Beneficial impact of high-field intraoperative magnetic resonance imaging on the efficacy of pediatric low-grade glioma surgery

How modern treatments have modified the role of surgery in pediatric low-grade glioma

Low-grade gliomas are the most common brain tumor of childhood, and complete resection offers a high likelihood of cure. However, in many instances, tumors may not be surgically accessible without substantial morbidity, particularly in regard to gliomas arising from the optic or hypothalamic regions, as well as the brainstem. When gross total resection is not feasible, alternative treatment strategies must be considered. While conventional chemotherapy and radiation therapy have long been the backbone of adjuvant therapy for low-grade glioma, emerging techniques and technologies are rapidly changing the landscape of care for patients with this disease. This article seeks to review the current and emerging modalities of treatment for pediatric low-grade glioma.

Intraoperative MRI: A Review of Applications Across Neurosurgical Specialties

Intraoperative MRI (iMRI) made its debut to great fanfare in the mid-1990s. However, the enthusiasm for this technology with seemingly obvious benefits for neurosurgeons has waned. We review the benefits and utility of iMRI across the field of neurosurgery and present an overview of the evidence for iMRI for multiple neurosurgical disciplines: tumor, skull base, vascular, pediatric, functional, and spine. Publications on iMRI have steadily increased since 1996, plateauing with approximately 52 publications per year since 2011. Tumor surgery, especially glioma surgery, has the most evidence for the use of iMRI contributing more than 50% of all iMRI publications, with increased rates of gross total resection in both adults and children, providing a potential survival benefit. Across multiple neurosurgical disciplines, the ability to use a multitude of unique sequences (diffusion tract imaging, diffusion-weighted imaging, magnetic resonance angiography, blood oxygenation level-dependent) allows for specialization of imaging for various types of surgery. Generally, iMRI allows for consideration of anatomic changes and real-time feedback on surgical outcomes such as extent of resection and instrument (screw, lead, electrode) placement. However, implementation of iMRI is limited by cost and feasibility, including the need for installation, shielding, and compatible tools. Evidence for iMRI use varies greatly by specialty, with the most evidence for tumor, vascular, and pediatric neurosurgery. The benefits of real-time anatomic imaging, a lack of radiation, and evaluation of surgical outcomes are limited by the cost and difficulty of iMRI integration. Nonetheless, the ability to ensure patients are provided by a maximal yet safe treatment that specifically accounts for their own anatomy and highlights why iMRI is a valuable and underutilized tool across multiple neurosurgical subspecialties.

Evaluating the use of intraoperative magnetic resonance imaging in paediatric brain tumour resection surgeries: a literature review

Brain tumours are the most common solid neoplasm in children, posing a significant challenge in oncology due to the limited range of treatment. Intraoperative magnetic resonance imaging (iMRI) has recently emerged to aid surgical intervention in neurosurgery resection with the potential to delineate tumour boundaries. This narrative literature review aimed to provide an updated evaluation of the clinical implementation of iMRI in paediatric neurosurgical resection, with an emphasis on the extent of brain tumour resection, patient outcomes and its drawbacks. Databases including MEDLINE, PubMed, Scopus and Web of Science were used to investigate this topic with key terms: paediatric, brain tumour, and iMRI. Exclusion criteria included literature comprised of adult populations and the use of iMRI in neurosurgery in the absence of brain tumours. The limited body of research evaluating the clinical implementation of iMRI in paediatric cohorts has been predominantly positive. Current evidence demonstrates the potential for iMRI use to increase rates of gross total resection (GTR), assess the extent of resection, and improve patient outcomes, such as progression-free survival. Limitations regarding the use of iMRI include prolonged operation times and complications associated with head immobilisation devices. iMRI has the potential to aid in the achievement of maximal brain tumour resection in paediatric patients. Future prospective randomised controlled trials are necessary to determine the clinical significance and benefits of using iMRI during neurosurgical resection for clinical management of brain neoplasms in children.

Increasing Patient Safety and Treatment Quality by Using Intraoperative MRI for Organ-Preserving Tumor Resection and High-Dose Rate Brachytherapy in Children with Bladder/Prostate and Perianal Rhabdomyosarcoma

In children with bladder/prostate (BP) and perianal rhabdomyosarcoma (RMS), we use a hybrid treatment concept for those suitable, combining organ-preserving tumor resection and high-dose rate brachytherapy (HDR-BT). This treatment concept has been shown to improve outcomes. However, it is associated with specific challenges for the clinicians. The exact position of the tubes for BT is a prerequisite for precise radiotherapy. It can finally be determined only with an MRI or CT scan. We evaluated the use of an intraoperative MRI (iMRI) to control the position of the BT tubes and for radiotherapy planning in all patients with BP and perianal RMS who received the above-mentioned combination therapy in our department since January 2021. iMRI was used in 12 children. All tubes were clearly localized. No adverse events occurred. In all 12 children, radiotherapy could be started on time. In a historical cohort without iMRI, this was not possible in 3 out of 20 children. The use of iMRI in children with BP and perianal RMS improved patient safety and treatment quality. This technology has proven to be successful for the patient population we have defined and has become a standard procedure in our institution.

The impact of 1.5-T intraoperative magnetic resonance imaging in pediatric tumor surgery: Safety, utility, and challenges

Objective

In this study, we present our experience with 1.5-T high-field intraoperative magnetic resonance imaging (ioMRI) for different neuro-oncological procedures in a pediatric population, and we discuss the safety, utility, and challenges of this intraoperative imaging technology.

Methods

A pediatric consecutive-case series of neuro-oncological surgeries performed between February 2020 and May 2022 was analyzed from a prospective ioMRI registry. Patients were divided into four groups according to the surgical procedure: intracranial tumors (group 1), intraspinal tumors (group 2), stereotactic biopsy for unresectable tumors (group 3), and catheter placement for cystic tumors (group 4). The goal of surgery, the volume of residual tumor, preoperative and discharge neurological status, and postoperative complications related to ioMRI were evaluated.

Results

A total of 146 procedures with ioMRI were performed during this period. Of these, 62 were oncology surgeries: 45 in group 1, two in group 2, 10 in group 3, and five in group 4. The mean age of our patients was 8.91 years, with the youngest being 12 months. ioMRI identified residual tumors and prompted further resection in 14% of the cases. The mean time for intraoperative image processing was 54 ± 6 min. There were no intra- or postoperative security incidents related to the use of ioMRI. The reoperation rate in the early postoperative period was 0%.

Conclusion

ioMRI in pediatric neuro-oncology surgery is a safe and reliable tool. Its routine use maximized the extent of tumor resection and did not result in increased neurological deficits or complications in our series. The main limitations included the need for strict safety protocols in a highly complex surgical environment as well as the inherent limitations on certain patient positions with available MR-compatible headrests.

