High-frequency intra-operative ultrasound-guided surgery of superficial intra-cerebral lesions via a single-burr-hole approach

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.

Mini-craniotomy for intra-axial brain tumors: a comparison with conventional craniotomy in 306 patients harboring non-dural based lesions

The use of a mini-craniotomy approach involving linear skin incision and a bone flap of about 3 cm has been reported for several neurosurgical diseases, such as aneurysms or cranial base tumors. More superficial lesions, including intra-axial tumors, may occasionally raise concerns due to insufficient control of the tumor boundaries. The convenience of a minimally invasive approach to intrinsic brain tumors was evaluated by comparing 161 patients who underwent mini-craniotomy (MC) for intra-axial brain tumors with a group of 145 patients operated on by the same surgical team through a conventional craniotomy (CC). Groups were propensity-matched for age, preoperative condition, size and location of the tumor, and pathological diagnosis. Results were analyzed focusing on operative time, the extent of resection, clinical outcome, hospitalization time, and time to start adjuvant therapy. Mini-craniotomy was equally effective in terms of extent of resection (GTR: 70.9% in the MC group vs 70.5% in the CC group) but had shorter operative time (average: 165 min in the MC group vs 205 min in the CC group p < 0.001) and lower rate of postoperative complications both superficial (1.03% vs 6.5% in the CC group p = 0.009) and deep (4% in the MC group vs 5.5% in the CC group p = 0,47). No relationship was found between the size or location of the tumor and resection rate. The MC group had reduced hospitalization time (average: 5.8 days vs 7.6 in CC group p < 0.001) and faster access to adjuvant therapies. 92.5% of the MC patients, which were scheduled for treatment, started radiotherapy within 8 weeks after surgery as opposed to 84.1% in the CC group (p = 0.04). These findings support the increasing use of mini-craniotomy for intra-axial brain tumors.

Emergency Intraoperative Ultrasound for the Neurosurgical Trainee

The use of intraoperative ultrasound in emergency cranial neurosurgical procedures is not well described. It may improve surgical outcomes and is useful when other neuro-navigation systems are not readily available. We provide a practical guide for neurosurgical trainees to utilize ultrasound for various emergency cranial neurosurgical procedures, including lesion localization, insertion of an external ventricular drain, and shunt revision surgery. Intraoperative ultrasound is a useful modality for urgent neurosurgical procedures.

Machine Vision for Real-Time Intraoperative Anatomic Guidance: A Proof-of-Concept Study in Endoscopic Pituitary Surgery

BACKGROUND

Current intraoperative orientation methods either rely on preoperative imaging, are resource-intensive to implement, or difficult to interpret. Real-time, reliable anatomic recognition would constitute another strong pillar on which neurosurgeons could rest for intraoperative orientation.

OBJECTIVE

To assess the feasibility of machine vision algorithms to identify anatomic structures using only the endoscopic camera without prior explicit anatomo-topographic knowledge in a proof-of-concept study.

METHODS

We developed and validated a deep learning algorithm to detect the nasal septum, the middle turbinate, and the inferior turbinate during endoscopic endonasal approaches based on endoscopy videos from 23 different patients. The model was trained in a weakly supervised manner on 18 and validated on 5 patients. Performance was compared against a baseline consisting of the average positions of the training ground truth labels using a semiquantitative 3-tiered system.

RESULTS

We used 367 images extracted from the videos of 18 patients for training, as well as 182 test images extracted from the videos of another 5 patients for testing the fully developed model. The prototype machine vision algorithm was able to identify the 3 endonasal structures qualitatively well. Compared to the baseline model based on location priors, the algorithm demonstrated slightly but statistically significantly (P < .001) improved annotation performance.

CONCLUSION

Automated recognition of anatomic structures in endoscopic videos by means of a machine vision model using only the endoscopic camera without prior explicit anatomo-topographic knowledge is feasible. This proof of concept encourages further development of fully automated software for real-time intraoperative anatomic guidance during surgery.

Ultrasonographic features of focal cortical dysplasia and their relevance for epilepsy surgery

