Search

Abstract Chronic pain, a complex and debilitating condition, poses a significant challenge to both patients and healthcare providers worldwide. Conventional pharmacological interventions often prove inadequate in delivering satisfactory relief while carrying the risks of addiction and adverse reactions. In recent years, electric neuromodulation emerged as a promising alternative in chronic pain management. This method entails the precise administration of electrical stimulation to specific nerves or regions within the central nervous system to regulate pain signals. Through mechanisms that include the alteration of neural activity and the release of endogenous pain-relieving substances, electric neuromodulation can effectively alleviate pain and improve patients' quality of life. Several modalities of electric neuromodulation, with a different grade of invasiveness, provide tailored strategies to tackle various forms and origins of chronic pain. Through an exploration of the anatomical and physiological pathways of chronic pain, encompassing neurotransmitter involvement, this narrative review offers insights into electrical therapies’ mechanisms of action, clinical utility, and future perspectives in chronic pain management.

Encoding artificial perceptions through brain stimulation, especially that of higher cognitive functions such as speech perception, is one of the most formidable challenges in brain-computer interfaces (BCI). Brain stimulation has been used for functional mapping in clinical practices for the last 70 years to treat various disorders affecting the nervous system, including epilepsy, Parkinson's disease, essential tremors, and dystonia. Recently, direct electrical stimulation has been used to evoke various forms of perception in humans, ranging from sensorimotor, auditory, and visual to speech cognition. Successfully evoking and fine-tuning artificial perceptions could revolutionize communication for individuals with speech disorders and significantly enhance the capabilities of brain-computer interface technologies. However, despite the extensive literature on encoding various perceptions and the rising popularity of speech BCIs, inducing artificial speech perception is still largely unexplored, and its potential has yet to be determined. In this paper, we examine the various stimulation techniques used to evoke complex percepts and the target brain areas for the input of speech-like information. Finally, we discuss strategies to address the challenges of speech encoding and discuss the prospects of these approaches. [ABSTRACT FROM AUTHOR]

Intraoperative neurophysiological monitoring (IONM) is a crucial advancement in neurosurgery, enhancing procedural safety and precision. This technique involves continuous real-time assessment of neurophysiological signals, aiding surgeons in timely interventions to protect neural structures. In addition to inherent limitations, IONM necessitates a detailed anesthetic plan for accurate signal recording. Given the growing importance of IONM in neurosurgery, we conducted a narrative review including the most relevant studies about the modalities and their application in different fields of neurosurgery. In particular, this review provides insights for all physicians and healthcare professionals unfamiliar with IONM, elucidating commonly used techniques in neurosurgery. In particular, it discusses the roles of IONM in various neurosurgical settings such as tumoral brain resection, neurovascular surgery, epilepsy surgery, spinal surgery, and peripheral nerve surgery. Furthermore, it offers an overview of the anesthesiologic strategies and limitations of techniques essential for the effective implementation of IONM. [ABSTRACT FROM AUTHOR]

During intraoperative neurophysiological monitoring in neurosurgery, brain electrodes are placed to record electrocorticography or to inject current for direct cortical stimulation. A low impedance electrode may improve signal quality. We review here a brain electrode (WISE Cortical Strip, WCS®), where a thin polymer strip embeds platinum nanoparticles to create conductive electrode contacts. The low impedance contacts enable a high signal-to-noise ratio, allowing for better detection of small signals such as high-frequency oscillations (HFO). The softness of the WCS may hinder sliding the electrode under the dura or advancing it to deeper structures as the hippocampus but assures conformability with the cortex even in the resection cavity. We provide an extensive review on WCS including a market overview, an introduction to the device (mechanistics, cost aspects, performance standards, safety and contraindications) and an overview of the available pre- and post-approval data. The WCS improves signal detection by lower impedance and better conformability to the cortex. The higher signal-to-noise ratio improves the detection of challenging signals. The softness of the electrode may be a disadvantage in some applications and an advantage in others. [ABSTRACT FROM AUTHOR]

Chronic pain, a complex and debilitating condition, poses a significant challenge to both patients and healthcare providers worldwide. Conventional pharmacological interventions often prove inadequate in delivering satisfactory relief while carrying the risks of addiction and adverse reactions. In recent years, electric neuromodulation emerged as a promising alternative in chronic pain management. This method entails the precise administration of electrical stimulation to specific nerves or regions within the central nervous system to regulate pain signals. Through mechanisms that include the alteration of neural activity and the release of endogenous pain-relieving substances, electric neuromodulation can effectively alleviate pain and improve patients' quality of life. Several modalities of electric neuromodulation, with a different grade of invasiveness, provide tailored strategies to tackle various forms and origins of chronic pain. Through an exploration of the anatomical and physiological pathways of chronic pain, encompassing neurotransmitter involvement, this narrative review offers insights into electrical therapies' mechanisms of action, clinical utility, and future perspectives in chronic pain management. [ABSTRACT FROM AUTHOR]

• Direct stimulation affected the subregions responsible for cognitive processes. • Cognitive processes were linked to changes in gamma power. • Direct cortical stimulation has the potential to enhance cognitive processes. This study aims to investigate the potential of direct cortical stimulation (DCS) to modulate tactile categorization and decision-making, as well as to identify the specific locations where these cognitive functions occur. We analyzed behavioral changes in three epilepsy patients with implanted electrodes using electrocorticography (ECoG) and a vibrotactile discrimination task. DCS was applied to investigate its impact on tactile categorization and decision-making processes. We determined the precise location of the electrodes where each cognitive function was modulated. This functional discrimination was related with gamma band activity from ECoG. DCS selectively affected either tactile categorization or decision-making processes. Tactile categorization was modulated by stimulating the rostral part of the supramarginal gyrus, while decision-making was modulated by stimulating the caudal part. DCS can enhance cognitive processes and map brain regions responsible for tactile categorization and decision-making within the supramarginal gyrus. This study also demonstrates that DCS and the gamma activity of ECoG can concordantly identify the detailed brain mapping in a tactile process compared to other functional neuroimaging. The combination of DCS and ECoG gamma activity provides a more nuanced and detailed understanding of brain function than traditional neuroimaging techniques alone. [ABSTRACT FROM AUTHOR]

Functions of the human insula have been explored extensively with neuroimaging methods and intracranial electrical stimulation studies that have highlighted a functional segregation across its subregions. A recently developed cytoarchitectonic map of the human insula has also segregated this brain region into various areas. Our knowledge of the functional organization of this brain region at the level of these fine-parceled microstructural areas remains only partially understood. We address this gap of knowledge by applying a multimodal approach linking direct electrical stimulation and task-evoked intracranial EEG recordings with microstructural subdivisions of the human insular cortex. In 17 neurosurgical patients with 142 implanted electrodes, stimulation of 40 % of the sites induced a reportable change in the conscious experience of the subjects in visceral/autonomic, anxiety, taste/olfactory, pain/temperature as well as somatosensory domains. These subjective responses showed a topographical allocation to microstructural areas defined by probabilistic cytoarchitectonic parcellation maps of the human insula. We found the pain and thermal responses to be located in areas lg2/ld2, while non-painful/non-thermal somatosensory responses corresponded to area ld3 and visceroceptive responses to area Id6. Lastly, the stimulation of area Id7 in the dorsal anterior insula, failed to induce reportable changes to subjective experience even though intracranial EEG recordings from this region captured significant time-locked high-frequency activity (HFA). Our results provide a multimodal map of functional subdivisions within the human insular cortex at the individual brain basis and characterize their anatomical association with fine-grained cytoarchitectonic parcellations of this brain structure.

