Mapping of language and motor function during awake neurosurgery with intraoperative optical imaging.

Intraoperative optical imaging (IOI) is a marker-free, contactless, and noninvasive imaging technique that is able to visualize metabolic changes of the brain surface following neuronal activation. Although it has been used in the past mainly for the identification of functional brain areas under general anesthesia, the authors investigated the potential of the method during awake surgery. Measurements were performed in 10 patients who underwent resection of lesions within or adjacent to cortical language or motor sites. IOI was applied in 3 different scenarios: identification of motor areas by using finger-tapping tasks, identification of language areas by using speech tasks (overt and silent speech), and a novel approach-the application of IOI as a feedback tool during direct electrical stimulation (DES) mapping of language. The functional maps, which were calculated from the IOI data (activity maps), were qualitatively compared with the functional MRI (fMRI) and the electrophysiological testing results during the surgical procedure to assess their potential benefit for surgical decision-making.The results reveal that the intraoperative identification of motor sites with IOI in good agreement with the preoperatively acquired fMRI and the intraoperative electrophysiological measurements is possible. Because IOI provides spatially highly resolved maps with minimal additional hardware effort, the application of the technique for motor site identification seems to be beneficial in awake procedures. The identification of language processing sites with IOI was also possible, but in the majority of cases significant differences between fMRI, IOI, and DES were visible, and therefore according to the authors' findings the IOI results are too unspecific to be useful for intraoperative decision-making with respect to exact language localization. For this purpose, DES mapping will remain the method of choice.Nevertheless, the IOI technique can provide additional value during the language mapping procedure with DES. Using a simple difference imaging approach, the authors were able to visualize and calculate the spatial extent of activation for each stimulation. This might enable surgeons in the future to optimize the mapping process. Additionally, differences between tumor and nontumor stimulation sites were observed with respect to the spatial extent of the changes in cortical optical properties. These findings provide further evidence that the method allows the assessment of the functional state of neurovascular coupling and is therefore suited for the delineation of pathologically altered tissue.

Limitations of functional neuroimaging for patient selection and surgical planning in glioma surgery.

The optimal surgical management of gliomas requires a balance between surgical cytoreduction and preservation of neurological function. Preoperative functional neuroimaging, such as functional MRI (fMRI) and diffusion tensor imaging (DTI), has emerged as a possible tool to inform patient selection and surgical planning. However, evidence that preoperative fMRI or DTI improves extent of resection, limits neurological morbidity, and broadens surgical indications in classically eloquent areas is lacking. In this review, the authors describe facets of functional neuroimaging techniques that may limit their impact on neurosurgical oncology and critically evaluate the evidence supporting fMRI and DTI for patient selection and operative planning in glioma surgery. The authors also propose alternative applications for functional neuroimaging in the care of glioma patients.

Mapping cognitive and emotional networks in neurosurgical patients using resting-state functional magnetic resonance imaging.

Neurosurgery has been at the forefront of a paradigm shift from a localizationist perspective to a network-based approach to brain mapping. Over the last 2 decades, we have seen dramatic improvements in the way we can image the human brain and noninvasively estimate the location of critical functional networks. In certain patients with brain tumors and epilepsy, intraoperative electrical stimulation has revealed direct links between these networks and their function. The focus of these techniques has rightfully been identification and preservation of so-called "eloquent" brain functions (i.e., motor and language), but there is building momentum for more extensive mapping of cognitive and emotional networks. In addition, there is growing interest in mapping these functions in patients with a broad range of neurosurgical diseases. Resting-state functional MRI (rs-fMRI) is a noninvasive imaging modality that is able to measure spontaneous low-frequency blood oxygen level-dependent signal fluctuations at rest to infer neuronal activity. Rs-fMRI may be able to map cognitive and emotional networks for individual patients. In this review, the authors give an overview of the rs-fMRI technique and associated cognitive and emotional resting-state networks, discuss the potential applications of rs-fMRI, and propose future directions for the mapping of cognition and emotion in neurosurgical patients.

