Comment on the article "Real-time intraoperative contrast-enhanced ultrasound (CEUS) in vascularized spinal tumors: a technical note"

Combined Use of Color Doppler Ultrasound and Contrast-Enhanced Ultrasound in the Intraoperative Armamentarium for Arteriovenous Malformation Surgery

BACKGROUND

Safety and efficacy in surgical treatment of cerebral arteriovenous malformations (AVMs) are dictated by thorough understanding of angioarchitectural features, intraoperative identification of feeding vessels, and appreciation of surrounding eloquent areas. Our aim was to describe the preliminary results of combined application of color Doppler ultrasound (CDUS) and contrast-enhanced ultrasound (CEUS) in a consecutive surgical series of AVM. We pointed out the tool's efficacy in distinguishing feeding from bystander vessels and in identifying pattern of venous drainage. We examined its role as an adjunct for semiquantitative evaluation of the nidus inflow.

METHODS

We used combined CDUS and CEUS in patients surgically treated for cerebral AVMs. We adopted these techniques following a designed protocol to guide safer AVM resection as an adjunct to indocyanine green videoangiography. Intraoperative assessment by ultrasound was performed before, during, and following nidus resection.

RESULTS

Four surgically treated cerebral AVMs availed of the ultrasound protocol. Postoperative conventional angiography showed complete resection of the AVMs. CDUS and CEUS proved to be valuable adjunctive tools to indocyanine green videoangiography and micro-Doppler in properly navigating and discerning vascular structures, especially vessel feeders from bystanders. The protocol allows us to identify flow direction, estimate blood velocity within the nidus, and appreciate flow modifications following temporary clipping. Ultimately, it allows us to evaluate the degree of nidus deafferentation, residual flow, restoration of venous drainage and absence of arteriovenous shunts.

CONCLUSIONS

The CDUS and CEUS protocol is safe and repeatable and works as real-time imaging, further supporting complete surgical resection of AVMs.

State of the art of fluorescence guided techniques in neurosurgery

Achieving a safe and extensive neoplasm resection can be considered the main goal of brain tumor surgery. This paper is first aimed at providing an overview of the evolution of those tools serving the purpose. From the dawn of neurosurgery to the present days, major innovations have followed one another. However, those techniques may frequently lack of an instant biological feedback on the true extension and the infiltration of the tumor. Intraoperative fluorescence modalities could indeed fill this gap. Fluorescence guided surgery will be therefore introduced and discussed in this context. Our focus will be on the most common fluorescence techniques used in neurosurgery, namely 5-aminolevulinic acid, sodium fluorescein and in indocyanine green. Mode of action, strengths and weaknesses and level of evidence of each modality will be discussed.

"Dark corridors" in 5-ALA resection of high-grade gliomas: combining fluorescence-guided surgery and contrast-enhanced ultrasonography to better explore the surgical field

BACKGROUND

Increasing the extent of resection (EOR) is considered a main goal in high grade glioma (HGG) surgery. Significant advancements have been recently made to assist surgery: namely the use of 5-aminolevulinic acid (5ALA) and the application of contrast-enhanced ultrasound (CEUS) embody two of the most recently introduced tools in the neuro-oncology field. A combined approach including the two techniques has been suggested in literature. Our primary aim is to identify in which conditions CEUS final survey has a real impact in a 5-ALA guided context and assess which preoperative tumor characteristics, with specific attention to working corridors can predict strains of the fluorescence guided procedure and hence recommend the use of the combined technique.

METHODS

Forty-nine HGG glioma surgeries were performed at our institution with the abovementioned protocol between January 2016 and June 2016. Based on preoperative MRI, we stratified glioma characteristics according to three determinants: localization (deep versus superficial), size (<3.5 versus >3.5 cm) and shape (regular versus irregular).

RESULTS

CEUS modified 5-ALA guided resection in 11 cases (22.45%): this appeared to be associated with statistically significance to deep tumor localization (P=0.04) and irregular/multi-lobulated margins (P=0.003). On the other hand, tumor size alone did not appear as a statistically significant determinant.

CONCLUSIONS

When dark corridors are presents or when overlying brain parenchyma hinders illumination, drawbacks to the 5-ALA assistance can be expected, hence CEUS final survey has a crucial role of 'refinement'. In those selected cases, an integrated 5ALA+CEUS protocol was shown as advisable in EOR improvement.

5-Aminolevulinic Acid and Contrast-Enhanced Ultrasound: The Combination of the Two Techniques to Optimize the Extent of Resection in Glioblastoma Surgery

BACKGROUND

The survival benefit in maximizing resection in glioblastomas (GBMs) has been demonstrated by numerous studies. The true limit of infiltration of GBMs has been an overwhelming obstacle, and several technological advances have been introduced to improve the identification of residual tumors.

OBJECTIVE

To evaluate whether the integration of 5-aminolevulinic acid (5-ALA) with microbubble contrast-enhanced ultrasound (CEUS) improves residual tumor identification and has an impact on the extent of resection (EOR), overall survival (OS), and progression-free survival (PFS).

METHODS

A total of 230 GBM procedures were retrospectively studied. Cases were stratified according to the surgical procedure into 4 groups: 5-ALA- and CEUS-guided surgeries, 5-ALA-guided surgeries, CEUS-guided surgeries, and conventional microsurgical procedures.

RESULTS

Patients undergoing conventional microsurgical procedures showed the worst EORs compared to the assisted techniques (5-ALA and CEUS procedures). Both 5-ALA and CEUS techniques improved the EOR compared to conventional microsurgical procedures. However, their combination gave the best results in terms of the EOR (P = .0003). The median EOR% and the number of supramarginal resections are hence superior in the 5-ALA + CEUS + group compared to the others; this observation had consequences on PFS and OS in our series.

CONCLUSION

In terms of the EOR, the best results can be achieved through a combination of both techniques, where the 5-ALA-guided procedure is followed by a final survey with CEUS. Compared with other intraoperative imaging techniques, CEUS is a real-time, readily repeatable, safe, and inexpensive technique that provides valuable information to the surgeon before, during, and after resection.