Abstract Objective Cortical stimulation is an important component of stereoelectroencephalography (SEEG). Despite this, there is currently no standardized approach and significant heterogeneity in the literature regarding cortical stimulation practices. Via an international survey of SEEG clinicians, we sought to examine the spectrum of cortical stimulation practices to reveal areas of consensus and variability. Methods A 68‐item questionnaire was developed to understand cortical stimulation practices including neurostimulation parameters, interpretation of epileptogenicity, functional and cognitive assessment and subsequent surgical decisions. Multiple recruitment pathways were pursued, with the questionnaire distributed directly to 183 clinicians. Results Responses were received from 56 clinicians across 17 countries with experience ranging from 2 to 60 years (M = 10.73, SD = 9.44). Neurostimulation parameters varied considerably, with maximum current ranging from 3 to 10 mA (M = 5.33, SD = 2.29) for 1 Hz and from 2 to 15 mA (M = 6.54, SD = 3.68) for 50 Hz stimulation. Charge density ranged from 8 to 200 μC/cm2, with up to 43% of responders utilizing charge densities higher than recommended upper safety limits, i.e. 55 μC/cm2. North American responders reported statistically significant higher maximum current (P

Functions of the human insula have been explored extensively with neuroimaging methods and intracranial electrical stimulation studies that have highlighted a functional segregation across its subregions. A recently developed cytoarchitectonic map of the human insula has also segregated this brain region into various areas. Our knowledge of the functional organization of this brain region at the level of these fine-parceled microstructural areas remains only partially understood. We address this gap of knowledge by applying a multimodal approach linking direct electrical stimulation and task-evoked intracranial EEG recordings with microstructural subdivisions of the human insular cortex. In 17 neurosurgical patients with 142 implanted electrodes, stimulation of 40 % of the sites induced a reportable change in the conscious experience of the subjects in visceral/autonomic, anxiety, taste/olfactory, pain/temperature as well as somatosensory domains. These subjective responses showed a topographical allocation to microstructural areas defined by probabilistic cytoarchitectonic parcellation maps of the human insula. We found the pain and thermal responses to be located in areas lg2/ld2, while non-painful/non-thermal somatosensory responses corresponded to area ld3 and visceroceptive responses to area Id6. Lastly, the stimulation of area Id7 in the dorsal anterior insula, failed to induce reportable changes to subjective experience even though intracranial EEG recordings from this region captured significant time-locked high-frequency activity (HFA). Our results provide a multimodal map of functional subdivisions within the human insular cortex at the individual brain basis and characterize their anatomical association with fine-grained cytoarchitectonic parcellations of this brain structure. • Stimulation of various insular subregions elicited regionally-specific changes in the subjective states. • These changes were topographically correlated with probabilistic cytoarchitectonic parcellation maps of insular subregions. • In the insula subregion, stimulation caused no subjective changes but higher activity was seen during salience task. [ABSTRACT FROM AUTHOR]

Intraoperative language mapping of tumor and peritumor tissue is a well-established technique for avoiding permanent neurological deficits and maximizing extent of resection. Although there are several components of language that may be tested intraoperatively (eg, naming, writing, reading, and repetition), there is a lack of consistency in how patients are tested intraoperatively as well as the techniques involved to ensure safety during an awake procedure. Here, we review appropriate patient selection, neuroanesthetic techniques, cortical and subcortical language mapping stimulation paradigms, and selection of intraoperative language tasks used during awake craniotomies. We also expand on existing language mapping reviews by considering how intensity and timing of electrical stimulation may impact interpretation of mapping results.

Early postoperative seizures (EPS) are a common complication of brain tumor surgery. EPS can lead to hemorrhage, cerebral hypoxia, increased intracranial pressure, longer hospitalization, reduced quality of life, decreased overall survival, and increased morbidity. However, there are no formal guidelines on perioperative antiseizure medication (ASM) management in patients with tumor-related epilepsy who are deemed high risk for EPS. In this study, we describe the case of a 38-year-old man with isocitrate dehydrogenase-mutant mixed glioma and two episodes of EPS manifesting with status epilepticus during prior tumor surgeries and who presented with tumor progression. The Tumor Board recommended awake craniotomy with direct electrical stimulation (DES). The patient was administered aggressive preoperative “prophylactic” ASMs by increasing the maintenance doses of lacosamide and levetiracetam by 25% 48 h before surgery. An intravenous load of fosphenytoin (20 mg/kg) was administered in the operating room before DES, followed by a maintenance dosing of 300 mg/day for 14 days. EPS did not occur, and he was discharged home on postoperative day 4. Our case illustrates that aggressive perioperative prophylactic ASM therapy beyond the maintenance ASM regimen can be considered in patients with tumor-related epilepsy at risk of EPS.

Objective: Stimulation-based language mapping relies on identifying stimulation-induced language disruptions, which preexisting speech disorders affecting the laryngeal and orofacial speech system can confound. This study ascertained the effects of preexisting stuttering on pre- and intraoperative language mapping to improve the reliability and specificity of established language mapping protocols in the context of speech fluency disorders. Method: Differentiation-ability of a speech therapist and two experienced nrTMS examiners between stuttering symptoms and stimulation-induced language errors during preoperative mappings were retrospectively compared (05/2018-01/2021). Subsequently, the impact of stuttering on intraoperative mappings was evaluated in all prospective patients (01/2021-12/2022). Results: In the first part, 4.85 % of 103 glioma patients stuttered. While both examiners had a significant agreement for misclassifying pauses in speech flow and prolongations (Κ ≥ 0.50, p ≤ 0.02, respectively), less experience resulted in more misclassified stuttering symptoms. In one awake surgery case within the second part, stuttering decreased the reliability of intraoperative language mapping.Comparison with Existing Method(s): By thoroughly differentiating speech fluency symptoms from stimulation-induced disruptions, the reliability and proportion of stuttering symptoms falsely attributed to stimulation-induced language network disruptions can be improved. This may increase the consistency and specificity of language mapping results in stuttering glioma patients. Conclusions: Preexisting stuttering negatively impacted language mapping specificity. Thus, surgical planning and the functional outcome may benefit substantially from thoroughly differentiating speech fluency symptoms from stimulation-induced disruptions by trained specialists.

