failed to provide reliable preoperative language mapping, showing only minor correlation with intraoperative DCS.…”

Impairment of preoperative language mapping by lesion location: a functional magnetic resonance imaging, navigated transcranial magnetic stimulation, and direct cortical stimulation study

“…Both PTIs proved to be effective in former studies. 39,52 The display time (time of picture presentation on screen) was 700 msec, and the interpicture interval (time between 2 pictures) was 2500 msec. During the interpicture interval, the stimulation coil was moved to the next stimulation site.…”

Integrating nTMS Data into a Radiology Picture Archiving System

“…Radiology information system . Transcranial magnetic stimulation Background Navigated transcranial magnetic stimulation (nTMS) has been successfully applied in noninvasive presurgical mapping of motor- [1][2][3][4][5] and speech-related cortical areas [6,7] and in planning dosimetry distribution in radiosurgery [8,9]. As the Food and Drug Administration of the USA has recently approved presurgical motor and language nTMS mapping as a clinical tool [10], its clinical use is rapidly expanding.…”