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Under what circumstances, is it ethical to perform tumor surgery on a brain-dead individual? The neurosurgeons at Brigham and Women's Hospital were recently faced with such a question when asked to operate on a 28-year-old man who was pronounced brain-dead secondary to a severe brain-stem injury. His advanced directives clearly documented a desire for organ donation. During his transplant work-up, cranial imaging suggested a possible cerebellar mass of unknown etiology that was concerning for metastatic disease. Despite negative full body imaging, the neurosurgical team was asked to perform an open biopsy of the intracranial lesion to rule out occult systemic cancer. This case invites many nuanced questions related to the decisions surgeons and the broader medical community must make in the face of pursuing viable organs for the many in need. What is the moral standing and personhood eligibility of brain-dead individuals? What is the scope of medical interventions and procedures that surgeons are ethically bound to carry out? How ought the desire for increased medical intervention to try to save organs be balanced with practical limitations given limited medical resources?, Competing Interests: JDB has an equity position in Treovir Inc. and is a member of the board of scientific advisors for Upfront Diagnostics, Centile Biosciences, and NeuroX1. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (© 2023 Bernstock, Chalif, Jha, Brown, Essayed, Caplan and Peruzzi.)

Background: Meckel cave tumors are relatively rare, especially trigeminal nerve (TN) schwannomas. These tumors frequently project through the trigeminal pore, occupying the middle and posterior fossae. The most used routes to this region are the suboccipital retrosigmoid intradural approach (SORSA) and the transzygomatic middle fossa approach (TZMFA). Both approaches allow further exposure by adding intraoperative techniques, such as removing the suprameatal tubercle (retrosigmoid intradural suprameatal approach [RISA]) and the petrous apex (TZMFA-PA), respectively. This study aims to understand how TN exposure differs between both surgical approaches and how it increases by adding specific surgical maneuvers to these techniques., Methods: Five formalin-fixed adult cadaver heads were submitted to high-resolution computed tomography and their images were loaded into the neuronavigation device. Anatomic key points were defined along the outline of the TN, and their three-dimensional spatial locations were collected following each surgical approach. This process allowed the calculation of the TN exposed area obtained through each technique., Results: The mean areas of exposure of the TN were 125.9 mm 2 with SORSA and 208.9 mm 2 with RISA, which represents an additional mean gain of 61.92% (P = 0.047). Using TZMFA, a mean exposure of 419.24 mm 2 was obtained. When TZMFA-PA was used, the mean exposed area was 486.03 mm 2 , representing a mean gain in the exposure area of 16.81% (P = 0.072)., Conclusions: Our study suggests that TZMFA allows better exposure of TN ganglionic and postganglionic segments, and the removal of the PA adds the preganglionic segment visualization, although with less TN exposed area compared with RISA. With SORSA, the additional suprameatal tubercle removal shows the trigeminal pore and the medial margin of the central portion of the TN ganglionic segment, making it possible to expose the mouth of the Meckel cave and part of its contents., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Background: Diffusion magnetic resonance imaging white matter tractography, an increasingly popular preoperative planning modality used for pre-surgical planning in brain tumor patients, is employed with the goal of maximizing tumor resection while sparing postoperative neurological function. Clinical translation of white matter tractography has been limited by several shortcomings of standard diffusion tensor imaging (DTI), including poor modeling of fibers crossing through regions of peritumoral edema and low spatial resolution for typical clinical diffusion MRI (dMRI) sequences. Track density imaging (TDI) is a post-tractography technique that uses the number of tractography streamlines and their long-range continuity to map the white matter connections of the brain with enhanced image resolution relative to the acquired dMRI data, potentially offering improved white matter visualization in patients with brain tumors. The aim of this study was to assess the utility of TDI-based white matter maps in a neurosurgical planning context compared to the current clinical standard of DTI-based white matter maps., Methods: Fourteen consecutive brain tumor patients from a single institution were retrospectively selected for the study. Each patient underwent 3-Tesla dMRI scanning with 30 gradient directions and a b-value of 1000 s/mm 2 . For each patient, two directionally encoded color (DEC) maps were produced as follows. DTI-based DEC-fractional anisotropy maps (DEC-FA) were generated on the scanner, while DEC-track density images (DEC-TDI) were generated using constrained spherical deconvolution based tractography. The potential clinical utility of each map was assessed by five practicing neurosurgeons, who rated the maps according to four clinical utility statements regarding different clinical aspects of pre-surgical planning. The neurosurgeons rated each map according to their agreement with four clinical utility statements regarding if the map 1 identified clinically relevant tracts, (2) helped establish a goal resection margin, (3) influenced a planned surgical route, and (4) was useful overall. Cumulative link mixed effect modeling and analysis of variance were performed to test the primary effect of map type (DEC-TDI vs. DEC-FA) on rater score. Pairwise comparisons using estimated marginal means were then calculated to determine the magnitude and directionality of differences in rater scores by map type., Results: A majority of rater responses agreed with the four clinical utility statements, indicating that neurosurgeons found both DEC maps to be useful. Across all four investigated clinical utility statements, the DEC map type significantly influenced rater score. Rater scores were significantly higher for DEC-TDI maps compared to DEC-FA maps. The largest effect size in rater scores in favor of DEC-TDI maps was observed for clinical utility statement 2, which assessed establishing a goal resection margin., Conclusion: We observed a significant neurosurgeon preference for DEC-TDI maps, indicating their potential utility for neurosurgical planning., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Given the difficulty and importance of achieving maximal resection in chordomas and chondrosarcomas, all available tools offered by modern neurosurgery are to be deployed for planning and resection of these complex lesions. As demonstrated by the review of our series of skull base chordoma and chondrosarcoma resections in the Advanced Multimodality Image-Guided Operating (AMIGO) suite, as well as by the recently published literature, we describe the use of advanced multimodality intraoperative imaging and neuronavigation as pivotal to successful radical resection of these skull base lesions while preventing and managing eventual complications.

