Modern intraoperative imaging modalities for the vascular neurosurgeon treating intracerebral hemorrhage

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.

Acute evacuation of 54 intracerebral hematomas (aICH) during the microsurgical clipping of a ruptured middle cerebral artery bifurcation aneurysm-illustration of the individual clinical courses and outcomes with a serial brain CT/MRI panel until 12 months

PURPOSE

In aneurysmal intracerebral hemorrhage (aICH), our review showed the lack of the patient's individual (i) timeline panels and (ii) serial brain CT/MRI slice panels through the aICH evacuation and neurointensive care until the final brain tissue outcome.

METHODS

Our retrospective cohort consists of 54 consecutive aICH patients from a defined population who acutely underwent the clipping of a middle cerebral artery bifurcation saccular aneurysm (Mbif sIA) with the aICH evacuation at Kuopio University Hospital (KUH) from 2010 to 2019. We constructed the patient's individual timeline panels since the emergency call and serial brain CT/MRI slice panels through the aICH evacuation and neurointensive care until the final brain tissue outcome. The patients were indicated by numbers (1.-54.) in the pseudonymized panels, tables, results, and discussion.

RESULTS

The aICH volumes on KUH admission (median 46 cm3) plotted against the time from the emergency call to the evacuation (median 8 hours) associated significantly with the rebleeds (n=25) and the deaths (n=12). The serial CT/MRI slice panels illustrated the aICHs, intraventricular hemorrhages (aIVHs), residuals after the aICH evacuations, perihematomal edema (PHE), delayed cerebral injury (DCI), and in the 42 survivors, the clinical outcome (mRS) and the brain tissue outcome.

CONCLUSIONS

Regarding aICH evacuations, serial brain CT/MRI panels present more information than words, figures, and graphs. Re-bleeds associated with larger aICH volumes and worse outcomes. Swift logistics until the sIA occlusion with aICH evacuation is required, also in duty hours and weekends. Intraoperative CT is needed to illustrate the degree of aICH evacuation. PHE may evoke uncontrollable intracranial pressure (ICP) in spite of the acute aICH volume reduction.

Potential benefits of intraoperative ultrasound in neurosurgery

Computed tomography and magnetic resonance imaging are the most popular diagnostic tools to visualize intracranial pathology and help surgical planning in the neurosurgical practice. However, these preoperative techniques need to be supplemented with intraoperative methods, if the lesion size may increase or preoperative anatomy may change after the primary imaging due to rapid progression of the underlying intracranial disease. In such situations intraoperative ultrasound could be a valuable technique in real-time imaging of intracranial pathologic processes, real-time control of surgical procedure, assistance in drain or catheter placement, and real-time assessment of residual tumor or hematoma volume during neurosurgical interventions.

Side-firing intraoperative ultrasound applied to resection of pituitary macroadenomas and giant adenomas: A single-center retrospective case-control study

Introduction

Multiple intraoperative navigation and imaging modalities are currently available as an adjunct to endoscopic transsphenoidal resection of pituitary adenomas, including intraoperative CT and MRI, fluorescence guidance, and neuronavigation. However, these imaging techniques have several limitations, including intraoperative tissue shift, lack of availability in some centers, and the increased cost and time associated with their use. The side-firing intraoperative ultrasound (IOUS) probe is a relatively new technology in endoscopic endonasal surgery that may help overcome these obstacles.

Methods

A retrospective analysis was performed on patients admitted for resection of pituitary adenomas by a single surgeon at the University of Mississippi Medical Center. The control (non-ultrasound) group consisted of twelve (n=12) patients who received surgery without IOUS guidance, and the IOUS group was composed of fifteen (n=15) patients who underwent IOUS-guided surgery. Outcome measures used to assess the side-firing IOUS were the extent of tumor resection, postoperative complications, length of hospital stay (LOS) in days, operative time, and self-reported surgeon confidence in estimating the extent of resection intraoperatively.

Results

Preoperative data analysis showed no significant differences in patient demographics or presenting symptoms between the two groups. Postoperative data revealed no significant difference in the rate of gross total resection between the groups (p = 0.716). Compared to the non-US group, surgeon confidence was significantly higher (p < 0.001), and operative time was significantly lower for the US group in univariate analysis (p = 0.011). Multivariate analysis accounting for tumor size, surgeon confidence, and operative time confirmed these findings. Interestingly, we noted a trend for a lower incidence of postoperative diabetes insipidus in the US group, although this did not quite reach our threshold for statistical significance.