Resection extent and BRAF V600E mutation status determine postoperative tumor growth velocity in pediatric low-grade glioma: results from a single-center cohort analysis

PURPOSE

Despite excellent long-term overall survival rates, pediatric low-grade gliomas (pLGG) show high variety of clinical behavior regarding progress or senescence post incomplete resection (IR). This study retrospectively analyzes tumor growth velocity (TGV) of pLGG before surgery and after IR to investigate the impact of surgical extent, tumor location and molecular BRAF status on postoperative residual tumor growth behavior.

METHODS

Of a total of 172 patients with pLGG receiving surgical treatment, 107 underwent IR (66%). Fifty-three vs 94 patients could be included in the pre- and post-operative cohort, respectively, and were observed over a mean follow-up time of 40.2 vs 60.1 months. Sequential three-dimensional MRI-based tumor volumetry of a total of 407 MRI scans was performed to calculate pre- and postoperative TGV.

RESULTS

Mean preoperative TGV of 0.264 cm3/month showed significant deceleration of tumor growth to 0.085 cm3/month, 0.024 cm3/month and -0.016 cm3/month after 1st, 2nd, and 3rd IR, respectively (p < 0.001). Results remained significant after excluding patients undergoing (neo)adjuvant treatment. Resection extent showed correlation with postoperative reduction of TGV (R = 0.97, p < 0.001). ROC analysis identified a residual cut-off tumor volume > 2.03 cm3 associated with a higher risk of progress post IR (sensitivity 78,6%, specificity 76.3%, AUC 0.88). Postoperative TGV of BRAF V600E-mutant LGG was significantly higher than of BRAF wild-type LGG (0.123 cm3/month vs. 0.016 cm3/month, p = 0.047).

CONCLUSION

This data suggests that extensive surgical resection may impact pediatric LGG growth kinetics post incomplete resection by inducing a significant deceleration of tumor growth. BRAF-V600E mutation may be a risk factor for higher postoperative TGV.

Survival After Resection of Newly-Diagnosed Intracranial Grade II Ependymomas: An Initial Multicenter Analysis and the Logistics of Intraoperative Magnetic Resonance Imaging

OBJECTIVE

To identify factors, including the use of intraoperative magnetic resonance imaging (iMRI), impacting overall survival (OS) and progression-free survival (PFS) after resections of newly diagnosed intracranial grade II ependymomas performed across 4 different institutions.

METHODS

Analyses of a multicenter mixed retrospective/prospective database assessed the impact of patient, treatment, and tumor characteristics on OS and PFS. iMRI workflow and logistics were also outlined.

RESULTS

Forty-three patients were identified (mean age 25.4 years, mean follow-up 52.8 months). The mean OS was 52.8 ± 44.7 months. Univariate analyses failed to identify prognostic factors associated with OS, likely due to relatively shorter follow-up time for this less aggressive glioma subtype. The mean PFS was 43.7 ± 39.8 months. Multivariate analyses demonstrated that gross-total resection was associated with prolonged PFS compared to both subtotal resection (STR) (P = 0.005) and near-total resection (P = 0.01). Infratentorial location was associated with improved PFS compared to supratentorial location (P = 0.04). Log-rank analyses of Kaplan-Meier survival curves showed that increasing extent of resection (EOR) led to improved OS specifically for supratentorial tumors (P = 0.02) and improved PFS for all tumors (P < 0.001). Thirty cases (69.8%) utilized iMRI, of which 12 (27.9%) involved additional resection after iMRI. Of these, 8/12 (66.7%) resulted in gross-total resection, while 2/12 (16.7%) were near-total resection and 2/12 (16.7%) were subtotal resection. iMRI was not an independent prognosticator of PFS (P = 0.72).

CONCLUSIONS

Greater EOR and infratentorial location were associated with increased PFS for grade II ependymomas. Greater EOR was associated with longer OS only for supratentorial tumors. A longer follow-up is needed to establish prognostic factors for this cohort, including use of iMRI.

Retrospective and integrative analyses of molecular characteristics and their specific imaging parameters in pediatric grade 1 gliomas

BACKGROUND

Pediatric low-grade gliomas (PLGG) are the most common brain tumors diagnosed during childhood and represent a heterogeneous group associating variable molecular abnormalities. To go further and develop specific statistical patterns between tumor molecular background, imaging features, and patient outcome, a retrospective study was performed in a group of non-neurofibromatosis type 1 (non-NF1) grade 1 PLGGs.

PATIENTS AND METHODS

Seventy-eight children, followed from 2004 to 2017, were retrospectively reported. In this population, we analyzed radiological and molecular parameters. Their therapeutic management comprised surgery or surgery plus chemotherapies.

RESULTS

Considering all 78 patients, 59 had only a surgical removal and 19 patients were treated with postoperative chemotherapy. Twelve progressions were reported in the partially resected and chemotherapeutic groups, whereas four deaths occurred only in the highly treated patients. As expected, in the global cohort, PLGG with BRAF p.V600E and/or CDKN2A loss exhibited poor outcomes and we evidenced significant associations between those molecular characteristics and their imaging presentation. In the chemo-treated patients, when associating initial and 6-month magnetic resonance imaging (MRI) parameters to the molecular features, the good risk situations were significantly linked to the presence of a large tumor cyst at diagnosis and the appearance during treatment of a higher cystic proportion that we called cystic conversion.

CONCLUSION

So, additionally to the presence of BRAF p.V600E or CDKN2A deletion in grade 1 PLGGs, the absence on diagnostic MRI of cystic parts and/or cystic conversion at 6-month chemotherapy were significantly linked to a worst prognosis and response to treatment. These imaging features should be considered as prognostic markers in future PLGG studies.

Intraoperative MRI versus intraoperative ultrasound in pediatric brain tumor surgery: is expensive better than cheap? A review of the literature

PURPOSE

The extent of brain tumor resection (EOR) is a fundamental prognostic factor in pediatric neuro-oncology in association with the histology. In general, resection aims at gross total resection (GTR). Intraoperative imaging like intraoperative US (iOUS) and MRI have been developed in order to find any tumoral remnant but with different costs. Aim of our work is to review the current literature in order to better understand the differences between costs and efficacy of MRI and iOUS to evaluate tumor remnants intraoperatively.

METHODS

We reviewed the existing literature on PubMed until 31st December 2021 including the sequential keywords "intraoperative ultrasound and pediatric brain tumors", "iUS and pediatric brain tumors", "intraoperative magnetic resonance AND pediatric brain tumors", and "intraoperative MRI AND pediatric brain tumors.

