Resection of supplementary motor area gliomas: revisiting supplementary motor syndrome and the role of the frontal aslant tract

Anatomical Heterogeneity in Low-grade and High-grade Gliomas: A Multiscale Perspective

BACKGROUND

Low-grade gliomas (LGGs) and high-grade gliomas (HGGs) often exhibit distinct spatial distributions, a phenomenon that remains incompletely understood. Based on previous research, we hypothesized that functional networks, neurotransmitters, and isocitrate dehydrogenase-1 (IDH-1) status characterize the spatial patterns of LGG and HGG.

METHODS

We analyzed 399 patients diagnosed with primary gliomas. First, we generated glioma frequency maps based on tumor grade, neurotransmitters, and IDH-1 status and constructed a brain functional connectivity network to explore heterogeneity in glioma location. Second, all tumor masks were mirror-symmetrized onto the brain's left hemisphere to facilitate feature extraction. We performed independent component analysis on merged four-dimensional files using Multivariate Exploratory Linear Optimized Decomposition into Independent Component (MELODIC), identifying four IDH-1 wild-type lesion covariance networks (IDHwt-LCNs) and three IDH-1 mutant lesion covariance networks (IDHmut-LCNs) with distinct spatial distributions, and analyzing correlation between the neurotransmitter levels and the IDH-wt/mut specific LCNs. Finally, we compared 42 white matter fibers extracted using XTRACT with 39 functional brain connective networks from the multi-subject dictionary learning (MSDL) atlas, revealing significant associations among the frontal aslant tract (FAT) and the intraparietal sulcus (IPS).

RESULTS

Our findings revealed high anatomical heterogeneity between LGG and HGG. Moreover, the high node strength played a critical role in the distinct spatial distribution of glioma. Significant correlations were observed between glioma frequency maps and dopaminergic, cholinergic, μ-opioid, and serotonergic neurotransmission. Furthermore, IDHwt/mut-LCNs analysis demonstrated that IDH-1 status influences glioma distribution, involving key brain structures. Lastly, we also found significant correlations between IDHwt/mut-LCNs and the neurotransmission of dopaminergic, cholinergic, μ-opioid, and serotonergic systems.

CONCLUSION

Our study highlighted the mechanisms by which functional networks, neurotransmitter systems, and IDH-1 status collectively contribute to the anatomical heterogeneity observed in LGG and HGG.

The Variation of White Matter Connectome After Surgery Revealed Factors Affecting Supplementary Syndrome Recovery Time in Low-Grade Glioma Patients

OBJECTIVE

Supplementary motor area (SMA) syndrome is a common complication after SMA glioma resection. The compensatory mechanism of the structural sensorimotor network (SMN) and the factors influencing the recovery time of SMA syndrome have not been investigated.

METHODS

Pre- and postoperative diffusion tensor images of 42 low-grade glioma patients with SMA syndrome were processed to construct white matter connectomes. Patients were classified into fast and slow-recovery groups according to whether postoperative motor disorder recovers within 7 days. Fiber counts between nodes and graph theory topological properties were calculated. The shortest distance from the surgical region to the corticospinal tract (dCST) and the upper limb region of Brodmann area 4 (A4ul) was measured to find correlations with recovery time. Cox regressions were conducted to identify factors associated with SMA syndrome recovery time. A general linear model was formed using significant factors in multivariate Cox analysis to predict recovery time.

RESULTS

Decrease of fiber number between lesioned-hemispheric A4ul and contralateral SMN is correlated with prolongation of recovery time. Compared with the slow-recovery group, a higher increase of nodal degree centrality and nodal efficiency of ipsilateral A4ul was found in the fast-recovery group (nodal efficiency: left pre-op: 0.182 ± 0.009, left post-op: 0.231 ± 0.008, p < 0.0001; right pre-op: 0.157 ± 0.021, right post-op: 0.195 ± 0.018, p = 0.0011); (nodal degree centrality: left pre-op: 1.985 ± 0.166; left post-op: 3.195 ± 0.230, p < 0.0001; right pre-op: 1.620 ± 0.389; right post-op: 2.411 ± 0.452, p = 0.0005). Multivariate Cox analysis indicated that the increase in nodal efficiency of A4ul and dCST were protective factors for SMA syndrome recovery time. A significant negative correlation between the predict score and recovery time was found in the left lesion group (r = -0.756, p < 0.0001), and the same trend was found in the right lesion group (r = -0.531, p = 0.076).