Intraoperative functional mapping of tumor and peri-tumor tissue is a well-established technique for avoiding permanent neurologic deficits and maximizing extent of resection. Motor, language, and other cognitive domains may be assessed with intraoperative tasks. This article describes techniques used for motor and language mapping including awake mapping considerations in addition to less traditional intraoperative testing paradigms for cognition. It also discusses complications associated with mapping and insights into complication avoidance.

Objective: Cortical stimulation is an important component of stereoelectroencephalography (SEEG). Despite this, there is currently no standardized approach and significant heterogeneity in the literature regarding cortical stimulation practices. Via an international survey of SEEG clinicians, we sought to examine the spectrum of cortical stimulation practices to reveal areas of consensus and variability. Methods: A 68‐item questionnaire was developed to understand cortical stimulation practices including neurostimulation parameters, interpretation of epileptogenicity, functional and cognitive assessment and subsequent surgical decisions. Multiple recruitment pathways were pursued, with the questionnaire distributed directly to 183 clinicians. Results: Responses were received from 56 clinicians across 17 countries with experience ranging from 2 to 60 years (M = 10.73, SD = 9.44). Neurostimulation parameters varied considerably, with maximum current ranging from 3 to 10 mA (M = 5.33, SD = 2.29) for 1 Hz and from 2 to 15 mA (M = 6.54, SD = 3.68) for 50 Hz stimulation. Charge density ranged from 8 to 200 μC/cm2, with up to 43% of responders utilizing charge densities higher than recommended upper safety limits, i.e. 55 μC/cm2. North American responders reported statistically significant higher maximum current (P < 0.001) for 1 Hz stimulation and lower pulse width for 1 and 50 Hz stimulation (P = 0.008, P < 0.001, respectively) compared to European responders. All clinicians evaluated language, speech, and motor function during cortical stimulation; in contrast, 42% assessed visuospatial or visual function, 29% memory, and 13% executive function. Striking differences were reported in approaches to assessment, classification of positive sites, and surgical decisions guided by cortical stimulation. Patterns of consistency were observed for interpretation of the localizing capacity of stimulated electroclinical seizures and auras, with habitual electroclinical seizures induced by 1 Hz stimulation considered the most localizing. Significance: SEEG cortical stimulation practices differed vastly across clinicians internationally, highlighting the need for consensus‐based clinical guidelines. In particular, an internationally standardized approach to assessment, classification, and functional prognostication will provide a common clinical and research framework for optimizing outcomes for people with drug‐resistant epilepsy. [ABSTRACT FROM AUTHOR]

In recent years, a paradigm shift in neuroscience has been occurring from "localizationism," or the idea that the brain is organized into separately functioning modules, toward "connectomics," or the idea that interconnected nodes form networks as the underlying substrates of behavior and thought. Accordingly, our understanding of mechanisms of neurological function, dysfunction, and recovery has evolved to include connections, disconnections, and reconnections. Brain tumors provide a unique opportunity to probe large-scale neural networks with focal and sometimes reversible lesions, allowing neuroscientists the unique opportunity to directly test newly formed hypotheses about underlying brain structural-functional relationships and network properties. Moreover, if a more complete model of neurological dysfunction is to be defined as a "disconnectome," potential avenues for recovery might be mapped through a "reconnectome." Such insight may open the door to novel therapeutic approaches where previous attempts have failed. In this review, we briefly delve into the most clinically relevant neural networks and brain mapping techniques, and we examine how they are being applied to modern neurosurgical brain tumor practices. We then explore how brain tumors might teach us more about mechanisms of global brain dysfunction and recovery through pre- and postoperative longitudinal connectomic and behavioral analyses. [ABSTRACT FROM AUTHOR]

• Own voice perception might be a complex process including emotional, memory, somatosensory, auditory, and facial recognition processing. • Right superior temporal gyrus, transverse temporal gyrus, amygdala, hippocampus, and fusiform gyrus (FG) are likely part of the neural network subjacent to own human voice perception. • Cortico-cortical evoked potentials might help to understand neurophysiological bases of own voice perception. • Own voice perception seem to be related to facial perception as well. The neural bases for language perception have been studied elsewhere using Transcranial Magnetic Stimulation, functional Magnetic Resonance Imaging and Direct Cortical Stimulation. However, to our knowledge, there is no previous report about a patient identifying the change in his voice tone, speed, and prosody because of right temporal cortical stimulation. Nor has there been a cortico-cortical evoked potential (CCEP) assessment of the network underlying this process. We present CCEP from a patient with right focal refractory temporal lobe epilepsy of tumoral etiology who reported changes in the perception of his own speech prosody during stimulation. This report will serve as a complement to the understanding of the neural networks of language and prosody. The present report shows that right superior temporal gyrus, transverse temporal gyrus, right amygdala, hippocampus, and fusiform gyrus (FG) are part of the neural network subjacent to own human voice perception. [ABSTRACT FROM AUTHOR]

Introduction: Brain malignancy and, at the same time central nervous system malignancy are two of the most difficult problems in the oncology field of practice. Brain tumors located near or within eloquent areas may represent another challenge toward neurosurgeon treatment. As such, electrical stimulation, either directly or through other methods, may prove necessary as proper mapping of the eloquent area thus may create a proper resection guide. Minimal resection will hopefully preserve patient neurological function and ensure patient quality of life. Methods: This research is a systematic review and meta-analysis that aim to compare outcomes, primarily adverse event analysis, between direct cortical stimulation and transcortical magnetic stimulation. Results: Fourteen studies were identified between 2010 and the 2023 interval. While this number is sufficient, most studies were not randomized and were not accompanied by blinding. Meta-analysis was then applied as a hypothesis test, which showed that TMS were not inferior compared to DCS in terms of motoric and lingual outcome which were marked subjectively by diamond location and objectively through a p-value above 0.05. Conclusion: TMS is a noninvasive imaging method for the evaluation of eloquent brain areas that is not inferior compared to the invasive gold-standard imaging method (DCS). However its role as adjuvant to DCS and alternative only when awake surgery is not available must be emphasized. [ABSTRACT FROM AUTHOR]

The purpose of the direct cortical and subcortical stimulation technique is to prevent false positives caused by transcranial electrical motor evoked potentials (TceMEP) in surgery on patients with brain tumors that have occurred around the motor cortex and to preserve the correct mapping of motor areas during surgery and the corticospinal tract. In addition, it reduces the trial and error that occurs during the intraoperative neurophysiological monitoring (INM) process and minimizes the test time, so that accurate information is communicated to the surgeon with quick feedback on the test results. The most important factors of this technique are, first, examination at a stimulus threshold of a certain intensity, and second, maintaining anesthesia depth at an appropriate level to prevent false positives from occurring during surgery. The third is the installation of a multi-level channel recording electrode on the opposite side of the area of operation to measure the TceMEP waveform and the response to direct cortical and subcortical stimulation in as many muscles as possible. If these conditions are maintained, it is possible to predict causes that may occur in other factors, not false positives, from the INM test.