RESULTS

A total of 300 papers were screened through analysis of title and abstract; 254 were excluded. After selection, a total of 23 articles were used for this systematic review. Among the 929 patients described, a total of 349(38%) of the cases required an additional resection after an iMRI scan. GTR was measured on 794 patients (data of 69 patients lost), and it was achieved in 552(70%) patients. In case of iOUS, GTR was estimated in 291 out of 379 (77%) cases. This finding was confirmed at the post-operative MRI in 256(68%) cases.

CONCLUSIONS

The analysis of the available literature demonstrates that expensive equipment does not always mean better. In fact, for the majority of pediatric brain tumors, iOUS is comparable to iMRI in estimating the EOR.

Essential Management of Pediatric Brain Tumors

Brain tumors are the most common solid tumors in children and are associated with high mortality. The most common childhood brain tumors are grouped as low-grade gliomas (LGG), high grade gliomas (HGG), ependymomas, and embryonal tumors, according to the World Health Organization (WHO). Advances in molecular genetics have led to a shift from pure histopathological diagnosis to integrated diagnosis. For the first time, these new criteria were included in the WHO classification published in 2016 and has been further updated in the 2021 edition. Integrated diagnosis is based on molecular genomic similarities of the tumor subclasses, and it can better explain the differences in clinical courses of previously histopathologically identical entities. Important advances have also been made in pediatric neuro-oncology. A growing understanding of the molecular-genetic background of tumorigenesis has improved the diagnostic accuracy. Re-stratification of treatment protocols and the development of targeted therapies will significantly affect overall survival and quality of life. For some pediatric tumors, these advances have significantly improved therapeutic management and prognosis in certain tumor subgroups. Some therapeutic approaches also have serious long-term consequences. Therefore, optimized treatments are greatly needed. Here, we discuss the importance of multidisciplinary collaboration and the role of (pediatric) neurosurgery by briefly describing the most common childhood brain tumors and their currently recognized molecular subgroups.

Rapid intraoperative diagnosis of pediatric brain tumors using Raman spectroscopy: A machine learning approach

Background

Surgical resection is a mainstay in the treatment of pediatric brain tumors to achieve tissue diagnosis and tumor debulking. While maximal safe resection of tumors is desired, it can be challenging to differentiate normal brain from neoplastic tissue using only microscopic visualization, intraoperative navigation, and tactile feedback. Here, we investigate the potential for Raman spectroscopy (RS) to accurately diagnose pediatric brain tumors intraoperatively.

Methods

Using a rapid acquisition RS device, we intraoperatively imaged fresh ex vivo brain tissue samples from 29 pediatric patients at the Lucile Packard Children’s Hospital between October 2018 and March 2020 in a prospective fashion. Small tissue samples measuring 2-4 mm per dimension were obtained with each individual tissue sample undergoing multiple unique Raman spectra acquisitions. All tissue samples from which Raman spectra were acquired underwent individual histopathology review. A labeled dataset of 678 unique Raman spectra gathered from 160 samples was then used to develop a machine learning model capable of (1) differentiating normal brain from tumor tissue and (2) normal brain from low-grade glioma (LGG) tissue.

Results

Trained logistic regression model classifiers were developed using our labeled dataset. Model performance was evaluated using leave-one-patient-out cross-validation. The area under the curve (AUC) of the receiver-operating characteristic (ROC) curve for our tumor vs normal brain model was 0.94. The AUC of the ROC curve for LGG vs normal brain was 0.91.

Conclusions

Our work suggests that RS can be used to develop a machine learning-based classifier to differentiate tumor vs non-tumor tissue during resection of pediatric brain tumors.

Neurosurgical Advances for Malignant Gliomas: Intersection of Biology and Technology

ABSTRACT

The intersection of biology and technology has led to many advancements for the field of neurosurgery. Molecular developments have led to the identification of specific mutations, allowing for more accurate discussions in regard to prognosis and treatment effect. Even amid the progress from basic science benchwork, malignant gliomas continue to have a bleak natural history in lieu of the resistance to chemotherapy and the diffuse nature of the disease, leaving room for further research to discover more effective treatment modalities. Novel imaging methods, including the emerging field of radiogenomics, involve the merging of molecular and radiographic data, enabling earlier, detailed molecular diagnoses and improved surveillance of this pathology. Furthermore, surgical advancements have led to safer and more extensive resections. This review aims to delineate the various advancements in the many facets that are used daily in the care of our glioma population, specifically pertaining to its biology, imaging modalities, and perioperative adjuncts used in the operating room.

Immune Checkpoint-Associated Locations of Diffuse Gliomas Comparing Pediatric With Adult Patients Based on Voxel-Wise Analysis

Objective: Pediatric diffuse gliomas (pDGs) are relatively rare and molecularly distinct from pediatric pilocytic astrocytoma and adult DGs. Immunotherapy is a promising therapeutic strategy, requiring a deep understanding of tumor immune profiles. The spatial locations of brain tumors might be related to the molecular profiles. We aimed to analyze the relationship between the immune checkpoint molecules with the locations of DGs comparing pediatric with adult patients.

Method: We studied 20 pDGs patients (age ≤ 21 years old), and 20 paired adult patients according to gender and histological types selected from 641 adult patients with DGs. Immune checkpoint molecules including B7-H3, CD47, and PD-L1, as well as tumor-infiltrating lymphocytes (TILs) and tumor-associated macrophages (TAMs), were manifested by immunohistochemical staining. Expression difference analyses and Spearman's correlation were performed. MRI data were voxel-wise normalized, segmented, and analyzed by Fisher's exact test to construct the tumor frequency and p value heatmaps. Survival analyses were conducted by Log-rank tests.

Result: The median age of pediatric patients was 16 years. 55% and 30% of patients were WHO II and III grades, respectively. The left frontal lobe and right cerebellum were the statistically significant locations for pDGs, while the anterior horn of ventricles for adult DGs. A potential association between the expression of PD-L1 and TAMs was found in pDGs (p = 0.002, R = 0.670). The right posterior external capsule and the lateral side of the anterior horn of the left ventricle were predominant locations for the adult patients with high expression of B7-H3 and low expression of PD-L1 compared to pediatric ones, respectively. Pediatric patients showed significantly improved overall survival compared with adults. The prognostic roles of immune checkpoint molecules and TILs/TAMs were not significantly different between the two groups.

Conclusion: Immune checkpoint-associated locations of diffuse gliomas comparing pediatric with adult patients could be helpful for the immunotherapy decisions and design of clinical trials.