Conclusion

Incorporating IOUS as an aid for endonasal resection of pituitary adenomas provides real-time image guidance that increases surgeon confidence in intraoperative assessment of the extent of resection and decreases operative time without posing additional risk to the patient. Additionally, we identified a trend for reduced diabetes insipidus with IOUS.

Application of Intraoperative Ultrasound Navigation in Neurosurgery

Effective intraoperative image navigation techniques are necessary in modern neurosurgery. In the last decade, intraoperative ultrasonography (iUS), a relatively inexpensive procedure, has gained widespread acceptance.

Application of intraoperative ultrasound in neurosurgery for hypertensive intracerebral hemorrhage

OBJECTIVE

To explore the clinical significance of intraoperative ultrasound in neurosurgery for hypertensive intracerebral hemorrhage (ICH).

METHODS

Patients with hypertensive ICH who required to undergo surgical treatment were assigned into treatment group (126 cases), who were assisted by intraoperative ultrasound, and control group (122 cases), who were not assisted by intraoperative ultrasound. In the treatment group, intraoperative ultrasound was used for real-time positioning after opening the bone flap, so as to guide the surgery. After surgery, conventional treatment and follow-up were conducted, and the statistical analysis was eventually performed to compare the therapeutic efficacy of the two groups.

RESULTS

The mean rate of hematoma clearance was (95.20 ± 5.18)% in the treatment group and (86.20 ± 4.85)% in the control group (P<0.05); the average time required for intraoperative hematoma clearance was 44.5±3.2 min in the treatment group and 66.3±5.1 min in the control group (P < 0.05). Finally, the treatment group was superior to the control group in terms of therapeutic efficacy and overall prognosis (P = 0.03 and 0.025, respectively).

CONCLUSIONS

Intraoperative ultrasound possessed the features of precise positioning, real-time guidance, and being user-friendly, which can shorten the operation time, increase the efficacy of surgery, and improve patients' overall prognosis, highlighting high clinical significance of intraoperative ultrasound in neurosurgery.

Intraoperative magnetic resonance imaging for cerebral cavernous malformations: When is it maybe worth it?

OBJECTIVE

Intraoperative magnetic resonance imaging (iMRI) can be useful for cerebral cavernous malformations (CCM) surgery. However, literature on this topic is scarce. We aim to investigate its clinical utility and propose criteria for the selection of patients who may benefit the most from iMRI.

METHODS

From 2017 to 2019, all patients with CCMs who required surgery assisted with iMRI were included in the study. Clinical and radiological features were analyzed. Outcome measures included the need for an immediate second-look resection and clinical course in early post-surgery -Timepoint 1- (Tp1) and at the 6-to-12-month follow-up -Timepoint2- (Tp2).

RESULTS

Out of 19 patients with 20 CCMs, 89% had bleeding in the past, and in 75% the CCM affected an eloquent area. According to the iMRI results, an immediate second-look resection was needed in 16% of them. In one patient, a remnant was not seen on iMRI. The mRS worsened in the immediate post-surgical exam (median, 1; IQR, 1) with improvements on the 6-month visit (median, 1; IQR, 2), (p = 0.018). When comparing the outcome of patients with and without symptoms at baseline, the latter fared better at Tp2 (p = 0.005).

CONCLUSIONS

iMRI is an intraoperative imaging tool that seems safe for CCM surgery and might reduce the risk of lesion remnants. In our series, it allowed additional revision for further resection in 16% of the patients. In our experience, iMRI may be especially useful for lesions in eloquent areas, those with a significant risk of brain shift and for large CCMs.

The value of intraoperative angiography in the time of indocyanine green videoangiography in the treatment of cerebrovascular lesions: Efficacy, workflow, risk-benefit and cost analysis A prospective study

INTRODUCTION

Intraoperative digital subtraction angiography (ioDSA) allows early treatment evaluation after neurovascular procedures. However, the value and efficiency of this procedure has been discussed controversially. We have evaluated the additional value of hybrid operating room equipped with an Artis Zeego robotic c-arm regarding cost, efficiency and workflow. Furthermore, we have performed a risk-benefit analysis and compared it with indocyanine green (ICG) angiography.