CONCLUSIONS

This study revealed an increase in lesioned-hemispheric A4ul nodal efficiency and long dCST as protective factors in SMA syndrome recovery. A decrease in the number of interhemispheric fibers connecting lesioned-hemispheric A4ul to nodes on the contralateral hemisphere was correlated with the long recovery time of SMA syndrome.

Severity of Clinical Symptoms of Supplementary Motor Area Syndrome Correlates with the Extent of Tumor Resection in the Brain

A unified view on recovery from supplementary motor area syndrome after glioma resection is lacking. This study retrospectively examined the relationship between motor function, higher brain function, the ability to perform activities of daily living, and social reintegration and the extent of tumor resection in patients who underwent resection of tumors near the supplementary motor area. We assigned 24 consecutive patients into 3 groups according to the depth of tumor resection: resection involving (A) only the supplementary motor area (5 patients); (B) the supplementary motor area and cingulate gyrus (11 patients); and (C) the supplementary motor area, cingulate gyrus, and corpus callosum (8 patients). Motor paralysis, language function, and the ability to perform activities of daily living were evaluated perioperatively and 2 months postoperatively, whereas successful social reintegration was examined retrospectively. In group C, 62% of patients developed severe paralysis after surgery, with slow recovery and delayed ambulation (p = 0.0869). Patients with tumors in the left hemisphere, specifically those extending to the cingulate gyrus and corpus callosum, showed decreased scores for postoperative word recall; however, recovery was observed after 2 months. The Functional Instrumental Measure score, which indicates the activity of daily living ability, showed the largest difference preoperatively and postoperatively in group C. The World Health Organization tumor grade (p = 0.0445) and extent of tumor resection (p = 0.0011) were inversely correlated with social reintegration 6 months postoperatively. Overall, the findings suggest that early social reintegration is influenced by the World Health Organization tumor grade (2021 World Health Organization classification) and the extent of tumor resection.

Precision Surgery for Glioblastomas

Glioblastomas are the most common primary malignant brain tumor. Most of the recent improvements their treatment are due to improvements in surgery. Although many would consider surgery as the most personalized treatment, the variation in resection between surgeons suggests there remains a need for objective measures to determine the best surgical treatment for individualizing therapy for glioblastoma. We propose applying a personalized medicine approach to improve outcomes for patients. We suggest looking at personalizing preoperative preparation, improving the resection target by understanding what needs removing and what ca not be removed, and better patient selection with personalized rehabilitation plans for all patients.

Asymmetry of the Frontal Aslant Tract and Development of Supplementary Motor Area Syndrome

Background/Objectives: The purpose of this study was to investigate preoperative interhemispheric differences of the FAT in relation to the onset of postoperative SMA syndrome. Methods: This was a single-center retrospective analysis of patients who underwent surgical resection of diffuse gliomas involving the SMA between 2018 and 2022. Inclusion criteria were availability of preoperative and postoperative Magnetic Resonance Imaging, no previous surgery, and no neurological deficits at presentation. Diffusion-weighted data were processed by spherical deconvolution (SD) and diffusion tensor imaging tractography algorithms, and TrackVis was used to dissect the FAT of both hemispheres. The FAT data were analyzed for correlation with postoperative SMA syndrome onset. Results:N = 25 cases were included in the study, among which n = 23 had preoperative bilaterally identifiable FAT by SD. N = 12 developed an SMA syndrome, 6 demonstrated a motor-only syndrome, 4 had a verbal-only syndrome, and 2 had mixed verbal and motor features. The SMA syndrome incidence was significantly more frequent in lower-grade gliomas (p = 0.005). On the tumor side, the FAT identified by SD was smaller than the contralateral (mean volume 6.53 cm3 and 13.33 cm3, respectively, p < 0.001). In the 6 cases that developed a verbal SMA syndrome, a normalized FAT volume asymmetry (FAT-VA) demonstrated an asymmetry shifted towards the non-dominant side (mean FAT-VA = -0.68), while the cases with no postoperative verbal impairment had opposite asymmetry towards the dominant side (mean FAT-VA = 0.42, p = 0.010). Conclusions: Preoperative interhemispheric FAT volume asymmetry estimated according to functional dominance can predict postoperative onset of verbal SMA syndrome, with proportionally smaller FAT on the affected dominant hemisphere.

