Application of Multiparametric Intraoperative Ultrasound in Glioma Surgery

Concordance of Extent of Resection Between Intraoperative Ultrasound and Postoperative MRI in Brain and Spine Tumor Resection

Objective Evaluate the utility of intraoperative ultrasound (IOUS) in brain and spinal tumor resections and the concordance of the extent of resection between IOUS and postoperative magnetic resonance imaging (MRI). Methods A retrospective analysis of prospectively collected data was performed. Thirty-nine lesions (36 patients) in the brain and spine were operated on for resection using IOUS between May 2020 and December 2022. All patients who underwent brain or spinal tumor resection were included, and who underwent IOUS during tumor resection and postoperative MRI was done within 48 hours of surgery. The Cohen's kappa coefficient was performed to the concordance of resection by IOUS and postoperative MRI. Results Forty-one patients underwent surgery, of which 36 met the inclusion criteria and five were excluded due to incomplete clinical records. Of the 36 patients included, two presented lesions in different locations, one with frontal and parietal metastases and the other with extradural and intradural spinal lesions, and one patient had a recurrence of glioblastoma, for which 39 procedures were included. Of the 36 patients, 36% were women, and the average age was 51.4 years with an age range of one year and two months to 94 years. The concordance of the degree of resection by ultrasound and the degree of resection by postoperative magnetic resonance is high. Conclusions The higher degree of concordance between IOUS and postoperative MRI would suggest that IOUS is a reliable tool for assessing the extent of tumor resection during surgery and provides real-time information to make decisions to adjust surgery plans based on the benefit/risk ratio.

Approach to a cerebral hernia caused by an intratumoral hemorrhage of a cystic oligodendroglioma: a case report

The incidence of cerebral herniation caused by intratumoral hemorrhage (ITH) in cystic oligodendroglioma (COD) is exceedingly rare. This study presents a case of cerebral herniation subsequent to cystic oligodendroglioma (COD) and sudden intratumoral hemorrhage. Following initial emergency treatment and evaluation, we successfully circumvented the solid component of the tumor and proceeded with cystic puncture and external drainage to prevent the incidence of brain herniation and mitigate the severity of associated symptoms. Based on preoperative examination results, the cystic glioma was successfully resected, and the patient experienced an uneventful recovery. According to the pathological findings, the oligodendroglioma was classified as World Health Organization (WHO) grade III. The treatment efficacy was comparable to cases of the same pathological grade, in which neither intratumoral hemorrhage nor cerebral hernia was observed.

Advances in Intraoperative Glioma Tissue Sampling and Infiltration Assessment

Gliomas are infiltrative brain tumors that often involve functional tissue. While maximal safe resection is critical for maximizing survival, this is challenged by the difficult intraoperative discrimination between tumor-infiltrated and normal structures. Surgical expertise is essential for identifying safe margins, and while the intraoperative pathological review of frozen tissue is possible, this is a time-consuming task. Advances in intraoperative stimulation mapping have aided surgeons in identifying functional structures and, as such, has become the gold standard for this purpose. However, intraoperative margin assessment lacks a similar consensus. Nonetheless, recent advances in intraoperative imaging techniques and tissue examination methods have demonstrated promise for the accurate and efficient assessment of tumor infiltration and margin delineation within the operating room, respectively. In this review, we describe these innovative technologies that neurosurgeons should be aware of.

Application of intraoperative ultrasound in the resection of high-grade gliomas

The incidence of gliomas is approximately 3-5/100,000, with high-grade gliomas accounting for approximately 30-40% of these tumors. Surgery is a confirmed positive factor in prolonging the survival of these patients, and a larger resection range means a longer survival time. Therefore, surgery for high-grade glioma patients should aim to maximize the extent of resection while preserving neurological function to achieve a better quality of life. There is consensus regarding the need to lengthen progression-free survival (PFS) and overall survival (OS) times. In glioma surgery, methods such as intraoperative computed tomography (ICT), intraoperative magnetic resonance imaging (IMRI), navigation, 5-aminolevulinic acid (5-ALA), and intraoperative ultrasound (IOUS) are used to achieve an expanded resection during the surgical procedure. IOUS has been increasingly used in the surgery of high-grade gliomas and various tumors due to its convenient intraoperative use, its flexible repeatability, and the relatively low cost of operating room construction. With the continuous upgrading of ultrasound equipment, IOUS has been able to better assist surgeons in achieving an increased extent of resection. This review aims to summarize the application of ultrasound in the surgery of high-grade gliomas in the past decade, its improvement in patient prognosis, and its prospects.

