Intraoperative use of real-time ultrasonography in neurosurgery

Portable ultrasound-guided keyhole evacuation of intracerebral hemorrhage: a detailed case report highlighting technical nuances

Intracerebral hemorrhage (ICH) is a common neurosurgical emergency that is associated with high morbidity and mortality. Minimally invasive or endoscopic hematoma evacuation has emerged in recent years as a viable alternative to conventional large craniotomies. However, accurate trajectory planning and placement of the tubular retractor remains a challenge. We describe a novel technique for handheld portable ultrasound-guided minimally invasive endoscopic evacuation of supratentorial hematomas. A 64-year-old male diagnosed right hematoma (48.5 mL) at the basal ganglia was treated with emergent ultrasound-guided endoscopic transtubular evacuation through a small craniotomy. Ultrasound-guidance facilitated optimal placement of the tubular retractor into the long axis of the hematoma, and allowed for near-total evacuation, reducing iatrogenic tissue damage by mitigating the need for wanding or repositioning of the retractor. The emergence of a new generation of small portable phased array ultrasound probes with improved resolution and clarity has broadened ultrasound's clinical applications.

Resection of supratentorial high-grade gliomas availing of neuronavigation matched intraoperative ultrasound and Fluorescein: How far is it safe to push the resection?

Background

High-Grade Gliomas are the most common primary brain malignancies and despite the multimodal treatment, and the increasing amount of adjuvant treatment options the overall prognosis remains dismal. The present investigation aims to analyze the safety profile of the use of intraoperative ultrasounds (Io-US) in a homogeneous and matched cohort of patients suffering from High-grade gliomas (HGG) operated on with or without the aid of Io-US and Fluorescein in specific relation to the incidence of neurological and functional status sequelae.

Methods and materials

A retrospective analysis was performed on 74 patients affected by HGG. 22 patients were treated with Io-US matched with neuronavigational system (Group A); 15 patients were treated both with the use of Io-US and Fluorescein matched with neuronavigational system (Group B); 37 patients were treated with the use of the neuronavigational system only (Group C). Primary endpoints were the extent of resection and functional outcome (measured with Karnofski Performance Status).

Results

Significative differences were observed in terms of a higher extent of resection in Group B. In a multivariate analysis, this data appears to be independent of the location (eloquent/non-eloquent) of the lesion and from its histology. Regarding functional outcomes, no differences were detected between the two groups.

Conclusions

The present study is the first that analyzes the simultaneous use of Io-US and Fluorescein, and the results demonstrate that these two instruments together could improve the extent of resection in HGG while ensuring good outcomes in terms of functional status.

Transcortical transcatheter ultrasound-assisted technique for deep-seated brain tumors. Technical note

PURPOSE

Surgery of deep-seated brain tumors can be challenging. Several methods have been described to facilitate transcortical approaches, including ultrasound-assisted resection. Ultrasound-guided placement of a standard ventricular catheter is a widely reported technique and has been used to approach these lesions via the transcortical route. We describe how we usually perform this useful technique to assist and enhance the transcortical resection of some deep-seated brain tumors.

METHODS

Standard electromagnetic frameless navigation (S8 Neuronavigation System, Medtronic, Minneapolis, USA) was employed to focus the craniotomy and to plan the trajectory of the ventricular catheter. After dural opening, an ultrasound device (Arietta 850, Hitachi-Aloka Medical, Tokyo, Japan) was used for intraoperative ultrasound (IOUS) assessment. A ventricular catheter was placed from the cortex to the lateral wall of the tumor under direct real-time IOUS visualization to guide the further transcortical dissection.

RESULTS

Transcortical transcatheter ultrasound-assisted technique involved minimal time and infrastructure requirements. There were no major technical difficulties during its use, providing confidence and improving subcortical white matter dissection by guiding the route to the tumor.

CONCLUSIONS

Recent improvement of IOUS image-quality devices offers several attractive options for real-time navigation. The combination of conventional neuronavigation systems with real-time IOUS assessment during the intradural step provides a higher degree of control by improving the execution of the surgery. We hope this description may be a useful tool for some selected cases and contribute to the further enhancement and improvement of this widely used technique.

Intraoperative ultrasonography in microsurgical resection of vestibular schwannomas via retrosigmoid approach: surgical technique and proof-of-concept illustrative case series

PURPOSE

Intraoperative ultrasonography (ioUS) is an established tool for the real-time intraoperative orientation and resection control in intra-axial oncological neurosurgery. Conversely, reports about its implementation in the resection of vestibular schwannomas (VS) are scarce. The aim of this study is to describe the role of ioUS in microsurgical resection of VS.

METHODS

ioUS (Craniotomy Transducer N13C5, BK5000, B Freq 8 MHz, BK Medical, Burlington, MA, USA) is integrated into the surgical workflow according to a 4-step protocol (transdural preresection, intradural debulking control, intradural resection control, transdural postclosure). Illustrative cases of patients undergoing VS resection through a retrosigmoid approach with the use of ioUS are showed to illustrate advantages and pitfalls of the technique.

RESULTS

ioUS allows clear transdural identification of the VS and its relationships with surgically relevant structures of the posterior fossa and of the cerebellopontine cistern prior to dural opening. Intradural ioUS reliably estimates the extent of tumor debulking, thereby helping in the choice of the right moment to start peripheral preparation and in the optimization of the extent of resection in those cases where subtotal resection is the ultimate goal of surgery. Transdural postclosure ioUS accurately depicts surgical situs.

CONCLUSION

ioUS is a cost-effective, safe, and easy-to-use intraoperative adjunctive tool that can provide a significant assistance during VS surgery. It can potentially improve patient safety and reduce complication rates. Its efficacy on clinical outcomes, operative time, and complication rate should be validated in further studies.

