Authors :
Presenting Author: Negar Noorizadeh, Ph.D. – University of Tennessee Health Science Center and Le Bonheur Neuroscience Institute, Le Bonheur Children's Hospital, Memphis, TN, USA
Ardalan Aarabi, PhD – University Research Center (CURS), University of Picardie-Jules Verne
Maedeh Khalilian, PhD – University Research Center (CURS), University of Picardie-Jules Verne
Radha Kodali, PhD – University of Tennessee Health Science Center, Le Bonheur Children's Hospital
James Wheless, BScPharm, MD, FAAP, FACP, FAAN, FAES, FCNS – University of Tennessee Health Science Center and Le Bonheur Children's Hospital
Shalini Narayana, PhD – University of Tennessee Health Science Center and Le Bonheur Neuroscience Institute, Le Bonheur Children's Hospital, Memphis, TN, USA
Rationale:
The distribution of language cortex and hemispheric dominance (HD) are critical considerations in planning surgery for patients undergoing epilepsy or brain tumor surgery. While transcranial magnetic stimulation (TMS) provides a noninvasive tool for language mapping, its spatial specificity remains limited. Incorporating individualized tractography with TMS mapping may improve the accuracy of language localization and lateralization and functional risk assessment.Methods:
Thirteen pediatric patients (6 females; mean age 14.9 ± 4.2 years) diagnosed with brain tumor (Table 1) underwent TMS language mapping targeting frontal and temporal regions. Language-positive sites were categorized by error type: performance error (PE), semantic error (SE), or speech arrest (SA). A weighted language laterality index (LI) was calculated for each patient, assigning greater weight to SA and SE. The diffusion-weighted images were processed in DSI-Studio using generalized Q-sampling imaging [1] and deterministic fiber tracking with augmented strategies [2, 3] and bilateral arcuate fasciculus (AF), frontal aslant tract (FAT), inferior fronto-occipital fasciculus (IFOF), inferior longitudinal fasciculus (ILF), and uncinate fasciculus (UF) were reconstructed. TMS error sites within 8 mm [4] of these language-associated tracts were classified as functionally meaningful and reflective of language network involvement, while those beyond this distance were excluded. LI and HD were reassessed based on these tract-informed TMS results.Results:
Initial TMS mapping identified 101 PE, 11 SE, and 3 SA in the left-hemisphere and 82 PE, 13 SE, and 4 SA in the right-hemisphere. After integrating tractography, 69.3% of left and 74.4% of right PEs were retained, while SE and SA errors demonstrated higher retention rates (left: 90.9-100%, right: 76.9-100%). Tract-informed optimization altered HD in 5 of 13 patients: 2 shifted from bilateral to left dominance, 1 from right to left, and 2 from left to bilateral. Proximity to AF (Figure 1) accounted for the majority of TMS error sites in both hemispheres (left: 69.6% PE, 61.5% SE, 75% SA; right: 45.1% PE, 53.8% SE, 42.9% SA), followed by FAT and ILF.Conclusions:
Integrating patient-specific diffusion tractography with TMS mapping enhances anatomical specificity and improves accuracy in localizing and determining language dominance in pediatric epilepsy and brain tumor patients. This combined approach identifies functionally relevant language sites with greater precision, refines lateralization, and has the potential to better inform surgical planning and risk prediction.
References:
1. Yeh, F.C., V.J. Wedeen, and W.Y. Tseng, Generalized q-sampling imaging. IEEE Trans Med Imaging, 2010. 29(9): p. 1626-35.
2. Yeh, F.C., Shape analysis of the human association pathways. Neuroimage, 2020. 223: p. 117329.
3. Yeh, F.C., et al., Deterministic diffusion fiber tracking improved by quantitative anisotropy. PLoS One, 2013. 8(11): p. e80713.
4. Sollmann, N., et al., Risk assessment by presurgical tractography using navigated TMS maps in patients with highly motor-or language-eloquent brain tumors. Cancers, 2020. 12(5): p. 1264.
Funding: None