Background: Cortico-cortical evoked potentials (CCEPs) have been used to map the frontal (FLA) and parietal (PLA) cortical regions related to language function. However, they have usually been employed as a complementary method during sleep-awake surgery. Methods: Five male and two female patients received surgery for tumors located near language areas. Six patients received general anesthesia and the sleep-awake method was used for patients with tumors located near the cortical language areas. We performed motor and somatosensory mapping with CCEPs to identify language areas and we monitored responses during surgery based on the mapping results. Electrocorticography was performed throughout the surgery. Single pulses of 1 ms duration at 5--20 mA were delivered by direct cortical stimulation using one grid at one region (e.g., FLA) and then recording using a second gird at another area (i.e., PLA). Next, reversed stimulation (from PLA to FLA) was performed. The charge density for electrical stimulation was computed. Sensibility, specificity, predictive positive values, and predicted negative values were also computed for warning alterations of CCEPs. Results: Gross tumor resection was achieved in four cases. The first postsurgical day showed language alterations in three patients, but one year later six patients remained asymptomatic and one patient showed the same symptomatology as previously. Seizures were observed in two patients that were easily jugulated. CCEPs predicted warning events with high sensibility and specificity. Postsurgical language deficits were mostly transitory. Although the latency between frontal and parietal regions showed symmetry, the amplitude and the relationship between amplitude and latency were different for FLA than for PLA. The charge density elicited by CCEPs ranged from 442 to 1768 µC/cm2. Conclusions: CCEPs have proven to be a reliable neurophysiological technique for mapping and monitoring the regions associated with language function in a small group of anesthetized patients. The high correlation between warning events and postsurgical outcomes suggested a high sensitivity and specificity and CCEPs can be used systematically in patients under general anesthesia. Nevertheless, the small number of studied patients suggests considering these results cautiously. [ABSTRACT FROM AUTHOR]

The letter to the editor expresses appreciation for an article on the WISE cortical strip for intraoperative neurophysiological monitoring. The authors highlight the capabilities of the WISE cortical strip in enhancing signal-to-noise ratio and providing real-time feedback to neurosurgeons during critical procedures. However, there are limitations to consider, such as the trade-off between electrode contact density and impedance, the need for specialized expertise, and the need for further investigation into the clinical relevance of recording high-frequency oscillations and the impact of improved electrodes on patient outcomes. The letter concludes by recommending future research and development to optimize electrode design, facilitate collaboration between specialists, and evaluate the clinical significance of recording high-frequency oscillations. Overall, the letter provides valuable insights into the potential of the WISE cortical strip for neurophysiological monitoring in neurosurgery. [Extracted from the article]

• We performed a prospective multicenter medical device study. • Polymer strips with embedded metal nanoparticles had lower impedance than the comparator device. • The electrodes achieved good signal-to-noise-ratio. During neurosurgical procedures, strip electrodes should have low impedance and sufficient adherence on the brain surface. We evaluated the signal quality, safety, and performance of a novel strip electrode (WISE Cortical Strip, WCS®), with conductive electrode contacts created with platinum nanoparticles embedded in a polymer base. In a multicenter interventional, non-inferiority study, we compared WCS to a conventional strip electrode (Ad-Tech). We recorded impedance and somatosensory evoked potentials (SEP) and determined the signal-to-noise ratio (SNR). We performed direct stimulation of the motor cortex. An external clinical event committee rated safety and adverse events and users rated usability. During 32 brain surgeries in the paracentral region, WCS was rated safe and effective in signal transmission. Two seizure events were classified as probably related to the stimulation with WCS. The users rated WCS adhesion to the brain as satisfactory but reported difficulties sliding the WCS under the dura. The median (IQR) impedance of WCS was lower than for Ad-Tech: 2.7 (2.3–3.7) vs 5.30 (4.3–6.6) kΩ (p < 0.005). The SNR of SEP was non-inferior for WCS compared to Ad-Tech. The impedance of WCS was lower than Ad-Tech without safety limitations. In small craniotomies not exposing the motor cortex its use may be limited. Low impedance electrodes facilitate recordings with high SNR. [ABSTRACT FROM AUTHOR]

Tractography is one way to predict the distribution of cortical functional domains preoperatively. Diffusion tensor tractography (DTT) is commonly used in clinical practice, but is known to have limitations in delineating crossed fibers, which can be overcome by Q-ball imaging tractography (QBT). We aimed to compare the reliability of these 2 methods based on the spatial correlation between the arcuate fasciculus depicted by tractography and direct cortical stimulation during awake surgery. In this study, 15 patients with glioma underwent awake surgery with direct cortical stimulation. Tractography was depicted in a three-dimensional computer graphic model preoperatively, which was integrated with a photograph of the actual brain cortex using our novel mixed-reality technology. The termination of the arcuate fasciculus depicted by either DTT or QBT and the results of direct cortical stimulation were compared, and sensitivity and specificity were calculated in speech-associated brain gyri: pars triangularis, pars opercularis, ventral precentral gyrus, and middle frontal gyrus. QBT had significantly better sensitivity and lower false-positive rate than DTT in the pars opercularis. The same trend was noted for the other gyri. QBT is more reliable than DTT in identification of the motor speech area and may be clinically useful in brain tumor surgery. [ABSTRACT FROM AUTHOR]

Aneurysms arising from the anterior communicating artery (ACOA) are the most common intracranial aneurysms encountered. Most aneurysms can be treated with surgical clipping or endovascular coiling; however, there are times when parent vessel sacrifice (PVS) is necessary such as aneurysms with fragile necks or large/giant aneurysms. Application of intraoperative neurophysiological monitoring (IONM) can assist in guiding permissive temporary vessel occlusion during complex aneurysm clippings. However, to-date there is no literature that describes how IONM can be used as a predictor of post-operative neurological status when PVS is employed or as a guide to determine whether PVS is safe. We present a case where IONM guided the sacrifice of the A1 and anterior communicating arteries after 2 hours and 25 min of temporary vessel occlusion. No attenuation was noted in the IONM at any point during the procedure, and the IONM predicted the patient would awake neurologically intact. [ABSTRACT FROM AUTHOR]