Complication Avoidance in Neurosurgery with Use of Intraoperative Ultrasonography

Intraoperative ultrasonography is an extremely valuable tool for avoidance of complications during neurosurgical procedures, including resection of intracranial and spinal cord tumors, removal of spontaneous intracerebral hemorrhages and arteriovenous malformations, and ventricular access for shunt placements. Nevertheless, application of this highly useful technique may be accompanied by some challenges and difficulties, as well as human errors; thus, it requires specific knowledge and continuous training.

Ultrasound localization of embolic material to guide resection of brain AVM: Report of two cases

Background

The Spetzler-Martin Grade (SMG) is widely used to evaluate the risk of resection of cerebral arteriovenous malformation (AVM), and direct surgery is strongly recommended for low SMG lesions. Micro-AVMs are defined as AVMs with a nidus <1 cm in diameter, and sometimes, the challenge is identifying the exact lesion site during AVM resection, although identification of the site is very important in the procedure. Here, we present two cases in which the sites of micro-AVM were marked using presurgical embolization and easily confirmed by intraoperative ultrasonography (IUS) and discuss the benefits of IUS in combination with presurgical embolization for low-grade micro-AVM.

Case Description

(Patient 1) A 30-year-old man was brought to our hospital and diagnosed with a micro-AVM, which was classified as SMG II AVM. He underwent evacuation of the intracerebral hematoma and subsequently underwent AVM resection. However, the lesion was not identified because it was not exposed in the cerebral cortex although we searched for the lesion. Therefore, endovascular embolization was performed before subsequent surgical resection. During AVM resection following embolization with Onyx, the IUS clearly demonstrated the Onyx-embolized lesion, and it was resected uneventfully. (Patient 2) A 46-year-old man with a ruptured SMG II AVM underwent AVM resection using a microsurgical technique with IUS after embolization for AVM preoperatively. IUS clearly showed abnormal vessels embolized with Onyx and indicated the correct location of the nidus, although the lesion was not observed directly from the brain surface. After identifying some embolized AVM constructions, we excised the entire AVM with ease and safety.

Conclusion

The combined use of presurgical embolization, which focuses on marking the lesions and IUS, may contribute to improving surgical outcomes of low SMG micro-AVMs, which are not exposed on the brain surface.

Navigated 3D ultrasound-guided resection of high-grade gliomas: A case series and review

Background:

The crux in high-grade glioma surgery remains maximizing resection without affecting eloquent brain areas. Toward this, a myriad of adjunct tools and techniques has been employed to enhance surgical safety and efficacy. Despite intraoperative MRI and advanced neuronavigational techniques, as well as augmented reality, to date, the only true real-time visualization tool remains the ultrasound (US). Neuroultrasonography is a cost-efficient imaging modality that offers instant, real-time information about the changing anatomical landscape intraoperatively. Recent advances in technology now allow for the integration of intraoperative US with neuronavigation.

Case Description:

In this report, we present the resection technique for three cases of high-grade gliomas (two glioblastomas and one anaplastic astrocytoma). The patient presented with a variable clinical spectrum. All three cases have been performed using the Brainlab^® neuronavigation system (BrainLAB, Munich, Germany) and the bk5000 US Machine^® (BK Medical, Analogic Corporation, Peabody, Massachusetts, USA).

Conclusion:

Gross total resection was achieved in all three cases. The use of 3D navigated US was a reliable adjunct surgical tool in achieving favorable resection outcomes in these patients.

Navigated Intraoperative 3D Ultrasound in Glioblastoma Surgery: Analysis of Imaging Features and Impact on Extent of Resection

Background

Neuronavigation is routinely used in glioblastoma surgery, but its accuracy decreases during the operative procedure due to brain shift, which can be addressed utilizing intraoperative imaging. Intraoperative ultrasound (iUS) is widely available, offers excellent live imaging, and can be fully integrated into modern navigational systems. Here, we analyze the imaging features of navigated i3D US and its impact on the extent of resection (EOR) in glioblastoma surgery.

Methods

Datasets of 31 glioblastoma resection procedures were evaluated. Patient registration was established using intraoperative computed tomography (iCT). Pre-operative MRI (pre-MRI) and pre-resectional ultrasound (pre-US) datasets were compared regarding segmented tumor volume, spatial overlap (Dice coefficient), the Euclidean distance of the geometric center of gravity (CoG), and the Hausdorff distance. Post-resectional ultrasound (post-US) and post-operative MRI (post-MRI) tumor volumes were analyzed and categorized into subtotal resection (STR) or gross total resection (GTR) cases.

Results

The mean patient age was 59.3 ± 11.9 years. There was no significant difference in pre-resectional segmented tumor volumes (pre-MRI: 24.2 ± 22.3 cm³; pre-US: 24.0 ± 21.8 cm³). The Dice coefficient was 0.71 ± 0.21, the Euclidean distance of the CoG was 3.9 ± 3.0 mm, and the Hausdorff distance was 12.2 ± 6.9 mm. A total of 18 cases were categorized as GTR, 10 cases were concordantly classified as STR on MRI and ultrasound, and 3 cases had to be excluded from post-resectional analysis. In four cases, i3D US triggered further resection.

Conclusion

Navigated i3D US is reliably adjunct in a multimodal navigational setup for glioblastoma resection. Tumor segmentations revealed similar results in i3D US and MRI, demonstrating the capability of i3D US to delineate tumor boundaries. Additionally, i3D US has a positive influence on the EOR, allows live imaging, and depicts brain shift.