Anatomical analysis of white fiber tracts in SMA and its implications related to en-masse tumor resection technique

OBJECTIVE

Anatomy and connections of the supplementary motor area (SMA) are studied essentially to analyze the SMA syndrome. Experience with surgical treatment of 19 tumors located in SMA is analyzed.

MATERIAL AND METHODS

The cortical anatomy and subcortical connectivity of the SMA was studied on ten previously frozen and formalin fixed human cadaveric brain specimens. The white fiber dissection was performed using Klingler's method. Nineteen patients with low grade gliomas in the region of the SMA treated surgically were clinically analyzed.

RESULTS

The white fiber connections of the SMA include short arcuate connections with the pre-central, middle and inferior frontal gyri, the medial part of the SLF, the cingulum, the frontal aslant tract (FAT), the claustro-cortical fibers, the fronto-striatal tract and the crossed frontal aslant tract. All tumors were operated using en-masse surgical technique described by us and its subsequent modifications that focused on attempts towards preservation of related critical fiber tracts namely FAT, cingulum and corpus callosum presumed to be responsible for postoperative SMA syndrome. Eight patients developed an SMA syndrome in the immediate post-operative period. Eleven patients did not develop any post-operative neurological deficits. In all these 11 patients it was apparent that the cingulum, FAT and the corpus callosal fibers were preserved during surgery by modifying the tumor resection technique.

CONCLUSIONS

SMA syndrome is a frequent occurrence following surgery in patients with tumors in the region of the SMA complex. Surgical strategy that preserves the cingulum and the FAT can prevent the occurrence of the SMA syndrome.

Permanent deterioration of fine motor skills after the resection of tumors in the supplementary motor area

Supplementary motor area syndrome (SMAS) represents a common neurosurgical sequela. The incidence and time frame of its occurrence have yet to be characterized after surgery for brain tumors. We examined patients suffering from a brain tumor preoperatively, postoperatively, and during follow-up examinations after three months, including fine motor skills testing and transcranial magnetic stimulation (TMS). 13 patients suffering from a tumor in the dorsal part of the superior frontal gyrus underwent preoperative, early postoperative, and 3-month follow-up testing of fine motor skills using the Jebsen-Taylor Hand Function Test (JHFT) and the Nine-Hole Peg Test (NHPT) consisting of 8 subtests for both upper extremities. They completed TMS for cortical motor function mapping. Test completion times (TCTs) were recorded and compared. No patient suffered from neurological deficits before surgery. On postoperative day one, we detected motor deficits in two patients, which remained clinically stable at a 3-month follow-up. Except for page-turning, every subtest indicated a significant worsening of function, reflected by longer TCTs (p < 0.05) in the postoperative examinations for the contralateral upper extremity (contralateral to the tumor manifestation). At 3-month follow-up examinations for the contralateral upper extremity, each subtest indicated significant worsening compared to the preoperative status despite improvement to the immediate postoperative level. We also detected significantly longer TCTs (p < 0.05) postoperatively in the ipsilateral upper extremity. This study suggests a long-term worsening of fine motor skills even three months after SMA tumor resection, indicating the necessity of targeted physical therapy for these patients.

