The role of probabilistic tractography in the surgical treatment of thalamic gliomas

[Surgical treatment of brain tumors adjacent to corticospinal tract in children]

An urgent problem in modern neurosurgery is resection of brain tumors adjacent to corticospinal tract (CST) due to high risk of its damage and subsequent disability. The main methods for prevention of intraoperative damage to CST are preoperative MR tractography and intraoperative electrophysiological monitoring. Both methods are used in pediatric neurosurgery. We reviewed the PubMed database since 2000 using the following keywords: «tumors of the hemispheres in children», «corticospinal tract», «MR tractography», «intraoperative electrophysiological monitoring». We present available literature data on preoperative MR tractography and intraoperative electrophysiological monitoring in children with supratentorial tumors near CST. Algorithm of intraoperative electrophysiological monitoring is often missing or insufficiently described. MR tractography is usually presented in case reports. Researchers do not compare the effectiveness of MR tractography and intraoperative electrophysiological monitoring. In case of MR tractography, a limitation is impossible CST reconstruction in children 2-3 years old. This may be due to unformed pyramidal system in these children.

CONCLUSION

Preoperative MR tractography and intraoperative electrophysiological monitoring are valid methods for assessment of CST. Optimal research parameters in children require careful study that will allow objective planning of each stage of preoperative management and increase resection quality for gliomas near CST in children without neurological deterioration.

Predicting the true extent of glioblastoma based on probabilistic tractography

Glioblastoma is the most frequent type of primary brain tumors. Despite the advanced therapy, most of the patients die within 2 years after the diagnosis. The tumor has a typical appearance on MRI: a central hypointensity surrounded by an inhomogeneous, ring-shaped contrast enhancement along its border. Too small to be recognized by MRI, detached individual tumor cells migrate along white matter fiber tracts several centimeters away from the edge of the tumor. Usually these cells are the source of tumor recurrence. If the infiltrated brain areas could be identified, longer survival time could be achieved through supratotal resection and individually planned radiation therapy. Probabilistic tractography is an advanced imaging method that can potentially be used to identify infiltrated pathways, thus the real extent of the glioblastoma. Our study consisted of twenty high grade glioma patients. Probabilistic tractography was started from the tumor. The location of tumor recurrence on follow-up MRI was considered as the primary infiltrated white matter tracts. The results of probabilistic tractography were evaluated at thirteen different thresholds. The overlap with the tumor recurrence of each threshold level was then defined to calculate the sensitivity and specificity. In the group level, sensitivity (81%) and specificity (90%) were the most reliable at 5% threshold level. There were two outliers in the study group, both with high specificity and very low sensitivity. According to our results, probabilistic tractography can help to define the true extent of the glioblastoma at the time of diagnosis with high sensitivity and specificity. Individually planned surgery and irradiation could provide a better chance of survival in these patients.

Thalamic gliomas in adults: a systematic review of clinical characteristics, treatment strategies, and survival outcomes

PURPOSE

Thalamic gliomas are rare neoplasms that pose significant surgical challenges. The literature is limited to single-institution retrospective case series. We systematically review the literature and describe the clinical characteristics, treatment strategies, and survival outcomes of adult thalamic gliomas.

METHODS

Relevant articles were identified on PubMed, Scopus, and Cochrane databases. Papers containing cases of adult thalamic gliomas with clinical outcome data were included. A comprehensive review of clinical characteristics and survival analysis was conducted.

RESULTS

We included 25 studies comprising 617 patients. The median age was 45 years (male = 58.6%). Glioblastoma was the most frequent histological type (47.2%), and 82 tumors were H3 K27M-mutant. Motor deficit was the most common presenting symptom (51.8%). Surgical resection was performed in 69.1% of cases while adjuvant chemotherapy and radiotherapy were administered in 56.3% and 72.6%, respectively. Other treatments included laser interstitial thermal therapy, which was performed in 15 patients (2.4%). The lesion laterality (P = 0.754) and the surgical approach (P = 0.111) did not correlate with overall survival. The median progression-free survival was 9 months, and the overall two-year survival rate was 19.7%. The two-year survival rates of low-grade and high-grade thalamic gliomas were 31.0% and 16.5%, respectively. H3 K27M-mutant gliomas showed worse overall survival (P = 0.017).

CONCLUSION

Adult thalamic gliomas are associated with poor survival. Complete surgical resection is associated with improved survival rates but is not always feasible. H3 K27M mutation is associated with worse survival and a more aggressive approach should be considered for mutant neoplasms.