Comparison of intraoperative and post-operative 3-T MRI performed at 24-72 h following brain tumour resection in children

PURPOSE

Intraoperative MRI (ioMRI) is a valuable tool aiding paediatric brain tumour resection. There is no published evidence comparing the effectiveness of the final intraoperative MRI and early post-operative (24-72 h) MRI as baseline scans following brain tumour resection. We aimed to evaluate whether the final ioMRI scan could serve as the post-operative baseline scan after paediatric brain tumour resections.

METHODS

This prospective study compared the final ioMRI scan with the immediate post-operative MRI scan performed 24-72 h post-surgery. We included 20 patients aged 6.6-21 years undergoing brain tumour resection using ioMRI and were suitable for MRI scan without general anaesthesia. The scans were independently evaluated by experienced local and external paediatric neuroradiologists. Identical sequences in the final ioMRI and the 24-72-h MRI were compared to assess the extent of resection, imaging characteristics of residual tumour, the surgical field, extent of surgically induced contrast enhancement, and diffusion abnormalities.

RESULTS

In 20 patients undergoing intraoperative and early post-operative MRI, there was no difference between ioMRI and 24-72-h post-op scans in identifying residual tumour. Surgically induced contrast enhancement was similar in both groups. There were more abnormalities on diffusion imaging and a greater degree of oedema around the surgical cavity on the 24-72-h scan.

CONCLUSION

The final 3-T ioMRI scan may be used as a baseline post-operative scan provided standard imaging guidelines are followed and is evaluated jointly by the operating neurosurgeon and neuroradiologist. Advantages of final ioMRI as a baseline scan are identified.

Intraoperative MRI for Adult and Pediatric Neurosurgery

Intraoperative MRI (iMRI) technology and its use in both adult and pediatric neurosurgery have advanced significantly over the past 2 decades, allowing neurosurgeons to account for brain shift and optimize resection of brain lesions. Combining the risks of the MR environment with those of the operating room creates a challenging, zero-tolerance environment for the anesthesiologist. This article provides an overview of the currently available iMRI systems, the neurosurgical evidence supporting iMRI use, and the anesthetic and safety considerations for iMRI procedures.

Using Histopathology to Assess the Reliability of Intraoperative Magnetic Resonance Imaging in Guiding Additional Brain Tumor Resection: A Multicenter Study

BACKGROUND

Intraoperative magnetic resonance imaging (iMRI) is a powerful tool for guiding brain tumor resections, provided that it accurately discerns residual tumor.

OBJECTIVE

To use histopathology to assess how reliably iMRI may discern additional tumor for a variety of tumor types, independent of the indications for iMRI.

METHODS

A multicenter database was used to calculate the odds of additional resection during the same surgical session for grade I to IV gliomas and pituitary adenomas. The reliability of iMRI for identifying residual tumor was assessed using histopathology of tissue resected after iMRI.

RESULTS

Gliomas (904/1517 cases, 59.6%) were more likely than pituitary adenomas (176/515, 34.2%) to receive additional resection after iMRI (P < .001), but these tumors were equally likely to have additional tissue sent for histopathology (398/904, 44.4% vs 66/176, 37.5%; P = .11). Tissue samples were available for resections after iMRI for 464 cases, with 415 (89.4%) positive for tumor. Additional resections after iMRI for gliomas (361/398, 90.7%) were more likely to yield additional tumor compared to pituitary adenomas (54/66, 81.8%) (P = .03). There were no significant differences in resection after iMRI yielding histopathologically positive tumor between grade I (58/65 cases, 89.2%; referent), grade II (82/92, 89.1%) (P = .98), grade III (72/81, 88.9%) (P = .95), or grade IV gliomas (149/160, 93.1%) (P = .33). Additional resection for previously resected tumors (122/135 cases, 90.4%) was equally likely to yield histopathologically confirmed tumor compared to newly-diagnosed tumors (293/329, 89.0%) (P = .83).

CONCLUSION

Histopathological analysis of tissue resected after use of iMRI for grade I to IV gliomas and pituitary adenomas demonstrates that iMRI is highly reliable for identifying residual tumor.

MR Imaging Safety in the Interventional Environment

Interventional MR imaging procedures are rapidly growing in number owing to the excellent soft tissue resolution of MR imaging, lack of ionizing radiation, hardware and software advancements, and technical developments in MR imaging-compatible robots, lasers, and ultrasound equipment. The safe operation of an interventional MR imaging system is a complex undertaking, which is only possible with multidisciplinary planning, training, operations and oversight. Safety for both patients and operators is essential for successful operations. Herein, we review the safety concerns, solutions and challenges associated with the operation of a modern interventional MR imaging system.

Intraoperative MRI-guided Resection in Pediatric Brain Tumor Surgery: A Meta-analysis of Extent of Resection and Safety Outcomes

BACKGROUND

 The objective of this meta-analysis was to analyze the impact of intraoperative magnetic resonance imaging (iMRI) on pediatric brain tumor surgery with regard to the frequency of histopathologic entities, additional resections secondary to iMRI, rate of gross total resections (GTR) in glioma surgery, extent of resection (EoR) in supra- and infratentorial compartment, surgical site infections (SSIs), and neurologic outcome after surgery.

METHODS

 MEDLINE/PubMed Service was searched for the terms "intraoperative MRI," "pediatric," "brain," "tumor," "glioma," and "surgery." The review produced 126 potential publications; 11 fulfilled the inclusion criteria, including 584 patients treated with iMRI-guided resections. Studies reporting about patients <18 years, setup of iMRI, surgical workflow, and extent of resection of iMRI-guided glioma resections were included.

RESULTS

 IMRI-guided surgery is mainly used for pediatric low-grade gliomas. The mean rate of GTR in low- and high-grade gliomas was 78.5% (207/254; 95% confidence interval [CI]: 64.6-89.7, p < 0.001). The mean rate of GTR in iMRI-assisted low-grade glioma surgery was 74.3% (35/47; 95% CI: 61.1-85.5, p = 0.759). The rate of SSI in surgery assisted by iMRI was 1.6% (6/482; 95% CI: 0.7-2.9). New onset of transient postoperative neurologic deficits were observed in 37 (33.0%) of 112 patients.

CONCLUSION

 IMRI-guided surgery seems to improve the EoR in pediatric glioma surgery. The rate of SSI and the frequency of new neurologic deficits after IMRI-guided surgery are within the normal range of pediatric neuro-oncologic surgery.

Impact of Intraoperative Magnetic Resonance Imaging and Other Factors on Surgical Outcomes for Newly Diagnosed Grade II Astrocytomas and Oligodendrogliomas: A Multicenter Study

BACKGROUND

Few studies use large, multi-institutional patient cohorts to examine the role of intraoperative magnetic resonance imaging (iMRI) in the resection of grade II gliomas.

