Ultra-early navigated transcranial magnetic stimulation for perioperative stroke: anatomo-functional report.

Navigated repetitive transmagnetic stimulation is a non-invasive and safe brain activity modulation technique. When combined with the classical rehabilitation process in stroke patients it has the potential to enhance the overall neurologic recovery. We present a case of a peri-operative stroke, treated with ultra-early low frequency navigated repetitive transmagnetic stimulation over the contralesional hemisphere. The patient received low frequency navigated repetitive transmagnetic stimulation within 12 hours of stroke onset for seven consecutive days and a significant improvement in his right sided weakness was noticed and he was discharge with normal power. This was accompanied by an increase in the number of positive responses evoked by navigated repetitive transmagnetic stimulation and a decrease of the resting motor thresholds at a cortical level. Subcortically, a decrease in the radial, axial, and mean diffusivity were recorded in the ipsilateral corticospinal tract and an increase in fractional anisotropy, axial diffusivity, and mean diffusivity was observed in the interhemispheric fibers of the corpus callosum responsible for the interhemispheric connectivity between motor areas. Our case demonstrates clearly that ultra-early low frequency navigated repetitive transmagnetic stimulation applied to the contralateral motor cortex can lead to significant clinical motor improvement in patients with subcortical stroke.

Cortical resting motor threshold difference in asleep-awake craniotomy for motor eloquent gliomas: WHO grading influences motor pathway excitability.

Developing neurophysiological tools to predict WHO tumor grade can empower the treating teams for a better surgical decision-making process. A total of 38 patients with supratentorial diffuse gliomas underwent an asleep-awake-sedated craniotomies for tumor removal with intraoperative neuromonitoring. The resting motor threshold was calculated for different train stimulation paradigms during awake and asleep phases. Receiver operating characteristic analysis and Bayesian regression models were performed to analyze the prediction of tumor grading based on the resting motor threshold differences. Significant positive spearman correlations were observed between resting motor threshold excitability difference and WHO tumor grade for train stimulation paradigms of 5 (R = 0.54, P = 0.00063), 4 (R = 0.49, P = 0.002), 3 (R = 0.51, P = 0.001), and 2 pulses (R = 0.54, P = 0.0007). Kruskal-Wallis analysis of the median revealed a positive significant difference between the median of excitability difference and WHO tumor grade in all paradigms. Receiver operating characteristic analysis showed 3 mA difference as the best predictor of high-grade glioma across different patterns of motor pathway stimulation. Bayesian regression found that an excitability difference above 3 mA would indicate a 75.8% probability of a glioma being high grade. Our results suggest that cortical motor excitability difference between the asleep and awake phases in glioma surgery could correlate with tumor grade.

To scan or not to scan? A retrospective cohort study analysing the efficacy of routine post-operative CT after brain biopsy.

PURPOSE: Postoperative management following elective cranial surgery, particularly after biopsy procedures, varies significantly across neurosurgical centres. Routine postoperative head CT scans, traditionally performed to detect complications such as intracranial bleeding or cerebral oedema, lack substantial evidence supporting their necessity. METHODS: This study is a retrospective cohort analysis conducted at a regional neurosurgical department of 236 patients who underwent brain biopsies between 2018 and 2022. Patient data, including demographics, surgical details, and postoperative outcomes, were collected and analysed. The outcomes investigated were the incidence and impact of postoperative CT scans on time to discharge, management changes, and the influence of preoperative anticoagulation. RESULTS: Out of 236 patients, 205 (86.86%) underwent postoperative CT scans. There was no significant relationship between postoperative hematoma, as detected on a CT scan, and neurological deficit (p = 0.443), or between preoperative anticoagulation and postoperative bleeding on CT scans (p = 0.464). Patients who had postoperative CT scans had a significantly longer length of stay (LOS) compared to those who did not (p < 0.001). Intraoperative bleeding was a predictor of hematoma on postoperative CT (p = 0.017) but not of postoperative neurological deficit. The routine postoperative CT scan showed limited predictive value for symptomatic deficits, with a positive predictive value of 6.67% and a negative predictive value of 96.88%. CONCLUSIONS: Routine postoperative CT scans after brain biopsies do not significantly impact management or improve patient outcomes but are associated with longer hospital stays. CT scans should be reserved for patients showing clinical signs of complications rather than used as a routine procedure after a brain biopsy.