Evolution of surgical attitudes to paediatric thalamic tumours: the alder hey experience

PURPOSE

Attitudes to surgery for paediatric thalamic tumours have evolved due to improved preoperative imaging modalities and the advent of intraoperative MRI (iMRI) as well as enhanced understanding of tumour biology. We review the developments in our local practice over the last three decades with particular attention to the impact of iMRI.

METHODS

We identified all paediatric patients from a prospectively maintained neuro-oncology database who received surgery for a thalamic tumour (n = 30). All children were treated in a single UK tertiary paediatric neurosurgery centre between January 1991 and June 2020. Twenty patients underwent surgical resection, the remainder (10) undergoing biopsy only. Pre-operative surgical intent (biopsy versus debulking, near-total resection, or complete resection) as well as the use of iMRI were prospectively recorded. Complications recorded in clinical documentation between postoperative days 0 and 30 were retrospectively graded using a modified version of the Clavien Dindo scale. The extent of resection with respect to the pre-determined surgical aim was also recorded. Data on patient survival and disease progression status were obtained retrospectively.

RESULTS

In our series, there were 42 procedures (25 craniotomies, 17 biopsies) performed on 30 patients (17 male, with a median age of 8 at surgery). Of the 25 surgical resections performed, complete resection was achieved in 9 (36%), near-total resection in 10 (40%), and limited debulking in 6 (24%). The predetermined surgical aim was achieved or exceeded in 91.3% of cases. The proportion of craniotomies for which substantial resection was achieved, increased from 37.5 to 94.2% with use of iMRI (p = 0.014). Surgical morbidity was not associated with greater extent of surgical resection. High-grade histology is identified as the only independent significant factor influencing overall survival as calculated by Cox proportional hazards model (p = 0.006).

CONCLUSION

We note a significant change in the rate and extent of attempted resection of paediatric thalamic tumours that has developed over the last 3 decades. Use of iMRI is associated with a significant increase in substantial tumour resection surgeries. This is not associated with any significant level of surgical morbidity. Improvements in pre- and intra-operative imaging alongside better understanding of tumour biology facilitate patient selection and a surgically more aggressive approach in selected cases whilst maintaining safety and avoiding operative morbidity.

Infiltrative gliomas of the thalamus in children: the role of surgery in the era of H3 K27M mutant midline gliomas

Background

The role of surgery in the management of pediatric non-pilocytic infiltrative thalamic gliomas needs to be revisited specifically with regard to molecularly defined subtypes.

Methods

A retrospective review of a consecutive series of children operated on a thalamic tumor between 1992 and May 2018 was performed. Neuroimaging data were reviewed for localization and extent of resection; pathology was re-reviewed according to the current WHO classification, including assessment of histone H3 K27 mutational status.

Results

Forty-nine patients with a thalamic tumor aged < 18 years at diagnosis were identified. Twenty-five patients (51%) had a non-pilocytic infiltrative glioma, of which the H3 K27M status was available in 22. Fourteen patients were diagnosed as diffuse midline glioma (DMG) H3 K27M mutant. There was no statistically significant difference in survival between patients harboring the H3 K27M mutation and wildtype. Resection (“any resection > 50%” vs “biopsy”) and histological tumor grade (“°II” vs “°III+°IV”) were statistically significant predictors of survival (univariate: p = 0.044 and p = 0.013, respectively). These results remained significant on multivariate analysis (HR 0.371/p = 0.048, HR 9.433/p = 0.035).

Conclusion

We advocate to still consider an attempt at maximal safe resection in the multidisciplinary treatment of unilateral thalamic non-pilocytic gliomas irrespective of their H3 K27-mutational status.

The concept of "Four Walls, Two Poles" in the lesions of the thalamus and ganglion regions: case report and literature review

Background

There are few articles about the surgical techniques of thalamic glioma and the lesions in the basal ganglia area. According to three existing cases and the literature review (Twelve articles were summarized which mainly described the surgical techniques), we discuss the surgical characteristics of lesions of the thalamus and basal ganglia area and summarize the relevant surgical skills.

