Predictive value of inferior fronto-occipital fasciculus (IFO) DTI-fiber tracking for determining the extent of resection for surgery of frontal and temporal gliomas preoperatively.

AIM: This work reports the analysis of the relationship between inferior fronto-occipital fasciculus (IFO), neoplastic lesions and surgical resection, in patients operated for gliomas located in the frontal, temporal and insular lobes of the dominant hemisphere. Aim of the study is evaluating the predictive value of inferior fronto-occipital fasciculus DTI-fiber tracking (FT) for determining the extent of resection preoperatively. METHODS: We selected 38 cases affected by lesions located in the frontal, temporal and insular lobes of the dominant hemisphere, which were related to the trajectory of the IFO. For each patient preoperative and postoperative MR images and DTI-FT were loaded into the neuronavigation system and merged; volumetric scan analysis was used for establishing tumor location and topography, as well as the volume of the lesion and of the residual tumor. All preoperative fiber tracking datasets were evaluated and the position of the tract (IFO) compared to the tumor was recorded. Postoperative MR scans were then compared with DTI-FT, in order to evaluate the correspondence between the resection boundaries and the trajectory of the fiber tract. RESULTS: Amongst the cases in which the IFO was inside the lesion, we found only incomplete resections (5 subtotal and 6 partial resections), while considering the cases in which the IFO was located outside the tumor, it was possible to perform a relevant (total/subtotal) resection in 18 of them (78%). CONCLUSION: FT of the inferior frontal-occipital fasciculus predicts the possibility and the extent of the resection for a frontal, temporal and/or insular lesion of the dominant hemisphere.

Defective recognition and naming of famous people from voice in patients with unilateral temporal lobe tumours.

Twenty-nine patients who underwent surgery for a temporal glioma, either in the left (16 patients) or right (13 patients) hemisphere, were administered standardized tests of unknown voice discrimination (UVD) and of famous voice recognition (VO-REC), which included tasks of familiarity evaluation, semantic identification and naming of famous voices. The UVD consisted of twenty stimuli, in which two audio files were consecutively presented; the subject was requested to judge whether the voices belonged to the same or different persons. In the VO-REC, patients were requested to recognize the voices of 40 very well known people; these voices were intermingled with the voices of 20 unknown people for a familiarity check, followed by identification and naming of persons recognized as familiar. We aimed at verifying the effect of laterality and intra-temporal site of lesion on familiarity assessment, false alarms, identification and naming of familiar people. As for the effect of lesion side, our results showed that patients with right temporal gliomas were significantly more impaired in voices discrimination and produced more false alarms than patients with a left glioma, who, in turn, were significantly more impaired in name retrieval than patients with a right temporal glioma. The high number of false alarms in patients with a right temporal glioma suggests that familiarity judgment was impaired. Regarding the neuroanatomical correlates of these different patterns of impairment, MRI data suggested that: (a) UVD disorders are due to lesions involving the whole right anterior temporal lobe and extending to lateral portions of the temporal and frontal lobes; (b) familiarity judgments (testified by an increased number of false alarms) are impaired in lesions restricted to the right anterior temporal lobe; (c) name retrieval deficits are found only in patients with left temporal lesions. UVD disorders were interpreted, at least in part, as due to an impairment of executive functions, resulting from a disconnection of the right temporal lobe from the frontal lobe control. A partly unexpected finding was that some patients with a right temporal tumour had a normal performance in famous voice recognition and identification, in spite of having severe voice discrimination disturbances. These unexpected results, in agreement with previous observation made in the visual (face) modality, are inconsistent with strictly hierarchical models of voice processing.