• DCS is a technique with high specificity (96.9%) for defining the seizure-onset zone in the presurgical evaluation of drug-resistant epilepsy. • DCS has low sensitivity (23.0%) due to a high percentage of false-negative stimulations obtained during SEEG monitoring. • The resection of the contacts involved in eliciting true positive seizures is associated with a good surgical outcome. Direct cortical stimulation (DCS) is standard for intracranial presurgical evaluation in drug-resistant epilepsy (DRE). Few studies have reported levels of concordance between spontaneous seizure generators and triggered seizures during DCS. The present work reports validity measures of DCS for detecting the seizure onset zone (SOZ) during stereoelectroencephalography (SEEG). We evaluated all patients who underwent SEEG evaluation at our epilepsy center between 2013 and 2019. Data were analyzed using contingency tables. Validity measures of the diagnostic test were computed for all patients evaluated with DCS and for seizure free patients. Fifty-eight consecutive patients were evaluated through DCS. One hundred seventy-three clinical seizures were elicited with DCS. Electroclinical identical to spontaneous seizures were considered true positive (TP) seizures. They showed a high specificity (96.9%) for detecting the SOZ in patients that remained seizure free one year after treatment. Sensitivity was low (23.0%), and a high percentage of false-negative stimulations was documented in the SOZ. The accuracy was 87.9%. DCS is a technique with high specificity but a low sensitivity for the localization of the SOZ. The DCS validity measures need to be known when considered for surgical decisions. The interpretation of DCS-triggered seizures and the differentiation of true-positive vs false-positive seizures should be carefully evaluated. DCS seizure triggering is highly specific for SOZ localization. [ABSTRACT FROM AUTHOR]

The infiltrative character of supratentorial lower grade glioma makes it possible for eloquent neural pathways to remain within tumoural tissue, which renders complete surgical resection challenging. Neuromodulation-Induced Cortical Prehabilitation (NICP) is intended to reduce the likelihood of premeditated neurologic sequelae that otherwise would have resulted in extensive rehabilitation or permanent injury following surgery. This review aims to conceptualise current approaches involving Repetitive Transcranial Magnetic Stimulation (rTMS-NICP) and extraoperative Direct Cortical Stimulation (eDCS-NICP) for the purposes of inducing cortical reorganisation prior to surgery, with considerations derived from psychiatric, rehabilitative and electrophysiologic findings related to previous reports of prehabilitation. Despite the promise of reduced risk and incidence of neurologic injury in glioma surgery, the current data indicates a broad but compelling possibility of effective cortical prehabilitation relating to perisylvian cortex, though it remains an under-explored investigational tool. Preliminary findings may prove sufficient for the continued investigation of prehabilitation in small-volume lower-grade tumour or epilepsy patients. However, considering the very low number of peer-reviewed case reports, optimal stimulation parameters and duration of therapy necessary to catalyse functional reorganisation remain equivocal. The non-invasive nature and low risk profile of rTMS-NICP may permit larger sample sizes and control groups until such time that eDCS-NICP protocols can be further elucidated. [ABSTRACT FROM AUTHOR]

Many studies have established a link between extent of resection and survival in patients with gliomas. Surgeons must optimize the oncofunctional balance by maximizing the extent of resection and minimizing postoperative neurological morbidity. Preoperative functional imaging modalities are important tools for optimizing the oncofunctional balance. Transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) are non-invasive imaging modalities that can be used for preoperative functional language mapping. Scarce data exist evaluating the accuracy of these preoperative modalities for language mapping compared with gold standard intraoperative data in the same cohort. This study compares the accuracy of fMRI and TMS for language mapping compared with intraoperative direct cortical stimulation (DCS). We also identified significant predictors of preoperative functional imaging accuracy, as well as significant predictors of functional outcomes. Evidence from this study could inform clinical judgment as well as provide neuroscientific insight. We used geometric distances to determine copositivity between preoperative data and intraoperative data. Twenty-eight patients were included who underwent both preoperative fMRI and TMS procedures, as well as an awake craniotomy and intraoperative language mapping. We found that TMS shows significantly superior correlation to intraoperative DCS compared with fMRI. TMS also showed significantly higher sensitivity and negative predictive value than specificity and positive predictive value. Poor cognitive baseline was associated with decreased TMS accuracy as well as increased risk for worsened aphasia postoperatively. TMS has emerged as a promising preoperative language mapping tool. Future work should be done to identify the proper role of each imaging modality in a comprehensive, multimodal approach to optimize the oncofunctional balance. [ABSTRACT FROM AUTHOR]

Many studies have established a link between extent of resection and survival in patients with gliomas. Surgeons must optimize the oncofunctional balance by maximizing the extent of resection and minimizing postoperative neurological morbidity. Preoperative functional imaging modalities are important tools for optimizing the oncofunctional balance. Transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) are non-invasive imaging modalities that can be used for preoperative functional language mapping. Scarce data exist evaluating the accuracy of these preoperative modalities for language mapping compared with gold standard intraoperative data in the same cohort. This study compares the accuracy of fMRI and TMS for language mapping compared with intraoperative direct cortical stimulation (DCS). We also identified significant predictors of preoperative functional imaging accuracy, as well as significant predictors of functional outcomes. Evidence from this study could inform clinical judgment as well as provide neuroscientific insight. We used geometric distances to determine copositivity between preoperative data and intraoperative data. Twenty-eight patients were included who underwent both preoperative fMRI and TMS procedures, as well as an awake craniotomy and intraoperative language mapping. We found that TMS shows significantly superior correlation to intraoperative DCS compared with fMRI. TMS also showed significantly higher sensitivity and negative predictive value than specificity and positive predictive value. Poor cognitive baseline was associated with decreased TMS accuracy as well as increased risk for worsened aphasia postoperatively. TMS has emerged as a promising preoperative language mapping tool. Future work should be done to identify the proper role of each imaging modality in a comprehensive, multimodal approach to optimize the oncofunctional balance.

Accurate mapping of the seizure onset zone (SOZ) is critical to the success of epilepsy surgery outcomes. Epileptogenicity index (EI) is a statistical method that delineates hyperexcitable brain regions involved in the generation and early propagation of seizures. However, EI can overestimate the SOZ for particular electrographic seizure onset patterns. Therefore, using direct cortical stimulation (DCS) as a probing tool to identify seizure generators, we systematically evaluated the causality of the high EI nodes (>0.3) in replicating the patient's habitual seizures. Specifically, we assessed the diagnostic yield of high EI nodes, i.e., the proportion of high EI nodes that evoked habitual seizures. A retrospective single-center study that included post-stereo encephalography (SEEG) confirmed TLE patients (n = 37) that had all high EI nodes stimulated, intending to induce a seizure. We evaluated the nodal responses (true and false responder rate) to stimulation and correlated with electrographic seizure onset patterns (hypersynchronous-HYP and low amplitude fast activity patterns-LAFA) and clinically defined SOZ. The ictogenicity (i.e., the propensity to induce the patient's habitual seizure) of a high EI node was only 44.5%. The LAFA onset pattern had a significantly higher response rate to DCS (i.e., higher evoked seizures). The concordance of an evoked habitual seizure with a clinically defined SOZ with good outcomes was over 50% (p = 0.0025). These results support targeted mapping of SOZ in LAFA onset patterns by performing DCS in high EI nodes to distinguish seizure generators (true responders) from hyperexcitable nodes that may be involved in early propagation.