The surgical management of diffuse gliomas: Current state of neurosurgical management and future directions

After recent updates to the World Health Organization pathological criteria for diagnosing and grading diffuse gliomas, all major North American and European neuro-oncology societies recommend a maximal safe resection as the initial management of a diffuse glioma. For neurosurgeons to achieve this goal, the surgical plan for both low- and high-grade gliomas should be to perform a supramaximal resection when feasible based on preoperative imaging and the patient's performance status, utilizing every intraoperative adjunct to minimize postoperative neurological deficits. While the surgical approach and technique can vary, every effort must be taken to identify and preserve functional cortical and subcortical regions. In this summary statement on the current state of the field, we describe the tools and technologies that facilitate the safe removal of diffuse gliomas and highlight intraoperative and postoperative management strategies to minimize complications for these patients. Moreover, we discuss how surgical resections can go beyond cytoreduction by facilitating biological discoveries and improving the local delivery of adjuvant chemo- and radiotherapies.

Preserved White Matter Integrity and Recovery After Brain Tumor Surgery: A Prospective Pilot Study on the Frontal Aslant Tract

Introduction: Damage to white matter tracts can cause severe neurological deficits, which are often hardly predictable before brain tumor surgery. To explore the possibility of assessing white matter integrity and its preservation, we chose the frontal aslant tract (FAT) due to its involvement in multiple neurological functions such as speech and movement initiation. Methods: Right-handed patients with left hemispheric intracerebral tumors underwent FAT tractography within 7 days before and 3 days after surgery. Neurological performance score and aphasia score were assessed within 7 days before and after surgery, as well as at follow-up 3 months postoperatively. Results: Fifteen patients were prospectively analyzed. After multivariate analysis and receiver operating characteristic analysis, we found that preoperative fractional anisotropy (FA) of the left FAT indicated the preoperative aphasia score (cutoff 0.40, p = 0.015). Aphasia scores 3 months postoperatively were predicted by both postoperative FA of the left FAT (cutoff 0.35, p = 0.005) and postoperatively preserved FA of the left FAT (cutoff 95.8%, p = 0.017). Postoperatively preserved right FAT FA inversely predicted postoperative aphasia score (cutoff 95.1%, p = 0.016). Discussion: Assessment of white matter integrity preservation is possible and correlates with outcome after brain tumor surgery. It may be useful for patient counseling and assessment of rehabilitation potential, as well as to investigate relevant brain networks in the future. Clinical Trial Registration: The trial was prospectively registered at ClinicalTrials.gov (NCT04302857).

Supplementary Motor Area Syndrome After Resection of a Dominant Hemisphere Parasagittal Meningioma: A Case Report

BACKGROUND AND IMPORTANCE

Supplementary motor area (SMA) syndrome is a common, transient postoperative complication of intra-axial tumor resections involving the SMA and posterior cingulate gyrus. It is also reported as a rare complication of resecting extra-axial lesions. Meningiomas represent the most common, nonmalignant primary central nervous system tumor in adults, which present most commonly in parasagittal locations. Resection of dominant hemisphere parasagittal meningiomas overlying or infiltrating into the SMA region carry a recognizable risk for developing SMA syndrome postoperatively.

CLINICAL PRESENTATION

We present a 58-year-old woman with intermittent headaches and concern for new-onset seizures. MRI demonstrated an extra-axial mass involving the left frontal convexity and SMA region with homogenous postcontrast enhancement. There was radiographic involvement of the superior sagittal sinus and inner table of the skull. Fluid-attenuated recovery signal and perilesional vasogenic edema were also noted. The imaging findings favored a parasagittal meningioma, and surgical resection was performed. Arachnoid invasion and pial infiltration of the tumor over the SMA were evident during the operation.

CONCLUSION

A detailed understanding of the functional neuroanatomy and clinical pathophysiology of eloquent cortical regions is important for preoperative planning and patient counseling. Surgical resection of lesions in such areas can result in rare complications uniquely implicated in specific patient subsets. Recognizing these patients in the preoperative setting is imperative for proper counseling of patients and families.

Large-scale brain networks and intra-axial tumor surgery: a narrative review of functional mapping techniques, critical needs, and scientific opportunities

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.