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.

A review on surgical treatment options in gliomas

Gliomas are one of the most common primary central nervous system tumors, and surgical treatment remains the principal role in the management of any grade of gliomas. In this study, based on the introduction of gliomas, we review the novel surgical techniques and technologies in support of the extent of resection to achieve long-term disease control and summarize the findings on how to keep the balance between cytoreduction and neurological morbidity from a list of literature searched. With modern neurosurgical techniques, gliomas resection can be safely performed with low morbidity and extraordinary long-term functional outcomes.

Contrast-Enhanced Ultrasound in Resection of Spinal Cord Gliomas

BACKGROUND

Intraoperative contrast-enhanced ultrasound (iCEUS) is a relatively new technique for visualizing brain gliomas and can help achieve maximum resection, but its potential in evaluation of spinal cord gliomas has not been well defined. The aim of this study was to describe the iCEUS characterization of and evaluate its role in visualizing intramedullary gliomas.

METHODS

A retrospective review of patients who underwent intramedullary glioma resection with iCEUS guidance from 2019 to 2021 was conducted. An offline analysis was performed to compare and characterize the perfusion features of each glioma.

RESULTS

This study included 36 patients who underwent iCEUS for spinal cord gliomas. iCEUS was performed successfully, and all gliomas were clearly identified. The distribution of contrast agent showed different dynamic phases (arterial, peak, and washout) from those observed in brain gliomas, generally appearing slower and less intense in spinal cord gliomas. iCEUS helped highlight intramedullary gliomas, each of which demonstrated specific iCEUS features depending on the grade. Gross total resection was achieved in 20 patients (55.6%), subtotal resection was achieved in 11 patients (30.6%), and partial resection was achieved in 5 patients (13.8%).

CONCLUSIONS

ICEUS adds valuable information in highlighting spinal cord gliomas in real time. It allows the neurosurgeon to assess the anatomical location of the glioma and delineate the tumor margins. iCEUS could play a potentially important role in guiding spinal cord glioma resection. Further study with more cases is needed to better understand the microbubble distribution dynamics in intramedullary gliomas.

Ultrasound-Oriented Surgical Planning ("UOSP") for Intracranial Lesions: A Systematic Integration to the Standard Preoperative Planning

OBJECTIVE

Intraoperative ultrasound (iUS) is a well-established technique whose aim is to provide real-time visualization of deep lesions during brain surgery. The lack of definition of anatomic semeiotics and the unusual direction of the insonation plane make interpretation and orientation challenging for the surgeon who newly approaches to such a tool. We propose a novel protocol to be applied during the surgical planning for intracranial lesions surgery, a so-called ultrasound-oriented surgical planning ("UOSP") protocol, and we provide a retrospective analysis of 21 patients who underwent surgery for an intracranial lesion in which UOSP was applied. To further enlighten different surgical orientation strategies and possible limitations given by the technique, we discuss 3 illustrative cases assigned to 3 categories ("basic," "intermediate," and "challenging" lesions) with progressively growing difficulty in anatomic orientation during a surgical procedure.

METHODS

A total of 21 patients operated between March 2021 and July 2021 and where the UOSP protocol was applied during surgical planning were evaluated retrospectively. The UOSP protocol was performed the days before the surgical intervention by the same surgical team.

RESULTS

The UOSP protocol was successfully applied in all 21 patients. In all cases, the preoperative imaging obtained during surgical planning corresponded to the images observed during the application of iUS.

