Figure 12.

Case 2. (A) Preoperative MRI of this patient revealed a tumour infiltrating the left dominant TO region. (B) After identifying the limits of the lesion using ultrasonography (letter tags), cortical awake mapping induced reproducible speech arrests at the level of the VPMC (tag 1) and anomias at the level of the posterior part of the STG, corresponding to Wernicke's area. (C) The resection included the middle and posterior part of the MTG and the IFG. More ventrally, under the fusiform gyrus, semantic paraphasias and anomia episodes were elicited using DES at tag 46, not visible in the intraoperative photograph, and tag 48. Specific reading troubles were induced in areas more posterior and laterally (tag 49). (D) We performed a dissection of the TO region and oriented the specimen according to the intraoperative perspective. We demonstrated the anatomical substrate responsible for functional intraoperative responses. Tags 46 and 48 correspond to the IFOF (violet arrows), which was exposed from the limen insulae to the parietal and occipital regions passing along the lateral ventricular wall (pink arrow). The location of tag 49 indicates stimulation of the ILF, which connects the temporal and occipital basal regions (yellow arrow). The intraoperative result was most likely dependent upon stimulation where the ILF and IFOF fibres crossed (green arrow, blue tags). (E) Post-operative MRI revealed subtotal resection that produced only left inferior quadrantanopia. IFG, inferior frontal gyrus; STG, superior temporal gyrus; VPMC, ventral pre-motor cortex.