Sentinel bleeds in head and neck cancer patients present as an ominous symptom often necessitating urgent endovascular embolization. However, this approach can be complicated in patients who have previously undergone head and neck cancer ablation and reconstruction, thus altering the standard arterial vascular supply. Herein we describe an innovative method of internal maxillary artery (IMA) access in a patient with a sentinel bleed who previously underwent proximal external carotid artery (ECA) rerouting for free flap reconstruction. The open retrograde superficial temporal artery approach for IMA embolization is minimally invasive and effective and should be considered for head and neck cancer patients at risk of hemorrhage from distal ECA branches without a proximal ECA embolization option., (Published by Oxford University Press and JSCR Publishing Ltd. © The Author(s) 2021.)

In this chapter, we describe advances in endoscopic endonasal surgery that have impacted skull base meningioma surgery. After reviewing the technical innovations in endoscopy, we describe the advances as they relate to each surgical step. We discuss preoperative planning and approach and the utility of neuronavigation and neuromonitoring. We then discuss endoscopic instrumentation, technology for tumor debulking (ultrasonic aspirators, radiofrequency ablators, suction debriders), and hemostatic agents as they relate to tumor resection and hemostasis. In the end, we discuss techniques of skull base reconstruction and closure (nasoseptal flap, gasket seal and bilayer button)., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Background: Described variations of tentorial venous anatomy impact surgical sectioning of the tentorium in skull base approaches; however, described configurations do not consistently explain postoperative complications. To understand the outcomes of 2 clinical cases we studied the tentorial venous anatomy of 2 cadavers., Methods: The venous anatomy of the tentorium isolated in 2 uninjected fresh cadaver head specimens with preserved bridging veins was observed by transillumination before and after methylene blue injection of the dural sinuses and tentorial veins. Our findings in cadavers were applied to explain the clinical and radiologic (magnetic resonance imaging and computed tomographic venography) findings in the 2 cases presented., Results: A consistent transtentorial venous system, arising from transverse and straight sinuses, communicating with supra- and infratentorial bridging veins was seen in the cadaver and patient radiography (magnetic resonance imaging and computed tomographic venography). Our first patient had a cerebellar venous infarct from compromise of the venous drainage from the adjacent brain after ligation of a temporal lobe bridging vein to the tentorium. Our second patient suffered no clinical effects from bilateral transverse sinus occlusion due to drainage through the accessory venous system within the tentorium., Conclusions: Herein, we elaborate on transtentorial venous anatomy. These veins, previously reported to obliterate in completed development of the tentorium, remain patent with consistent observed configuration. The same transtentorial venous system was observed in both cases and provided insight to their outcomes. These findings emphasize the importance of the transtentorial venous system physiologically and in surgical approaches., (Published by Elsevier Inc.)