Bayesian networks for Risk Assessment and postoperative deficit prediction in intraoperative neurophysiology for brain surgery.

PURPOSE: To this day there is no consensus regarding evidence of usefulness of Intraoperative Neurophysiological Monitoring (IONM). Randomized controlled trials have not been performed in the past mainly because of difficulties in recruitment control subjects. In this study, we propose the use of Bayesian Networks to assess evidence in IONM. METHODS: Single center retrospective study from January 2020 to January 2022. Patients admitted for cranial neurosurgery with intraoperative neuromonitoring were enrolled. We built a Bayesian Network with utility calculation using expert domain knowledge based on logistic regression as potential causal inference between events in surgery that could lead to central nervous system injury and postoperative neurological function. RESULTS: A total of 267 patients were included in the study: 198 (73.9%) underwent neuro-oncology surgery and 69 (26.1%) neurovascular surgery. 50.7% of patients were female while 49.3% were male. Using the Bayesian Network´s original state probabilities, we found that among patients who presented with a reversible signal change that was acted upon, 59% of patients would wake up with no new neurological deficits, 33% with a transitory deficit and 8% with a permanent deficit. If the signal change was permanent, in 16% of the patients the deficit would be transitory and in 51% it would be permanent. 33% of patients would wake up with no new postoperative deficit. Our network also shows that utility increases when corrective actions are taken to revert a signal change. CONCLUSIONS: Bayesian Networks are an effective way to audit clinical practice within IONM. We have found that IONM warnings can serve to prevent neurological deficits in patients, especially when corrective surgical action is taken to attempt to revert signals changes back to baseline properties. We show that Bayesian Networks could be used as a mathematical tool to calculate the utility of conducting IONM, which could save costs in healthcare when performed.

H3 G34-mutant high-grade gliomas: integrated clinical, imaging and pathological characterisation of a single-centre case series.

BACKGROUND: Diffuse hemispheric glioma, H3 G34-mutant, is a novel paediatric tumour type in the fifth edition of the WHO classification of CNS tumours associated with an invariably poor outcome. We present a comprehensive clinical, imaging and pathological review of this entity. METHODS: Patients with confirmed H3 G34R-mutant high-grade glioma were included in a single-centre retrospective cohort study and examined for clinical, radiological and histo-molecular data. RESULTS: Twelve patients were enrolled in the study - 7 males/5 females; the mean age was 17.5 years (10-57 years). Most patients presented with signs of raised intracranial pressure (8/12). The frontal lobe (60%) was the prevalent location, with a mixed cystic-nodular appearance (10/12) and presence of vascular flow voids coursing through/being encased by the mass (8/12), and all tumours showed cortical invasion. Nine patients had subtotal resection limited by functional margins, two patients underwent supra-total resection, and one patient had biopsy only. 5-ALA was administered to 6 patients, all of whom showed positive fluorescence. Histologically, the tumours showed a marked heterogeneity and aggressive spread along pre-existing brain structures and leptomeninges. In addition to the diagnostic H3 G34R/V mutation, pathogenic variants in TP53 and ATRX genes were found in most cases. Potential targetable mutations in PDGFRA and PIK3CA genes were detected in five cases. The MGMT promoter was highly methylated in half of the samples. Methylation profiling was a useful diagnostic tool and highlighted recurrent structural chromosome abnormalities, such as PDGFRA amplification, CDKN2A/B deletion, PTEN loss and various copy number changes in the cyclin D-CDK4/Rb pathway. Radiochemotherapy was the most common adjuvant treatment (9/12), and the average survival was 19.3 months. CONCLUSIONS: H3 G34R-mutant hemispheric glioma is a distinct entity with characteristic imaging and pathological features. Genomic landscaping of individual tumours can offer an opportunity to adapt individual therapies and improve patient management.