Cottonoid-guided intraoperative ultrasonography in neurosurgery: a proof-of-concept single surgeon case series

Ultrasonography was introduced into neurosurgery in the 1950s, but its successful utilization as an intraoperative tool dates from the early 1980s. However, it was not used widely because of limited technology, a lack of specific training, and, most importantly, the concurrent evolution of computerized tomography and magnetic resonance imaging. The intraoperative use of cottonoid patties as acoustical markers was first described in 1984, but the practice did not gain acceptance, and no articles have been published since. Herein, we reconsider the echogenic properties of the surgical cottonoid patty and demonstrate its usefulness with intraoperative ultrasonography (ioUS) in neurosurgical practice as a truly real-time neuronavigation tool. We also discuss its advantages and compare it with other intraoperative image guidance tools. The echogenic properties of the handmade cottonoid patties in various sizes used with ioUS are described. Details of our cottonoid-guided ioUS technique and its advantages with illustrated cases are also described. As an echogenic marker, cottonoid patties can be easily recognized with ioUS. Their usage with ultrasonography provides truly real-time anatomical orientation throughout the surgery, allowing easy access to intraparenchymal pathologies, and precise and safer resection. Cottonoid-guided ioUS helps not only to localize intraparenchymal pathologies but also to delineate the exact surgical trajectory for each type of lesion. Furthermore, it is not affected by brain shift and distortion. Thus, it is a truly real-time, dynamic, cost-effective, and easy-to-use image guidance tool. This technique can be used safely for every intraparenchymal pathology and increases the accuracy and safety of the surgeries.

Surgical advances in the management of brain metastases

As the epidemiological and clinical burden of brain metastases continues to grow, advances in neurosurgical care are imperative. From standard magnetic resonance imaging (MRI) sequences to functional neuroimaging, preoperative workups for metastatic disease allow high-resolution detection of lesions and at-risk structures, facilitating safe and effective surgical planning. Minimally invasive neurosurgical approaches, including keyhole craniotomies and tubular retractors, optimize the preservation of normal parenchyma without compromising extent of resection. Supramarginal surgery has pushed the boundaries of achieving complete removal of metastases without recurrence, especially in eloquent regions when paired with intraoperative neuromonitoring. Brachytherapy has highlighted the potential of locally delivering therapeutic agents to the resection cavity with high rates of local control. Neuronavigation has become a cornerstone of operative workflow, while intraoperative ultrasound (iUS) and intraoperative brain mapping generate real-time renderings of the brain unaffected by brain shift. Endoscopes, exoscopes, and fluorescent-guided surgery enable increasingly high-definition visualizations of metastatic lesions that were previously difficult to achieve. Pushed forward by these multidisciplinary innovations, neurosurgery has never been a safer, more effective treatment for patients with brain metastases.

The surgical resection of dysplastic cerebellar gangliocytoma assisted by intraoperative sonography: illustrative case

BACKGROUND

Dysplastic gangliocytoma of the cerebellum (Lhermitte-Duclos disease) is an extremely rare, slow-growing hereditary mass lesion that is mainly characterized by both specific neuroradiological features and secondary hydrocephalus. Patients may present with symptoms of cerebellar mass lesion and increased intracranial pressure. As an important part of Cowden syndrome, Lhermitte-Duclos disease in adults is typically marked by PTEN gene mutation.

OBSERVATIONS

The clinical management of a 31-year-old woman who suffered Lhermitte-Duclos disease was introduced in this case report. Subtotal resection was performed with the assistance of intraoperative sonography to relieve obstructive hydrocephalus, and prophylactic C1 laminectomy was performed to prevent possible postoperative progression of the residual lesion. Perioperative care and surgical process were clearly revealed in an accompanying video. Intraoperative sonography of Lhermitte-Duclos disease presents hyperechoic distorted thickening cortices surrounded by hypoechoic edema belt. The patient did not report any significant neurological complications or sequelae after the lesion resection.

LESSONS

The authors first reported the use of intraoperative sonography in resection of adult-onset Lhermitte-Duclos disease. Hopefully, the educative case report can provide a feasible experience in the diagnosis and treatment of Lhermitte-Duclos disease.

How to Perform Intra-Operative Contrast-Enhanced Ultrasound of the Brain-A WFUMB Position Paper

Intra-operative ultrasound has become a relevant imaging modality in neurosurgical procedures. While B-mode, with its intrinsic limitations, is still considered the primary ultrasound modality, intra-operative contrast-enhanced ultrasound (ioCEUS) has more recently emerged as a powerful tool in neurosurgery. Though still not used on a large scale, ioCEUS has proven its utility in defining tumor boundaries, identifying lesion vascular supply and mapping neurovascular architecture. Here we propose a step-by-step procedure for performing ioCEUS analysis of the brain, highlighting its neurosurgical applications. Moreover, we provide practical advice on the use of ultrasound contrast agents and review technical ultrasound parameters influencing ioCEUS imaging.

Brain Shift in Neuronavigation of Brain Tumors: An Updated Review of Intra-Operative Ultrasound Applications

Neuronavigation using pre-operative imaging data for neurosurgical guidance is a ubiquitous tool for the planning and resection of oncologic brain disease. These systems are rendered unreliable when brain shift invalidates the patient-image registration. Our previous review in 2015, Brain shift in neuronavigation of brain tumours: A review offered a new taxonomy, classification system, and a historical perspective on the causes, measurement, and pre- and intra-operative compensation of this phenomenon. Here we present an updated review using the same taxonomy and framework, focused on the developments of intra-operative ultrasound-based brain shift research from 2015 to the present (2020). The review was performed using PubMed to identify articles since 2015 with the specific words and phrases: “Brain shift” AND “Ultrasound”. Since 2015, the rate of publication of intra-operative ultrasound based articles in the context of brain shift has increased from 2–3 per year to 8–10 per year. This efficient and low-cost technology and increasing comfort among clinicians and researchers have allowed unique avenues of development. Since 2015, there has been a trend towards more mathematical advancements in the field which is often validated on publicly available datasets from early intra-operative ultrasound research, and may not give a just representation to the intra-operative imaging landscape in modern image-guided neurosurgery. Focus on vessel-based registration and virtual and augmented reality paradigms have seen traction, offering new perspectives to overcome some of the different pitfalls of ultrasound based technologies. Unfortunately, clinical adaptation and evaluation has not seen as significant of a publication boost. Brain shift continues to be a highly prevalent pitfall in maintaining accuracy throughout oncologic neurosurgical intervention and continues to be an area of active research. Intra-operative ultrasound continues to show promise as an effective, efficient, and low-cost solution for intra-operative accuracy management. A major drawback of the current research landscape is that mathematical tool validation based on retrospective data outpaces prospective clinical evaluations decreasing the strength of the evidence. The need for newer and more publicly available clinical datasets will be instrumental in more reliable validation of these methods that reflect the modern intra-operative imaging in these procedures.