CONCLUSIONS

The introduction of the UOSP protocol during the planification of the surgical intervention for an intracerebral lesion may serve as a key factor to overcome the actual limitations inherent to the iUS technique. Utilization of this protocol may facilitate wider use of iUS in neurosurgery.

Intraoperative ultrasound in recurrent gliomas surgery: Impact on residual tumor volume and patient outcomes

Background

Reoperation may be beneficial for patients with recurrent gliomas. Minimizing the residual tumor volume (RTV) while ensuring the functionality of relevant structures is the goal of the reoperation of recurrent gliomas. Intraoperative ultrasound (IoUS) may be helpful for intraoperative tumor localization, intraoperative real-time imaging to guide surgical resection, and postoperative evaluation of the RTV in the reoperation for recurrent gliomas.

Objective

To assess the effect of real-time ioUS on minimizing RTV in recurrent glioma surgery compared to Non-ioUS.

Methods

We retrospectively analyzed the data from 92 patients who had recurrent glioma surgical resection: 45 were resected with ioUS guidance and 47 were resected without ioUS guidance. RTV, Karnofsky Performance Status (KPS) at 6 months after the operation, the number of recurrent patients, and the time to recurrence were evaluated.

Results

The average RTV in the ioUS group was significantly less than the Non-ioUS group (0.27 cm³ vs. 1.33 cm³, p = 0.0004). Patients in the ioUS group tended to have higher KPS scores at 6 months of follow-up after the operation than those in the Non-ioUS group (70.00 vs. 60.00, p = 0.0185). More patients in the Non-ioUS group experienced a recurrence than in the ioUS group (43 (91.49%) vs. 32 (71.11%), p = 0.0118). The ioUS group had a longer mean time to recurrence than the Non-ioUS group (7.9 vs. 6.3 months, p = 0.0013).

Conclusion

The use of ioUS-based real-time for resection of recurrent gliomas has been beneficial in terms of both RTV and postoperative outcomes, compared to the Non-ioUS group.

MRI-Based Risk Assessment for Incomplete Resection of Brain Metastases

Object

Recent studies demonstrated that gross total resection of brain metastases cannot always be achieved. Subtotal resection (STR) can result in an early recurrence and might affect patient survival. We initiated a prospective observational study to establish a MRI-based risk assessment for incomplete resection of brain metastases.

Methods

All patients in whom ≥1 brain metastasis was resected were prospectively included in this study (DRKS ID: DRKS00021224; Nov 2020 - Nov 2021). An interdisciplinary board of neurosurgeons and neuroradiologists evaluated the pre- and postoperative MRI (≤48h after surgery) for residual tumor. Extensive neuroradiological analyses were performed to identify risk factors for an unintended STR which were integrated into a regression tree analysis to determine the patients' individual risk for a STR.

Results

We included 150 patients (74 female; mean age: 61 years), in whom 165 brain metastases were resected. A STR was detected in 32 cases (19.4%) (median residual tumor volume: 1.36ml, median EOR_rel: 93.6%), of which 6 (3.6%) were intended STR (median residual tumor volume: 3.27ml, median EOR_rel: 67.3%) - mainly due to motor-eloquent location - and 26 (15.8%) were unintended STR (uSTR) (median residual tumor volume: 0.64ml, median EOR_rel: 94.7%). The following risk factors for an uSTR could be identified: subcortical metastasis ≥5mm distant from cortex, diffuse contrast agent enhancement, proximity to the ventricles, contact to falx/tentorium and non-transcortical approaches. Regression tree analysis revealed that the individual risk for an uSTR was mainly associated to the distance from the cortex (distance ≥5mm vs. <5mm: OR 8.0; 95%CI: 2.7 - 24.4) and the contrast agent patterns (diffuse vs. non-diffuse in those with distance ≥5mm: OR: 4.2; 95%CI: 1.3 - 13.7). The preoperative tumor volume was not substantially associated with the extent of resection.

Conclusions

Subcortical metastases ≥5mm distant from cortex with diffuse contrast agent enhancement showed the highest incidence of uSTR. The proposed MRI-based assessment allows estimation of the individual risk for uSTR and can help indicating intraoperative imaging.