Objective: Endoscopic endonasal approaches are increasingly performed for the surgical treatment of multiple skull base pathologies. Preventing postoperative CSF leaks remains a major challenge, particularly in extended approaches. In this study, the authors assessed the potential use of modern multimaterial 3D printing and neuronavigation to help model these extended defects and develop specifically tailored prostheses for reconstructive purposes., Methods: Extended endoscopic endonasal skull base approaches were performed on 3 human cadaveric heads. Pre-Preprocedure and intraprocedure CT scans were completed and were used to segment and design extended and tailored skull base models. Multimaterial models with different core/edge interfaces were 3D printed for implantation trials. A novel application of the intraoperative landmark acquisition method was used to transfer the navigation, helping to tailor the extended models., Results: Prostheses were created based on preoperative and intraoperative CT scans. The navigation transfer offered sufficiently accurate data to tailor the preprinted extended skull base defect prostheses. Successful implantation of the skull base prostheses was achieved in all specimens. The progressive flexibility gradient of the models’ edges offered the best compromise for easy intranasal maneuverability, anchoring, and structural stability. Prostheses printed based on intraprocedure CT scans were accurate in shape but slightly undersized., Conclusions: Preoperative 3D printing of patient-specific skull base models is achievable for extended endoscopic endonasal surgery. The careful spatial modeling and the use of a flexibility gradient in the design helped achieve the most stable reconstruction. Neuronavigation can help tailor preprinted prostheses.

Purpose: Peritumoral edema impedes the full delineation of fiber tracts due to partial volume effects in image voxels that contain a mixture of cerebral parenchyma and extracellular water. The purpose of this study is to investigate the effect of incorporating a free water (FW) model of edema for white matter tractography in the presence of edema., Materials and Methods: We retrospectively evaluated 26 consecutive brain tumor patients with diffusion MRI and T2-weighted images acquired presurgically. Tractography of the arcuate fasciculus (AF) was performed using the two-tensor unscented Kalman filter tractography (UKFt) method, the UKFt method with a reduced fiber tracking stopping fractional anisotropy (FA) threshold (UKFt+rFA), and the UKFt method with the addition of a FW compartment (UKFt+FW). An automated white matter fiber tract identification approach was applied to delineate the AF. Quantitative measurements included tract volume, edema volume, and mean FW fraction. Visual comparisons were performed by three experts to evaluate the quality of the detected AF tracts., Results: The AF volume in edematous brain hemispheres was significantly larger using the UKFt+FW method (p<0.0001) compared to UKFt, but not significantly larger (p = 0.0996) in hemispheres without edema. The AF size increase depended on the volume of edema: a significant correlation was found between AF volume affected by (intersecting) edema and AF volume change with the FW model (Pearson r = 0.806, p<0.0001). The mean FW fraction was significantly larger in tracts intersecting edema (p = 0.0271). Compared to the UKFt+rFA method, there was a significant increase of the volume of the AF tract that intersected the edema using the UKFt+FW method, while the whole AF volumes were similar. Expert judgment results, based on the five patients with the smallest AF volumes, indicated that the expert readers generally preferred the AF tract obtained by using the FW model, according to their anatomical knowledge and considering the potential influence of the final results on the surgical route., Conclusion: Our results indicate that incorporating biophysical models of edema can increase the sensitivity of tractography in regions of peritumoral edema, allowing better tract visualization in patients with high grade gliomas and metastases.

The authors present 4 cases in which they used intraoperative CT (iCT) scanning to provide real-time image guidance during endonasal odontoid resection. While intraoperative CT has previously been used as a confirmatory test after resection, to the authors' knowledge this is the first time it has been used to provide real-time image guidance during endonasal odontoid resection. The operating room setup, as well as the advantages and pitfalls of this approach, are discussed. A mobile intraoperative CT scanner was used in conjunction with real-time craniospinal neuronavigation in 4 patients who underwent endoscopic endonasal odontoidectomy for basilar invagination. All patients underwent a successful decompression. In 3 of the 4 patients, real-time intraoperative CT image guidance was instrumental in achieving a comprehensive decompression. In 3 (75%) cases in which the right nostril was the predominant working channel, there was a tendency for asymmetrical decompression toward the right side, meaning that residual bone was seen on the left, which was subsequently removed prior to completion of the surgery. Endoscopic endonasal odontoid resection with real-time intraoperative image-guided CT scanning is feasible and provides accurate intraoperative localization of pathology, thereby increasing the chance of a complete odontoidectomy. For right-handed surgeons operating predominantly through the right nostril, special attention should be paid to the contralateral side of the resection, where there is often a tendency for residual pathology.