METHODS

For 3 consecutive years, we examined all neurovascular patients, treated in the hybrid operating theater in a risk-benefit analysis. After using microdoppler and ICG angiography for best operative result, every patient received an additional ioDSA to look for remnants or unfavorable clip placement which might lead to a change of operating strategy or results. Furthermore, a workflow-analysis reviewing operating steps, staff positioning, costs, technical errors or complications were conducted on randomly selected cases.

RESULTS

54 patients were enrolled in the risk-benefit analysis, 22 in the workflow analysis. The average duration of a cerebrovascular operation was 4 h 58 min 2 min 35 s accounted for ICG angiography, 46 min 4 s for ioDSA. Adverse events occurred during one ioDSA. In risk-benefit analysis, ioDSA was able to detect a perfusion rest in 2 out of 43 cases (4,7%) of aneurysm surgery, which could not have been visualized by ICG angiography before. In arterio-venous-malformation (AVM) surgery, one of 11 examined patients (7,7%) showed a remnant in ioDSA and resulted in additional resection. The average cost of an ioDSA in Ulm University can be estimated with 1928,00€.

CONCLUSION

According to our results ioDSA associated complications are low. Relevant findings in ioDSA can potentially avoid additional intervention, however, due to the high costs and lower availability, the main advantage might lie in the treatment of selected patients with complexes neurovascular pathologies since ICG angiography is equally safe but associated with lower costs and better availability.

Neuroimaging of Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) accounts for 10% to 20% of strokes worldwide and is associated with high morbidity and mortality rates. Neuroimaging is indispensable for rapid diagnosis of ICH and identification of the underlying etiology, thus facilitating triage and appropriate treatment of patients. The most common neuroimaging modalities include noncontrast computed tomography (CT), CT angiography (CTA), digital subtraction angiography, and magnetic resonance imaging (MRI). The strengths and disadvantages of each modality will be reviewed. Novel technologies such as dual-energy CT/CTA, rapid MRI techniques, near-infrared spectroscopy, and automated ICH detection hold promise for faster pre- and in-hospital ICH diagnosis that may impact patient management.

The role of intraoperative ultrasound in gross total resection of brain mass lesions and outcome

Background

Surgical resection of brain mass lesion mandates safety and the best outcome for the patient.

Objectives

The aim of this study was the evaluation of intraoperative ultrasound (IOUS) in gross total resection of brain mass lesions and patients’ safety in comparison to conventional surgery.

Materials and methods

In total, 632 patients were operated for brain mass lesion resection at Neurosurgery Department, Zagazig University Hospitals, during the period from January 2011 to October 2018 and divided randomly into two groups, IOUS group and conventional group, for the detection value of IOUS in resection, safety, and outcome after 3 months follow-up.

Results

The IOUS group showed statistically significant gross total resection regardless to pathology, location, size, age, and sex in favor of IOUS use, and also, there were significantly less complications and better outcome after 3 months follow-up with the IOUS group. Significantly better outcome was found with gross total resection in total surgeries.

Conclusions

The use of IOUS during brain mass lesion surgery is safe and can assist the surgeon in gross total resection with better outcome.

Contemporary Management of Increased Intraoperative Intracranial Pressure: Evidence-Based Anesthetic and Surgical Review

Increased intracranial pressure (ICP) is frequently encountered in the neurosurgical setting. A multitude of tactics exists to reduce ICP, ranging from patient position and medications to cerebrospinal fluid diversion and surgical decompression. A vast amount of literature has been published regarding ICP management in the critical care setting, but studies specifically tailored toward the management of intraoperative acute increases in ICP or brain bulk are lacking. Compartmentalizing the intracranial space into blood, brain tissue, and cerebrospinal fluid and understanding the numerous techniques available to affect these individual compartments can guide the surgical team to quickly identify increased brain bulk and respond appropriately. Rapidly instituting measures for brain relaxation in the operating room is essential in optimizing patient outcomes. Knowledge of the efficacy, rapidity, feasibility, and risks of the various available interventions can aid the team to properly tailor their approach to each individual patient. In this article, we present the first evidence-based review of intraoperative management of ICP and brain bulk.

