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

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 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.

Intraoperative low-field magnetic resonance imaging-guided tumor resection in glioma surgery: Pros and cons

BACKGROUNDIntraoperative magnetic resonance imaging (MRI) is useful for identifying residual tumors during surgery. It can improve the resection rate; however, complications related to prolonged operating time may be increased. We assessed the advantages and disadvantages of using low-field intraoperative MRI and compared them with non-use of iMRI during glioma surgery.METHODSThe study included 22 consecutive patients who underwent total tumor resection at Shinshu University Hospital between September 2017 and October 2020. Patients were divided into two groups (before and after introducing 0.4-T low-field open intraoperative MRI at the hospital). Patient demographics, gross total resection (GTR) rate, postoperative neurological deficits, need for reoperation, and operating time were compared between the groups.RESULTSNo significant differences were observed in patient demographics. While GTR of the tumor was achieved in 8/11 cases (73%) with intraoperative MRI, 2/11 cases (18%) of the control group achieved GTR (p=0.033). Seven patients had transient neurological deficits: 3 in the intraoperative MRI group and 4 in the control group, without significant differences between groups. There was no unintended reoperation in the intraoperative MRI group, except for one case in the control group. Mean operating time (465.8 vs. 483.6 minutes for the intraoperative MRI and control groups, respectively) did not differ.CONCLUSIONSLow-field intraoperative MRI improves the GTR rate and reduces unintentional reoperation incidence compared to the conventional technique. Our findings showed no operating time prolongation in the MRI group despite intraoperative imaging, which considered that intraoperative MRI helped reduce decision-making time and procedural hesitation during surgery.

Intraoperative MRI for Brain Tumors

INTRODUCTION

The use of intraoperative imaging has been a critical tool in the neurosurgeon's armamentarium and is of particular benefit during tumor surgery. This article summarizes the history of its development, implementation, clinical experience and future directions.

METHODS

We reviewed the literature focusing on the development and clinical experience with intraoperative MRI. Utilizing the authors' personal experience as well as evidence from the literature, we present an overview of the utility of MRI during neurosurgery.

RESULTS

In the 1990s, the first description of using a low field MRI in the operating room was published describing the additional benefit provided by improved resolution of MRI as compared to ultrasound. Since then, implementation has varied in magnetic field strength and in configuration from floor mounted to ceiling mounted units as well as those that are accessible to the operating room for use during surgery and via an outpatient entrance to use for diagnostic imaging. The experience shows utility of this technique for increasing extent of resection for low and high grade tumors as well as preventing injury to important structures while incorporating techniques such as intraoperative monitoring.

CONCLUSION

This article reviews the history of intraoperative MRI and presents a review of the literature revealing the successful implementation of this technology and benefits noted for the patient and the surgeon.

Elastic Fusion Enables Fusion of Intraoperative Magnetic Resonance Imaging Data with Preoperative Neuronavigation Data

OBJECTIVE

Intraoperative magnetic resonance imaging (iMRI) has been shown to optimize the extent of resection of parenchymal brain tumors. To facilitate the use of preoperative treatment plans after an intraoperative navigation update via iMRI, an elastic image fusion (EIF) algorithm was developed.

METHODS

Ten MRI-iMRI data pairs of patients with brain tumor were evaluated and typical anatomic landmarks were assessed. The pre- and iMRI scans were elastically fused by using a prototype EIF software (Elements Virtual iMRI [Brainlab AG]). For each landmark pair, the Euclidean distance was calculated for rigidly and elastically fused image data.

RESULTS

The Euclidean distance was 2.67 ± 2.62 mm using standard rigid image fusion and 1.8 ± 1.57 mm using our EIF algorithm (P = 0.005). For landmarks near the resected lesion, which were subject to higher anatomic distortion, the Euclidian distances were 4.38 ± 2.51 and 2.52 ± 1.9 mm (P = 0.003).

CONCLUSIONS

This feasibility study shows that EIF can compensate for surgery-related brain shift in a highly significant manner even in this small number of cases. The establishment of an easy applicable and reliable EIF tool integrated in the clinical workflow could open a large variety of new options for image-guided tumor surgery.