Navigated 3D Ultrasound in Brain Metastasis Surgery: Analyzing the Differences in Object Appearances in Ultrasound and Magnetic Resonance Imaging

Background: Implementation of intraoperative 3D ultrasound (i3D US) into modern neuronavigational systems offers the possibility of live imaging and subsequent imaging updates. However, different modalities, image acquisition strategies, and timing of imaging influence object appearances. We analyzed the differences in object appearances in ultrasound (US) and magnetic resonance imaging (MRI) in 35 cases of brain metastasis, which were operated in a multimodal navigational setup after intraoperative computed tomography based (iCT) registration. Method: Registration accuracy was determined using the target registration error (TRE). Lesions segmented in preoperative magnetic resonance imaging (preMRI) and i3D US were compared focusing on object size, location, and similarity. Results: The mean and standard deviation (SD) of the TRE was 0.84 ± 0.36 mm. Objects were similar in size (mean ± SD in preMRI: 13.6 ± 16.0 cm3 vs. i3D US: 13.5 ± 16.0 cm3). The Dice coefficient was 0.68 ± 0.22 (mean ± SD), the Hausdorff distance 8.1 ± 2.9 mm (mean ± SD), and the Euclidean distance of the centers of gravity 3.7 ± 2.5 mm (mean ± SD). Conclusion: i3D US clearly delineates tumor boundaries and allows live updating of imaging for compensation of brain shift, which can already be identified to a significant amount before dural opening.

Utility of Tubular Retractors Augmented with Intraoperative Ultrasound in the Resection of Deep-seated Brain Lesions: Technical Note

Traditional brain retraction has been associated with significant damage to the healthy brain tissue particularly when attempting to expose a deep-seated lesion of the brain. Tubular retractors tend to provide a surgical corridor to treat these lesions while minimizing the extent of retraction on the brain. Intraoperative ultrasound can be used as a handy adjunct in maximizing the safe resection primarily by identifying the entry point, visualizing the lesion, and providing real-time feedback on the extent of resection. The authors provide a technical note with case illustrations on the use of tubular retractors augmented with intraoperative ultrasound to ensure a maximal safe resection of deep-seated brain lesions.

Comparison of Stereotactic and Ultrasound-guided Biopsy of Solid Supratentorial Tumor: A Preliminary Report

Introduction:

The computed tomography (CT) guided stereotactic biopsy (STB) is considered as method of choice for biopsy of intracranial mass lesions. However, it's disadvantages are frame fixation, time requirement for transportation between CT scan suit to the operation theater with added much higher equipment cost in the relatively resource scarred developing country. Ultrasound-guided biopsy (USGB) is relatively simpler, economical, less time consuming, and real-time procedure.

Clinical Materials and Methods:

Thirty-seven consecutively admitted patients with supratentorial brain tumors, who underwent biopsy of the lesion using CT compatible stereotactic and ultrasound-guided (USGB) procedure formed cohort of the study. Based on location and size of the lesions, the cases were divided into two groups, superficial and deep. Twenty-two patients underwent ultrasound-guided biopsy and 15 with STB.

Results:

The diagnostic yield of STB was 93% and 91% for ultrasound-guided biopsy. The mean operation time of STB group was 149.00 min and 94 min for USGB, which was statistically significant. Two cases in each group developed hematoma; however, one case in USGB group needed surgical evacuation. The real-time monitoring detected two hematoma intraoperatively, which were further also confirmed on postoperative CT scan head.

Conclusions:

The ultrasound-guided biopsy procedure (USGB) was simple, relatively shorter time-consuming procedure and equally efficacious and utilizing economical equipment and can act as a safer alternative to CT STB process for biopsy of the intracranial mass lesion. Furthermore, USGB also provided intra-operative real-time monitoring, which provided clue for close monitoring in the postoperative period after completion of biopsy to look for development of fresh hematoma development not only at the biopsy site but also along the biopsy track and adjoining area. Perhaps, a longer period of ultrasonic monitoring following the procedure would be of greater help to detect hematoma formation, which is one of the most common complications of the biopsy procedure.

Intraoperative Ultrasound for Peripheral Nerve Applications

Offering real-time, high-resolution images via intraoperative ultrasound is advantageous for a variety of peripheral nerve applications. To highlight the advantages of ultrasound, its extraoperative uses are reviewed. The current intraoperative uses, including nerve localization, real-time evaluation of peripheral nerve tumors, and implantation of leads for peripheral nerve stimulation, are reviewed. Although intraoperative peripheral nerve localization has been performed previously using guide wires and surgical dyes, the authors' approach using ultrasound-guided instrument clamps helps guide surgical dissection to the target nerve, which could lead to more timely operations and shorter incisions.

USim: A New Device and App for Case-Specific, Intraoperative Ultrasound Simulation and Rehearsal in Neurosurgery. A Preliminary Study

BACKGROUND

Intraoperative ultrasound (iUS) is an excellent aid for neurosurgeons to perform better and safer operations thanks to real time, continuous, and high-quality intraoperative visualization.