Case presentation

Of the three cases, two were thalamic gliomas and one was brain abscess in basal ganglia. According to the three-dimensional concept of the “Four Walls, Two Poles”, lesions of the thalamus and basal ganglia were surgically removed, and the operative effect was analysed by relevant surgical techniques. Surgical resection of the lesions of the thalamus and basal ganglia area according to the three-dimensional concept of the “Four Walls, Two Poles” has achieved good surgical results. Relevant surgical techniques, such as the use of retractors, the use of aspirators, the choice of surgical approaches, and the haemostasis strategy, also played an important role in the operation process.

Conclusions

In the presented three cases the three-dimensional concept of the “Four Walls, Two Poles” allowed for safe surgical resection of lesions of the thalamus and basal ganglia.

The role of diffusion tractography in refining glial tumor resection

Primary brain tumors are notoriously hard to resect surgically. Due to their infiltrative nature, finding the optimal resection boundary without damaging healthy tissue can be challenging. One potential tool to help make this decision is diffusion-weighted magnetic resonance imaging (dMRI) tractography. dMRI exploits the diffusion of water molecule along axons to generate a 3D modelization of the white matter bundles in the brain. This feature is particularly useful to visualize how a tumor affects its surrounding white matter and plan a surgical path. This paper reviews the different ways in which dMRI can be used to improve brain tumor resection, its benefits and also its limitations. We expose surgical tools that can be paired with dMRI to improve its impact on surgical outcome, such as loading the 3D tractography in the neuronavigation system and direct electrical stimulation to validate the position of the white matter bundles of interest. We also review articles validating dMRI findings using other anatomical investigation techniques, such as postmortem dissections, manganese-enhanced MRI, electrophysiological stimulations, and phantom studies with known ground truth. We will be discussing the areas of the brain where dMRI performs well and where the future challenges are. We will conclude this review with suggestions and take home messages for neurosurgeons, tractographers, and vendors for advancing the field and on how to benefit from tractography's use in clinical practice.

Surgical treatment and survival outcome of patients with adult thalamic glioma: a single institution experience of 8 years

PURPOSE

Given the rarity in the population with adult thalamic gliomas (ATGs), comprehensive characteristics, treatments and survival outcome are not well characterized. This study was conducted to investigate the comprehensive characteristic and treatment of ATGs and identify the prognostic factors associated with overall survival (OS).

METHODS

A retrospective analysis of newly diagnosed ATGs who underwent surgical resection consecutively was conducted. Survival analysis of OS was performed by Kaplan-Meier analysis. Cox proportional hazard model was used to investigate the possible prognostic factors associated with OS.

RESULTS

A total of 102 patients with ATG were enrolled in this study. The median age was 41 years (range 18-68 years). There were 56 (54.9%) males. Sixty-two patients (60.8%) had glioblastoma (GBM). Among these patients, 46 patients (45.1%) had GTR/NTR, 50 patients (49.0%) had STR and 6 patients (5.9%) had PR. Postoperatively, 71.6% of these patients received adjuvant therapy. The median OS was 13.6 months (range 1 week-75 months). COX regression analysis revealed that ATG patients with longer duration of symptoms (p = 0.024), better pre-KPS (p = 0.045), maximal resection (p = 0.013), or lower tumor grade (p = 0.002) had longer OS, and these predictors are considered as independent prognostic factors. Survival analysis showed that ATGs with GTR/NTR plus chemoradiotherapy had significant OS advantage compared with other treatment regimens.

CONCLUSIONS

This study comprehensively summarized the characteristics, treatments and survival outcomes of ATGs in the largest sample size. Maximal surgical resection can bring survival benefit. Combined-modality therapy regimen of GTR/NTR plus chemoradiotherapy may be better beneficial for OS than other regimens.

Application of diffusion tensor tractography in the surgical treatment of brain tumors located in functional areas

The present study aimed to explore the application of diffusion tensor tractography (DTT) in the preoperative planning and prognostic evaluation of tumors located in the functional areas of the brain. A total of 42 patients diagnosed with intracranial tumors were randomly assigned to either the trial or the control group. DT imaging (DTI) was performed on the basis of preoperative conventional magnetic resonance imaging (MRI) and analyzed for patients in the trial group. Patients in the control group underwent only routine MRI scans. The effect of DTT on the prognosis of patients was evaluated by tumor resection rate and quality of life evaluation using Karnofsky performance score (KPS) comparison between the trial and control groups. There were no significant differences for total tumor removal rate in the trial group (85.71%) compared with that in the control group (71.43%) (P>0.05). The rate of postoperative symptom improvement in the trial group (85.71%) was significantly higher compared with that in the control group (47.62%) (P<0.05). The KPS value of the trial group was significantly higher postoperatively (78.57±17.40) compared with that preoperatively (66.67±16.23) (P<0.05). The KPS value of the control group postoperatively (72.38±19.21) was significantly higher compared with that preoperatively (66.67±16.00) (P<0.05). The postoperative KPS improvement rate [postoperative value-preoperative value)/preoperative value] of the trial group was significantly higher compared with that in the control group. In conclusion, the use of DTT is an effective supplement to traditional MRI, with particular relevance in preoperative planning, particularly for tumors in the functional area of the brain, and can significantly improve the prognostic function of patients.