History of awake mapping and speech and language localization: from modules to networks.

Lesion-symptom correlations shaped the early understanding of cortical localization. The classic Broca-Wernicke model of cortical speech and language organization underwent a paradigm shift in large part due to advances in brain mapping techniques. This initially started by demonstrating that the cortex was excitable. Later, advancements in neuroanesthesia led to awake surgery for epilepsy focus and tumor resection, providing neurosurgeons with a means of studying cortical and subcortical pathways to understand neural architecture and obtain maximal resection while avoiding so-called critical structures. The aim of this historical review is to highlight the essential role of direct electrical stimulation and cortical-subcortical mapping and the advancements it has made to our understanding of speech and language cortical organization. Specifically, using cortical and subcortical mapping, neurosurgeons shifted from a localist view in which the brain is composed of rigid functional modules to one of dynamic and integrative large-scale networks consisting of interconnected cortical subregions.

When imaging meets neurophysiology: the value of navigated transcranial magnetic stimulation for preoperative neurophysiological mapping prior to brain tumor surgery.

Maximal safe resection is the modern goal for surgery of intrinsic brain tumors located in or close to brain eloquent areas. Nowadays different neuroimaging techniques provide important anatomical and functional information regarding the brain functional organization that can be used to plan a customized surgical strategy to preserve functional networks, and to increase the extent of tumor resection. Among these techniques, navigated transcranial magnetic stimulation (nTMS) has recently gained great favor among the neurosurgical community for preoperative mapping and planning prior to brain tumor surgery. It represents an advanced neuroimaging technique based on the neurophysiological mapping of the functional cortical brain organization. Moreover, it can be combined with other neuroimaging techniques such as diffusion tensor imaging tractography, thus providing a reliable reconstruction of brain eloquent networks. Consequently, nTMS mapping may provide reliable noninvasive brain functional mapping, anticipating information that otherwise may be available to neurosurgeons only in the operating theater by using direct electrical stimulation. The authors describe the reliability and usefulness of the preoperative nTMS-based approach in neurosurgical practice, and briefly discuss their experience using nTMS as well as currently available evidence in the literature supporting its clinical use. In particular, special attention is reserved for the discussion of the role of nTMS as a novel tool for the preoperative neurophysiological mapping of motor and language networks prior to surgery of intrinsic brain tumors located in or close to eloquent networks, as well as for future and promising applications of nTMS in neurosurgical practice.

Setup presentation and clinical outcome analysis of treating highly language-eloquent gliomas via preoperative navigated transcranial magnetic stimulation and tractography.

OBJECTIVE Awake surgery combined with intraoperative direct electrical stimulation (DES) and intraoperative neuromonitoring (IONM) is considered the gold standard for the resection of highly language-eloquent brain tumors. Different modalities, such as functional magnetic resonance imaging (fMRI) or magnetoencephalography (MEG), are commonly added as adjuncts for preoperative language mapping but have been shown to have relevant limitations. Thus, this study presents a novel multimodal setup consisting of preoperative navigated transcranial magnetic stimulation (nTMS) and nTMS-based diffusion tensor imaging fiber tracking (DTI FT) as an adjunct to awake surgery. METHODS Sixty consecutive patients (63.3% men, mean age 47.6 ± 13.3 years) suffering from highly language-eloquent left-hemispheric low- or high-grade glioma underwent preoperative nTMS language mapping and nTMS-based DTI FT, followed by awake surgery for tumor resection. Both nTMS language mapping and DTI FT data were available for resection planning and intraoperative guidance. Clinical outcome parameters, including craniotomy size, extent of resection (EOR), language deficits at different time points, Karnofsky Performance Scale (KPS) score, duration of surgery, and inpatient stay, were assessed. RESULTS According to postoperative evaluation, 28.3% of patients showed tumor residuals, whereas new surgery-related permanent language deficits occurred in 8.3% of patients. KPS scores remained unchanged (median preoperative score 90, median follow-up score 90). CONCLUSIONS This is the first study to present a clinical outcome analysis of this very modern approach, which is increasingly applied in neurooncological centers worldwide. Although human language function is a highly complex and dynamic cortico-subcortical network, the presented approach offers excellent functional and oncological outcomes in patients undergoing surgery of lesions affecting this network.