OBJECTIVE

To assess the impact of iMRI and other factors on overall survival (OS) and progression-free survival (PFS) for newly diagnosed grade II astrocytomas and oligodendrogliomas.

METHODS

Retrospective analyses of a multicenter database assessed the impact of patient-, treatment-, and tumor-related factors on OS and PFS.

RESULTS

A total of 232 resections (112 astrocytomas and 120 oligodendrogliomas) were analyzed. Oligodendrogliomas had longer OS (P &lt; .001) and PFS (P = .01) than astrocytomas. Multivariate analyses demonstrated improved OS for gross total resection (GTR) vs subtotal resection (STR; P = .006, hazard ratio [HR]: .23) and near total resection (NTR; P = .02, HR: .64). GTR vs STR (P = .02, HR: .54), GTR vs NTR (P = .04, HR: .49), and iMRI use (P = .02, HR: .54) were associated with longer PFS. Frontal (P = .048, HR: 2.11) and occipital/parietal (P = .003, HR: 3.59) locations were associated with shorter PFS (vs temporal). Kaplan-Meier analyses showed longer OS with increasing extent of surgical resection (EOR) (P = .03) and 1p/19q gene deletions (P = .02). PFS improved with increasing EOR (P = .01), GTR vs NTR (P = .02), and resections above STR (P = .04). Factors influencing adjuvant treatment (35.3% of patients) included age (P = .002, odds ratio [OR]: 1.04) and EOR (P = .003, OR: .39) but not glioma subtype or location. Additional tumor resection after iMRI was performed in 105/159 (66%) iMRI cases, yielding GTR in 54.5% of these instances.

CONCLUSION

EOR is a major determinant of OS and PFS for patients with grade II astrocytomas and oligodendrogliomas. Intraoperative MRI may improve EOR and was associated with increased PFS.

The Ethical Dilemma in the Surgical Management of Low Grade Gliomas According to the Variable Availability of Resources and Surgeon Experience

Low grade gliomas (LGGs) affect young individuals in the prime of life. Management may alternatively include biopsy and observation or surgical resection. Recent evidence strongly favors maximal and supramaximal resection of LGGs in optimizing survival metrics. Awake craniotomy with cortical mapping and electrical stimulation along with other preoperative and intraoperative surgical adjuncts, including intraoperative magnetic resonance and diffusion tensor imaging, facilitates maximization of resection and eschews precipitating neurological deficits. Intraoperative imaging permits additional resection of identified residual to be completed within the same surgical session, improving extent of resection and consequently progression free and overall survival. These resources are available in only a few centers throughout the United States, raising an ethical dilemma as to where patients harboring LGGs should most appropriately be treated.

Loss of efficacy of subsequent nonsurgical therapy after primary treatment failure in pediatric low-grade glioma patients-Report from the German SIOP-LGG 2004 cohort

First-line treatment of pediatric low-grade glioma using surgery, radio- or chemotherapy fails in a relevant proportion of patients. We analyzed efficacy of subsequent surgical and nonsurgical therapies of the German cohort of the SIOP-LGG 2004 study (2004-2012, 1558 registered patients; median age at diagnosis 7.6 years, median observation time 9.2 years, overall survival 98%/96% at 5/10 years, 15% neurofibromatosis type 1 [NF1]). During follow-up, 1078/1558 patients remained observed without (n = 217), with 1 (n = 707), 2 (n = 124) or 3 to 6 (n = 30) tumor volume reductions; 480/1558 had 1 (n = 332), 2 (n = 80), 3 or more (n = 68) nonsurgical treatment-lines, accompanied by up to 4 tumor-reductive surgeries in 215/480; 265/480 patients never underwent any neurosurgical tumor volume reduction (163/265 optic pathway glioma). Patients with progressing tumors after first-line adjuvant treatment were at increased risk of suffering further progressions. Risk factors were young age (<1 year) at start of treatment, tumor dissemination or progression within 18 months after start of chemotherapy. Progression-free survival rates declined with subsequent treatment-lines, yet remaining higher for patients with NF1. In non-NF1-associated tumors, vinblastine monotherapy vs platinum-based chemotherapy was noticeably less effective when used as second-line treatment. Yet, for the entire cohort, results did not favor a certain sequence of specific treatment options. Rather, all can be aligned as a portfolio of choices which need careful balancing of risks and benefits. Future molecular data may predict long-term tumor biology.

Intraoperative MRI versus 5-ALA in high-grade glioma resection: a network meta-analysis

OBJECTIVE

High-grade gliomas (HGGs) continue to carry poor prognoses, and patient outcomes depend heavily on the extent of resection (EOR). The utility of conventional image-guided surgery is limited by intraoperative brain shift. More recent techniques to maximize EOR, including intraoperative imaging and the use of fluorescent dyes, combat these limitations. However, the relative efficacy of these two techniques has never been systematically compared. Thus, the authors performed an exhaustive systematic review in conjunction with quantitative network meta-analyses to evaluate the comparative effectiveness of 5-aminolevulinic acid (5-ALA) and intraoperative MRI (IMRI) in optimizing EOR in HGG. They secondarily analyzed associated progression-free and overall survival and performed subgroup analyses by level of evidence.

METHODS

PubMed, Embase, Cochrane Central, and Web of Science were searched for studies evaluating conventional neuronavigation, IMRI, and 5-ALA in HGG resection. The primary study endpoint was the proportion of patients attaining gross-total resection (GTR), defined as 100% elimination of contrast-enhancing lesion on postoperative MRI. Secondary endpoints included overall and progression-free survival and subgroup analyses for level of evidence. Comparative efficacy analysis of IMRI and 5-ALA was performed using Bayesian network meta-analysis models.

RESULTS

This analysis included 11 studies. In a classic meta-analysis, both IMRI (OR 4.99, 95% CI 2.65-9.39, p < 0.001) and 5-ALA (OR 2.866, 95% CI 2.127-3.863, p < 0.001) were superior to conventional navigation in achieving GTR. Bayesian network analysis was employed to indirectly compare IMRI to 5-ALA, and no significant difference in GTR was found between the two (OR 1.9 favoring IMRI, 95% CI 0.905-3.989, p = 0.090). A handful of studies additionally suggested that the use of either IMRI (2 and 4 studies, respectively) or 5-ALA (2 and 2 studies, respectively) improves progression-free and overall survival.

CONCLUSIONS

IMRI and 5-ALA are individually superior to conventional neuronavigation for achieving GTR of HGG. Between IMRI and 5-ALA, neither method is clearly more effective. Future studies evaluating the comparative cost and surgical time associated with IMRI and 5-ALA will better inform any cost-benefit analysis.

