Intraoperative Real-Time Near-Infrared Image-Guided Surgery to Identify Intracranial Meningiomas via Microscope

Achieving Gross Total Resection in Neurosurgery: A Review of Intraoperative Techniques and Their Influence on Surgical Goals

The definition of complete resection in neurosurgery depends on tumor type, surgical aims, and postoperative investigations, directly guiding the choice of intraoperative tools. Most common tumor types present challenges in achieving complete resection due to their infiltrative nature and anatomical constraints. The development of adjuvant treatments has altered the balance between oncological aims and surgical risks. We review local recurrence associated with incomplete resection based on different definitions and emphasize the importance of achieving maximal safe resection in all tumor types. Intraoperative techniques that aid surgeons in identifying tumor boundaries are used in practice and in preclinical or clinical research settings. They encompass both conservative and invasive techniques. Among them, morphological tools include imaging modalities such as intraoperative magnetic resonance imaging, ultrasound, and optical coherence tomography. Fluorescence-guided surgery, mainly using 5-aminolevulinic acid, enhances gross total resection in glioblastomas. Nuclear methods, including positron emission tomography probes, provide tumor detection based on beta or gamma emission after a radiotracer injection. Mass spectrometry- and spectroscopy-based methods offer molecular insights. The adoption of these techniques depends on their relevance, effectiveness, and feasibility. With the emergence of positron emission tomography imaging for use in recurrence benchmarking, positron emission tomography probes raise particular interest among those tools. While all such tools provide valuable insights, their clinical benefits need further evaluation.

Intraoperative visualization of cranial nerve schwannomas using second-window indocyanine green: A case series

BACKGROUND

Second Window Indocyanine Green (SWIG) is a novel intraoperative imaging technique that uses near-infrared (NIR) light for intra-operative tumor visualization using the well-known fluorophore indocyanine green (ICG). Because schwannomas often incorporate the nerve into the encapsulated tumor and impinge on surrounding neural structures, SWIG is a promising technique to improve tumor resection while sparing the nerve.

OBJECTIVE

To demonstrate the use of SWIG in resection of cranial nerve schwannomas.

METHODS

Three patients with cranial nerve schwannomas (i.e., trigeminal, vestibular, and vagus) underwent SWIG-guided resection. During surgery, NIR visualization was used intermittently used to detect fluorescence to guide resection. Signal-to-background ratio was then calculated to quantify fluorescence.

RESULTS

Patients were infused with ICG at a dose of 5.0 mg/kg 24 hours before surgery. Each patient achieved total or near-total resection and relief of symptoms with lack of recurrence at six-month follow-up. The average SBR calculated was 3.79, comparable to values for SWIG-guided resection of other brain and spine tumors.

CONCLUSION

This case series is the first published report of trigeminal and vagus nerve schwannoma resection using the SWIG technique and suggests that SWIG may be used to detect all schwannomas, alongside many other types of brain tumor. This paper also demonstrates the importance of preoperative ICG infusion timing and discusses the inverse pattern of NIR signal that may be observed when infusion occurs outside of the optimal timing. This provides direction for future studies investigating the administration of SWIG to resect cranial nerve schwannomas and other brain tumors.

Dielectric Spectroscopy Shows a Permittivity Contrast between Meningioma Tissue and Brain White and Gray Matter-A Potential Physical Biomarker for Meningioma Discrimination

The effectiveness of surgical resection of meningioma, the most common primary CNS tumor, depends on the capability to intraoperatively discriminate between the meningioma tissue and the surrounding brain white and gray matter tissues. Aiming to find a potential biomarker based on tissue permittivity, dielectric spectroscopy of meningioma, white matter, and gray matter ex vivo tissues was performed using the open-ended coaxial probe method in the microwave frequency range from 0.5 to 18 GHz. The averages and the 95% confidence intervals of the measured permittivity for each tissue were compared. The results showed the absence of overlap between the 95% confidence intervals for meningioma tissue and for brain white and gray matter, indicating a significant difference in average permittivity (p ≤ 0.05) throughout almost the entire measured frequency range, with the most pronounced contrast found between 2 GHz and 5 GHz. The discovered contrast is relevant as a potential physical biomarker to discriminate meningioma tissue from the surrounding brain tissues by means of permittivity measurement, e.g., for intraoperative meningioma margin assessment. The permittivity models for each tissue, developed in this study as its byproducts, will allow more accurate electromagnetic modeling of brain tumor and healthy tissues, facilitating the development of new microwave-based medical devices and tools.

[Surgical treatment of large and giant recurrent meningiomas near the middle and posterior third part of the superior sagittal sinus with extracranial invading]

OBJECTIVE

To investigate the surgical strategy for large and giant recurrent meningiomas near the middle and posterior third part of the superior sagittal sinus with extracranial invading.

METHODS

The clinical data of 16 patients with large and giant recurrent meningioma in the middle and posterior third part of the superior sagittal sinus with extracranial invasion who underwent surgery in the Department of Neurosurgery of Peking University Third Hospital from May 2019 to May 2022 were retrospectively analyzed. All the patients underwent brain-enhanced magnetic resonance imaging (MRI), magnetic resonance venography (MRV), computed tomography angiography (CTA) and three-dimensional skull computed tomography (CT) before, to evaluate the extent of tumor invasion, the edema of brain tissue, the degree of skull damage, the blood supply of the tumor, and the degree of compression of the superior sagittal sinus, etc, and to formulate an individualized surgical plan. The neurological function of the patients was evaluated 1 week, 1 month, and 3 months after the operation, and the tumor condition was evaluated by brain-enhanced MRI 3 months, 6 months, and 1 year after the operation.

RESULTS

The tumors in the 16 patients were all located in the middle and posterior 1/3 part of the superior sagittal sinus and invaded extracranially. Among them, 8 cases were operated for the second time, 6 cases for the third time, and 2 cases for the fourth time; In the last operation, the bone flap was used to repair the skull in 4 cases, and the titanium mesh was used in 12 cases; Tumor arterials of 3 cases were embolized under digital subtraction angiography (DSA). Tumors of 10 cases were resected at Simpson grade Ⅰ, and 6 cases at Simpson grade Ⅱ; 2 cases underwent decompressive craniectomy during operation, and 14 cases underwent cranioplasty at the same time; scalp incisions of 14 cases were directly sutured, and flap transposition was used in 14 cases. When evaluating nerve function after operation, the limb muscle strength was improved compared with that before operation, and the Karnofsky performance scale (KPS) score reached 100 points 3 months after operation. During the follow-up, 1 patient's tumor recurred after 1 year and received Gamma Knife treatment, and the rest of the patients had no recurrence during the follow-up period.

CONCLUSION

Surgical treatment is the first choice for large and giant recurrent meningiomas near the middle and posterior third part of the superior sagittal sinus with extracranial invading. It is a safe and effective surgical method to take individualized surgical plan after detailed preoperative assessment of cerebral edema, tumor blood supply, venous sinus compression, and scalp invasion.