OBJECTIVE Surgery has proven to be the best therapeutic option for drug-refractory cases of focal cortical dysplasia (FCD)-associated epilepsy. Seizure outcome primarily depends on the completeness of resection, rendering the intraoperative FCD identification and delineation particularly important. This study aims to assess the diagnostic yield of intraoperative ultrasound (IOUS) in surgery for FCD-associated drug-refractory epilepsy. METHODS The authors prospectively enrolled 15 consecutive patients with drug-refractory epilepsy who underwent an IOUS-assisted microsurgical resection of a radiologically suspected FCD between January 2013 and July 2016. The findings of IOUS were compared with those of presurgical MRI postprocessing and the sonographic characteristics were analyzed in relation to the histopathological findings. The authors investigated the added value of IOUS in achieving completeness of resection and improving postsurgical seizure outcome. RESULTS The neurosurgeon was able to identify the dysplastic tissue by IOUS in all cases. The visualization of FCD type I was more challenging compared to FCD II and the demarcation of its borders was less clear. Postsurgical MRI showed residual dysplasia in 2 of the 3 patients with FCD type I. In all FCD type II cases, IOUS allowed for a clear intraoperative visualization and demarcation, strongly correlating with presurgical MRI postprocessing. Postsurgical MRI confirmed complete resection in all FCD type II cases. Sonographic features correlated with the histopathological classification of dysplasia (sonographic abnormalities increase continuously in the following order: FCD IA/IB, FCD IC, FCD IIA, FCD IIB). In 1 patient with IOUS features atypical for FCD, histopathological investigation showed nonspecific gliosis. CONCLUSIONS Morphological features of FCD, as identified by IOUS, correlate well with advanced presurgical imaging. The resolution of IOUS was superior to MRI in all FCD types. The appreciation of distinct sonographic features on IOUS allows the intraoperative differentiation between FCD and non-FCD lesions as well as the discrimination of different histological subtypes of FCD. Sonographic demarcation depends on the underlying degree of dysplasia. IOUS allows for more tailored resections by facilitating the delineation of the dysplastic tissue.

Forgotten? Not Yet. Cardiogenic Brain Abscess in Children: A Case Series-Based Review

BACKGROUND

Brain abscess is a significant cause of morbidity in patients with uncorrected or partially palliated congenital cyanotic heart disease (CCHD). Unfortunately, in the developing world, the majority of patients with CCHD remain either uncorrected or only partially palliated. Furthermore, a risk of this feared complication also exists even among those undergoing staged corrective operations in the interval in between operations. There have been no recent articles in the literature on the outcomes of surgical management of cardiogenic brain abscess in children. In this study, we aimed to describe the clinical and demographic profile of patients with cardiogenic cerebral abscess and to highlight the fact that uncorrected or palliated CCHD continue to be at risk for brain abscess.

METHODS

This study was a retrospective analysis of 26 children (age <19 years) being managed for CCHD who were diagnosed with cerebral abscess managed surgically (26 of 39 of cases cerebral abscess in children), at Amrita Institute of Medical Sciences and Research Centre, Kochi, India between December 2000 and January 2014. Data collected retrospectively included demographic information, modes of presentation, diagnosis, location of abscess, details of the underlying heart disease, management of the cerebral abscess, and outcomes of management.

RESULTS

The patient cohort comprised 26 patients (16 males and 10 females), with a mean age of 7.19 years (range, 1.5-19 years). Ten of the 26 patients (38%) required reaspiration after the initial surgery. On follow-up, all the patients had improved symptomatically and demonstrated no signs of cerebral abscess.

CONCLUSIONS

Cardiogenic origin of cerebral abscess is the most common cause of cerebral abscess in children. Unresolved CCHD is a risk factor for the occurrence, persistence, and recurrence of cerebral abscess.

The use of ultrasound in intracranial tumor surgery

BACKGROUND

As an intraoperative imaging modality, ultrasound is a user-friendly and cost-effective real-time imaging technique. Despite this, it is still not routinely employed for brain tumor surgery. This may be due to the poor image quality in inexperienced hands, and the well-documented learning curve. However, with regular use, the operator issues are addressed, and intraoperative ultrasound can provide valuable real-time information. The aim of this review is to provide an understanding for neurosurgeons of the development and use of ultrasound in intracranial tumor surgery, and possible future advances.

METHODS

A systematic search of the electronic databases Embase, Medline OvidSP, PubMed, Cochrane, and Google Scholar regarding the use of ultrasound in intracranial tumor surgery was undertaken.

RESULTS AND DISCUSSION

Intraoperative ultrasound has been shown to be able to accurately account for brain shift and has potential for regular use in brain tumor surgery. Further developments in probe size, resolution, and image reconstruction techniques will ensure that intraoperative ultrasound is more accessible and attractive to the neuro-oncological surgeon.

CONCLUSIONS

This review has summarized the development of ultrasound and its uses with particular reference to brain tumor surgery, detailing the ongoing challenges in this area.