OBJECTIVE

To develop an innovative training method to teach how to perform iUS in neurosurgery.

METHODS

Patients undergoing surgery for different brain or spine lesions were iUS scanned (before opening the dura) in order to arrange a collection of 3-dimensional, US images; this set of data was matched and paired to preoperatively acquired magnetic resonance images in order to create a library of neurosurgical cases to be studied offline for training and rehearsal purposes. This new iUS training approach was preliminarily tested on 14 European neurosurgery residents, who participated at the 2016 European Association of Neurosurgical Societies Training Course (Sofia, Bulgaria).

RESULTS

USim was developed by Camelot and the Besta NeuroSim Center as a dedicated app that transforms any smartphone into a “virtual US probe,” in order to simulate iUS applied to neurosurgery on a series of anonymized, patient-specific cases of different central nervous system tumors (eg, gliomas, metastases, meningiomas) for education, simulation, and rehearsal purposes. USim proved to be easy to use and allowed residents to quickly learn to handle a US probe and interpret iUS semiotics.

CONCLUSION

USim could help neurosurgeons learn neurosurgical iUS safely. Furthermore, neurosurgeons could simulate many cases, of different brain/spinal cord tumors, that resemble the specific cases they have to operate on. Finally, the library of cases would be continuously updated, upgraded, and made available to neurosurgeons.

Applications of Ultrasound in the Resection of Brain Tumors

Neurosurgery makes use of preoperative imaging to visualize pathology, inform surgical planning, and evaluate the safety of selected approaches. The utility of preoperative imaging for neuronavigation, however, is diminished by the well-characterized phenomenon of brain shift, in which the brain deforms intraoperatively as a result of craniotomy, swelling, gravity, tumor resection, cerebrospinal fluid (CSF) drainage, and many other factors. As such, there is a need for updated intraoperative information that accurately reflects intraoperative conditions. Since 1982, intraoperative ultrasound has allowed neurosurgeons to craft and update operative plans without ionizing radiation exposure or major workflow interruption. Continued evolution of ultrasound technology since its introduction has resulted in superior imaging quality, smaller probes, and more seamless integration with neuronavigation systems. Furthermore, the introduction of related imaging modalities, such as 3-dimensional ultrasound, contrast-enhanced ultrasound, high-frequency ultrasound, and ultrasound elastography, has dramatically expanded the options available to the neurosurgeon intraoperatively. In the context of these advances, we review the current state, potential, and challenges of intraoperative ultrasound for brain tumor resection. We begin by evaluating these ultrasound technologies and their relative advantages and disadvantages. We then review three specific applications of these ultrasound technologies to brain tumor resection: (1) intraoperative navigation, (2) assessment of extent of resection, and (3) brain shift monitoring and compensation. We conclude by identifying opportunities for future directions in the development of ultrasound technologies.

Intramedullary Spinal Cord Tumors: Part II-Management Options and Outcomes

Study Design Broad narrative review. Objectives Intramedullary spinal cord tumors (IMSCT) are uncommon lesions that can affect any age group or sex. However, numerous IMSCT exist and the clinical course of each tumor varies. The following article addresses the various management options and outcomes in patients with IMSCT. Methods An extensive review of the peer-reviewed literature was performed, addressing management options and clinical outcomes of patients with IMSCT. Results Early diagnosis and intervention are essential to obtain optimal functional outcome. Each IMSCT have specific imaging characteristics, which help in the clinical decision-making and prognostication. A comprehension of the tumor pathology and the clinical course associated with each tumor can allow for the proper surgical and nonsurgical management of these tumors, and reduce any associated morbidity and mortality. Recent advances in the operative management of such lesions have increased the success rate of tumor removal while minimizing iatrogenic-related trauma to the patient and, in tandem, improving patient outcomes. Conclusions Awareness and understanding of IMSCT is imperative to design proper management and obtain optimal patient outcomes. Meticulous operative technique and the use of surgical adjuncts are essential to accomplish proper tumor removal, diminish the risk of recurrence, and preserve neurologic function. Operative management of IMSCT should be individualized and based on tumor type, location, and dimensional extensions. To assist with preoperative and intraoperative decision-making, a general algorithm is provided.

Ultrasound stylet for non-image-guided ventricular catheterization

OBJECT Urgent ventriculostomy placement can be a lifesaving procedure in the setting of hydrocephalus or elevated intracranial pressure. While external ventricular drain (EVD) insertion is common, there remains a high rate of suboptimal drain placement. Here, the authors seek to demonstrate the feasibility of an ultrasound-based guidance system that can be inserted into an existing EVD catheter to provide a linear ultrasound trace that guides the user toward the ventricle. METHODS The ultrasound stylet was constructed as a thin metal tube, with dimensions equivalent to standard catheter stylets, bearing a single-element, ceramic ultrasound transducer at the tip. Ultrasound backscatter signals from the porcine ventricle were processed by custom electronics to offer real-time information about ventricular location relative to the catheter. Data collected from the prototype device were compared with reference measurements obtained using standard clinical ultrasound imaging. RESULTS A study of porcine ventricular catheterization using the experimental device yielded a high rate of successful catheter placement after a single pass (10 of 12 trials), despite the small size of pig ventricles and the lack of prior instruction on porcine ventricular architecture. A characteristic double-peak signal was identified, which originated from ultrasound reflections off of the near and far ventricular walls. Ventricular dimensions, as obtained from the width between peaks, were in agreement with standard ultrasound reference measurements (p < 0.05). Furthermore, linear ultrasound backscatter data permitted in situ measurement of the stylet distance to the ventricular wall (p < 0.05), which assisted in catheter guidance. CONCLUSIONS The authors have demonstrated the ability of the prototype ultrasound stylet to guide ventricular access in the porcine brain. The alternative design of the device makes it potentially easy to integrate into the standard workflow for bedside EVD placement. The availability of a fast, easy-to-use, inexpensive guidance system can play a role in reducing the complication rate for EVD placement.