Connectivity-based segmentation of the brainstem by probabilistic tractography

Diffusion magnetic resonance imaging is a non-invasive tool increasingly used for the investigation of brain connectivity in vivo. In this paper we propose a method that allows segmentation of the brainstem to four subregions (frontopontine, motor, sensory and reticular) based on connections to supratentorial structures, thereby eliminating the need for using anatomical landmarks within the brainstem for the identification of these subregions. The feasibility of connectivity-based brainstem segmentation was investigated in a group of healthy subjects (n = 20). Multifiber probabilistic tractography was performed using the FMRIB Software Library, and connections between a pontomesencephalic seed mask and four supratentorial target regions (anterior and posterior limbs of the internal capsule, sensory and medial thalamus) were used to determine connectivity maps of the brainstem. Results were compared with a neuroanatomy atlas and histological sections, confirming good anatomic correspondence. The four subregions detected by the connectivity-based segmentation showed good intersubject reproducibility. The presented method may be a potential tool to investigate brainstem connectivity in diseases that distort normal anatomy, and quantitative analyses of the diffusion-related parameters may provide additional information on the involvement of brainstem pathways in certain disease states (e.g., traumatic brain injury, demyelinating disorders, brainstem tumors). The potential clinical applicability of the method is demonstrated in two cases of severe traumatic brain injury.

Chaperonology: The Third Eye on Brain Gliomas

The European Organization for Research and Treatment of Cancer/National Cancer Institute of Canada Phase III trial has validated as a current regimen for high-grade gliomas (HGG) a maximal safe surgical resection followed by radiotherapy with concurrent temozolamide. However, it is essential to balance maximal tumor resection with preservation of the patient&rsquo;s neurological functions. Important developments in the fields of pre-operative and intra-operative neuro-imaging and neuro-monitoring have ameliorated the survival rate and the quality of life for patients affected by HGG. Moreover, even though the natural history remains extremely poor, advancement in the molecular and genetic fields have opened up new potential frontiers in the management of this devastating brain disease. In this review, we aim to present a comprehensive account of the main current pre-operative, intra-operative and molecular approaches to HGG with particular attention to specific chaperones, also called heat shock proteins (Hsps), which represent potential novel biomarkers to detect and follow up HGG, and could also be therapeutic agents.

[MR tractography in diagnosis and choice of a neurosurgical approach to basal ganglia tumors]

We describe two cases of surgical treatment of well-circumscribed basal ganglia tumors. The choice of a neurosurgical approach to a deep tumor was based on the MR tractography data and depended on the course and dislocation extent of the corticospinal tract. MR tractography provides information on the course and dislocation or destruction extent of the corticospinal tract running in the internal capsule and brainstem and clarifies the exact location of a tumor within the basal ganglia. This information promotes the choice of an optimal approach for radical resection of well-circumscribed tumor, leading to improvement in neurological symptoms and patient's quality of life.

Surgical Outcomes of Thalamic Tumors in Children: The Importance of Diffusion Tensor Imaging, Neuro-Navigation and Intraoperative Neurophysiological Monitoring

Background

Recently, modern technology such as diffusion tensor imaging (DTI), neuro-navigation and intraoperative neurophysiological monitoring (IOM) have been actively adopted for the treatment of thalamic tumors. We evaluated surgical outcomes and efficacy of the aforementioned technologies for the treatment of pediatric thalamic tumors.

Methods

We retrospectively reviewed clinical data from 37 children with thalamic tumors between 2004 and 2017. There were 44 operations (27 tumor resections, 17 biopsies). DTI was employed in 17 cases, neuro-navigation in 23 cases and IOM in 14 cases. All diagnoses were revised according to the 2016 World Health Organization Classification of Tumors of the Central Nervous System. Progression-free survival (PFS) and overall survival (OS) rates were calculated, and relevant prognostic factors were analyzed. The median follow-up duration was 19 months.

