Fig. 1.

(A) On the left side, the pre-operative coronal T1-wighted MRI with integrated 60-directions DTI (superior OR in purple and IFOF in red) shows the LGG harbouring the posterior two-third of T5, T4 and partially T3. On the right side, the early post-operative coronal FLAIR sequence demonstrated the LGG resection with the opening of the floor of the trigone and temporal horn. (B) The tag 11 highlights the subcortical limit of resection at the inferior border of the trigone evoking flashes at the limit between the inferior and superior contralateral visual quadrants. Posteriorly, the tag 10 shows the point evoking also visual recognition troubles, suggesting the deactivation of the IFOF at its inferior margin, overlapping the superior OR, according to the course of this bundle in the pre-operative DTI (C). (D) The post-operative digital visual field examination showed the contralateral quadrantopia tailored with the DES-guided resection. DES, direct electrical stimulation; DTI, diffusion tensor imaging; IFOF, inferior fronto-occipital fascicle; LGG, low-grade glioma; MRI, magnetic resonance imaging; OR, optic radiation.