Intraoperative neuronavigation integrated high resolution 3D ultrasound for brainshift and tumor resection control

INTRODUCTION: The link between the neurosurgeon’s knowledge and the scientific improvements made a dramatic change in the field expressed both in impressive drop in the mortality and morbidity rates that were operated in the beginning of the XXth century and in operating with high rates of success cases that were considered inoperable in the past. Neuronavigation systems have been used for many years on surgical orientation purposes especially for small, deep seated lesions where the use of neuronavigation is correlated with smaller corticotomies and with the extended use of transulcal approaches. The major problem of neuronavigation, the brainshift once the dura is opened can be solved either by integrated ultrasound or intraoperative MRI which is out of reach for many neurosurgical departments. METHOD: The procedure of neuronavigation and ultrasonic localization of the tumor is described starting with positioning the patient in the visual field of the neuronavigation integrated 3D ultrasonography system to the control of tumor resection by repeating the ultrasonographic scan in the end of the procedure. DISCUSSION: As demonstrated by many clinical trials on gliomas, the more tumor removed, the better long term control of tumor regrowth and the longer survival with a good quality of life. Of course, no matter how aggressive the surgery, no new deficits are acceptable in the modern era neurosurgery. There are many adjuvant methods for the neurosurgeon to achieve this maximal and safe tumor removal, including the 3T MRI combined with tractography and functional MRI, the intraoperative neuronavigation and neurophysiologic monitoring in both anesthetized and awake patients. The ultrasonography integrated in neuronavigaton comes as a welcomed addition to this adjuvants to help the surgeon achieve the set purpose. CONCLUSION: With the use of this real time imaging device, the common problem of brainshift encountered with the neuronavigation systems is covered and any eventual tumor residue can be spotted by ultrasonography and resected

Brain motion in patients with skull defects: B-mode ultrasound observations on respiration-induced movements

BACKGROUND

Since ancient times, brain motion has captured the attention of human beings. However, there are no reports about morphological changes that occur below the cortex or skin flap when a patient, with an open skull breathes, coughs, or engages effort. Thus, the aim of this study was to characterize brain motion caused by breathing movements in adults with an open skull.

METHODS

Twenty-five craniectomized patients were studied using B-mode ultrasonography during early and late postoperative periods. Twelve patients were analysed during surgery. Brain movements induced by breathing activity were assessed in this prospective observational study.

RESULTS

Taking as a reference the cranial base, an increase in intrathoracic pressure was accompanied by a rise of the brain due to the expansion of the basal cisterns. Greater increases in intrathoracic pressure (resulting from the Valsalva manoeuvre and coughing) propelled the brain in a block from the foramen magnum towards the craniectomy, mainly in structures near the tentorial incisure. Prolonging the Valsalva manoeuvre also resulted in thickening of the cortical mantle attributable to vascular congestion. The magnitude of these movements was directly related to breathing effort.

CONCLUSIONS

The increase in intrathoracic pressure was immediately transmitted to the brain by the rise of cerebrospinal fluid, while brain swelling attributable to vascular congestion showed a brief delay. The Valsalva manoeuvre and coughing caused abrupt morphological changes in the tentorial hiatus neighbouring structures because of the distension of the basal cisterns. These movements could play a role in the pathophysiology of the syndrome of trephined.

Comparison of the accuracy of ventricular catheter placement using freehand placement, ultrasonic guidance, and stereotactic neuronavigation

Object

The objective of this study was to compare the accuracy of 3 methods of ventricular catheter placement during CSF shunt operations: the freehand technique using surface anatomy, ultrasonic guidance, and stereotactic neuronavigation.

Methods

This retrospective cohort study included all patients from a single institution who underwent a ventricular CSF shunting procedure in which a new ventricular catheter was placed between January 2005 and March 2010. Data abstracted for each patient included age, sex, diagnosis, method of ventricular catheter placement, site and side of ventricular catheter placement, Evans ratio, and bifrontal ventricular span. Postoperative radiographic studies were reviewed for accuracy of ventricular catheter placement. Medical records were also reviewed for evidence of shunt failure requiring revision through December 2011. Statistical analysis was then performed comparing the 3 methods of ventricular catheter placement and to determine risk factors for inaccurate placement.

Results

There were 249 patients included in the study; 170 ventricular catheters were freehand passed, 51 were placed using stereotactic neuronavigation, and 28 were placed under intraoperative ultrasonic guidance. There was a statistically significant difference between freehand catheters and stereotactic-guided catheters (p < 0.001), as well as between freehand catheters and ultrasound-guided catheters (p < 0.001). The only risk factor for inaccurate placement identified in this study was use of the freehand technique. The use of stereotactic neuronavigation and ultrasonic guidance reduced proximal shunt failure rates (p < 0.05) in comparison with a freehand technique.

Conclusions

Stereotactic- and ultrasound-guided ventricular catheter placements are significantly more accurate than freehand placement, and the use of these intraoperative guidance techniques reduced proximal shunt failure in this study.

Brain tumor surgery with 3-dimensional surface navigation

BACKGROUND

Precise lesion localization is necessary for neurosurgical procedures not only during the operative approach, but also during the preoperative planning phase.

OBJECTIVE

To evaluate the advantages of 3-dimensional (3-D) brain surface visualization over conventional 2-dimensional (2-D) magnetic resonance images for surgical planning and intraoperative guidance in brain tumor surgery.

