During the rubber hand illusion (RHI), subjects experience an artificial hand as part of their own body, while the real hand is subject to a sort of 'disembodiment'. Can this altered belief about the body also affect physiological mechanisms involved in body-ownership, such as motor control? Here we ask whether the excitability of the motor pathways to the real (disembodied) hand are affected by the illusion. Our results show that the amplitude of the motor-evoked potentials recorded from the real hand is significantly reduced, with respect to baseline, when subjects in the synchronous (but not in the asynchronous) condition experience the fake hand as their own. This finding contributes to the theoretical understanding of the relationship between body-ownership and motor system, and provides the first physiological evidence that a significant drop in motor excitability in M1 hand circuits accompanies the disembodiment of the real hand during the RHI experience.DOI: http://dx.doi.org/10.7554/eLife.14972.001

Background supratotal resection is advocated in lower-grade-gliomas (LGGs) based on theoretical advantages, but with limited verification of functional risk and data on oncological outcomes. We assessed the association of supratotal resection in molecular-defined LGGs with oncological outcomes. Methods 460 presumptive LGGs included; 404 resected; 347 were LGGs, 319 IDH-mutated, 28 wildtype. All patients had clinical, imaging, molecular data. Resection aimed at supratotal resection without any patient or tumor a-priori selection. The association of Extent-of-Resection (EOR), categorized on volumetric-FLAIR-images as residual-tumor-volume, along with post-surgical-management with Progression-free-survival (PFS), malignant-progression-free-survival (MPFS), and Overall-Survival (OS) assessed by univariate, multivariate, propensity-score-analysis. The study mainly focused on IDH-mutated-LGGs, the “typical LGGs”. Results Median follow-up:6.8 years(IQR:5-8). Out of 319 IDH-mutated-LGGs, 190 (59.6%) progressed, median PFS:4.7 years(95%CI:4–5.3). Total and supratotal resection obtained in 39% and 35% of patients of IDH1-mutated tumors. In IDH-mutated, most patients in partial/subtotal group progressed, 82.4% in total, only 6 (5.4%) in supratotal. Median PFS was 29 months(95%CI:25-36) in subtotal, 46 months(95%CI:38-48) in total, while at 92 months, PFS in supratotal was 94.0%. There was no association with molecular-subtypes and grade. At random-forest-analysis, PFS strongly associated with EOR,RT, previous treatment. In the propensity-score analysis, EOR associated with PFS (HR,0.03;95%CI,0.01-0.13). MPFS occurred in 32.1% of subtotal-total groups; 1 event in supratotal. EOR, grade-III, previous treatment correlated to MPFS. At random-forest analysis, OS associated with EOR as well. Conclusions Supratotal resection strongly associated with PFS, MPFS and OS in LGGs, regardless of molecular subtypes and grade, right from the beginning of clinical presentation.

OBJECTIVE Apraxia is a cognitive-motor deficit affecting the execution of skilled movements, termed praxis gestures, in the absence of primary sensory or motor disorders. In patients affected by stroke, apraxia is associated with lesions of the lateral parietofrontal stream, connecting the posterior parietal areas with the ventrolateral premotor area and subserving sensory-motor integration for the hand movements. In the neurosurgical literature to date, there are few reports regarding the incidence of apraxia after glioma surgery. A retrospective analysis of patients who harbored a glioma around the central sulcus and close to the parietofrontal circuits in depth showed a high incidence of long-term postoperative hand apraxia, impairing the patients' quality of life. To avoid the occurrence of postoperative apraxia, the authors sought to develop an innovative intraoperative hand manipulation task (HMt) that can be used in association with the brain mapping technique to identify and preserve the cortical and subcortical structures belonging to the praxis network. METHODS The intraoperative efficacy of the HMt was investigated by comparing the incidence of postoperative ideomotor apraxia between patients undergoing mapping with (n = 79) and without (n = 41) the HMt. Patient groups were balanced for all demographic and clinical features. RESULTS In patients with lesions in the dominant hemisphere, the HMt dramatically reduced the incidence of apraxia, with a higher sensitivity for the ideomotor than for the constructional abilities; patients with lesions in the nondominant hemisphere benefitted from the HMt for both ideomotor and constructional abilities. The administration of the test did not reduce the extent of resection. CONCLUSIONS The HMt is a safe and feasible intraoperative tool that allowed surgeons to prevent the occurrence of long-term hand apraxia while attaining resection goals for the surgical treatment of glioma.

OBJECTIVEBrain mapping techniques allow one to effectively approach tumors involving the primary motor cortex (M1). Tumor resectability and maintenance of patient integrity depend on the ability to successfully identify motor tracts during resection by choosing the most appropriate neurophysiological paradigm for motor mapping. Mapping with a high-frequency (HF) stimulation technique has emerged as the most efficient tool to identify motor tracts because of its versatility in different clinical settings. At present, few data are available on the use of HF for removal of tumors predominantly involving M1.METHODSThe authors retrospectively analyzed a series of 102 patients with brain tumors within M1, by reviewing the use of HF as a guide. The neurophysiological protocols adopted during resections were described and correlated with patients’ clinical and tumor imaging features. Feasibility of mapping, extent of resection, and motor function assessment were used to evaluate the oncological and functional outcome to be correlated with the selected neurophysiological parameters used for guiding resection. The study aimed to define the most efficient protocol to guide resection for each clinical condition.RESULTSThe data confirmed HF as an efficient tool for guiding resection of M1 tumors, affording 85.3% complete resection and only 2% permanent morbidity. HF was highly versatile, adapting the stimulation paradigm and the probe to the clinical context. Three approaches were used. The first was a “standard approach” (HF “train of 5,” using a monopolar probe) applied in 51 patients with no motor deficit and seizure control, harboring a well-defined tumor, showing contrast enhancement in most cases, and reaching the M1 surface. Complete resection was achieved in 72.5%, and 2% had permanent morbidity. The second approach was an “increased train approach,” that is, an increase in the number of pulses (7–9) and of pulse duration, using a monopolar probe. This second approach was applied in 8 patients with a long clinical history, previous treatment (surgery, radiation therapy, chemotherapy), motor deficit at admission, poor seizure control, and mostly high-grade gliomas or metastases. Complete resection was achieved in 87.5% using this approach, along with 0% permanent morbidity. The final approach was a “reduced train approach,” which was the combined use of train of 2 or train of 1 pulses associated with the standard approach, using a monopolar or bipolar probe. This approach was used in 43 patients with a long clinical history and poorly controlled seizures, harboring tumors with irregular borders without contrast enhancement (low or lower grade), possibly not reaching the cortical surface. Complete resection was attained in 88.4%, and permanent morbidity was found in 2.3%.CONCLUSIONSResection of M1 tumors is feasible and safe. By adapting the stimulation paradigm and probe appropriately to the clinical context, the best resection and functional results can be achieved.