ReStNeuMap: a tool for automatic extraction of resting-state functional MRI networks in neurosurgical practice.

OBJECTIVE: Resting-state functional MRI (rs-fMRI) represents a promising and cost-effective alternative to task-based fMRI for presurgical mapping. However, the lack of clinically streamlined and reliable rs-fMRI analysis tools has prevented wide adoption of this technique. In this work, the authors introduce an rs-fMRI processing pipeline (ReStNeuMap) for automatic single-patient rs-fMRI network analysis. METHODS: The authors provide a description of the rs-fMRI network analysis steps implemented in ReStNeuMap and report their initial experience with this tool after performing presurgical mapping in 6 patients. They verified the spatial agreement between rs-fMRI networks derived by ReStNeuMap and localization of activation with intraoperative direct electrical stimulation (DES). RESULTS: The authors automatically extracted rs-fMRI networks including eloquent cortex in spatial proximity with the resected lesion in all patients. The distance between DES points and corresponding rs-fMRI networks was less than 1 cm in 78% of cases for motor, 100% of cases for visual, 87.5% of cases for language, and 100% of cases for speech articulation mapping. CONCLUSIONS: The authors' initial experience with ReStNeuMap showed good spatial agreement between presurgical rs-fMRI predictions and DES findings during awake surgery. The availability of the rs-fMRI analysis tools for clinicians aiming to perform noninvasive mapping of brain functional networks may extend its application beyond surgical practice.

Preserving executive functions in nondominant frontal lobe glioma surgery: an intraoperative tool.

OBJECTIVE: The goal of surgery for gliomas is maximal tumor removal while preserving the patient's full functional integrity. At present during frontal tumor removal, this goal is mostly achieved, although the risk of impairing the executive functions (EFs), and thus the quality of life, remains significant. The authors investigated the accuracy of an intraoperative version of the Stroop task (iST), adapted for intraoperative mapping, to detect EF-related brain sites by evaluating the impact of the iST brain mapping on preserving functional integrity following a maximal tumor resection. METHODS: Forty-five patients with nondominant frontal gliomas underwent awake surgery; brain mapping was used to establish the functional boundaries for the resection. In 18 patients language, praxis, and motor functions, but not EFs (control group), were mapped intraoperatively at the cortical-subcortical level. In 27 patients, in addition to language, praxis, and motor functions, EFs were mapped with the iST at the cortical-subcortical level (Stroop group). In both groups the EF performance was evaluated preoperatively, at 7 days and 3 months after surgery. RESULTS: The iST was successfully administered in all patients. Consistent interferences, such as color-word inversion/latency, were obtained by stimulating precise white matter sites below the inferior and middle frontal gyri, anterior to the insula and over the putamen, and these were used to establish the posterior functional limit of the resection. Procedures implemented with iST dramatically reduced the EF deficits at 3 months. The EOR was similar in Stroop and control groups. CONCLUSIONS: Brain mapping with the iST allows identification and preservation of the frontal lobe structures involved in inhibition of automatic responses, reducing the incidence of postoperative EF deficits and enhancing the further posterior and inferior margin of tumor resection.

Assessment of the praxis circuit in glioma surgery to reduce the incidence of postoperative and long-term apraxia: a new intraoperative test.

OBJECTIVEApraxia 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.METHODSThe 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.RESULTSIn 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.CONCLUSIONSThe 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.

Resection of gliomas deemed inoperable by neurosurgeons based on preoperative imaging studies.