Ultrasound-guided brain surgery: echographic visibility of different pathologies and surgical applications in neurosurgical routine

BACKGROUND

The use of intraoperative ultrasound (iUS) has increased in the last 15 years becoming a standard tool in many neurosurgical centers. Our aim was to assess the utility of routine use of iUS during various types of intracranial surgery. We reviewed our series to assess ultrasound visibility of different pathologies and iUS applications during the course of surgery.

MATERIALS AND METHODS

This is a retrospective review of 162 patients who underwent intracranial surgery with assistance of the iUS guidance system (SonoWand). Pathologic categories were neoplastic (135), vascular (20), infectious (2), and CSF related (5). Ultrasound visibility was assessed using the Mair classification, a four-tiered grading system that considers the echogenicity of the lesion and its border visibility (from 0 to 3; grade 0, pathology not visible; grade 3, visible with clear border with normal tissue). iUS applications included lesion localization, approach planning to deep-seated lesions, and lesion removal.

RESULTS

All pathologies were visible on iUS except one aneurysm. On average, extra-axial tumors were identified more easily and had clearer limits compared to intra-axial tumors (extra-axial 17% grade 2, 83% grade 3; intra-axial 5.5% grade 1, 46.5% grade 2, 48% grade 3). iUS provided precise and safe transcortical trajectories to deep-seated lesions (71 patients; tumors, hemangiomas, ICHs); iUS was judged to be less useful to approach skull base tumors and aneurysms. iUS was used to judge extent of resection in 152 cases; surgical artifacts reduced sonographic visibility in 25 cases: extent of resection was correctly checked in 127 patients (53 gliomas, 15 metastases, 39 meningiomas, 4 schwannomas, 4 sellar region tumors, 6 hemangiomas, 3 AVMs, 2 abscesses).

CONCLUSIONS

iUS was highly sensitive in detecting all types of pathology, was safe and precise in planning trajectories to intraparenchymal lesions (including minimally mini-invasive approaches), and was accurate in checking extent of resection in more than 80% of cases. iUS is a versatile and feasible tool; it could improve safety and its use may be considered in routine intracranial surgery.

Intracavitary ultrasound (ICARUS): a neuroendoscopic adaptation of intravascular ultrasound for intracerebral hemorrhage evacuation

Neurosurgeons performing intracerebral hemorrhage evacuation procedures have limited options for monitoring hematoma evacuation and assessing residual hematoma burden intraoperatively. Here, we report the successful neuroendoscopic adaptation of intravascular ultrasound, referred to here as intracavitary ultrasound (ICARUS), in two patients. Pre-evacuation ICARUS demonstrated dense hematomas in both patients. Post-evacuation ICARUS in patient 1 demonstrated significant reduction in clot burden and two focal hyperechoic regions consistent with pockets of hematoma not previously seen with the endoscope or burr hole ultrasound. These areas were directly targeted and resected with the endoscope and suction device. Post-evacuation ICARUS in patient 2 showed significant reduction of hematoma volume without indication of residual blood. ICARUS findings were confirmed on intraoperative DynaCT and postoperative CT 24 hours later. ICARUS is feasibly performed in a hematoma cavity both before and after hematoma aspiration. ICARUS may provide additional information to the operating surgeon and assist in maximizing hematoma removal.

Neuronavigated microvascular Doppler sonography for intraoperative monitoring of blood flow velocity changes during aneurysm surgery - a feasible monitoring technique

INTRODUCTION AND AIM OF THE STUDY

The intraoperative microvascular Doppler sonography (iMDS) is a well-established tool in vascular surgery for blood flow velocity (BFV) monitoring, capable of detecting vessel occlusion. However, identification of subtotal vessel compromise is more difficult, since the measured BFV may substantially vary with changing insonation angles and insonated vessel segments. To keep these parameters constant we combined neuronavigation with iMDS (niMDS). The question was if niMDS allows the detection of subtotal vessel compromise in aneurysm surgery.

METHODS

During surgery, the 3-dimensional reconstruction of the CT-angiography, which was obtained routinely prior to surgery, was displayed by the neuronavigational system. Prior to clipping, neuronavigation was used to define target point and trajectory, which, by coupling the neuronavigational pointer with the Doppler probe, correspond to the insonated vessel segment and the insonation angle. After clipping, for each vessel segment, the same trajectory was used for all consecutive measurements. The mean BFVs pre- and post-clipping were documented.