Accurate mapping of the seizure onset zone (SOZ) is critical to the success of epilepsy surgery outcomes. Epileptogenicity index (EI) is a statistical method that delineates hyperexcitable brain regions involved in the generation and early propagation of seizures. However, EI can overestimate the SOZ for particular electrographic seizure onset patterns. Therefore, using direct cortical stimulation (DCS) as a probing tool to identify seizure generators, we systematically evaluated the causality of the high EI nodes (>0.3) in replicating the patient's habitual seizures. Specifically, we assessed the diagnostic yield of high EI nodes, i.e., the proportion of high EI nodes that evoked habitual seizures. A retrospective single-center study that included post-stereo encephalography (SEEG) confirmed TLE patients (n = 37) that had all high EI nodes stimulated, intending to induce a seizure. We evaluated the nodal responses (true and false responder rate) to stimulation and correlated with electrographic seizure onset patterns (hypersynchronous-HYP and low amplitude fast activity patterns-LAFA) and clinically defined SOZ. The ictogenicity (i.e., the propensity to induce the patient's habitual seizure) of a high EI node was only 44.5%. The LAFA onset pattern had a significantly higher response rate to DCS (i.e., higher evoked seizures). The concordance of an evoked habitual seizure with a clinically defined SOZ with good outcomes was over 50% (p = 0.0025). These results support targeted mapping of SOZ in LAFA onset patterns by performing DCS in high EI nodes to distinguish seizure generators (true responders) from hyperexcitable nodes that may be involved in early propagation. [ABSTRACT FROM AUTHOR]

Background: Cortico-cortical evoked potentials (CCEPs) have been used to map the frontal (FLA) and parietal (PLA) cortical regions related to language function. However, they have usually been employed as a complementary method during sleep-awake surgery. Methods: Five male and two female patients received surgery for tumors located near language areas. Six patients received general anesthesia and the sleep-awake method was used for patients with tumors located near the cortical language areas. We performed motor and somatosensory mapping with CCEPs to identify language areas and we monitored responses during surgery based on the mapping results. Electrocorticography was performed throughout the surgery. Single pulses of 1 ms duration at 5–20 mA were delivered by direct cortical stimulation using one grid at one region (e.g., FLA) and then recording using a second gird at another area (i.e., PLA). Next, reversed stimulation (from PLA to FLA) was performed. The charge density for electrical stimulation was computed. Sensibility, specificity, predictive positive values, and predicted negative values were also computed for warning alterations of CCEPs. Results: Gross tumor resection was achieved in four cases. The first postsurgical day showed language alterations in three patients, but one year later six patients remained asymptomatic and one patient showed the same symptomatology as previously. Seizures were observed in two patients that were easily jugulated. CCEPs predicted warning events with high sensibility and specificity. Postsurgical language deficits were mostly transitory. Although the latency between frontal and parietal regions showed symmetry, the amplitude and the relationship between amplitude and latency were different for FLA than for PLA. The charge density elicited by CCEPs ranged from 442 to 1768 μC/cm2. Conclusions: CCEPs have proven to be a reliable neurophysiological technique for mapping and monitoring the regions associated with language function in a small group of anesthetized patients. The high correlation between warning events and postsurgical outcomes suggested a high sensitivity and specificity and CCEPs can be used systematically in patients under general anesthesia. Nevertheless, the small number of studied patients suggests considering these results cautiously.

We retrospectively analyzed data from 15 patients, with a normal pre-operative cognitive performance, undergoing awake surgery for left fronto-temporal low-grade glioma. We combined a pre-surgical measure (fMRI maps of motor- and language-related centers) with intra-surgical measures (MNI-registered cortical sites data obtained during intra-operative direct electrical stimulation, DES, while they performed the two most common language tasks: number counting and picture naming). Selective DES effects along the precentral gyrus/inferior frontal gyrus (and/or the connected speech articulation network) were obtained. DES of the precentral gyrus evoked the motor speech arrest, i.e., anarthria (with apparent mentalis muscle movements). We calculated the number of shared voxels between the lip-tongue and overt counting related- and silent naming-related fMRI maps and the Volumes of Interest (VOIs) obtained by merging together the MNI sites at which a given speech disturbance was observed, normalized on their mean the values (i.e., Z score). Both tongue- and lips-related movements fMRI maps maximally overlapped (Z = 1.05 and Z = 0.94 for lips and tongue vs. 0.16 and −1.003 for counting and naming) with the motor speech arrest seed. DES of the inferior frontal gyrus, pars opercularis and the rolandic operculum induced speech arrest proper (without apparent mentalis muscle movements). This area maximally overlapped with overt counting-related fMRI map (Z = −0.11 and Z = 0.09 for lips and tongue vs. 0.9 and 0.0006 for counting and naming). Interestingly, our fMRI maps indicated reduced Broca's area activity during silent speech compared to overt speech. Lastly, DES of the inferior frontal gyrus, pars opercularis and triangularis evoked variations of the output, i.e., dysarthria, a motor speech disorder occurring when patients cannot control the muscles used to produce articulated sounds (phonemes). Silent object naming-related fMRI map maximally overlapped (Z = −0.93 and Z = −1.04 for lips and tongue vs. −1.07 and 0.99 for counting and naming) with this seed. Speech disturbances evoked by DES may be thought of as selective interferences with specific recruitment of left inferior frontal gyrus and precentral cortex which are differentiable in terms of the specific interference induced. [ABSTRACT FROM AUTHOR]

Intraoperative neuromonitoring (IONM) is widely used for elective resection of eloquently located brain tumors to increase safety and extent of resection. Owing to the need for specially trained personnel for IONM and the sophisticated, time-consuming technical setup, standard IONM is usually not suitable for emergency situations. We report the use of a device that can be operated by the neurosurgeon autonomously for monopolar brain mapping in 2 emergency cases. Both patients were initially scheduled for elective neurosurgery under IONM. Acute neurological deterioration in both cases led to emergency surgery. For monopolar cortical/subcortical stimulation, a standard monopolar probe was connected to a new device enabling electromyography real-time tracking of 8 muscles. Preoperative application of subdermal electromyography needles and intraoperative handling of the device were performed by the neurosurgeons independently. Cortical mapping of the motor cortex was performed in both patients with a threshold of 4 mA in case 1 and 14 mA in case 2. Gross total resection with residual tumor volume of <2 mL in case 1 and subtotal resection with residual tumor volume of 4.2 mL in case 2 were achieved under use of the new device without any new neurological deficit. Grade IV glioblastoma was diagnosed in both patients. We demonstrate the feasibility of monopolar stimulation in 2 patients undergoing emergency neurosurgery using a device autonomously operated by the surgeon. Owing to fast setup and nondemanding handling, monopolar stimulation could be used during emergency neurosurgery to extend resection with preservation of neurological function in both cases. [ABSTRACT FROM AUTHOR]