A Multi-Institutional Analysis of Factors Influencing Surgical Outcomes for Patients with Newly Diagnosed Grade I Gliomas

OBJECTIVE

To assess the impact of intraoperative magnetic resonance imaging (iMRI), extent of resection (EOR), and other factors on overall survival (OS) and progression-free survival (PFS) for patients with newly diagnosed grade I gliomas.

METHODS

A multicenter database was queried to identify patients with grade I gliomas. Retrospective analyses assessed the impact of patient, treatment, and tumor characteristics on OS and PFS.

RESULTS

A total of 284 patients underwent treatment for grade I gliomas, including 248 resections (205 with iMRI, 43 without), 23 biopsies, and 13 laser interstitial thermal therapy treatments. Log-rank analyses of Kaplan-Meier plots showed improved 5-year OS (P = 0.0107) and PFS (P = 0.0009) with increasing EOR, and a trend toward improved 5-year OS for patients with lower American Society of Anesthesiologists score (P = 0.0528). Greater EOR was associated with significantly increased 5-year PFS for pilocytic astrocytoma (P < 0.0001), but not for ganglioglioma (P = 0.10) or dysembryoplastic neuroepithelial tumor (P = 0.57). Temporal tumors (P = 0.04) and location of "other" (P = 0.04) were associated with improved PFS, and occipital/parietal tumors (P = 0.02) were associated with decreased PFS compared with all other locations. Additional tumor resection was performed after iMRI in 49.7% of cases using iMRI, which produced gross total resection in 64% of these additional resection cases.

CONCLUSIONS

Patients with grade I gliomas have extended OS and PFS, which correlates positively with increasing EOR, especially for patients with pilocytic astrocytoma. iMRI may increase EOR, indicated by the rate of gross total resection after iMRI use but was not independently associated with increased OS or PFS.

Technical limitations and pitfalls of diffusion-weighted imaging in intraoperative high-field MRI

OBJECTIVE

Image quality in high-field intraoperative MRI (iMRI) is often influenced negatively by susceptibility artifacts. While routine sequences are rather robust, advanced imaging such as diffusion-weighted imaging (DWI) is very sensitive to susceptibility resulting in insufficient imaging data. This study aims to analyze intraoperatively acquired DWI to identify the main factors for susceptibility, to compare results with postoperative images and to identify technical aspects for improvement of intraoperative DWI.

METHODS

100 patients with intraaxial lesions operated in a high-field iMRI were analyzed retrospectively for the quality of intraoperative DWI in comparison to the postoperative scan. General quality of the MR scan, individual diffusion restrictions, artifacts, and their causes were analyzed.

RESULTS

Inclusion criteria were met in 78 patients, 124 diffusion restrictions were included in the comparative analysis. PPV and NPV for the detection of DWI changes intraoperatively were 0.94 and 0.56, respectively (SEN 0.94; SPE 0.56). Image quality was rated significantly (p < 0.0001) worse intraoperatively compared to the postoperative MRI. The main reasons for reduced image quality intraoperatively were air (64%) and artificial material (e.g., compress) (38%) in the resection cavity, as well as positioning of patient's head outside the MR's isocenter 37%. Analysis of surgical approaches showed that frontal craniotomies have the highest risk of limited image quality (40%), whereat better results (15% limited image quality) were seen for all other approaches (p = 0.059).

CONCLUSION

Intraoperative DWI showed reliable results in this analysis. However, image-quality was limited severely in many cases leading to uncertainty in the interpretation. Susceptibility-causing factors might be prevented in many cases, if the surgical team is aware of them. The most important factors are good filling of the resection cavity with irrigation fluid, not placing artificial materials in the resection cavity and adequate positioning of patient's head according to the MR isocenter.

Identification of tumor residuals in pituitary adenoma surgery with intraoperative MRI: do we need gadolinium?

OBJECTIVE

To evaluate the diagnostic accuracy of high-resolution T2w intraoperative magnetic resonance imaging (iMRI) for detecting pituitary adenoma remnants compared to contrast-enhanced T1-weighted images.

METHODS

42 patients underwent iMRI-guided resection of large pituitary macroadenomas and fulfilled the inclusion criteria for this retrospective analysis. Intraoperative and postoperative imaging evaluation of tumor residuals and localization were assessed by two experienced neuroradiologists in a blinded fashion. The diagnostic accuracy of T2w and contrast-enhanced T1w images were evaluated.

RESULTS

The diagnostic accuracy for detecting tumor residuals of high-resolution T2w images showed highly significant association to contrast-enhanced T1w images (p < 0.0001). Furthermore, identification rate of tumor remnants in different compartments, e.g., cavernous sinus, was comparable. In total, coronal T2w images provided a diagnostic sensitivity of 97.7% and specificity of 100% compared to the gold standard of contrast-enhanced T1w images. The postoperatively expected extent of resection proved to be true in 97.6% according to MRI 3 months after resection.

CONCLUSIONS

High-resolution T2w intraoperative MR images provide excellent diagnostic accuracy for detecting tumor remnants in macroadenoma surgery with highly significant association compared to T1w images with gadolinium. The routine-use and need of gadolinium in these patients should be questioned critically in each case in the future.

Use of an Offsite Intraoperative MRI Operating Theater for Pediatric Brain Tumor Surgery: Experience from a Singapore Children's Hospital

BACKGROUND

Intraoperative magnetic resonance imaging (iMRI) has been recognized as a useful adjunct for brain tumor surgery in pediatric patients. There is minimal data on the use of an offsite intraoperative magnetic resonance imaging operating theater (iMRI OT), whereby vehicle transfer of patients is involved. The primary aim of this study is to validate the feasibility of perioperative patient transfer to use an offsite iMRI OT for patients with pediatric brain tumor. Secondary objectives include the assessment of tumor resection efficacy and perioperative outcomes in our patient cohort.

METHODS

This is a retrospective, single-institution clinical study of prospectively collected data from Singapore's largest children hospital. Variables of interest include issues encountered during interhospital transfer, achievement of surgical aims, length of stay in hospital, and postoperative complications. Our findings were compared with results of related studies published in the literature.

RESULTS

From January 1, 2009 to December 31, 2018, a total of 35 pediatric operative cases were performed in our offsite iMRI OT. Within this cohort, 24 of these were brain tumor surgery cases. For all the patients in this study, use of the iMRI OT influenced intraoperative decisions. Average ambulance transport time from parent hospital to the iMRI OT was 30.5 minutes, and from iMRI OT back to the parent hospital after surgery was 27.7 minutes. The average length of hospitalization stay was 7.9 days per patient. There were no ferromagnetic accidents during perioperative iMRI scanning and no airway/hemodynamic incidents in patients encountered during interhospital transfer.