RESULTS

We performed 82 BFV-measurements in 39 aneurysm surgeries. Mean deviation between pre- and post-clipping BFV values was 2.12cm/s. There was a significant correlation between the mean BFV values before and after clipping (r=0.45 [95% CI 17-66%]; p=0.002). One patient experienced new neurological deficits due to occlusion of a perforating vessel that was not insonated.

CONCLUSION

The study could not answer the question if niMDS can detect BFV changes after clipping indicating vessel compromise, as no subtotal vessel occlusion occurred in the 39 operations. However, we proofed that niMDS-measured BFVs only varied minimally in uncompromised vessels pre- and post-clipping, suggesting that vessel compromises might be easily detected during aneurysm surgery.

Usefulness of repetitive intraoperative indocyanine green-based videoangiography to confirm complete obliteration of micro-arteriovenous malformations

Background:

It is difficult to intraoperatively confirm the total disappearance of arteriovenous (AV) shunts during surgery for microarteriovenous malformations (micro-AVMs), especially when the nidus is extremely small or diffuse on preoperative angiography. Although intraoperative angiography is effective for evaluating residual shunts, procedure-related risks raise important concerns. The purpose of this study was to assess the usefulness of intraoperative indocyanine green-based videoangiography (ICG–VA) to determine complete disappearance of micro-AVMs during surgery.

Methods:

We retrospectively analyzed eight patients with ruptured micro-AVMs who were treated using craniotomy with ICG–VA at our institution.

Results:

Two patients underwent emergency partial evacuation of hematoma and external decompression before the diagnostic angiography. While three patients had a nidus smaller than 1 cm, five patients had only early draining veins without an appreciable nidus. The draining veins were superficial in six cases and deep in two cases. The average interval from onset to surgery was 33 days (range, 2–57). ICG–VA was repetitively conducted until disappearance of the AV shunt was confirmed. No residual AV shunt was observed on postoperative radiological examinations. In all cases, the diagnosis of AVM was confirmed from the results of postoperative pathological examination.

Conclusions:

ICG–VA could detect early draining veins more clearly in situ than diagnostic angiography. Although it is not as effective for visualizing lesions with deep draining veins, repetitive ICG–VA was safe and effective for confirming the disappearance of AV shunts with superficial drainage.

Anatomical Variations of the Blood Vascular System in Veterinary Medicine: The Internal Iliac Artery of the Dog: Part One

Traditional veterinary anatomical models describe the branches of the caudal gluteal artery as the iliolumbar, cranial gluteal, lateral caudal, satellite of the ischiatic nerve and dorsal perineal arteries. However, some classical veterinary anatomy textbooks often indicate variations the general organization of the arterial tree, without giving any pattern of origin or illustrations of the different branching. The aim of this study was to investigate the presumptive variability of the caudal gluteal artery. Two hundred and thirty-two pelvic halves from 116 adult dogs were examined. Twelve anatomical variations were found, nine occurring in more than 5% of the dogs, and three in <5%. A 'long-type' internal iliac artery, which means short caudal gluteal and internal pudendal arteries, was identified, while a 'perineal trunk' was observed as an interesting arterial variation. If the caudal segment alone is taken into consideration, identical vascular patterns in both hemi-pelvises are found in 17% of the dogs. Significant statistical correlation was found for four different types of anatomic variations and gender, two types of variations and body size, one type of variation for body side and one type of variation for head shape.

Atypical radiological and intraoperative findings of acute cerebral hemorrhage caused by ruptured cerebral aneurysm in a patient with severe chronic anemia