Technical Aspects of Motor and Language Mapping in Glioma Patients

Gliomas are infiltrative primary brain tumors that often invade functional cortical and subcortical regions, and they mandate individualized brain mapping strategies to avoid postoperative neurological deficits. It is well known that maximal safe resection significantly improves survival, while postoperative deficits minimize the benefits associated with aggressive resections and diminish patients’ quality of life. Although non-invasive imaging tools serve as useful adjuncts, intraoperative stimulation mapping (ISM) is the gold standard for identifying functional cortical and subcortical regions and minimizing morbidity during these challenging resections. Current mapping methods rely on the use of low-frequency and high-frequency stimulation, delivered with monopolar or bipolar probes either directly to the cortical surface or to the subcortical white matter structures. Stimulation effects can be monitored through patient responses during awake mapping procedures and/or with motor-evoked and somatosensory-evoked potentials in patients who are asleep. Depending on the patient’s preoperative status and tumor location and size, neurosurgeons may choose to employ these mapping methods during awake or asleep craniotomies, both of which have their own benefits and challenges. Regardless of which method is used, the goal of intraoperative stimulation is to identify areas of non-functional tissue that can be safely removed to facilitate an approach trajectory to the equator, or center, of the tumor. Recent technological advances have improved ISM’s utility in identifying subcortical structures and minimized the seizure risk associated with cortical stimulation. In this review, we summarize the salient technical aspects of which neurosurgeons should be aware in order to implement intraoperative stimulation mapping effectively and safely during glioma surgery.

Involvement of White Matter Language Tracts in Glioma: Clinical Implications, Operative Management, and Functional Recovery After Injury

To achieve optimal survival and quality of life outcomes in patients with glioma, the extent of tumor resection must be maximized without causing injury to eloquent structures. Preservation of language function is of particular importance to patients and requires careful mapping to reveal the locations of cortical language hubs and their structural and functional connections. Within this language network, accurate mapping of eloquent white matter tracts is critical, given the high risk of permanent neurological impairment if they are injured during surgery. In this review, we start by describing the clinical implications of gliomas involving white matter language tracts. Next, we highlight the advantages and limitations of methods commonly used to identify these tracts during surgery including structural imaging techniques, functional imaging, non-invasive stimulation, and finally, awake craniotomy. We provide a rationale for combining these complementary techniques as part of a multimodal mapping paradigm to optimize postoperative language outcomes. Next, we review local and long-range adaptations that take place as the language network undergoes remodeling after tumor growth and surgical resection. We discuss the probable cellular mechanisms underlying this plasticity with emphasis on the white matter, which until recently was thought to have a limited role in adults. Finally, we provide an overview of emerging developments in targeting the glioma-neuronal network interface to achieve better disease control and promote recovery after injury.

Should Neurosurgeons Try to Preserve Non-Traditional Brain Networks? A Systematic Review of the Neuroscientific Evidence

The importance of large-scale brain networks in higher-order human functioning is well established in neuroscience, but has yet to deeply penetrate neurosurgical thinking due to concerns of clinical relevance. Here, we conducted the first systematic review examining the clinical importance of non-traditional, large-scale brain networks, including the default mode (DMN), central executive (CEN), salience (SN), dorsal attention (DAN), and ventral attention (VAN) networks. Studies which reported evidence of neurologic, cognitive, or emotional deficits in relation to damage or dysfunction in these networks were included. We screened 22,697 articles on PubMed, and 551 full-text articles were included and examined. Cognitive deficits were the most common symptom of network disturbances in varying amounts (36–56%), most frequently related to disruption of the DMN (n = 213) or some combination of DMN, CEN, and SN networks (n = 182). An increased proportion of motor symptoms was seen with CEN disruption (12%), and emotional (35%) or language/speech deficits (24%) with SN disruption. Disruption of the attention networks (VAN/DAN) with each other or the other networks mostly led to cognitive deficits (56%). A large body of evidence is available demonstrating the clinical importance of non-traditional, large-scale brain networks and suggests the need to preserve these networks is relevant for neurosurgical patients.