Introduction: Intraoperative neurophysiological monitoring is the golden standard for lesions located in eloquent areas of the brain. On the one hand, positive mapping offers a view of the relationship between the anatomo-functional cortical organisation of the patient and the lesion, facilitating the choice of the cerebrotomy entry point and the resection until the functional borders are found. On the other hand, negative mapping does not offer certainty that the absence of the motor response, from the operative field, is the real feedback or is the result of the false-negative response. In such a situation, a differentiation between those two must be done. Materials and methods: We evaluated the results of direct cortical stimulation of lesion located in or near the primary motor area, which were diagnosticated with contrast-enhancement head MRI and admitted to the Third Department of Neurosurgery, "Prof. Dr N. Oblu” Emergency Clinical Hospital, Iasi, Romania, between January 2014 and July 2018. Special attention was given especially to the negative mapping cases, regarding the histological type, imagistic localisation, symptoms and neurological outcome immediate postoperative, at 6 months and one-year follow-up. Results: From all 66 patients meeting the inclusion and exclusion criteria in 9,09% (6 cases) we did not obtain any motor response after direct cortical stimulation. The imagistic localisations of those cases were: 3 – Rolandic, 2 – pre-Rolandic and one retro-Rolandic. Tumors histological types were: glioblastoma, anaplastic astrocytoma, oligoastrocytoma and oligodendroglioma each one case and two cases of fibrillary astrocytoma. The intensity range was between 6 – 18mA, the mode – 12mA and the median – 10mA. Postoperatively the neurological condition of 3 patients worsened (4,54% from all the cases), while 3 had a favourable evolution with symptom remission. At 6monts and one-year follow-up in one case (1,51%), we observed no improvement in contrast with the other two, where dysfunction remission was highlighted. Conclusion: The possible technical, surgical and anesthesiologic causes of false-negative motor response must be eliminated to be able to differentiate from the real absence of the functional area from the operative field. In the first scenario, the resection may be associated with permanent postoperative neurologic deficit and major life quality alteration while in the second one the patient presents no motor dysfunction after surgery and the resection may be extensive with multiple oncological benefits.

ObjectiveLesion-based mapping of speech pathways has been possible only during invasive neurosurgical procedures using direct cortical stimulation (DCS). However, navigated transcranial magnetic stimulation (nTMS) may allow for lesion-based interrogation of language pathways noninvasively. Although not lesion-based, magnetoencephalographic imaging (MEGI) is another noninvasive modality for language mapping. In this study, we compare the accuracy of nTMS and MEGI with DCS.MethodsSubjects with lesions around cortical language areas underwent preoperative nTMS and MEGI for language mapping. nTMS maps were generated using a repetitive TMS protocol to deliver trains of stimulations during a picture naming task. MEGI activation maps were derived from adaptive spatial filtering of beta-band power decreases prior to overt speech during picture naming and verb generation tasks. The subjects subsequently underwent awake language mapping via intraoperative DCS. The language maps obtained from each of the 3 modalities were recorded and compared.ResultsnTMS and MEGI were performed on 12 subjects. nTMS yielded 21 positive language disruption sites (11 speech arrest, 5 anomia, and 5 other) while DCS yielded 10 positive sites (2 speech arrest, 5 anomia, and 3 other). MEGI isolated 32 sites of peak activation with language tasks. Positive language sites were most commonly found in the pars opercularis for all three modalities. In 9 instances the positive DCS site corresponded to a positive nTMS site, while in 1 instance it did not. In 4 instances, a positive nTMS site corresponded to a negative DCS site, while 169 instances of negative nTMS and DCS were recorded. The sensitivity of nTMS was therefore 90%, specificity was 98%, the positive predictive value was 69% and the negative predictive value was 99% as compared with intraoperative DCS. MEGI language sites for verb generation and object naming correlated with nTMS sites in 5 subjects, and with DCS sites in 2 subjects.ConclusionMaps of language function generated with nTMS correlate well with those generated by DCS. Negative nTMS mapping also correlates with negative DCS mapping. In our study, MEGI lacks the same level of correlation with intraoperative mapping; nevertheless it provides useful adjunct information in some cases. nTMS may offer a lesion-based method for noninvasively interrogating language pathways and be valuable in managing patients with peri-eloquent lesions.

Introduction: Intraoperative neurophysiological monitoring is the golden standard for lesions located in eloquent areas of the brain. On the one hand, positive mapping offers a view of the relationship between the anatomo-functional cortical organisation of the patient and the lesion, facilitating the choice of the cerebrotomy entry point and the resection until the functional borders are found. On the other hand, negative mapping does not offer certainty that the absence of the motor response, from the operative field, is the real feedback or is the result of the falsenegative response. In such a situation, a differentiation between those two must be done. Materials and methods: We evaluated the results of direct cortical stimulation of lesion located in or near the primary motor area, which were diagnosticated with contrast-enhancement head MRI and admitted to the Third Department of Neurosurgery, "Prof. Dr N. Oblu" Emergency Clinical Hospital, Iasi, Romania, between January 2014 and July 2018. Special attention was given especially to the negative mapping cases, regarding the histological type, imagistic localisation, symptoms and neurological outcome immediate postoperative, at 6 months and one-year follow-up. Results: From all 66 patients meeting the inclusion and exclusion criteria in 9,09% (6 cases) we did not obtain any motor response after direct cortical stimulation. The imagistic localisations of those cases were: 3 - Rolandic, 2 - pre-Rolandic and one retro-Rolandic. Tumors histological types were: glioblastoma, anaplastic astrocytoma, oligoastrocytoma and oligodendroglioma each one case and two cases of fibrillary astrocytoma. The intensity range was between 6 - 18mA, the mode - 12mA and the median - 10mA. Postoperatively the neurological condition of 3 patients worsened (4,54% from all the cases), while 3 had a favourable evolution with symptom remission. At 6monts and one-year follow-up in one case (1,51%), we observed no improvement in contrast with the other two, where dysfunction remission was highlighted. Conclusion: The possible technical, surgical and anesthesiologic causes of falsenegative motor response must be eliminated to be able to differentiate from the real absence of the functional area from the operative field. In the first scenario, the resection may be associated with permanent postoperative neurologic deficit and major life quality alteration while in the second one the patient presents no motor dysfunction after surgery and the resection may be extensive with multiple oncological benefits. [ABSTRACT FROM AUTHOR]

Background: The dilemma of neuro-oncological surgery involving suspected eloquent cortex is to maximize the extent of resection while minimizing neurological morbidity, referred to as the "onco-functional balance." Diffuse lower-grade gliomas are capable of infiltrating or displacing neural function within cortical regions and subcortical white matter tracts, which can render classical anatomic associations of eloquent function misleading., Observations: This study employed presurgical navigated transcranial magnetic stimulation (nTMS) to determine the motor eloquence of a diffuse lower-grade glioma at the superior frontal gyrus extending and intrinsic to the primary motor cortex in a 45-year-old female. Positive nTMS findings were confirmed intraoperatively with high-frequency direct cortico-subcortical stimulation (HF-DCS). Modification of the HF-DCS train count from train-of-five to train-of-two permitted resection beyond classic anatomical boundaries and conventional HF-DCS safe stopping criteria., Lessons: Anatomical correlates of function can inaccurately inform the surgical management of diffuse lower-grade glioma, which represents the utmost opportunity for progression-free survival. Integrating an individually tailored nTMS-DCS surgical strategy contributed to complete resection, negating the requirement for adjuvant therapy. Serial nTMS follow-up may assist with the characterization of tumor-induced functional reorganization. https://thejns.org/doi/10.3171/CASE24197.