OBJECTIVE Maximal safe resection is a primary objective in the management of gliomas. Despite this objective, surgeons and referring physicians may, on the basis of radiological studies alone, assume a glioma to be unresectable. Because imaging studies, including functional MRI, may not localize brain functions (such as language) with high fidelity, this simplistic approach may exclude some patients from what could be a safe resection. Intraoperative direct electrical stimulation (DES) allows for the accurate localization of functional areas, thereby enabling maximal resection of tumors, including those that may appear inoperable based solely on radiological studies. In this paper the authors describe the extent of resection (EOR) and functional outcomes following resections of tumors deemed inoperable by referring physicians and neurosurgeons. METHODS The authors retrospectively examined the cases of 58 adult patients who underwent glioma resection within 6 months of undergoing a brain biopsy of the same lesion at an outside hospital. All patients exhibited unifocal supratentorial disease and preoperative Karnofsky Performance Scale scores ≥ 70. The EOR and 6-month functional outcomes for this population were characterized. RESULTS Intraoperative DES mapping was performed on 96.6% (56 of 58) of patients. Nearly half of the patients (46.6%, 27 of 58) underwent an awake surgical procedure with DES. Overall, the mean EOR was 87.6% ± 13.6% (range 39.0%-100%). Gross-total resection (resection of more than 99% of the preoperative tumor volume) was achieved in 29.3% (17 of 58) of patients. Subtotal resection (95%-99% resection) and partial resection (PR; < 95% resection) were achieved in 12.1% (7 of 58) and 58.6% (34 of 58) of patients, respectively. Of the cases that involved PR, the mean EOR was 79.4% ± 12.2%. Six months after surgery, no patient was found to have a new postoperative neurological deficit. The majority of patients (89.7%, 52 of 58) were free of neurological deficits both pre- and postoperatively. The remainder of patients exhibited either residual but stable deficits (5.2%, 3 of 58) or complete correction of preoperative deficits (5.2%, 3 of 58). CONCLUSIONS The use of DES enabled maximal safe resections of gliomas deemed inoperable by referring neurosurgeons. With rare exceptions, tumor resectability cannot be determined solely by radiological studies.

Language outcomes after resection of dominant inferior parietal lobule gliomas.

OBJECTIVE The dominant inferior parietal lobule (IPL) contains cortical and subcortical regions essential for language. Although resection of IPL tumors could result in language deficits, little is known about the likelihood of postoperative language morbidity or the risk factors predisposing to this outcome. METHODS The authors retrospectively examined a series of patients who underwent resections of gliomas from the dominant IPL. Postoperative language outcomes were characterized across the patient population. To identify factors associated with postoperative language morbidity, the authors then compared features between those patients who experienced postoperative deficits and those who experienced no postoperative language dysfunction. RESULTS Twenty-four patients were identified for analysis. Long-term language deficits occurred in 29.2% of patients (7 of 24): 3 of these patients had experienced preoperative language deficits, whereas new long-term language deficits occurred in 4 patients (16.7%; 4 of 24). Of those patients who exhibited preoperative language deficits, 62.5% (5 of 8) experienced long-term resolution of their language deficits with surgical treatment. All patients underwent intraoperative brain mapping by direct electrical stimulation. Awake, intraoperative cortical language mapping was performed on 17 patients (70.8%). Positive cortical language sites were identified in 23.5% of these patients (4 of 17). Awake, intraoperative subcortical language mapping was performed in 8 patients (33.3%). Positive subcortical language sites were identified in 62.5% of these patients (5 of 8). Patients with positive cortical language sites exhibited a higher rate of long-term language deficits (3 of 4, 75%), compared with those who did not (1 of 13, 7.7%; p = 0.02). Although patients with positive subcortical language sites exhibited a higher rate of long-term language deficits than those who exhibited only negative sites (40.0% vs 0.0%, respectively), this difference was not statistically significant (p = 0.46). Additionally, patients with long-term language deficits were older than those without deficits (p < 0.05). CONCLUSIONS In a small number of patients with preoperative language deficits, IPL glioma resection resulted in improved language function. However, in patients with intact preoperative language function, resection of IPL gliomas may result in new language deficits, especially if the tumors are diffuse, high-grade lesions. Thus, language-dominant IPL glioma resection is not risk-free, yet it is safe and its morbidity can be reduced by the use of cortical and subcortical stimulation mapping.