Results

Fifteen cases were gross total resections (GTR), 6 subtotal resections (STR), and 6 partial resections (PR). Neurological status did not worsen after 22 tumor resections. There were statistically significant differences in terms of the extent of resection between the groups with DTI, neuro-navigation and IOM (n=12, GTR or STR=12) and the group without at least one of the three techniques (n=15, GTR or STR=9, p=0.020). The mean PFS was 87.2±38.0 months, and the mean OS 90.7±36.1 months. The 5-year PFS was 37%, and the 5-year OS 47%. The histological grade (p≤0.001) and adjuvant therapy (done vs. not done, p=0.016) were significantly related to longer PFS. The histological grade (p=0.002) and the extent of removal (GTR/STR vs. PR/biopsy, p=0.047) were significantly related to longer OS.

Conclusion

Maximal surgical resection was achieved with acceptable morbidity in children with thalamic tumors by employing DTI, neuro-navigation and IOM. Maximal tumor resection was a relevant clinical factor affecting OS; therefore, it should be considered the initial therapeutic option for pediatric thalamic tumors.

High-grade thalamic gliomas: Microsurgical treatment and prognosis analysis

This retrospective study is aimed to investigate the efficacy of microsurgical treatment for high-grade thalamic gliomas, and to analyze the relevant prognosis. From May 2011 to Aug 2015, 49 patients with thalamic gliomas underwent microsurgical resection, and received chemotherapy and radiotherapy postoperatively. The postoperative symptoms and complications were documented, and the overall survival (OS) and the progression-free survival (PFS) data were collected. The prognostic factors were evaluated by univariate and multivariate analyses. Finally, there was no perioperative death. Twenty cases, 24 cases and 5 cases were achieved subtotal resection (>90%), partial resection (70-90%) and less than partial resection (<70%) respectively. All patients' pathological diagnosis was confirmed. The symptoms were improved in 32 cases, unchanged in 11 cases, and worsen in 6 cases. Postoperative complications were absent in 9 cases. The 6-month, 12-month, and 24-month OS were 71.4%, 38.9%, and 12.1% respectively; corresponding PFS were 66.6%, 27.1%, and 10.2% respectively. The median OS time and PFS time were 9.0 months (95% CI 6.9-11.1) and 9.0 months (95% CI 6.6-11.4) respectively. Multivariate analysis revealed extent of resection were independent prognostic factors for OS (p < .05), patients with postoperative adjuvant chemotherapy and radiotherapy had a significant prolonged OS (p < .001) and PFS (p < .001). The study shows that the short-term efficacy of microsurgery for high-grade thalamic gliomas is satisfactory. Microsurgery can effectively alleviate patients' symptoms and improve life quality. Postoperative adjuvant chemotherapy and radiotherapy are helpful for prolonging the survival time.

Surgical and molecular considerations in the treatment of pediatric thalamopeduncular tumors

OBJECTIVE Thalamopeduncular tumors are a group of pediatric low-grade gliomas that arise at the interface of the thalamus and brainstem peduncle. They typically occur within the first 2 decades of life, presenting with progressive spastic hemiparesis. Treatment strategies, including surgical intervention, have varied significantly. The authors present their experience in the treatment of 13 children, ages 2-15 years, with non-neurofibromatosis-related pilocytic astrocytomas located in the thalamopeduncular region. METHODS Between 2003 and 2016, 13 children presenting with progressive spastic hemiparesis due to a pilocytic astrocytoma at the interface of the thalamus and cerebral peduncles were identified. Medical records were reviewed retrospectively for clinical, radiological, pathological, and surgical data. Formalin-fixed, paraffin-embedded tissue was obtained for 12 cases and tested for KIAA1549-BRAF fusion and BRAF V600E point mutation. RESULTS On preoperative diffusion tensor imaging tractography (performed in 12 patients), the ipsilateral corticospinal tract was displaced laterally in 1 case (8.3%), medially in 1 case (8.3%), anterolaterally in 10 cases (83%), and posteriorly in no cases. Ten patients underwent resection via a transtemporal, transchoroidal approach, which was chosen to avoid further damage to motor function in cases of tumors that caused anterolateral or medial corticospinal tract displacement. With this approach, complications included hemianopia, oculomotor palsy, and tremor at a rate of 50%. Among the 12 patients with obtainable follow-up (mean 50.9 months), none received adjuvant therapy, and only 2 (17%) experienced recurrence or progression. KIAA1549-BRAF fusions were present in 10 cases (83%), while BRAF V600E was absent (0%). The 2 fusion-negative tumors had clinical features atypical for the series, including multi-focality and infiltration. CONCLUSIONS Transcortical, transchoroidal resection of thalamopeduncular tumors through the middle temporal gyrus allows for a high rate of gross-total resection and cure. Diffuse tensor tractography is a critical component of the preoperative planning process to determine the location of white matter tracts in proximity. Molecular status may correlate with clinical features, and the presence of BRAF lesions offers an additional target for future novel therapeutics.