METHODS

Preoperative 3-D brain surface visualization was performed with neurosurgical planning software in 77 cases (58 gliomas, 7 cavernomas, 6 meningiomas, and 6 metastasis). Direct intraoperative navigation on the 3-D brain surface was additionally performed in the last 20 cases with a neurosurgical navigation system. For brain surface reconstruction, patient-specific anatomy was obtained from MR imaging and brain volume was extracted with skull stripping or watershed algorithms, respectively. Three-dimensional visualization was performed by direct volume rendering in both systems. To assess the value of 3-D brain surface visualization for topographic lesion localization, a multiple-choice test was developed. To assess accuracy and reliability of 3-D brain surface visualization for intraoperative orientation, we topographically correlated superficial vessels and gyral anatomy on 3-D brain models with intraoperative images.

RESULTS

The rate of correct lesion localization with 3-D was significantly higher (P = .001, χ), while being significantly less time consuming (P < .001, χ) compared with 2-D images. Intraoperatively, visual correlation was found between the 3-D images, superficial vessels, and gyral anatomy.

CONCLUSION

The proposed method of 3-D brain surface visualization is fast, clinically reliable for preoperative anatomic lesion localization and patient-specific planning, and, together with navigation, improves intraoperative orientation in brain tumor surgery and is relatively independent of brain shift.

Evidence-based clinical management and utilization of new technology in European neurosurgery

BACKGROUND

Evidence-based medicine (EBM) has become one of the pillars of modern patient care. However, neurosurgery has always been an experience-based and technology-driven discipline, and it remains unknown to which extent European neurosurgeons follow high-level evidence-based recommendations.

METHODS

We conducted a Web-based survey with a 15-item questionnaire about evidence-based clinical management and utilization of new technology among European neurosurgeons. Two different sum scores were calculated from the questions concerning clinical practice; evidence-based treatment score and new technology score. A high evidence-based treatment score means that more clinical conditions (i.e., study questions) were managed in compliance with the available highest levels of evidence from published clinical trials. A high new technology score reflects the use of a high number of modern tools in neurosurgical practice.

RESULTS

A total of 239 neurosurgeons from 30 different European countries answered the questionnaire. There were large variations among European neurosurgeons in providing evidence-based care and in utilization of various modern tools. There were significant regional differences in evidence-based treatment scores and modern technology scores with higher scores in northern and western Europe. High-volume institutions were not associated with better evidence-based treatment scores, but had significantly higher new technology scores. There were significantly higher new technology scores at university hospitals and a trend towards higher evidence-based treatment scores compared to other hospitals.

CONCLUSIONS

Clinical management in neurosurgery does not always comply with the best available evidence and there are large regional differences in clinical management and in utilization of various modern tools. The position of evidence-based medicine in European neurosurgery seems weak and this may be a threat to the quality of care.

Strategic placement of bedside ventriculostomies using ultrasound image guidance: report of three cases

BACKGROUND

The blind free-hand technique for external ventricular drain (EVD) placement sometimes requires multiple attempts, and catheter location is often less than ideal. Our institution has adapted an intraoperative ultrasound-guided ventriculostomy technique for the placement of EVDs at the bedside. Our experience with ultrasound at the bedside has proven to be invaluable in certain circumstances. We present three cases of strategic EVD catheter trajectories that were made possible at the bedside with the use of ultrasound.

METHODS

Illustrative cases were chosen from a larger prospective study investigating the ultrasound-guided EVD technique. A portable ultrasound with a "burr hole" probe was used with modification of the standard surgical technique for placement of EVDs at the bedside.

RESULTS

Case 1 describes an unexpected re-hemorrhage that was first realized by the ultrasound image obtained during the bedside EVD placement procedure. The catheter was purposefully directed across midline to the more prominent ventricle on the contralateral side based on this real-time finding. Case 2 describes how ultrasound was used to salvage the failed free-hand procedure and cannulate an extremely small ventricular space at the bedside. Case 3 describes an unconventionally placed burr hole that provided a customized trajectory in which the EVD catheter was placed just laterally and inferior to a large frontal hematoma.

CONCLUSION

Ultrasound-guided bedside EVD placement allows EVD trajectories to be customized based on real-time information to accommodate for distorted and dynamic anatomy of the brain and its ventricles.

Diagnostic usefulness of intraoperative ultrasonography for unexpected severe brain swelling in ultra-early surgery for ruptured intracranial aneurysms

BACKGROUND

In ultra-early aneurysm surgery, the few hours from admission to aneurysm clipping present the greatest risk for an in-hospital recurrent hemorrhage, the development of acute hydrocephalus, and severe brain edema. Thus, severe brain swelling encountered after dural opening in a craniotomy can sometimes not be explained by a preoperative computed tomography (CT) scan. Therefore, neurosurgeons need a diagnostic tool to determine the exact cause of the brain swelling to apply appropriate intraoperative management. Accordingly, the authors propose a designated optimal ultrasound window for evaluating brain swelling during a pterional craniotomy, and assess its diagnostic usefulness and clinical impact.

METHODS

Intraoperative ultrasonography was performed during pterional craniotomies to identify the causes of severe brain swelling in 23 out of 185 patients treated using a policy of ultra-early treatment after a subarachnoid hemorrhage. Paine's point was used as the sonographic window to provide axial images showing the anterior interhemispheric fissure, lentiform nucleus, insular cortex, sylvian fissure, and ventricular system.

RESULTS

The intraoperative ultrasonography revealed significant changes from the preoperative CT findings in 9 (39.1 %) of the 23 patients. These changes included the occurrence of an intracerebral hemorrhage (ICH, n = 2) related to aneurysm rebleeding with aggravated hydrocephalus and the development (n = 5) or aggravation (n = 2) of acute hydrocephalus without rebleeding. Meanwhile, for 14 (60.9 %) of the 23 patients, the ultrasonography showed no intracranial changes. For the total 23 patients with severe brain swelling, the intraoperative management included aspiration of an ICH (n = 3), a ventriculostomy (n = 16), and medical management (n = 8) with additional mannitol and/or mild hyperventilation.