Acute intracerebral hemorrhage (ICH) associated with mild anemia is commonly observed on radiological examination, and there are several reports of ruptured aneurysms occurring with ICH but without accompanying subarachnoid hemorrhage. However, the relationship among computed tomography (CT), magnetic resonance imaging (MRI), and intraoperative findings of ICH caused by ruptured cerebral aneurysm in patients with severe chronic anemia has been rarely reported and is poorly understood. Here, we report atypical radiological and intraoperative findings of acute ICH caused by ruptured cerebral aneurysm in a patient with severe chronic anemia. A 64-year-old man with anemia was admitted to our hospital after he experienced left hemiparesis and a disturbance of consciousness. At a referring institution, he showed evidence of macrocytic anemia (white blood cell count, 9,000/μL; red blood cell count, 104×10(4)/μL; hemoglobin, 4.0 g/dL; hematocrit, 12.2%; and platelet count, 26.6×10(4)/μL). Both CT and MRI showed a right frontal ICH. The outer ring of the hematoma appeared as low-density area on CT, a low-intensity area on T1-weighted MRI, and a high-intensity area on T2-weighted MRI with a serous component. The patient received a blood transfusion and underwent surgical removal of the hematoma the following day. The white serous effusion visualized with CT and MRI was identified as a blood clot in the hematoma cavity. The blood that leaks from blood vessels appears as a high-intensity area on CT because it undergoes plasma absorption in a solidification shrinkage process, and is, therefore, concentrated. Although we did not examine the white effusion to determine if serous components were present, we speculated that the effusion may have contained serous components. Therefore, we removed the part of the effusion that appeared as a low-density area on CT. The presence of ICH without subarachnoid hemorrhage suggested the possible adhesion and rupture of a previous aneurysm. Therefore, ICH appeared as a mixed density area on CT because bleeding may have occurred several times. Because radiological findings of ICH caused by ruptured cerebral aneurysm in patients with severe chronic anemia are similar to those of ICH and cerebral edema, we suggest that the atypical radiological findings of ICH caused by ruptured cerebral aneurysm in patients with severe chronic anemia should be carefully evaluated, especially when surgery is indicated.

Indocyanine green videoangiography methodological variations: review

Indocyanine green videoangiography (ICGVA) procedures have become widespread within the spectrum of microsurgical techniques for neurovascular pathologies. We have conducted a review to identify and assess the impact of all of the methodological variations of conventional ICGVA applied in the field of neurovascular pathology that have been published to date in the English literature. A total of 18 studies were included in this review, identifying four primary methodological variants compared to conventional ICGVA: techniques based on the transient occlusion, intra-arterial ICG administration via catheters, use of endoscope system with a filter to collect florescence of ICG, and quantitative fluorescence analysis. These variants offer some possibilities for resolving the limitations of the conventional technique (first, the vascular structure to be analyzed must be exposed and second, vascular filling with ICG follows an additive pattern) and allow qualitatively superior information to be obtained during surgery. Advantages and disadvantages of each procedure are discussed. More case studies with a greater number of patients are needed to compare the different procedures with their gold standard, in order to establish these results consistently.

A practical grading system of ultrasonographic visibility for intracerebral lesions

BACKGROUND

Intraoperative ultrasound for intracranial neurosurgery was largely abandoned in the 1980s due to poor image resolution. Despite many technological advances in ultrasound since then, the use of this imaging modality in contemporary practice remains limited. Our aim was to evaluate the utility of modern intraoperative ultrasound in the resection of a wide variety of intracranial pathologies.

METHODS

A total of 105 patients who underwent intracranial lesion resection in a contiguous fashion were prospectively included in the study. Ultrasound images acquired intraoperatively were used to stratify lesions into one of four grades (grades 0-3) on the basis of their ultrasonic echogenicity and border visibility.

RESULTS

Forty-two out of 105 lesions (40 %) were clearly identifiable and had a clear border with normal tissue (grade 3). Fifty-five of 105 lesions (52 %) were clearly identifiable but had no clear border with normal tissue (grade 2). Eight of 105 lesions (8 %) were difficult to identify and had no clear border with normal tissue (grade 1). None (0 %) of the lesions could not be identified (grade 0). High-grade gliomas, cerebral metastases, meningiomas, ependymomas, and haemangioblastomas all demonstrated a median ultrasonic visibility grade of 2 or greater. Low-grade astrocytomas and oligodendrogliomas demonstrated a median ultrasonic visibility grade of 2 or less.

CONCLUSION

Intraoperative ultrasound can be of tremendous benefit in allowing the surgeon to appraise the location, extent, and local environment of their target lesion, as well as to reduce the risk of preventable complications. We believe that our grading system will provide a useful adjunct to the neurosurgeon when deciding for which lesions intraoperative ultrasound would be useful.