The influence of intraoperative resection control modalities on survival following gross total resection of glioblastoma

The purpose of the present study is to analyze the impact of intraoperative resection control modalities on overall survival (OS) and progression-free survival (PFS) following gross total resection (GTR) of glioblastoma. We analyzed data of 76 glioblastoma patients (30f, mean age 57.4 ± 11.6 years) operated at our institution between 2009 and 2012. Patients were only included if GTR was achieved as judged by early postoperative high-field MRI. Intraoperative technical resection control modalities comprised intraoperative ultrasound (ioUS, n = 48), intraoperative low-field MRI (ioMRI, n = 22), and a control group without either modality (n = 11). The primary endpoint of our study was OS, and the secondary endpoint was PFS-both analyzed in Kaplan-Meier plots and Cox proportional hazards models. Median OS in all 76 glioblastoma patients after GTR was 20.4 months (95 % confidence interval (CI) 18.5-29.0)-median OS in patients where GTR was achieved using ioUS was prolonged (21.9 months) compared to those without ioUS usage (18.8 months). A multiple Cox model adjusting for age, preop Karnofsky performance status, tumor volume, and the use of 5-aminolevulinic acid showed a beneficial effect of ioUS use, and the estimated hazard ratio was 0.63 (95 % CI 0.31-1.2, p = 0.18) in favor of ioUS, however not reaching statistical significance. A similar effect was found for PFS (hazard ratio 0.59, p = 0.072). GTR of glioblastoma performed with ioUS guidance was associated with prolonged OS and PFS. IoUS should be compared to other resection control devices in larger patient cohorts.

Preoperative C-reactive protein predicts the need for repeated intracerebral brain abscess drainage

BACKGROUND

To determine predicting factors for repeated surgical drainage in patients with intracerebral brain abscesses.

METHODS

Patients operated between 01/2008 and 10/2013 with a single-burr-hole technique to drain an intracerebral brain abscess were included from our prospective database. Clinical and radiological characteristics were analyzed retrospectively and compared between patients requiring a single surgical abscess drainage (S group) vs. patients requiring multiple surgical abscess aspirations (M group).

RESULTS

Thirty-five patients (mean age 42.6 years, 14 females) including 27 patients in the S group and 8 in the M group were included in this study. Age, gender, causing bacterial agent, surgical technique and abscess volume were comparable for both groups. Preoperative mean C-reactive protein (CRP) (13.9 mg/l vs. 56.1 mg/l, p=0.015) was significantly higher in the M group. Preoperative mean leukocyte count (12.3×10(9)/l vs. 8.9×10(9)/l, p=0.050) was borderline significantly higher in the M group. Although the origin in the overall population was cryptogenic in 43% of the cases, this was never the case in the patient population needing multiple surgeries.

DISCUSSION

Patients with multiple intracerebral brain abscess aspirations showed significantly higher preoperative CRP values than patients who needed surgery only once. Patients with high CRP values at admission and obvious origin of infection might need closer radiographic as well as clinical and laboratory exams after surgery to earlier select patients, which need repeated surgery.

Relationship of intraoperative ultrasound characteristics with pathological grades and Ki-67 proliferation index in intracranial gliomas

OBJECTIVE

The purpose of the present study was to investigate the relationship between the intraoperative ultrasonographic appearances and the histopathological characteristics of glial tumors using the pathological grading system and the Ki-67 proliferation index.

MATERIALS AND METHODS

Patients with glial tumors who underwent surgery with the aid of intraoperative ultrasonography (IOUS) between September 2013 and August 2014 were included in the study. The lesions' IOUS characteristics were analyzed and compared with the results of surgical histopathological characteristics. Lesions were classified as low-grade gliomas (grade I-II, LGG) and high-grade gliomas (grade III-IV, HGG). The glioblastoma multiforme (grade IV, GBM) group was classified according to the Ki-67 values for further evaluation. The Chi square test (Fisher's exact test) was used for comparing the ultrasonographic characteristics of the low-grade and high-grade gliomas; HGG with different Ki-proliferation indexes. A value of P < 0.05 was considered statistically significant.

RESULTS

A total of 41 patients were included. The histopathological findings revealed 15 LGG and 26 HGG. Twenty of the 26 HGG were GBM. Differences were found between the intraoperative ultrasonographic characteristics of the low-grade and high-grade glial tumors. The majority of LGGs were mildly hyperechoic and homogeneous, with distinct margins and a regular contour. HGGs were mostly highly hyperechoic, with indistinct margins, irregular contours, and a heterogeneous internal texture. Surrounding edema was seen more often in HGGs. The differences in the echogenicity of the solid parts, the internal echo patterns, margins, contours, and peripheral edema (P < 0.05) were statistically significant, but the difference in the presence of cysts (P > 0.05) was not significant. In the GBM group, all of the lesions with distinct margins and regular contours had Ki-67 values ≤15 %. We compared the intraoperative ultrasonographic characteristics of the Ki-67 > 15 % group with those of the Ki-67 ≤ 15 % group for statistical significance. The difference between the echogenicity of the solid parts, margins, and contours was statistically significant between the groups (P < 0.05). The difference in the internal echo pattern, presence of cyst, and peripheral edema was insignificant (P > 0.05).

CONCLUSIONS

IOUS is a very useful imaging technique not only in defining the borders but also in characterizing the tumoral tissue. The IOUS characteristics of the glial tumors were a valuable tool in differentiating the grades of the glial tumors and might have a relationship with the Ki-67 proliferation index. We think this theory requires further investigation in more detailed comparative studies with larger numbers of patients.