Background and Purpose: Diffusion magnetic resonance imaging (dMRI) provides preoperative maps of neurosurgical patients' white matter tracts, but these maps suffer from echo-planar imaging (EPI) distortions caused by magnetic field inhomogeneities. In clinical neurosurgical planning, these distortions are generally not corrected and thus contribute to the uncertainty of fiber tracking. Multiple image processing pipelines have been proposed for image-registration-based EPI distortion correction in healthy subjects. In this article, we perform the first comparison of such pipelines in neurosurgical patient data., Methods: Five pipelines were tested in a retrospective clinical dMRI dataset of 9 patients with brain tumors. Pipelines differed in the choice of fixed and moving images and the similarity metric for image registration. Distortions were measured in two important tracts for neurosurgery, the arcuate fasciculus and corticospinal tracts., Results: Significant differences in distortion estimates were found across processing pipelines. The most successful pipeline used dMRI baseline and T2-weighted images as inputs for distortion correction. This pipeline gave the most consistent distortion estimates across image resolutions and brain hemispheres., Conclusions: Quantitative results of mean tract distortions on the order of 1-2 mm are in line with other recent studies, supporting the potential need for distortion correction in neurosurgical planning. Novel results include significantly higher distortion estimates in the tumor hemisphere and greater effect of image resolution choice on results in the tumor hemisphere. Overall, this study demonstrates possible pitfalls and indicates that care should be taken when implementing EPI distortion correction in clinical settings., (Copyright © 2018 by the American Society of Neuroimaging.)

OBJECTIVE Magnetic resonance-guided focused ultrasound (MRgFUS) thalamotomy was recently approved for use in the treatment of medication-refractory essential tremor (ET). Previous work has described lesion appearance and volume on MRI up to 6 months after treatment. Here, the authors report on the volumetric segmentation of the thalamotomy lesion and associated edema in the immediate postoperative period and 1 year following treatment, and relate these radiographic characteristics with clinical outcome. METHODS Seven patients with medication-refractory ET underwent MRgFUS thalamotomy at Brigham and Women's Hospital and were monitored clinically for 1 year posttreatment. Treatment effect was measured using the Clinical Rating Scale for Tremor (CRST). MRI was performed immediately postoperatively, 24 hours posttreatment, and at 1 year. Lesion location and the volumes of the necrotic core (zone I) and surrounding edema (cytotoxic, zone II; vasogenic, zone III) were measured on thin-slice T2-weighted images using Slicer 3D software. RESULTS Patients had significant improvement in overall CRST scores (baseline 51.4 ± 10.8 to 24.9 ± 11.0 at 1 year, p = 0.001). The most common adverse events (AEs) in the 1-month posttreatment period were transient gait disturbance (6 patients) and paresthesia (3 patients). The center of zone I immediately posttreatment was 5.61 ± 0.9 mm anterior to the posterior commissure, 14.6 ± 0.8 mm lateral to midline, and 11.0 ± 0.5 mm lateral to the border of the third ventricle on the anterior commissure-posterior commissure plane. Zone I, II, and III volumes immediately posttreatment were 0.01 ± 0.01, 0.05 ± 0.02, and 0.33 ± 0.21 cm 3 , respectively. These volumes increased significantly over the first 24 hours following surgery. The edema did not spread evenly, with more notable expansion in the superoinferior and lateral directions. The spread of edema inferiorly was associated with the incidence of gait disturbance. At 1 year, the remaining lesion location and size were comparable to those of zone I immediately posttreatment. Zone volumes were not associated with clinical efficacy in a statistically significant way. CONCLUSIONS MRgFUS thalamotomy demonstrates sustained clinical efficacy at 1 year for the treatment of medication-refractory ET. This technology can create accurate, predictable, and small-volume lesions that are stable over time. Instances of AEs are transient and are associated with the pattern of perilesional edema expansion. Additional analysis of a larger MRgFUS thalamotomy cohort could provide more information to maximize clinical effect and reduce the rate of long-lasting AEs.

Functional magnetic resonance imaging (fMRI) is increasingly used for preoperative counseling and planning, and intraoperative guidance for tumor resection in the eloquent cortex. Although there have been improvements in image resolution and artifact correction, there are still limitations of this modality. In this review, we discuss clinical fMRI's applications, limitations and potential solutions. These limitations depend on the following parameters: foundations of fMRI, physiologic effects of the disease, distinctions between clinical and research fMRI, and the design of the fMRI study. We also compare fMRI to other brain mapping modalities which should be considered as alternatives or adjuncts when appropriate, and discuss intraoperative use and validation of fMRI. These concepts direct the clinical application of fMRI in neurosurgical patients.