Measure thrice, cut twice: On the benefit of reoperation for failed pediatric epilepsy surgery

OBJECTIVE

To determine whether clinical outcomes are improved after repeat surgery for medically refractory epilepsy in children.

METHODS

This is a single-center retrospective cohort analysis of all patients who received repeat resective surgery for ongoing seizures from 2000-2017. From a total of 251 consecutive individual epilepsy surgical patients for focal resection, 53 patients met study inclusion criteria and had adequate follow-up documented.

RESULTS

Median age of seizure-onset was 2.0-years-old (IQR 0.3-5.5 years). The median age at first epilepsy surgery was 6.3-years-old (IQR 2.9-9.2 years) and at second epilepsy surgery was 8.4-years-old (IQR 4.7-12.6 years). Overall, 53 % (n = 28) of this series achieved Engel Class I (seizure freedom); with improved seizure control (Engel Class I-II) in 83 % (n = 44) of the cohort. 64 % (n = 34) had one reoperation; 26 % (n = 14) had two; and 9% (n = 5) had three. Pathology: 58 % (n = 31) had focal cortical dysplasia; 13 % (n = 10) tumor; 9% (n = 5) encephalitis; 6% (n = 3) gliosis; 4% (n = 2) mesial temporal sclerosis; and 2% (n = 1) hemimegalencephaly. Tumor pathology was associated with increased chance (p = 0.01) for seizure freedom (90 % of tumor patients had Engel Class I outcome). MTS had worse outcome with both patients having ongoing seizures (Engel II-IV). There were 6 patients who developed post-operative hemiparesis; one was unplanned but resolved.

SIGNIFICANCE

Reoperation for pediatric epilepsy surgery can lead to seizure freedom in many cases and improved seizure control in most cases. Reoperation for brain tumor pathology is associated with a high rate of seizure freedom.

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.

Can Intraoperative Magnetic Resonance Imaging Be Helpful in the Surgical Resection of Parasellar Meningiomas? A Case Series

OBJECTIVE

The surgery of parasellar meningiomas is crucial. There are only a few reports of the use of intraoperative magnetic resonance imaging (iMRI) for resection of these lesions. We discuss the safety and usefulness of this technique in achieving the planned surgical goal and analyze patients' outcomes.

METHODS

Nineteen cases of parasellar meningioma were treated in our institution using iMRI. We classified the tumors according to their primary location: tuberculum sellae, clinoidal, and cavernous sinus meningiomas. We evaluated the history of previous surgery, outcome, residual (if present) tumor volume, degree of resection, achievement of the surgical goal, and number of iMRI scans.

RESULTS

The preoperative surgical goal was achieved in all patients. In 7 of 19 patients, (37%) further tumor resection was performed after the first iMRI scan. Regarding the cavernous sinus group, the surgical resection was continued after the first iMRI in 56% of patients, obtaining substantial additional volume reduction. No complications were found related to the use of iMRI scan.

CONCLUSIONS

iMRI has been effective in safely increasing the extent of parasellar meningioma resection mainly for recurrent and invasive tumors. Its usefulness has been seen mostly in cavernous sinus lesions, in which it allowed the further safe resection in 56% of cases. Moreover, this tool was particularly useful in recurrent or residual meningiomas with extension in extracranial compartments.

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.

Continuous Dynamic Subcortical Mapping Using a Suction Monopolar Device in a Child: Case Report and Technical Note

Extent of resection is a very important prognostic marker in adult and pediatric brain tumors. Therefore, radical resections confer an oncological benefit. Resection of intra-axial tumors in proximity to eloquent regions requires intraoperative mapping and monitoring. Continuous subcortical mapping using a suction monopolar device has been recently described for adult tumors. This allows a real-time dynamic mapping of the advancing resection cavity walls, synchronized with the surgeon’s actions during resection. We describe the application of this technique in a child who presented with a rapidly increasing right parietal mass. It was resected using this dynamic mapping technique. This is the first such report of its use in a pediatric brain tumor. We also review the relevant literature briefly.