IgG4-related hypertrophic pachymeningitis with chronic subdural haematoma.

Hypertrophic pachymeningitis is a rare disorder of the dura mater of the spine or brain. It can be caused by inflammatory, infective or neoplastic conditions or can be idiopathic. We report a man with hypertrophic pachymeningitis and bilateral chronic subdural haematoma caused by IgG4-related disease. We highlight the diagnostic challenges and discuss possible underlying mechanisms of subdural haematoma formation in inflammatory conditions. Isolated IgG4-related hypertrophic pachymeningitis with chronic subdural haematoma is very rare; previously reported cases have suggested a possible predilection for men in their sixth decade, presenting with headache as the dominant symptom. Given the rarity and complexity of the condition, it should be managed in a multidisciplinary team setting.

Proposed definition of competencies for surgical neuro-oncology training.

OBJECTIVE: The aim of this work is to define competencies and entrustable professional activities (EPAs) to be imparted within the framework of surgical neuro-oncological residency and fellowship training as well as the education of medical students. Improved and specific training in surgical neuro-oncology promotes neuro-oncological expertise, quality of surgical neuro-oncological treatment and may also contribute to further development of neuro-oncological techniques and treatment protocols. Specific curricula for a surgical neuro-oncologic education have not yet been established. METHODS: We used a consensus-building approach to propose skills, competencies and EPAs to be imparted within the framework of surgical neuro-oncological training. We developed competencies and EPAs suitable for training in surgical neuro-oncology. RESULT: In total, 70 competencies and 8 EPAs for training in surgical neuro-oncology were proposed. EPAs were defined for the management of the deteriorating patient, the management of patients with the diagnosis of a brain tumour, tumour-based resections, function-based surgical resections of brain tumours, the postoperative management of patients, the collaboration as a member of an interdisciplinary and/or -professional team and finally for the care of palliative and dying patients and their families. CONCLUSIONS AND RELEVANCE: The present work should subsequently initiate a discussion about the proposed competencies and EPAs and, together with the following discussion, contribute to the creation of new training concepts in surgical neuro-oncology.

Medial-tonsillar telovelar approach for resection of a superior medullary velum cerebral cavernous malformation: anatomical and tractography study of the surgical approach and functional implications.

BACKGROUND: Superior medullary velum cerebral cavernous malformations pose a challenge in terms of appropriate microsurgical approach. Safe access to this deep location as well as preservation of surrounding anatomical structures, in particular the superior cerebellar peduncle just lateral to the superior medullary velum and the dentate nuclei, is paramount to achieve a good functional outcome. METHODS: Cadaveric dissections provide useful knowledge of the normal anatomy while tractography allows a better understanding of the individual anatomy in the presence of a lesion. The medial-tonsillar telovelar approach provides a feasible corridor for accessing superior velum cerebral cavernous malformations without compromising the fibres contained in the superior cerebellar peduncle. The major cerebellar efferents-cerebello-rubral, cerebello-thalamic and cerebello-vestibular tracts-and afferents, anterior spinocerebellar, tectocerebellar and trigeminocerebellar tracts, within the superior cerebellar peduncle are preserved, and the dentate nuclei are not affected. RESULTS AND CONCLUSION: A retraction-free exposure through this natural posterior fossa corridor allows the patient with the anatomical and functional subtract to make a good functional recovery by minimizing the risk of a superior cerebellar syndrome, ataxia, tremor and dysmetria; decomposition of movement in the ipsilateral extremities, nystagmus and hypotonia; or akinetic mutism, reduced or absent speech with onset within the first post-operative week.

Neurosurgery and coronavirus: impact and challenges-lessons learnt from the first wave of a global pandemic.