Navigated transcranial magnetic stimulation for glioma removal: prognostic value in motor function recovery from postsurgical neurological deficits.

OBJECTIVE The aim of the present study was to evaluate the usefulness of navigated transcranial magnetic stimulation (nTMS) as a prognostic predictor for upper-extremity motor functional recovery from postsurgical neurological deficits. METHODS Preoperative and postoperative nTMS studies were prospectively applied in 14 patients (mean age 39 ± 12 years) who had intraparenchymal brain neoplasms located within or adjacent to the motor eloquent area in the cerebral hemisphere. Mapping by nTMS was done 3 times, i.e., before surgery, and 1 week and 3 weeks after surgery. To assess the response induced by nTMS, motor evoked potential (nTMS-MEP) was recorded using a surface electromyography electrode attached to the abductor pollicis brevis (APB). The cortical locations that elicited the largest electromyography response by nTMS were defined as hotspots. Hotspots for APB were confirmed as positive responsive sites by direct electrical stimulation (DES) during awake craniotomy. The distances between hotspots and lesions (DHS-L) were measured. Postoperative neurological deficits were assessed by manual muscle test and dynamometer. To validate the prognostic value of nTMS in recovery from upper-extremity paresis, the following were investigated: 1) the correlation between DHS-L and the serial grip strength change, and 2) the correlation between positive nTMS-MEP at 1 week after surgery and the serial grip strength change. RESULTS From the presurgical nTMS study, MEPs from targeted muscles were identified in 13 cases from affected hemispheres. In one case, MEP was not evoked due to a huge tumor. Among 9 cases from which intraoperative DES mapping for hand motor area was available, hotspots for APB identified by nTMS were concordant with DES-positive sites. Compared with the adjacent group (DHS-L < 10 mm, n = 6), the nonadjacent group (DHS-L ≥ 10 mm, n = 7) showed significantly better recovery of grip strength at 3 months after surgery (p < 0.01). There were correlations between DHS-L and recovery of grip strength at 1 week, 3 weeks, and 3 months after surgery (r = 0.74, 0.68, and 0.65, respectively). Postsurgical nTMS was accomplished in 13 patients. In 9 of 13 cases, nTMS-MEP from APB muscle was positive at 1 week after surgery. Excluding the case in which nTMS-MEP was negative from the presurgical nTMS study, recoveries in grip strength were compared between 2 groups, in which nTMS-MEP at 1 week after surgery was positive (n = 9) or negative (n = 3). Significant differences were observed between the 2 groups at 1 week, 3 weeks, and 3 months after surgery (p < 0.01). Positive nTMS-MEP at 1 week after surgery correlated well with the motor recovery at 1 week, 3 weeks, and 3 months after surgery (r = 0.87, 0.88, and 0.77, respectively). CONCLUSIONS Navigated TMS is a useful tool for identifying motor eloquent areas. The results of the present study have demonstrated the predictive value of nTMS in upper-extremity motor function recovery from postsurgical neurological deficits. The longer DHS-L and positive nTMS-MEP at 1 week after surgery have prognostic values of better recovery from postsurgical neurological deficits.

Chronic spatial working memory deficit associated with the superior longitudinal fasciculus: a study using voxel-based lesion-symptom mapping and intraoperative direct stimulation in right prefrontal glioma surgery.

