ITVT-05. Intraoperative Ultrasound Guidance Improves Resection In Gliomas – Results From A Single Centre Propensity Matched Comparative Cohort Analysis Of 2D Vs Navigated 3D Ultrasound In 500 Gliomas

INTRODUCTION Intraoperative ultrasound (iUS) is a promising tool for glioma surgery. Navigated 3-D (n3D) iUS has many benefits over standard 2-D iUS. METHODS This was a retrospective comparative cohort study using propensity score matching (PSM). 500 consecutive histologically confirmed gliomas were divided into 2 cohorts – 2DiUS - Cohort A; and n3DiUS -Cohort B. PSM was used to account for known confounders (250 in each group; 1:1 matching). Gross total resection rates (based on iUS findings as well as postoperative MR) and perioperative morbidity were analyzed across the groups as were factors influencing these outcomes (using univariate as well as multivariate regression models). RESULTS Overall, the majority of the patients were adults (94%), males (71%) with hemispheric tumors (96%). 35% had tumors close to eloquent regions and 23% had received some prior treatment. The majority were high-grade gliomas (85%). 2D iUS was employed mainly for localization (80%) whereas n3D was used predominantly for resection control (84%) [p < 0.001]. GTR rate was higher in the n3D cohort (55.2% vs 38.4% in 2D; p = 0.001). The odds of having a complete resection in the n3D cohort was twice that of the 2D. Prior treatment, hemispheric location, and use of fluorescence were also significantly associated with higher GTR rates on univariate analysis. On multivariate analysis, all of these remained significant. There was no difference in the morbidity rates in the two cohorts. N3D iUS had a higher specificity and positive likelihood ratio in detecting tumor residue. CONCLUSION For hemispheric gliomas undergoing resective surgery, the use of navigated 3D ultrasound improves GTR rates, with no added morbidity. It is more likely to be used for resection control mode than is 2DUS and this is probably because n3DUS is more specific and likely to pick up tumor residues contributing to its better accuracy.

ITVT-08. Combined use of awake surgery and intraoperative MRI augments extent of resection in eloquent gliomas without neurological impairment

Maximizing the extent of resection (EOR) while preserving functional integrity is a mainstay of glioma surgery. Intraoperative MRI (iMRI) helps to augment the EOR. However, in eloquently located gliomas the significance of iMRI is controversial since the EOR is limited by functional rather than image-based boundaries. Thus, we sought to determine the impact of iMRI in our institutional series of awake glioma resections within or adjacent to eloquent (language, motor, sensory) areas since the implementation of a 1.5 Tesla iMRI in 2009. Tumor- and procedure-related data and functional outcome were assessed through medical charts review. The EOR was determined volumetrically on pre-, intra- and postoperative T1 contrast-enhanced (CE) and FLAIR MR images. 131 of 166 awake surgeries (79%) were performed under iMRI-guidance with concurrent language (n=72) and/or motor (n=50) mapping. iMRI was done when functional boundaries were reached (62%), for resection control (28%) or for other reasons (10%). Additional resection after iMRI (AR) was performed in 63 cases (73%); otherwise resection was terminated because the targeted EOR or functional boundaries were reached. New or deteriorated neurological deficits occurred in 20 patients prior and 15 patients post iMRI; however, all but 3 resolved within 6 months. Median EOR significantly increased after AR from 92.6% to 98.4% (∆5.8%; p<0.0001) in CE tumors and from 64.5% to 85.8% (∆21.3%; p<0.0001) in non-enhancing tumors. Remarkably, the reason to perform iMRI (resection control or functional limitations), did not affect the frequency of AR, deficits acquired post iMRI or the increase in EOR after AR. In conclusion, iMRI is a valuable adjunct to maximize the EOR in awake glioma resections without increasing the risk for functional impairment, particularly in non-enhancing tumors. Importantly, iMRI contributes to a maximized EOR even in cases where the resection had to be stopped because functional boundaries were reached.

Navigated ultrasound-based image guidance during resection of gliomas: practical utility in intraoperative decision-making and outcomes

OBJECTIVEIntraoperative imaging is increasingly being used for resection control in diffuse gliomas, in which the extent of resection (EOR) is important. Intraoperative ultrasound (iUS) has emerged as a highly effective tool in this context. Navigated ultrasound (NUS) combines the benefits of real-time imaging with the benefits of navigation guidance. In this study, the authors investigated the use of NUS as an intraoperative adjunct for resection control in gliomas.METHODSThe authors retrospectively analyzed 210 glioma patients who underwent surgery using NUS at their center. The analysis included intraoperative decision-making, diagnostic accuracy, and operative outcomes, particularly EOR and related factors influencing this.RESULTSUS-defined gross-total resection (GTR) was achieved in 57.6% of patients. Intermediate resection control scans were evaluable in 115 instances. These prompted a change in the operative decision in 42.5% of cases (the majority being further resection of unanticipated residual tumor). Eventual MRI-defined GTR rates were similar (58.6%), although the concordance between US and MRI was 81% (170/210 cases). There were 21 false positives and 19 false negatives with NUS, resulting in a sensitivity of 78%, specificity of 83%, positive predictive value of 77%, and negative predictive value of 84%. A large proportion of patients (13/19 patients, 68%) with false-negative results eventually had near-total resections. Tumor resectability, delineation, enhancement pattern, eloquent location, and US image resolution significantly influenced the GTR rate, though only resectability and eloquent location were significant on multivariate analysis.CONCLUSIONSNUS is a useful intraoperative adjunct for resection control in gliomas, detecting unanticipated tumor residues and positively influencing the course of the resection, eventually leading to higher resection rates. Nevertheless, resection is determined by the innate resectability of the tumor and its relationship to eloquent location, reinforcing the need to combine iUS with functional mapping techniques to optimize resections.