INTRODUCTION AND OBJECTIVES: The novel severe acute respiratory syndrome coronavirus 2 (COVID-19) pandemic has had drastic effects on global healthcare with the UK amongst the countries most severely impacted. The aim of this study was to examine how COVID-19 challenged the neurosurgical delivery of care in a busy tertiary unit serving a socio-economically diverse population. METHODS: A prospective single-centre cohort study including all patients referred to the acute neurosurgical service or the subspecialty multidisciplinary teams (MDT) as well as all emergency and elective admissions during COVID-19 (18th March 2020-15th May 2020) compared to pre-COVID-19 (18th of January 2020-17th March 2020). Data on demographics, diagnosis, operation, and treatment recommendation/outcome were collected and analysed. RESULTS: Overall, there was a reduction in neurosurgical emergency referrals by 33.6% and operations by 55.6% during the course of COVID-19. There was a significant increase in the proportion of emergency operations performed during COVID-19 (75.2% of total, n=155) when compared to pre-COVID-19 (n = 198, 43.7% of total, p < 0.00001). In contrast to other published series, the 30-day perioperative mortality remained low (2.0%) with the majority of post-operative COVID-19-infected patients (n = 13) having underlying medical co-morbidities and/or suffering from post-operative complications. CONCLUSION: The capacity to safely treat patients requiring urgent or emergency neurosurgical care was maintained at all times. Strategies adopted to enable this included proactively approaching the referrers to maintain lines of communications, incorporating modern technology to run clinics and MDTs, restructuring patient pathways/facilities, and initiating the delivery of NHS care within private sector hospitals. Through this multi-modal approach we were able to minimize service disruptions, the complications, and mortality.

How many patients require brain mapping in an adult neuro-oncology service?

Intraoperative mapping and neuromonitoring is an established technique to maximise tumour resection while minimising the risk of inducing permanent postoperative deficit. However, very little is known on how many patients require brain mapping within a general adult neuro-oncology service. A prospective study of all neuro-oncology patients operated over a 12 months' period (January-December 2017) was performed. All patients were seen in a dedicated neuro-oncology pre-assessment clinic after discussion in a neuro-oncology multidisciplinary team meeting. Inclusion criteria for brain mapping were age more than 18, performance status less than 2, tumour location in an eloquent area. Age, sex, histology, surgical technique, extent of resection and operative complications were analysed. Two hundred thirty-five craniotomies were performed in the study period. Intraoperative mapping was used for 57 (24%) cases. There were 22 females and 35 males; median age was 52 years (22-73).17 (30%) patients were operated awake for speech and 40 (70%) asleep for motor mapping. One hundred fifteen patients had a diagnosis of glioma; of these, 48 (42%) were operated with intraoperative mapping. Age (48.92 ± 2.18versus 58.43 ± 1.63, p = 0.001) and WHO grading were significantly lower in the mapping group and the extent of resection was significantly higher (GTR-81.25% versus 37.3%, p < .001). Within the mapping group, the awake subgroup had a better performance status (p = 0.039), less glioblastomas as histological diagnosis (p < 0.05) and an increased proportion of tumours in both temporal and insular locations (p < 0.05). Intraoperative mapping was employed in almost one quarter of our general adult neuro-oncology population. Four in 10 gliomas were operated with intraoperative mapping. This percentage reflects the need for specialised training in brain mapping and budget allocation within the neuro-oncology department.

The verb and noun test for peri-operative testing (VAN-POP): standardized language tests for navigated transcranial magnetic stimulation and direct electrical stimulation.

BACKGROUND: Protocols for intraoperative language mapping with direct electrical stimulation (DES) often include various language tasks triggering both nouns and verbs in sentences. Such protocols are not readily available for navigated transcranial magnetic stimulation (nTMS), where only single word object naming is generally used. Here, we present the development, norming, and standardization of the verb and noun test for peri-operative testing (VAN-POP) that measures language skills more extensively. METHODS: The VAN-POP tests noun and verb retrieval in sentence context. Items are marked and balanced for several linguistic factors known to influence word retrieval. The VAN-POP was administered in English, German, and Dutch under conditions that are used for nTMS and DES paradigms. For each language, 30 speakers were tested. RESULTS: At least 50 items per task per language were named fluently and reached a high naming agreement. CONCLUSION: The protocol proved to be suitable for pre- and intraoperative language mapping with nTMS and DES.