OBJECTIVE Although the right prefrontal region is regarded as a silent area, chronic deficits of the executive function, including working memory (WM), could occur after resection of a right prefrontal glioma. This may be overlooked by postoperative standard examinations, and the disabilities could affect the patient's professional life. The right prefrontal region is a part of the frontoparietal network and is subserved by the superior longitudinal fasciculus (SLF); however, the role of the SLF in spatial WM is unclear. This study investigated a persistent spatial WM deficit in patients who underwent right prefrontal glioma resection, and evaluated the relationship between the spatial WM deficit and the SLF. METHODS Spatial WM was examined in 24 patients who underwent prefrontal glioma resection (right, n = 14; left, n = 10) and in 14 healthy volunteers using a spatial 2-back task during the long-term postoperative period. The neural correlates of spatial WM were evaluated using lesion mapping and voxel-based lesion-symptom mapping. In addition, the spatial 2-back task was performed during surgery under direct subcortical electrical stimulation in 2 patients with right prefrontal gliomas. RESULTS Patients with a right prefrontal lesion had a significant chronic spatial WM deficit. Voxel-based lesion-symptom mapping analysis revealed a significant correlation between spatial WM deficit and the region that overlapped the first and second segments of the SLF (SLF I and SLF II). Two patients underwent awake surgery and had difficulties providing the correct responses in the spatial 2-back task with direct subcortical electrical stimulation on the SLF I, which was preserved and confirmed by postoperative diffusion tensor imaging tractography. These patients exhibited no spatial WM deficits during the postoperative immediate and long-term periods. CONCLUSIONS Spatial WM deficits may persist in patients who undergo resection of the tumor located in the right prefrontal brain parenchyma. Injury to the dorsal frontoparietal subcortical white matter pathway, i.e., the SLF I or SLF I and II, could play a causal role in this chronic deficit. A persistent spatial WM deficit, without motor and language deficits, could affect the professional life of the patient. In such cases, awake surgery would be useful to detect the spatial WM network with appropriate task during tumor exploration.

Monopolar high-frequency language mapping: can it help in the surgical management of gliomas? A comparative clinical study.

OBJECT Intraoperative language mapping is traditionally performed with low-frequency bipolar stimulation (LFBS). High-frequency train-of-five stimulation delivered by a monopolar probe (HFMS) is an alternative technique for motor mapping, with a lower reported seizure incidence. The application of HFMS in language mapping is still limited. Authors of this study assessed the efficacy and safety of HFMS for language mapping during awake surgery, exploring its clinical impact compared with that of LFBS. METHODS Fifty-nine patients underwent awake surgery with neuropsychological testing, and LFBS and HFMS were compared. Frequency, type, and site of evoked interference were recorded. Language was scored preoperatively and 1 week and 3 months after surgery. Extent of resection was calculated as well. RESULTS High-frequency monopolar stimulation induced a language disturbance when the repetition rate was set at 3 Hz. Interference with counting (p = 0.17) and naming (p = 0.228) did not vary between HFMS and LFBS. These results held true when preoperative tumor volume, lesion site, histology, and recurrent surgery were considered. Intraoperative responses (1603) in all patients were compared. The error rate for both modalities differed from baseline values (p < 0.001) but not with one another (p = 0.06). Low-frequency bipolar stimulation sensitivity (0.458) and precision (0.665) were slightly higher than the HFMS counterparts (0.367 and 0.582, respectively). The error rate across the 3 types of language errors (articulatory, anomia, paraphasia) did not differ between the 2 stimulation methods (p = 0.279). CONCLUSIONS With proper setting adjustments, HFMS is a safe and effective technique for language mapping.

Intraoperative mapping during repeat awake craniotomy reveals the functional plasticity of adult cortex.

