Functional neuroimaging has improved pre-planning of surgery in eloquent cortical areas, but remains unable to map white matter. Thus, tumour resection in functional subcortical regions still presents a high risk of sequelae. The authors successfully used intraoperative electrical stimulations to perform subcortical language pathway mapping in order to avoid postoperative definitive deficit, and correlated these functional findings with the anatomical location of the eloquent bundles detected using postoperative MRI. At the same time, this also improved knowledge of fibre connectivity. Thirty patients harbouring a cortico-subcortical low-grade glioma in the left dominant hemisphere were operated on whilst awake using intraoperative electrical functional mapping during surgical resection. Language cortical sites and subcortical pathways were clearly identified and preserved in the 30 cases. The anatomo-functional correlations between data obtained using intraoperative subcortical mapping and postoperative MRI revealed the existence in all patients of common pathways which seem essential to language. This was shown by inducing reproducible speech disturbances during stimulations as follows: the subcallosal fasciculus (initiation disorders), the periventricular white matter (dysarthria), the arcuate fasciculus and the insular connections (anomia). Clinically, all patients except three presented a transient postoperative dysphasia, which resolved within 3 months. On control MRI, 14 resections were total and 16 subtotal due to infiltration of functional bundles described above. It is recommended that the combination of the techniques as described could prove ideal for future non-invasive reliable subcortical mapping both in healthy volunteers and in patients harbouring a (cortico)subcortical lesion in order to optimize surgical pre-planning.

The use of functional mapping of the white matter together with cortical mapping allowed the authors to optimize the benefit/risk ratio of surgery of low-grade glioma invading eloquent regions. Given that preoperative fiber tracking with the aid of neuroimaging is not yet validated, we used intraoperative real-time cortical and subcortical stimulations as a valuable adjunct to the other mapping methods.

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Although a cortical network involving Broca's area and the supramarginal gyrus (SMG) was widely studied using neurofunctional imaging, the functional connectivity underlying this so-called articulatory loop remains poorly documented. We describe a patient operated on for a glioma invading the left parietal operculum, using intraoperative electrical functional mapping under local anesthesia. Following the identification of cortical language sites within Broca's area and SMG, the subcortical pathways connecting these regions were detected and preserved during the resection. Postoperatively, the patient presented a slight dysarthria, then recovered. This is the first report of direct tracking of the subcortical connectivity underlying the fronto-parietal articulatory loop, allowing to better understand the pathophysiology of this network and the consequences of its damage.

Objectives: Advances in neuroimaging studies have recently improved the understanding of the functional anatomy of the calculation processes, having in particular underlined the central role of the angular gyrus (AG). In this study, the authors applied this knowledge to the surgical resection of a glioma invading the left AG, by localising and sparing the cortical areas involved in two different components of calculation (multiplication and subtraction), using direct electrical stimulations. Methods: A calculation mapping was performed in a patient without deficit except a slightly impaired performance for serial arithmetic subtraction, during the resection under local anaesthesia of a left parieto-occipital glioma invading the dominant AG. After somatosensory and language mappings, cortical areas involved in single digit multiplications and subtractions of seven were mapped using the method of electrostimulation, before glioma removal. Results: Distinct sites specifically involved in multiplication or subtraction were detected within the left AG, with a precise spatial distribution and overlapping. All the eloquent (somatosensory, language, and calculation) areas were surgically spared. Postoperatively, the patient had a transient complete deficit for arithmetic subtraction, without either multiplication or language disturbance. The tumour removal was complete. Conclusions: These findings suggest: firstly, the usefulness of an intraoperative calculation mapping during the removal of a lesion involving the left dominant AG, to avoid permanent postoperative deficit of arithmetic processes while optimising the quality of tumour resection; secondly, the possible existence of a well ordered and dynamic anatomo-functional organisation for different components of calculation within the left AG. E ver since Henschen's seminal study, 1 evidence from neuropsychological reports in brain damaged patients [2][3][4][5][6][7][8] and functional neuroimaging studies 9-21 points toward a major involvement of inferior parietal regions in mental calculation. Moreover, there are indications that these areas include arithmetic components that may be selectively impaired or preserved following lesions. In this report, we applied this knowledge to the surgical resection of a glioma invading the left AG, by performing under local anaesthesia an intraoperative electrostimulation mapping of the cortical areas involved in calculation processes. Our goals were first to avoid permanent postoperative calculation deficit, and to study the involvement of different left parietal regions in multiplication versus subtraction, two operations that can be doubly dissociated after parietal lesions. On the basis of these findings, the anatomo-functional organisation of the AG, its integration in calculation networks, and its interaction with language and working memory functions are discussed. METHODS Case presentation PatientThe patient was a 44 year old right handed nurse. She was operated on in our institution for a left parieto-occipital low grade...

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These findings show that the nondominant striatum can be removed in cases of glioma invasion without inducing even transitory movement disorders. This phenomenon could be explained by the combined resection of the two classes of striatal neurons, an associated pallidal and thalamocortical resection, or a compensatory recruitment of parallel networks. Thus, these results may allow the surgeon to maximize the extent of removal of low-grade gliomas involving basal ganglia. Striatal resection may induce transient hemiparesis and "athymhormic syndrome," however, necessitating that the patient be clearly informed before surgery.

Although the occurrence of the supplementary motor area (SMA) syndrome has been extensively reported following mesial lobe surgery, to our knowledge the time course of disease onset was never accurately documented. We describe a patient without deficit, despite harboring a glioma invading the left SMA. This patient was operated under local anesthesia, to perform intraoperative online sensorimotor and language mapping using electrical stimulations throughout the resection. No deficit was noted at the end of the tumor and SMA removal. The patient was maintained awake to perform an immediate control MRI. Aphasia and right hemiplegia occurred 30 min after the SMA resection. Total recovery was observed within 2 months. This work shows that the SMA syndrome may not occur immediately after SMA resection. We suggest that the transient compensation of the SMA function is likely due to residual activity of an oscillatory loop and/or short-term plasticity (rapid unmasking of parallel networks), with final recovery occurring due to long-term plasticity (neosynaptogenesis).