Patient-reported experience measures in patients undergoing navigated transcranial magnetic stimulation (nTMS): the introduction of nTMS-PREMs.

BACKGROUND: Patient-reported experience measures (PREMs) are a unique measure of experience of patients which can help address the quality of care of the patients. OBJECTIVE: Our aim of the study is to collect quality of care outcomes with our newly navigated transcranial magnetic stimulation patient-reported experience measure (nTMS-PREMs) questionnaire among neurosurgical patients undergoing nTMS. METHODS: A single-centre prospective nTMS-PREMs 19-item questionnaire study was performed between February 2018 and December 2018 on patient referred for nTMS at our hospital. The Data was analysed using Likert scale, linear and logistic regression using statistical software (STATA 13.0®). RESULTS: Fifty patient questionnaires were collected (30 males, 20 females, mean age of 47.6 ± 2.1 years) among which 74% of patients underwent both motor and language mapping with a mean duration of 103.3 ± 5.1 min. An overall positive response was noted from the results of the questionnaire, tiredness and anxiety being the common effects noted. Patients with the left-sided disease appreciated more the conditions provided in our laboratory (Q4, p = 0.040) and increasing age was related to less confidence and trust (Q6, p = 0.038) in the staff performing the exam. Younger patients tolerated nTMS better than older patients (> 65 years). PubMed literature search resulted in no relevant articles on the use of PREMs in nTMS patients. CONCLUSION: nTMS is a well-tolerated non-invasive tool and nTMS-PREMS provides a promising role in identifying the unmet needs of the patients and improving the quality of their care.

5-ALA fluorescence in a WHO grade I papillary glioneuronal tumour: a case report.

5-ALA is proven to be effective in high-grade glioma operative resection. The use of 5-ALA in WHO grade I lesions is still controversial. A 49-year-old lady was diagnosed in 2004 with a left temporal lobe lesion as an incidental finding; she was followed up clinically and radiologically. In 2016, the lesion showed contrast enhancement and she was offered surgical resection but given she is asymptomatic, she refused. In 2018, the lesion showed signs of transformation with ring contrast enhancement, increased vasogenic oedema and perfusion; the patient accepted surgery at that point. She had preoperative mapping by navigated transcranial magnetic stimulation and she had operative resection with 5-ALA. The tumour was bright fluorescent under Blue 400 filter-Zeiss Pentero 900©(Carl Zeiss Meditec)-and both bright fluorescence and pale fluorescence were resected. Postoperative MRI showed complete resection and histopathology revealed WHO grade I papillary glioneuronal tumour, negative for BRAF V600 mutation. WHO grade I papillary glioneuronal tumour may present as 5-ALA fluorescent lesions. From a clinical perspective, 5-ALA can be used to achieve complete resections in these lesions which, in most cases, can be curative.

Safety and accuracy of frameless electromagnetic-navigated (AXIEMTM)-guided brain lesion biopsies: a large single-unit study.

BACKGROUND: Brain biopsies are required to establish a definitive histological diagnosis for brain lesions that have been identified on imaging in order to guide further treatment for patients. OBJECTIVE: Various navigation systems are in use but little up to date evidence is available regarding the safety and accuracy of a frameless, electromagnetic technique to target brain lesions. METHODS: Data was collected retrospectively on all patients that had brain biopsies at our institution from 01/01/2010 to 31/12/2017. Operation notes, neuropathology reports, and clinical notes on electronic patient record were used to determine whether biopsy of adequate identifiable abnormal tissue was achieved, whether a definitive diagnosis was established, any adverse events occurred, and if a repeat biopsy was carried out. RESULTS: Three hundred seventy-one AxiEM (Medtronic, Minneapolis, USA)-guided brain tumor biopsies were performed in this 8-year period. Three hundred forty-nine (94.07%) procedures provided definitive tissue diagnosis, 22 (5.93%) were non diagnostic; in 6 cases (1.62%), repeat biopsy was performed and adverse events which caused clinical compromise were observed in 4 patients (1.08%). CONCLUSIONS: The AxiEM is a fast, effective, and safe frameless and pinless neuronavigational system. It offers a high degree of accuracy required for the establishment of a definitive diagnosis, permitting optimal further treatment, and thus improving patient outcomes.