Ultrasound-triggered drug delivery for glioma therapy through gambogic acid-loaded nanobubble-microbubble complexes

Glioma is one of the most common primary brain tumors. Gambogic acid (GA) is widely used in tumor chemotherapy. However, GA has poor water solubility, low bioavailability, and difficult permeability across the blood-brain barrier (BBB), leading to poor efficacy against brain tumors. In our study, we developed negatively charged GA-loaded PLGA nanobubbles [GA/poly(lactic-co-glycolic acid) (PLGA)] and conjugated them onto the surface of cationic lipid microbubbles (CMBs) through electrostatic interactions. The resulting GA/PLGA-CMB complex was characterized for its particle size, distribution, drug encapsulation efficiency, and ultrasound imaging property, revealing a high drug encapsulation efficiency and excellent contrast imaging capability. Importantly, significantly enhanced GA delivery into the brain could be observed after the intravenous administration of GA/PLGA-CMBs combined with low-intensity focused ultrasound (FUS) due to the cavitation from CMBs, which mediated blood-brain barrier (BBB) opening. Taking advantage of the opened BBB, GA/PLGA nanobubbles could be delivered into the tumor. Then, the second FUS irradiation at higher energy was used to induce the cavitation of GA/PLGA nanobubbles, producing the second cavitation on tumor cells, significantly enhancing the ability of GA to enter tumor cells and inhibit tumor growth inhibition efficacy.

Sulci and gyri are topological cerebral landmarks in individual subjects: a study of brain navigation during tumor resection

Surgical resection of brain tumors aims at the maximal safe resection of the pathological tissue with minimal functional impairment. To achieve this objective, reliable anatomical landmarks are indispensable to navigate into the brain. The neuronavigation system can provide information to target the location of the patient's lesion, but after the craniotomy, a brain shift and relaxation mismatch with it often occurs. By contrast, sulci/gyri are topological cerebral landmarks in individual patients and do shift with the brain parenchyma during lesion removal, but remain independent from brain shift in relation to the sulci/gyri. Here we present a case report of a novel strategy based on anatomical landmarks to guide intra-operative brain tumor resection, without using a standard neuronavigation system. A pre-operative brain mapping of the peri-tumoral sulci by the MRI and surface reconstruction was followed by confirmation of the anatomical landmarks for the motor cortex using navigated transcranial magnetic stimulation. The resulting location was used as a seed for diffusion tensor imaging tractography to reconstruct the corticospinal tracts. These selected cortical landmarks (sulci/gyri) delimited the margins of the two lesions and the specific location under which the corticospinal tract courses, thus facilitating monitoring of the peri-tumoral region during brain resection. In this case, 96% of the brain tumor from the peri-central somatomotor region was successfully removed without chronic post-operative motor impairments. This approach is based on cortical anatomy that is fixed during surgery and does not suffer from the brain shift that could misplace the lesion according to the neuronavigation system.

Intraoperative MR Imaging during Glioma Resection

One of the major issues in the surgical treatment of gliomas is the concern about maximizing the extent of resection while minimizing neurological impairment. Thus, surgical planning by carefully observing the relationship between the glioma infiltration area and eloquent area of the connecting fibers is crucial. Neurosurgeons usually detect an eloquent area by functional MRI and identify a connecting fiber by diffusion tensor imaging. However, during surgery, the accuracy of neuronavigation can be decreased due to brain shift, but the positional information may be updated by intraoperative MRI and the next steps can be planned accordingly. In addition, various intraoperative modalities may be used to guide surgery, including neurophysiological monitoring that provides real-time information (e.g., awake surgery, motor-evoked potentials, and sensory evoked potential); photodynamic diagnosis, which can identify high-grade glioma cells; and other imaging techniques that provide anatomical information during the surgery. In this review, we present the historical and current context of the intraoperative MRI and some related approaches for an audience active in the technical, clinical, and research areas of radiology, as well as mention important aspects regarding safety and types of devices.