dti findings are complementary to intraoperative subcortical language mapping for surgical removal of low-grade gliomas involving speech areas

Surgical removal of low-grade gliomas in, or in close proximity to, speech areas or pathways requires the localization of cortical and subcorti- cal sites that mediate speech function. Intraoperative subcortical language mapping has been used to identify functional language tracts during resec- tion of hemispheric low-grade gliomas invading language areas, minimizing the definitive morbidity and maximizing the quality of resection. DTI is a technique that allows the identification of functional tracts in the preopera- tive MRI and establishes their anatomical relationship with the tumor mass. In this work, we used DTI for visualization of language tracts in patients with low-grade gliomas in or involving speech areas or pathways, and we correlated DTI data with those obtained during intraoperative subcorti- cal language or motor tract mapping. Thirty patients with low-grade glio- mas were included in the study: 17 males and 13 females, with 17 gliomas located in the left frontal lobe, four in the left parietal lob, and nine in left temporal lobe. DTI data were acquired by the use of 3T MR scanner (Phil- ips Intera) with a single-shot echo-planar sequence with gradients applied along 32 noncollinear directions. Fiber tracking was performed with a dedicated software. Intraoperative subcortical language tract mapping was performed dur- ing awake craniotomy, by the use of a Ojeman stimulator, during object, famous people, and action naming, and word and sentence comprehension tests. Data obtained during intraoperative mapping were correlated point by point with those identified with DTI by the aid of a neuronavigation system (Radionics). DTI allowed the reconstruction of fasciculus arcuatus, fronto-occipitalis, uncinatus, subcallusum in the frontal lobe, longitudi- nalis and uncinatus in the temporal lobe, and helped in understanding the anatomical relationship between tracts and the tumor mass during the pre- operative planning. Intraoperative language mapping identified functional subcortical sites in all patients. When DTI data were correlated with those from intraoperative mapping, sensitivity was 70% for motor tracts and 72% for language tracts. Our data support the use of DTI for language and motor tracts for surgical removal of low-grade gliomas involving speech areas or pathways.