The Significance of Intraoperative Magnetic Resonance Imaging in Resection of Skull Base Chordomas

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.

Intraoperative magnetic resonance imaging in glioma surgery: a single-center experience

PURPOSE

To investigate the effect of intraoperative magnetic resonance imaging (Io MRI) on overall and progression-free survival (OS and PFS), on the extent of resection (EOR) in patients with glioma, and impact of the radiological diagnosis on the decision to continue the surgery when a residual mass was detected on Io MRI.

METHODS

The study comprised 153 glioma patients who received surgical treatment between 2013 and 2023. One-hundred twenty-five of them had Io MRI guidance during surgery. The remainder 28 patients constituted the control group who did not undergo Io MRI. All patients' age at surgery, gender, initial radiological diagnosis, primary tumor localization, EOR, last histopathological diagnosis, and the follow-up periods were recorded.

RESULTS

The rate of tumor recurrence in Io MRI cases was significantly lower compared to the cases in the control group (p < .0001). It was decided to continue the operation in 45 Io MRI applied cases. This raised the gross total resection (GTR) rate from 33.6% to 49.6% in the Io MRI group. The frequency of GTR was significantly higher in patients with an initial radiological diagnosis of low grade glioma than those with high grade glioma. The shortest OS was seen in occipital gliomas.

CONCLUSION

In this study, the convenience provided by the high-field MRI device was explored and proven both in reducing the tumor burden, increasing the PFS, and providing the surgeon with a maximal resection in the first operation.

Skull-Base Surgery—A Narrative Review on Current Approaches and Future Developments in Surgical Navigation

Surgical navigation technology combines patient imaging studies with intraoperative real-time data to improve surgical precision and patient outcomes. The navigation workflow can also include preoperative planning, which can reliably simulate the intended resection and reconstruction. The advantage of this approach in skull-base surgery is that it guides access into a complex three-dimensional area and orients tumors intraoperatively with regard to critical structures, such as the orbit, carotid artery and brain. This enhances a surgeon’s capabilities to preserve normal anatomy while resecting tumors with adequate margins. The aim of this narrative review is to outline the state of the art and the future directions of surgical navigation in the skull base, focusing on the advantages and pitfalls of this technique. We will also present our group experience in this field, within the frame of the current research trends.

Multimodal Intraoperative Image-Driven Surgery for Skull Base Chordomas and Chondrosarcomas

Given the difficulty and importance of achieving maximal resection in chordomas and chondrosarcomas, all available tools offered by modern neurosurgery are to be deployed for planning and resection of these complex lesions. As demonstrated by the review of our series of skull base chordoma and chondrosarcoma resections in the Advanced Multimodality Image-Guided Operating (AMIGO) suite, as well as by the recently published literature, we describe the use of advanced multimodality intraoperative imaging and neuronavigation as pivotal to successful radical resection of these skull base lesions while preventing and managing eventual complications.

Intraoperative Magnetic Resonance Imaging Assisted Endoscopic Endonasal Resection of Clival Chordomas

BACKGROUND

Cranial base chordomas are typically indolent and usually appear as encapsulated tumors. They slowly grow by infiltrating the bone, along with the lines of least resistance. Due to its relationship with important neurovascular structures, skull base chordoma surgery is challenging.

OBJECTIVE

The usefulness of intraoperative magnetic resonance imaging (IO-MRI) in achieving the goal of surgery, is evaluated in this study.

METHODS

Between March 2018 and March 2020, 42 patients were operated on for resection of skull base chordomas in our institution. All of them were operated on under IO-MRI. Patients were analyzed retrospectively for identifying common residue locations, complications and early post-operative outcomes.

RESULTS

In 22 patients (52,4%) gross total resection was achieved according to the final IO-MRI. In 20 patients (47,6%) complete tumor removal was not possible because of extension to the petrous bone (8 patients), pontocerebellar angle (6 patients), prepontine cistern (4 patients), temporobasal (1 patient), cervical axis (1 patient). In 13 patients, the surgery was continued after the first IO-MRI control was performed, which showed a resectable residual tumor. 7 of these patients achieved total resection according to the second IO-MRI, in the other 6 patients all efforts were made to ensure maximal resection of the tumor as much as possible without morbidity. Repeated IO-MRI helped achieve gross total resection in 7 patients (53.8%).

CONCLUSIONS

Our study proves that the use of IO-MRI is a safe method that provides the opportunity to show the degree of resection in skull base chordomas and to evaluate the volume and location of the residual tumor intraoperatively. Hence IO-MRI can improve the life expectancy of patients because it provides an opportunity for both gross total resection and maximal safe resection in cases where total resection is not possible.

Imaging-based navigation technologies in head and neck surgery

PURPOSE OF REVIEW

Image guided navigation has had significant impact in head and neck surgery, and has been most prolific in endonasal surgeries. Although conventional image guidance involves static computed tomography (CT) images attained in the preoperative setting, the continual evolution of surgical navigation technologies is fast expanding to incorporate both real-time data and bioinformation that allows for improved precision in surgical guidance. With the rapid advances in technologies, this article allows for a timely review of the current and developing techniques in surgical navigation for head and neck surgery.

RECENT FINDINGS

Current advances for cross-sectional-based image-guided surgery include fusion of CT with other imaging modalities (e.g., magnetic resonance imaging and positron emission tomography) as well as the uptake in intraoperative real-time 'on the table' imaging (e.g., cone-beam CT). These advances, together with the integration of virtual/augmented reality, enable potential enhancements in surgical navigation. In addition to the advances in radiological imaging, the development of optical modalities such as fluorescence and spectroscopy techniques further allows the assimilation of biological data to improve navigation particularly for head and neck surgery.

SUMMARY

The steady development of radiological and optical imaging techniques shows great promise in changing the paradigm of head and neck surgery.