OBJECT To avoid iatrogenic injury during the removal of intrinsic cerebral neoplasms such as gliomas, direct electrical stimulation (DES) is used to identify cortical and subcortical white matter pathways critical for language, motor, and sensory function. When a patient undergoes more than 1 brain tumor resection as in the case of tumor recurrence, the use of DES provides an unusual opportunity to examine brain plasticity in the setting of neurological disease. METHODS The authors examined 561 consecutive cases in which patients underwent DES mapping during surgery forglioma resection. "Positive" and "negative" sites-discrete cortical regions where electrical stimulation did (positive) or did not (negative) produce transient sensory, motor, or language disturbance-were identified prior to tumor resection and documented by intraoperative photography for categorization into functional maps. In this group of 561 patients, 18 were identified who underwent repeat surgery in which 1 or more stimulation sites overlapped with those tested during the initial surgery. The authors compared intraoperative sensory, motor, or language mapping results between initial and repeat surgeries, and evaluated the clinical outcomes for these patients. RESULTS A total of 117 sites were tested for sensory (7 sites, 6.0%), motor (9 sites, 7.7%), or language (101 sites, 86.3%) function during both initial and repeat surgeries. The mean interval between surgical procedures was 4.1 years. During initial surgeries, 95 (81.2%) of 117 sites were found to be negative and 22 (18.8%) of 117 sites were found to be positive. During repeat surgeries, 103 (88.0%) of 117 sites were negative and 14 (12.0%) of 117 were positive. Of the 95 sites that were negative at the initial surgery, 94 (98.9%) were also negative at the repeat surgery, while 1 (1.1%) site was found to be positive. Of the 22 sites that were initially positive, 13 (59.1%) remained positive at repeat surgery, while 9 (40.9%) had become negative for function. Overall, 6 (33.3%) of 18 patients exhibited loss of function at 1 or more motor or language sites between surgeries. Loss of function at these sites was not associated with neurological impairment at the time of repeat surgery, suggesting that neurological function was preserved through neural circuit reorganization or activation of latent functional pathways. CONCLUSIONS The adult central nervous system reorganizes motor and language areas in patients with glioma. Ultimately, adult neural plasticity may help to preserve motor and language function in the presence of evolving structural lesions. The insight gained from this subset of patients has implications for our understanding of brain plasticity in clinical settings.

Brain mapping: a novel intraoperative neuropsychological approach.

OBJECTIVE Awake surgery and mapping are performed in patients with low-grade tumors infiltrating functional brain areas for which the greater the resection, the longer the patient survival. However, the extent of resection is subject to preservation of cognitive functions, and in the absence of proper feedback during mapping, the surgeon may be less prone to perform an extensive resection. The object of this study was to perform real-time continuous assessment of cognitive function during the resection of tumor tissue that could infiltrate eloquent tissue. METHODS The authors evaluated the use of new, complex real-time neuropsychological testing (RTNT) in a series of 92 patients. They reported normal scoring and decrements in patient performance as well as reversible intraoperative neuropsychological dysfunctions in tasks (for example, naming) associated with different cognitive abilities. RESULTS RTNT allowed one to obtain a more defined neuropsychological picture of the impact of surgery. The influence of this monitoring on surgical strategy was expressed as the mean extent of resection: 95% (range 73%-100%). At 1 week postsurgery, the neuropsychological scores were very similar to those detected with RTNT, revealing the validity of the RTNT technique as a predictive tool. At the follow-up, the majority of neuropsychological scores were still > 70%, indicating a decrease of < 30%. CONCLUSIONS RTNT enables continuous enriched intraoperative feedback, allowing the surgeon to increase the extent of resection. In sharp contrast to classic mapping techniques, RTNT allows testing of several cognitive functions for one brain area under surgery.

Disrupting the right pars opercularis with electrical stimulation frees the song: case report.

The authors report the first case of a strikingly unusual speech impairment evoked by intraoperative electrostimulation in a 36-year-old right-handed patient, a well-trained singer, who underwent awake surgery for a right fronto-temporo-insular low-grade glioma. Functionally disrupting the pars opercularis of the right inferior frontal gyrus led the patient to automatically switch from a speaking to a singing mode of language production. Given the central role of the right pars opercularis in the inhibitory control network, the authors propose that this finding may be interpreted as possible evidence for a competitive and independent neurocognitive subnetwork devoted to the melodically intoned articulation of words (normal language-based vs singing-based) in subjects with high expertise. From a more clinical perspective, such data may have implications for awake neurosurgery, especially to preserve the quality of life for singers.