CONCLUSIONS

In our local context, the use of interhospital transfers for access to iMRI OT is a safe and feasible option in ensuring good patient outcomes for a select group of patients with pediatric brain tumors.

The utility of intraoperative MRI during pediatric brain tumor surgery: a single-surgeon case series

OBJECTIVE

The authors sought to evaluate the utility of intraoperative MRI (ioMRI) during brain tumor excision in pediatric patients and to suggest guidelines for its future use.

METHODS

All patients who underwent brain tumor surgery by the senior author at Boston Children's Hospital using ioMRI between 2005 and 2009 were included in this retrospective review of hospital records and the neurosurgeon's operative database. Prior to the review, the authors defined the utility of ioMRI into useful and not useful categories based on how the technology affected operative management. They determined that ioMRI was useful if it 1) effectively guided the extent of resection; 2) provided a baseline postoperative scan during the same anesthesia session; or 3) demonstrated or helped to prevent an intraoperative complication. The authors determined that ioMRI was not useful if 1) the anatomical location of the tumor had precluded a tumor's total resection, even though the surgeon had employed ioMRI for that purpose; 2) the tumor's imaging characteristics prevented an accurate assessment of resection during intraoperative imaging; 3) the surgeon deemed the technology not required for tumor resection; or 4) the intraoperative MR images were uninterpretable for technical reasons. Follow-up data provided another gauge of the long-term benefit of ioMRI to the patient.

RESULTS

A total of 53 brain tumor patients were operated on using ioMRI, 6 of whom had a second ioMRI procedure during the study period. Twenty-six patients were female, and 27 were male. The mean follow-up was 4.8 ± 3.85 years (range 0-12 years). By the criteria outlined above, ioMRI technology was useful in 38 (64.4%) of the 59 cases, most frequently for its help in assessing extent of resection.

CONCLUSIONS

Intraoperative MRI technology was useful in the majority of brain tumor resections in this series, especially in those tumors that were contrast enhancing and located largely within accessible areas of the brain. The percentage of patients for whom ioMRI is useful could be increased by preoperatively evaluating the tumor's imaging characteristics to determine if ioMRI would accurately assess the extent of tumor resection, and by the surgeon's preoperative understanding that use of the ioMRI will not lead to resection of an anatomically unresectable tumor. The ioMRI can prove useful in unresectable tumors if specific operative goals are defined preoperatively.

Speckle modulation enables high-resolution wide-field human brain tumor margin detection and in vivo murine neuroimaging

Current in vivo neuroimaging techniques provide limited field of view or spatial resolution and often require exogenous contrast. These limitations prohibit detailed structural imaging across wide fields of view and hinder intraoperative tumor margin detection. Here we present a novel neuroimaging technique, speckle-modulating optical coherence tomography (SM-OCT), which allows us to image the brains of live mice and ex vivo human samples with unprecedented resolution and wide field of view using only endogenous contrast. The increased visibility provided by speckle elimination reveals white matter fascicles and cortical layer architecture in brains of live mice. To our knowledge, the data reported herein represents the highest resolution imaging of murine white matter structure achieved in vivo across a wide field of view of several millimeters. When applied to an orthotopic murine glioblastoma xenograft model, SM-OCT readily identifies brain tumor margins with resolution of approximately 10 μm. SM-OCT of ex vivo human temporal lobe tissue reveals fine structures including cortical layers and myelinated axons. Finally, when applied to an ex vivo sample of a low-grade glioma resection margin, SM-OCT is able to resolve the brain tumor margin. Based on these findings, SM-OCT represents a novel approach for intraoperative tumor margin detection and in vivo neuroimaging.

Evaluation of pediatric glioma outcomes using intraoperative MRI: a multicenter cohort study

BACKGROUND

The use of intraoperative MRI (iMRI) during treatment of gliomas may increase extent of resection (EOR), decrease need for early reoperation, and increase progression-free and overall survival, but has not been fully validated, particularly in the pediatric population.

OBJECTIVE

To assess the accuracy of iMRI to identify residual tumor in pediatric patients with glioma and determine the effect of iMRI on decisions for resection, complication rates, and other outcomes.

METHODS

We retrospectively analyzed a multicenter database of pediatric patients (age ≤ 18 years) who underwent resection of pathologically confirmed gliomas.

RESULTS

We identified 314 patients (mean age 9.7 ± 4.6 years) with mean follow-up of 48.3 ± 33.6 months (range 0.03-182.07 months) who underwent surgery with iMRI. There were 201 (64.0%) WHO grade I tumors, 57 (18.2%) grade II, 24 (7.6%) grade III, 9 (2.9%) grade IV, and 23 (7.3%) not classified. Among 280 patients who underwent resection using iMRI, 131 (46.8%) had some residual tumor and underwent additional resection after the first iMRI. Of the 33 tissue specimens sent for pathological analysis after iMRI, 29 (87.9%) showed positive tumor pathology. Gross total resection was identified in 156 patients (55.7%), but this was limited by 69 (24.6%) patients with unknown EOR.

CONCLUSIONS

Analysis of the largest multicenter database of pediatric gliomas resected using iMRI demonstrated additional tumor resection in a substantial portion of cases. However, determining the impact of iMRI on EOR and outcomes remains challenging because iMRI use varies among providers nationally. Continued refinement of iMRI techniques for use in pediatric patients with glioma may improve outcomes.

Open resection of hypothalamic hamartomas for intractable epilepsy revisited, using intraoperative MRI

INTRODUCTION

Hypothalamic hamartomas (HHs) are rare non-neoplastic lesions which cause drug-resistant epilepsy with associated behavioural, psychiatric and endocrine issues. With the development of new minimally invasive techniques for the treatment of HH, there is a need to reappraise the effectiveness and safety of each approach. We review the outcomes of HH patients treated surgically, utilizing intraoperative magnetic resonance imaging (IOMRI), by a team of Alder Hey NHS Foundation Trust tumour and epilepsy neurosurgeons since 2011.

METHODS

Patient records of all HH cases operated on since 2011 were reviewed to confirm history of presentation and clinical outcomes.

RESULTS

Ten patients have undergone surgery for HH under the dual care of Alder Hey tumour and epilepsy neurosurgeons during this period. Eight cases had a midline transcallosal, interforniceal approach with the remaining 2 having a transcallosal, transforaminal approach. All patients had an IOMRI scan, with 40% needing further tumour resection post-IOMRI. Forty percent had a total resection, 3 patients had near-total resection and 3 patients had subtotal resection (~ 30% tumour residual on post-operative MRI). No new neurological complications developed post-operatively. Hypothalamic axis derangements were seen in 3 cases, including 1 diabetes insipidus with hypocortisolaemia, 1 hypodipsia and 1 transient hyperphagia. Eighty percent are seizure free; the remaining two patients have had significant improvements in seizure frequency.