Pediatric thalamic glioma with H3F3A K27M mutation, which was detected before and after malignant transformation: a case report

PURPOSE

Histone H3.3 (H3F3A) mutation in the codon for lysine 27 (K27M) has been found as driver mutations in pediatric glioblastoma and has been suggested to play critical roles in the pathogenesis of thalamic gliomas and diffuse intrinsic pontine gliomas. We report a case of thalamic glioma with H3F3A K27M mutation, which was detected in both the primary tumor diagnosed as diffuse astrocytoma obtained during the first surgery and also in the tumor diagnosed as anaplastic astrocytoma obtained at the second surgery.

CASE PRESENTATION

A 14-year-old girl presented with mild headache. Magnetic resonance imaging (MRI) showed a small intraaxial lesion in the left thalamus, which increased in size. Stereotactic tumor biopsy was performed 2 years after the initial diagnosis, and a pathological diagnosis of diffuse astrocytoma (WHO grade 2) was made. The tumor grew further and showed contrast enhancement on MRI despite 16 months of chemotherapy. Surgical removal via the transcallosal approach was then performed, and postoperative pathological diagnosis was anaplastic astrocytoma (WHO grade 3), indicating malignant transformation of the tumor. Molecular diagnosis of tumor tissue obtained at first and second surgeries revealed H3F3A K27M mutation in both primary and secondary specimens.

CONCLUSION

This report demonstrates minute neuroradiological and pathological features of malignant transformation from thalamic low grade glioma with H3F3A K27M mutation. It is noteworthy that this mutation was found in this case when the tumor was still a low-grade glioma. Tissue sampling for genetic analysis is useful in patients with thalamic gliomas to predict the clinical course and efficacy of treatments.

Feasibility of the Combined Application of Navigated Probabilistic Fiber Tracking and Navigated Ultrasonography in Brain Tumor Surgery

BACKGROUND

Surgical resection of intra-axial tumors is a challenging procedure because of indistinct tumor margins, infiltration, and displacement of white matter tracts surrounding the lesion. Hence, gross total tumor resection without causing new neurologic deficits is demanding, especially in tumor sites adjoining eloquent structures. Feasibility of the combination of navigated probabilistic fiber tracking to identify eloquent fiber pathways and navigated ultrasonography to control brain shift was tested.

METHODS

Eleven patients with lesions adjacent to eloquent white matter structures (pyramidal tract, optic radiation and arcuate fascicle) were preoperatively subjected to magnetic resonance imaging including diffusion-weighted imaging on a 3-T magnetic resonance system (Trio [Siemens, Erlangen, Germany]). Probabilistic fiber tracking was performed using the tools of the FMRIB Software Library (FSL). Results of probabilistic fiber tracking and high-resolution anatomic images were integrated into the neuronavigation system Stealth Station (Medtronic, Minneapolis, Minnesota, USA) together with the navigated ultrasonography (SonoNav [Medtronic]).

RESULTS

FSL-based probabilistic fiber tracking depicted the pyramidal tract, the optic radiation, and arcuate fascicle anatomically plausibly. Integration of the probabilistic fiber tracking into neuronavigation was technically feasible and allowed visualization of the reconstructed fiber pathways. Navigated ultrasonography controlled brain shift.

CONCLUSIONS

Integration of probabilistic fiber tracking and navigated ultrasonography into intraoperative neuronavigation facilitated anatomic orientation during glioma resection. FSL-based probabilistic fiber tracking integrated sophisticated fiber tracking algorithms, including modeling of crossing fibers. Combination with navigated ultrasonography provided a three-dimensional estimation of intraoperative brain shift and, therefore, improved the reliability of neuronavigation.