Role of the frontal aslant tract in language preservation and recovery after surgery: a multicenter analysis of patients with left frontal glioma

Introduction: In glioma surgery, achieving maximal safe resection while preserving neurological function can be highly challenging, and the knowledge of white matter connectivity plays a key role in achieving this goal. Regarding language functions, the frontal aslant tract (FAT) plays a unique role in coordinating verbal sequences in the dominant hemisphere. Damage to this tract is associated with the development of verbal fluency disorders of varying severity and duration; however, its significance in the language function, as well as the association between the extent of damage and functional recovery, has not yet been well established. Methods: This prospective multicenter study, conducted at three different centers in northern Italy, aimed to evaluate the involvement of the FAT in the language function by analyzing a cohort of adult patients undergoing surgery for glial lesions in the dominant hemisphere and following them for 3 months to assess the potential for function recovery. Preoperative magnetic resonance imaging (MRI), with diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI) sequences—performed using deterministic algorithms implemented in Brainlab iPlan software—was compared with postoperative imaging to determine the extent of FAT injury. Results: A total of 51 patients who underwent tumor excision surgery were recruited for the study, with maximal tumor resection achieved in 58.8% of cases. Language function worsened postoperatively in 29 patients (56.9%), with the onset or worsening of aphasia. At the 3-month follow-up, persistent language deficits were observed in 14 cases. Surgical manipulation of the FAT was strongly associated with the development of language impairment, particularly with respect to the volume of fibers resected and the segment of FAT involved. Resection of the middle segment was associated with both immediate postoperative language worsening and poor long-term language outcomes. The integrity of this segment was also associated with the possibility of neurological recovery over time. A FAT resection volume of at least 0.5 cm3 was found to be a significant predictor of persistent language deficits. Discussion: Knowledge derived from tractography may help guide safe glial tumor resection while preserving language function, even when FAT fibers are involved. Since language deficit may be irreversible, particular attention should be paid to the middle segment and the volume of FAT fibers intersected intraoperatively.