CONCLUSIONS

IOMR was used to tailor the ideal tumour resection volume safely based on anatomy of the lesion, which combined with the open transcallosal, interforniceal route performed by surgeons experienced in the approach resulted in excellent, safe and effective seizure control.

The impact of intraoperative magnetic resonance in routine pediatric neurosurgical practice-a 6-year appraisal

BACKGROUND

The intraoperative magnetic resonance scanner (ioMR) was introduced in our unit in 2009, and has been used routinely since then.

OBJECTIVE

This study aims to describe indications, radiological features, and clinical outcomes of the patients operated on with ioMRI and analyze our experience.

METHODS

A retrospective analysis of a prospective surgical database has been performed, including surgical procedure, intent, radiological reports, need for second-look surgery, and complications, supplemented by further review of the clinical notes and the scans.

RESULTS

From 2009 to 2015, 255 surgical procedures with ioMR were performed: 175 were craniotomies for tumor excision, 65 were epilepsy related, and 15 were biopsies or cyst drainages. The mean age was 9.4 years. One ioMR was performed in 79.5% patients; the mean duration of the MR was 41 min. In 172 cases (67.4%), no actions followed the ioMR. When the aim of the surgery was debulking of the tumor, the percentage of patients in which the ioMR was followed by resection was higher than when complete resection was the aim (56 vs 27.5%). The complication rate was not increased when compared with our previous results (infection 1%, neurological deficits 12%).

CONCLUSION

This is the largest published series of ioMRI-aided pediatric neurosurgery to date. We have demonstrated that it can be used safely and routinely in pediatric neurosurgical procedures at any age, assisting the surgeon in achieving the best extent of resection and aiding in intra-operative decision-making for tumor- and non-tumor-related intracranial pathology.

Lumbar puncture-administered resveratrol inhibits STAT3 activation, enhancing autophagy and apoptosis in orthotopic rat glioblastomas

Trans-resveratrol suppresses glioblastoma growth in vitro, but its effects on intracranial glioblastomas remain untested. Resveratrol crosses the blood–brain barrier, and lumbar puncture (LP) greatly increases its bioavailability in rat brains; therefore, we investigated the effectiveness of LP-administered resveratrol on orthotopic rat glioblastomas. Twenty-four tumor-bearing rats were separated into two groups: Group 1 receiving 100 μl saline containing 0.3% DMSO and Group 2 receiving 100 μl resveratrol (300 μM). Treatments started 3 days after transplantation in 2-day intervals until death. Intracranial drug availabilities, tumor sizes, average life spans and the impacts on STAT3 signaling, apoptosis and autophagy rates were evaluated. MRI imaging revealed that average tumor size in the LP group (495.8 ± 22.3 mm²) was smaller than the control groups (810.3 ± 56.4 mm²; P<0.05). The mean survival time in the LP group (22.2 ± 2.1 d) was longer than control animals (16.0 ± 1.8 d; P<0.05). LP resveratrol-treated glioblastomas showed less Cyclin D1 staining, enhanced autophagy with up-regulated LC3 and Beclin1 expression, and widely distributed apoptotic foci around tumor capillaries with suppressed STAT3 expression and nuclear translocation. In conclusion, LP-delivered resveratrol efficiently inhibited orthotopic rat glioblastoma growth by inactivating STAT3 signaling and enhancing autophagy and apoptosis.

Safety, Utility, and Clinical Results of Continuous Intraoperative Electrophysiologic Monitoring in 1.5T iMRI-Guided Surgery

OBJECTIVE

To show that the combined use of intraoperative high-field MRI (iMRI) and electrophysiologic monitoring (IOM) is feasible, safe, and beneficial for patients.

METHODS

The setup, surgical, imaging, and clinical results of 110 patients with eloquent intracranial lesions with the combined use of 1.5T iMRI and IOM were analyzed.

RESULTS

187 iMRI scans were performed with IOM needles in place, resulting in a total experience of using >4000 electrodes in the iMRI. No complication (ferromagnetic or relevant heating/burning of skin) was caused by the combined use of both technologies. Surgically induced severe postoperative sensorimotor deficits were seen in 11.8%. The surgeon's estimation of a "complete resection" proved to be true postoperatively in 90.3%. If the resection was stopped due to worsening of IOM, postoperative MRI revealed residual disease to be located in direct vicinity of eloquence in 27 of 28 cases, but not in other parts of the resection cavity. Of these patients, only 7% (2 of 28) had relevant new deficits after 3 months. In 82 patients (74.5%), the resection was continued after the iMRI scan, whereas in only 18 patients (16.4%) the resection was already completed at this point.

CONCLUSION

The combined use of IOM and 1.5T iMRI is feasible and safe. The complementary use of both technologies might result in more radical resections at comparable surgically induced neurologic deficits. If available and indicated, the combined use of IOM and iMRI should be performed on a routine basis.

Neurosurgical tools to extend tumor resection in pediatric hemispheric low-grade gliomas: iMRI

INTRODUCTION

The treatment of low-grade gliomas (LGGs) in pediatric age is still controversial. However, most authors report longer life expectancy in case of completely removed cerebral gliomas. Intraoperative magnetic resonance imaging (iMRI) is increasingly utilized in the surgical management of intra-axial tumor in adults following the demonstration of its effectiveness. In this article, we analyze the management of LGG using iMRI focusing on its impact on resection rate and its limits in the pediatric population.

METHODS

We performed review of the literature regarding the treatment of LGG using iMRI focusing on its impact on resection rate and its limits in the pediatric population. Some exemplary cases are also described.

RESULTS

Intraoperative MRI allowed extension of tumor resection after the depiction of residual tumor at the intraoperative imaging control from 21 to 52 % of the cases in the published series. Moreover, the early reoperation rate was significantly lower when compared with the population treated without this tool (0 % vs 7-14 %). Some technical difficulties have been described in literature regarding the use of iMRI in the pediatric population especially for positioning due to the structure of the headrest coil designed for adult patients.

CONCLUSION

The analysis of the literature and our own experience with iMRI in children indicates significant advantages in the resection of LGG offered by the technique. All these advantages are obtained without elongation of the surgical times or increased risk for complications, namely infection. The main limit for a wider diffusion of iMRI for the pediatric neurosurgical center is the cost required, for acquisition of the system, especially for high-field magnet, and the environmental and organizational changes necessary for its use.