Encoding artificial perceptions through brain stimulation, especially that of higher cognitive functions such as speech perception, is one of the most formidable challenges in brain-computer interfaces (BCI). Brain stimulation has been used for functional mapping in clinical practices for the last 70 years to treat various disorders affecting the nervous system, including epilepsy, Parkinson's disease, essential tremors, and dystonia. Recently, direct electrical stimulation has been used to evoke various forms of perception in humans, ranging from sensorimotor, auditory, and visual to speech cognition. Successfully evoking and fine-tuning artificial perceptions could revolutionize communication for individuals with speech disorders and significantly enhance the capabilities of brain-computer interface technologies. However, despite the extensive literature on encoding various perceptions and the rising popularity of speech BCIs, inducing artificial speech perception is still largely unexplored, and its potential has yet to be determined. In this paper, we examine the various stimulation techniques used to evoke complex percepts and the target brain areas for the input of speech-like information. Finally, we discuss strategies to address the challenges of speech encoding and discuss the prospects of these approaches., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Hong, Ryun and Chung.)

ObjectDirect cortical stimulation (DCS) is the gold-standard technique for motor mapping during craniotomy. However, preoperative noninvasive motor mapping is becoming increasingly accurate. Two such noninvasive modalities are navigated transcranial magnetic stimulation (TMS) and magnetoencephalography (MEG) imaging. While MEG imaging has already been extensively validated as an accurate modality of noninvasive motor mapping, TMS is less well studied. In this study, the authors compared the accuracy of TMS to both DCS and MEG imaging.MethodsPatients with tumors in proximity to primary motor cortex underwent preoperative TMS and MEG imaging for motor mapping. The patients subsequently underwent motor mapping via intraoperative DCS. The loci of maximal response were recorded from each modality and compared. Motor strength was assessed at 3 months postoperatively.ResultsTranscranial magnetic stimulation and MEG imaging were performed on 24 patients. Intraoperative DCS yielded 8 positive motor sites in 5 patients. The median distance ± SEM between TMS and DCS motor sites was 2.13 ± 0.29 mm, and between TMS and MEG imaging motor sites was 4.71 ± 1.08 mm. In no patients did DCS motor mapping reveal a motor site that was unrecognized by TMS. Three of 24 patients developed new, early neurological deficit in the form of upper-extremity paresis. At the 3-month follow-up evaluation, 2 of these patients were significantly improved, experiencing difficulty only with fine motor tasks; the remaining patient had improvement to 4/5 strength. There were no deaths over the course of the study.ConclusionsMaps of the motor system generated with TMS correlate well with those generated by both MEG imaging and DCS. Negative TMS mapping also correlates with negative DCS mapping. Navigated TMS is an accurate modality for noninvasively generating preoperative motor maps.

Objectives. The genesis of tumors is unknown in our days. Surgery represents an effective treatment of this disorder. According to many studies of brain tumor surgery, a motor deficit rate of 30% has been observed, postoperatively, after surgeries on brain tumors in the motor areas. The aim of the study was to evaluate the direct cortical stimulation in the surgical treatment of glial brain tumors, in motor areas. Material and Methods. The examination group included 35 patients with brain tumors, localized in the parasilvian region. Direct cortical stimulation was used intraoperatively, in order to establish the motor areas. For the evaluation of the neurological deficit, a comparative analysis of the pre- and postoperative motor deficit was performed. Results. Direct cortical stimulation was performed in 35 patients. During its stimulation, the motor areas were detected in 32 patients. Under the control of Direct Cortical Stimulation, subtotal and partial tumor resection was performed in 31 patients and, due to the location of the tumor in the motor area, biopsy was performed in 1 patient. The worsening of the postoperative motor deficit was recorded in the partial ablation for 2 patients and biopsy for 1 patient, where the tumor was directly localized in the motor area. Direct cortical stimulation, in the extent of total and subtotal ablation, prevented postoperative motor deficit at discharge in 22 patients. Conclusions. In order to avoid postoperative neurological consequences and improve the patients' quality of life, it is appropriate to use intraoperative direct cortical stimulation.

The infiltrative character of supratentorial lower grade glioma makes it possible for eloquent neural pathways to remain within tumoural tissue, which renders complete surgical resection challenging. Neuromodulation-Induced Cortical Prehabilitation (NICP) is intended to reduce the likelihood of premeditated neurologic sequelae that otherwise would have resulted in extensive rehabilitation or permanent injury following surgery. This review aims to conceptualise current approaches involving Repetitive Transcranial Magnetic Stimulation (rTMS-NICP) and extraoperative Direct Cortical Stimulation (eDCS-NICP) for the purposes of inducing cortical reorganisation prior to surgery, with considerations derived from psychiatric, rehabilitative and electrophysiologic findings related to previous reports of prehabilitation. Despite the promise of reduced risk and incidence of neurologic injury in glioma surgery, the current data indicates a broad but compelling possibility of effective cortical prehabilitation relating to perisylvian cortex, though it remains an under-explored investigational tool. Preliminary findings may prove sufficient for the continued investigation of prehabilitation in small-volume lower-grade tumour or epilepsy patients. However, considering the very low number of peer-reviewed case reports, optimal stimulation parameters and duration of therapy necessary to catalyse functional reorganisation remain equivocal. The non-invasive nature and low risk profile of rTMS-NICP may permit larger sample sizes and control groups until such time that eDCS-NICP protocols can be further elucidated.

Transcranial electrical stimulation-motor evoked potential (TES-MEP) is a valuable intraoperative monitoring technique during brain tumor surgery. However, TES can stimulate deep subcortical areas located far from the motor cortex. There is a concern about false-negative results from the use of TES-MEP during resection of those tumors adjacent to the primary motor cortex. Our study reports three cases of TES-MEP monitoring with false-negative results due to deep axonal stimulation during brain tumor resection. Although no significant change in TES-MEP was observed during surgery, study subjects experienced muscle weakness after surgery. Deep axonal stimulation of TES could give false-negative results. Therefore, a combined method of TES-MEP and direct cortical stimulation-motor evoked potential (DCS-MEP) or direct subcortical stimulation should be considered to overcome the limitation of TES-MEP.