Tenorrhaphy as an Alternative to Resection in the Treatment of Horizontal Strabismus in Children

Purpose. To evaluate the effectiveness of surgical treatment of horizontal strabismus by modified tenorrhaphy in comparison with standard resection in children. Material and methods. For 3 years (2017–2019), 560 patients with horizontal strabismus at the age from 2 to 14 years were operated. Of these, 288 patients (51.4%) underwent tenorrhaphy using a modified technique (main group) as augmentation surgery, 272 patients (48.6%) underwent classical resection (control group). Results. The average age of patients in the main group was 6 (3.46) years, in the control group – 5.8 (3.34) years. In the main group of patients, orthotropy was achieved in 85.4% of cases, in the control group – in 83.5% of cases, p = 0.523. The residual strabismus angle (up to 5°) was observed in 40 patients (14%) in the main group and in 44 patients (16.5%) in the control group of patients, p = 0.449. In the main group, additional correction of the residual angle was performed on the day after the operation using adjustable suture in 8 patients (2.8%). Reoperation in the long-term period was required for 10 patients (3.7%) in the control group and 3 patients (0.7%) in the main group, p = 0.039. Significant postoperative conjunctival thickening was found in 7.2% of patients in the main group. Conclusion. The effectiveness of tenorrhaphy is not inferior to classical resection and, in combination with recession (tenomyoplasty), gives predictable stable results. The tenorrhaphy method is technically simpler, safer, more physiological, can be easily corrected in the immediate postoperative period, has no risk of «losing» muscle and can be recommended as an alternative method of resection.

PATH-29. POTENTIAL OF RAMAN SPECTROSCOPY IN ONCOLOGICAL NEUROSURGERY

Raman spectroscopy (RS) has gained increasing interest for the analysis of biological tissues within the recent years. It is a label-free, non-destructive method providing insights in biochemical properties of tumor cells. It is possible to compare RS signals with histological properties of identical tissue parts. Therefore, RS bears promising potentials in neurosurgical neurooncology. On one hand, it could potentially be used for both intraoperative tumor diagnostics and resection control. On the other hand, it could provide important knowledge on tumor biochemistry and used for a subclassification of tumors with a potential impact on personalized therapy approaches. Within our group, we analyzed over 3000 measurement points in different brain tumors ex vivo with a robotized RS system and correlated the spectral curves with histopathological results. We separated and subclassified the data by AI-based methods. Additionally, we compared the latter results with those of a handheld probe, which is potentially navigatable for in vivo, intraoperative applications. We could demonstrate, that it is possible to separate distinct tumor groups only based on RS signals, especially by using computer-based signal analysis. Furthermore, we could demonstrate the differences of the spectra of deep-frozen and formalin-fixed tissues versus non-fixed tissues. Based on our results, we will highlight the potentials of RS for intraoperative neurosurgical application in resection control for brain tumors, as well as we will focus on the potentials for brain tumor diagnostics based purely on this method or by using it as an adjunct. Those methods bear additional potentials in the field of personalized chemotherapy approaches.

389 Advanced Intraoperative Navigated Ultrasound in Brain Tumor Surgery Lessons Learnt from a Personal Experience of 300 Cases

INTRODUCTION Navigated 3D-ultrasound (nUS) is a powerful and multi-purpose adjunct during tumor resections. We review our cumulative results in a dedicated neuro-oncology service spanning a six year period, highlighting its role in glioma surgery. METHODS Since 2011 we have been used a navigated 3D ultrasound system for intraoperative image guidance during brain tumor surgery in 300 cases. A prospectively updated database was queried to retrieve demographic, clinico-radiological and pathological details. Specifically, we evaluated the utility of the IOUS in different setups and assessed its predictive accuracy and impact on extent of resection (EOR) as well as survival in gliomas. RESULTS >300 (204 males/96 females) brain tumors were operated [197 high grade gliomas, 28 LGG, 24 Meningiomas, and 51 other tumors]. Radical resection/debulking was intended in 270 (90%). In 30 (10%), only frameless biopsy was performed. The US was intended for resection control in 219 (73%) tumors, most of them being intrinsic gliomas. Intermediate scans prompted further resection in 101 cases (46%). A final resection control scan was performed in 176 cases (confirming complete excision in 99, and residual tumor which could not be further resected in 77). The nUS was a very useful tool in tumor surgery, providing a good diagnostic accuracy (85-90%) in predicting tumor residue. It also helped us improve the EOR in malignant gliomas as well as non-enhancing gliomas. In the subset of resectable tumors, the gross total resection rate was 88%. Further, in a small subset of malignant gliomas, we demonstrated that it helps extend tumor resection beyond the contrast enhancement zone. In GBMs, in a multivariate model, use of the nUS was an independent predictor of survival. CONCLUSION Considering the ease of use, widespread accessibility and low-cost nature, IOUS can be a potentially useful adjunct during a range of neurosurgical procedures, especially tumor resections.