Two-year experience of multi-disciplinary team (MDT) outcomes for brain metastases in a tertiary neuro-oncology centre.

Brain metastases (BMs) are the most common intracranial tumour in adults and form a significant proportion of the neuro-oncology workload. Their management has progressed significantly in the last few decades but a gold-standard evidence-based management strategy has not been defined to date and several guidelines based on available evidence exist to support clinical decision-making. This paper evaluates the decision-making process of the neuro-oncology multi-disciplinary team (MDT) in a tertiary neuro-oncology centre over a two-year period. A retrospective review of all patients with BM discussed in the MDT was conducted. Data on patient demographics, tumour characteristics and MDT decision were collected from the MDT database, clinical notes and imaging studies. Patients were stratified into the three recursive partitioning analysis (RPA) classes and according to the graded prognostic assessment (GPA) score. MDT decisions were analysed by RPA class and for GPA score as well as single versus multiple BM. There were 362 patients with BM, representing 22% of the total cases discussed at the MDT. Decision-making was largely consistent with available guidelines. A concrete treatment decision was reached in 77.5% of patients and 32.2% of these received neurosurgical input. More patients with solitary BM underwent surgery compared to multiple BM (p = 0.001), and more patients in RPA classes I and II had surgical resection compared to class III (p = 0.005 and 0.001, respectively). Surgical patients also had higher GPA scores compared to palliative patients (p = 0.005). A greater absolute number and proportion of patients in RPA class II vs. class I underwent neurosurgical intervention. These patients were stratified into class II because of their age but would otherwise have been placed into class I. Survival data were available for 195 patients (53.8%) at 1 year post MDT discussion. A pattern of declining survival was observed along RPA classes which was statistically significant (p = 0.0025). Median survival was 4.7 (0-41), 3.7 (0-23), and 2.5 (range 0-24) months for RPA class I, II and III respectively. A similar pattern that did not reach statistical significance was found between GPA scores (p = 0.101). Median survival was 3 (0-13), 4.6 (range 0-41), and 4.6 (0-35) months for GPA scores 0-1.0, 1.5-2.5 and 3-4.0, respectively. Patient selection was generally in accordance to RPA class and GPA scoring, with the exception of surgery offered to elderly patients: this can be explained by the increasing number of otherwise fit patients as population ages.

5-ALA fluorescence in intraparenchymal endodermal cysts.

In recent years, new indications have been suggested for 5-ALA, particularly for cystic lesions. We report the use of 5-ALA fluorescence in an intraparenchymal supratentorial endodermal cyst of a 52-year-old female presenting with headache, progressive right side hemiparesis and anomic aphasia. She underwent an image-guided 5-ALA-assisted left minicraniotomy for fenestration of the cystic lesion into the ventricular system. The capsule of the cyst was noted to fluoresce with 5-ALA. She recovered from the previous deficits and the cyst decreased in size. To the best of our knowledge, this is the first time 5-ALA fluorescence is reported in a case of endodermal cyst.

Third-ventricle enterogenous cyst presentation mimicking a colloid cyst: uncommon presentation of a rare disease and literature review.

Enterogenous cysts (ECs) are endodermal lesions resulting from splitting anomalies in the neuroenteric canal. We report the case of a 64-year-old patient who presented with a sudden headache followed by collapse. Brain computed tomography revealed a hyperdense lesion in the anterior part of the third ventricle with obstructive hydrocephalus. A presumptive diagnosis of colloid cyst was made and he underwent a right transcortical approach for lesion resection. The histopathological examination revealed an EC. ECs are common lesions in the cervical-thoracic spine but rare in the supratentorial compartment with only two previously described cases occurring in the third ventricle.

Trigeminal neuralgia from an Arteriovenous malformation: An intra-operative diagnosis.