CONCLUSIONS

When severe brain swelling is encountered during a pterional craniotomy for clipping a ruptured aneurysm, an intraoperative ultrasonography technique using Paine's point as a sonographic window provides useful and reliable diagnostic information on the causes of the brain swelling, enabling the neurosurgeon to select appropriate intraoperative management.

Use of a simple internal fiducial as an adjunct to enhance intraoperative ultrasound-assisted guidance: technical note

BACKGROUND

Image-based navigational techniques have been used increasingly in neurosurgery to improve intraoperative precision. These techniques, however, have the disadvantage of inherent inaccuracies, which are significant especially when targeting small, subcortical lesions in eloquent areas. Intraoperative ultrasound serves as a useful, real-time adjunct to these techniques, but at times, precise correlation of the true anatomical location to the ultrasound image can be challenging.

OBJECTIVE

: To improve the accuracy and precision of intraoperative ultrasound by using a simple internal fiducial marker made from materials already present on the sterile field.

METHODS

We present 3 cases (2 cranial, 1 spinal) of small lesions with deep and eloquent locations. Magnetic resonance imaging (MRI)-based frameless stereotaxy or spinal fluoroscopy was used to modify the incision and to approximate the surgical trajectory, which was marked intradurally with a small piece of Gelfoam soaked in autologous blood. Ultrasound was used to visualize the echogenic lesion, and the precise trajectory was then refined using the echogenic blood-soaked Gelfoam on the cortical or spinal cord surface.

RESULTS

In all 2 patients, the combined use of MRI-based frameless stereotaxy (cranial cases only) and ultrasound guidance minimized dissection through normal tissue. All cases resulted in a gross total resection and no added long-term surgical morbidity.

CONCLUSION

We describe a neuronavigational tool to aid in the precise localization of a subcortical or spinal lesion, particularly one that is small and in close proximity to eloquent areas.

The evolution of intramedullary spinal cord tumor surgery

OBJECTIVE

Resections of intramedullary spinal cord tumors were attempted as early as 1890. More than a century after these primitive efforts, profound advancements in imaging, instrumentation, and operative techniques have greatly improved the modern surgeon's ability to treat such lesions successfully, often with curative results.

METHODS

We review the history of intramedullary spinal cord tumor surgery, as well as the evolution and advancement of technologies and surgical techniques that have defined the procedure over the past 100 years.

RESULTS

Surgery to remove intramedullary spinal cord tumors has evolved to include sophisticated imaging equipment to pinpoint tumor location, laser scalpel systems to provide precise incisions with minimal damage to surrounding tissue, and physiological monitoring to detect and prevent intraoperative motor deficits.

CONCLUSION

Modern surgical devices and techniques have developed dramatically with the availability of new technologies. As a result, continual advancements have been achieved in intramedullary spinal cord tumor surgery, thus increasing the safety and effectiveness of tumor resection, and progressively improving the overall outcomes in patients undergoing such procedures.

Reliability of intraoperative high-resolution 2D ultrasound as an alternative to high–field strength MR imaging for tumor resection control: a prospective comparative study

Object

Ultrasound may be a reliable but simpler alternative to intraoperative MR imaging (iMR imaging) for tumor resection control. However, its reliability in the detection of tumor remnants has not been definitely proven. The aim of the study was to compare high-field iMR imaging (1.5 T) and high-resolution 2D ultrasound in terms of tumor resection control.

Methods

A prospective comparative study of 26 consecutive patients was performed. The following parameters were compared: the existence of tumor remnants after presumed radical removal and the quality of the images. Tumor remnants were categorized as: detectable with both imaging modalities or visible only with 1 modality.

Results

Tumor remnants were detected in 21 cases (80.8%) with iMR imaging. All large remnants were demonstrated with both modalities, and their image quality was good. Two-dimensional ultrasound was not as effective in detecting remnants < 1 cm. Two remnants detected with iMR imaging were missed by ultrasound. In 2 cases suspicious signals visible only on ultrasound images were misinterpreted as remnants but turned out to be a blood clot and peritumoral parenchyma. The average time for acquisition of an ultrasound image was 2 minutes, whereas that for an iMR image was ~ 10 minutes. Neither modality resulted in any procedure-related complications or morbidity.

Conclusions

Intraoperative MR imaging is more precise in detecting small tumor remnants than 2D ultrasound. Nevertheless, the latter may be used as a less expensive and less time-consuming alternative that provides almost real-time feedback information. Its accuracy is highest in case of more confined, deeply located remnants. In cases of more superficially located remnants, its role is more limited.

Mutual-information-based image to patient re-registration using intraoperative ultrasound in image-guided neurosurgery

An image-based re-registration scheme has been developed and evaluated that uses fiducial registration as a starting point to maximize the normalized mutual information (nMI) between intraoperative ultrasound (iUS) and preoperative magnetic resonance images (pMR). We show that this scheme significantly (p<0.001) reduces tumor boundary misalignment between iUS pre-durotomy and pMR from an average of 2.5 mm to 1.0 mm in six resection surgeries. The corrected tumor alignment before dural opening provides a more accurate reference for assessing subsequent intraoperative tumor displacement, which is important for brain shift compensation as surgery progresses. In addition, we report the translational and rotational capture ranges necessary for successful convergence of the nMI registration technique (5.9 mm and 5.2 deg, respectively). The proposed scheme is automatic, sufficiently robust, and computationally efficient (<2 min), and holds promise for routine clinical use in the operating room during image-guided neurosurgical procedures.