Introduction

Preservation of language function during glioma resection relies on the integrity of subcortical white matter pathways. Among available non-invasive methods, diffusion tensor imaging (DTI) has proved particularly valuable for preoperative visualization of these fiber tracts, enabling neurosurgeons to assess potential tract infiltration and plan resections that minimize postoperative language deficits (Abdullah et al., 2013; Salvati et al., 2021; Ille et al., 2018; Chang et al., 2015).

The frontal aslant tract (FAT) is a white matter pathway that predominantly originates from the convexity of the superior frontal gyrus, with additional contributions from medial frontal regions including the supplementary motor area (SMA), and projects to the inferior frontal gyrus (IFG). It has been implicated in speech initiation and verbal fluency (Catani et al., 2013; La Corte et al., 2021; Aliaga-Arias et al., 2024; Chernoff et al., 2019; Burkhardt et al., 2022; Dick et al., 2019; Tagliaferri et al., 2024). Yet, its relevance in surgical planning remains debated. Some advocate for its preservation to reduce the risk of permanent language impairments, while others consider its involvement to result primarily in transient speech initiation deficits akin to SMA syndrome (La Corte et al., 2021; Young et al., 2020, 2022; Agyemang et al., 2023; Briggs et al., 2021). Considering the onco-functional balance, this would raise question if those transient deficits might be tolerated in the sake of a more radical tumor resection.

The arcuate fasciculus (AF) is a prominent tract within the language network, contributing to both the dorsal phonological and ventral semantic stream supporting functions beyond straightforward speech repetition (Bernal and Ardila, 2009; Catani and Mesulam, 2008; Fridriksson et al., 2013; Giampiccolo and Duffau, 2022; Ivanova et al., 2021). Evidence indicates that injury to major language-related white matter pathways, such as the AF, during glioma surgery results in permanent aphasia, underscoring its clinical importance (Giampiccolo and Duffau, 2022; Tuncer et al., 2021; Forkel et al., 2014).

Against this backdrop, the present study examines the functional significance of the FAT integrity alone or combined with the AF integrity in patients who underwent resection of non-contrast-enhancing gliomas in the left frontal lobe (Fig. 1). We investigate whether disruption of these tracts is associated with transient and lasting language deficits. Further, we investigated the assumption that FAT disruption invariably corresponds to a transient, reversible SMA-related syndrome.

Fig. 1: Coronal slide of a T2 postoperative MRI. The resection cavity of the low-grade glioma involving the supplementary motor area region of the superior frontal gyrus is depicted in green. The frontal aslant tract crossing the glioma is visualized in blue, whereas the arcuate fasciculus is shown in orange. DTI fiber-tracking parameters were set to FA = 0.15, length = 50 mm, angulation = 45° as described under methods 2.5.