We report the case of a 72-year-old lady with a magnetic resonance imaging (MRI) occult arteriovenous malformation (AVM) causing trigeminal neuralgia (TN). The possibility of an AVM when managing patients with TN should be borne in mind. Where possible, decompression of the trigeminal nerve should be attempted, as first-line therapy.

White matter connections of the supplementary motor area in humans.

INTRODUCTION: The supplementary motor area (SMA) is frequently involved by brain tumours (particularly WHO grade II gliomas). Surgery in this area can be followed by the 'SMA syndrome', characterised by contralateral akinesia and mutism. Knowledge of the connections of the SMA can provide new insights on the genesis of the SMA syndrome, and a better understanding of the challenges related to operating in this region. METHODS: White matter connections of the SMA were studied with both postmortem dissection and advance diffusion imaging tractography. Postmortem dissections were performed according to the Klingler technique. 12 specimens were fixed in 10% formalin and frozen at -15°C for 2 weeks. After thawing, dissection was performed with blunt dissectors. For diffusion tractography, high-resolution diffusion imaging datasets from 10 adult healthy controls from the Human Connectome Project database were used. Whole brain tractography was performed using a spherical deconvolution approach. RESULTS: Five main connections were identified in both postmortem dissections and tractography reconstructions: (1) U-fibres running in the precentral sulcus, connecting the precentral gyrus and the SMA; (2) U-fibres running in the cingulate sulcus, connecting the SMA with the cingulate gyrus; (3) frontal 'aslant' fascicle, directly connecting the SMA with the pars opercularis of the inferior frontal gyrus; (4) medial fibres connecting the SMA with the striatum; and (5) SMA callosal fibres. Good concordance was observed between postmortem dissections and diffusion tractography. CONCLUSIONS: The SMA shows a wide range of white matter connections with motor, language and lymbic areas. Features of the SMA syndrome (akinesia and mutism) can be better understood on the basis of these findings.

Nonenhancing motor eloquent gliomas: navigated transcranial magnetic stimulation oncobiological signature.

OBJECTIVE: Preoperative grading of nonenhancing motor eloquent gliomas is hampered by a lack of specific imaging surrogates. Tumor grading is crucial for the informed consent discussion before tumor resection. In this paper, the authors hypothesized that navigated transcranial magnetic stimulation (nTMS)-derived metrics could provide significant information to distinguish between high- and low-grade motor eloquent gliomas that present as nonenhancing tumors and therefore contribute to improving patient counseling, timing of treatment, preoperative planning, and intraoperative strategies. METHODS: The authors conducted a retrospective single-center cohort study of patients admitted for tumor surgery between January 2018 and April 2022 with a nonenhancing motor eloquent glioma and preoperative bilateral nTMS mapping. nTMS data including resting motor threshold (RMT), interhemispheric RMT ratio (iRMTr), Cortical Excitability Score (CES), area and volume of cortical activation, and motor evoked potential (MEP) characteristics were obtained and integrated with demographic and clinical data. RESULTS: Thirty patients met the inclusion criteria, and 10 healthy participants were recruited for comparison. Seizures were the most common presenting symptom (25 patients) and WHO grade 3 the most common tumor grade (21 patients). The area and volume of functional cortical activation of both the abductor pollicis brevis and first dorsal interosseous muscles were decreased in healthy participants compared with patients with WHO grade 3 glioma (p < 0.05). An abnormal iRMTr for the lower limbs (16.7% [1/6] WHO grade 2, 76.2% [16/21] WHO grade 3, 100% [3/3] WHO grade 4; p = 0.015) and a higher CES (maximal abnormal CES: 0% [0/6] WHO grade 2, 38% [8/21] WHO grade 3, 66.7% [2/3] WHO grade 4; p = 0.010) were associated with the prediction of high-grade lesions. A total of 7280 MEPs were analyzed. A significant increase in the amplitude and a significant decrease in latency in the MEPs for the first dorsal interosseous and abductor digiti minimi muscles (p < 0.0001) were identified in healthy participants compared with WHO grade 3 glioma patients. CONCLUSIONS: Nonenhancing motor eloquent gliomas have a different impact on both anatomical and functional reorganization of motor areas according to their WHO grading.