OBJECTIVE Sporadic cases of endonasal intraaxial brainstem surgery have been reported in the recent literature. The authors endeavored to assess the feasibility and limitations of endonasal endoscopic surgery for approaching lesions in the ventral portion of the brainstem. METHODS Five human cadaveric heads were used to assess the anatomy and to record various measurements. Extended transsphenoidal and transclival approaches were performed. After exposing the brainstem, white matter dissection was attempted through this endoscopic window, and additional key measurements were taken. RESULTS The rostral exposure of the brainstem was limited by the sella. The lateral limits of the exposure were the intracavernous carotid arteries at the level of the sellar floor, the intrapetrous carotid arteries at the level of the petrous apex, and the inferior petrosal sinuses toward the basion. Caudal extension necessitated partial resection of the anterior C-1 arch and the odontoid process. The midline pons and medulla were exposed in all specimens. Trigeminal nerves were barely visible without the use of angled endoscopes. Access to the peritrigeminal safe zone for gaining entry into the brainstem is medially limited by the pyramidal tract, with a mean lateral pyramidal distance (LPD) of 4.8 ± 0.8 mm. The mean interpyramidal distance was 3.6 ± 0.5 mm, and it progressively decreased toward the pontomedullary junction. The corticospinal tracts (CSTs) coursed from deep to superficial in a craniocaudal direction. The small caliber of the medulla with very superficial CSTs left no room for a safe ventral dissection. The mean pontobasilar midline index averaged at 0.44 ± 0.1. CONCLUSIONS Endoscopic endonasal approaches are best suited for pontine intraaxial tumors when they are close to the midline and strictly anterior to the CST, or for exophytic lesions. Approaching the medulla is anatomically feasible, but the superficiality of the eloquent tracts and interposed nerves limit the safe entry zones. Pituitary transposition after sellar opening is necessary to access the mesencephalon.

We perform a review of the literature in the field of white matter tractography for neurosurgical planning, focusing on those works where tractography was correlated with clinical information such as patient outcome, clinical functional testing, or electro-cortical stimulation. We organize the review by anatomical location in the brain and by surgical procedure, including both supratentorial and infratentorial pathologies, and excluding spinal cord applications. Where possible, we discuss implications of tractography for clinical care, as well as clinically relevant technical considerations regarding the tractography methods. We find that tractography is a valuable tool in variable situations in modern neurosurgery. Our survey of recent reports demonstrates multiple potentially successful applications of white matter tractography in neurosurgery, with progress towards overcoming clinical challenges of standardization and interpretation.

Objective: Surgery for recurrent/residual pituitary adenomas is increasingly being performed through endoscopic surgery. Whether this new technology has altered the indications and outcomes of surgery is unknown. We conducted a systematic review and meta-analysis of published studies to compare the indications and outcomes between microscopic and endoscopic approaches., Methods: A PubMed search was conducted (1985-2015) to identify surgical series of endoscopic endonasal and microscopic transsphenoidal resection of residual or recurrent pituitary adenomas. Data were extracted regarding tumor characteristics, surgical treatment, extent of resection, endocrine remission, visual outcome, and complications., Results: Twenty-one studies met inclusion criteria. A total of 292 patients were in the endoscopic group, and 648 patients were in the microscopic group. Endoscopic cases were more likely nonfunctional (P < 0.001) macroadenomas (P < 0.001) with higher rates of cavernous sinus invasion (P = 0.012). The pooled rate of gross total tumor resection was 53.5% for the endoscopic group and 46.6% for the microscopic group. Endocrine remission was achieved in 53.0% and 46.7% of patients, and visual improvement occurred in 73.2% and 49.6% for the endoscopic and microscopic groups. Cerebrospinal fluid leak and pituitary insufficiency were higher in the endoscopic group., Conclusion: This meta-analysis indicates that the use of the endoscope to reoperate on residual or recurrent adenomas has only led to modest increases in resection rates. However, larger more complex cases are being tackled, so direct comparisons are misleading. The most dramatic change has been in visual improvement along with modest increases in risk. Reoperation for recurrent or residual adenomas is a safe and effective treatment option., (Copyright © 2017 Elsevier Inc. All rights reserved.)

OBJECTIVE The authors describe the supraorbital keyhole approach to the contralateral medial optic nerve and tract, both in a series of cadaveric dissections and in 2 patients. They also discuss the indications and contraindications for this procedure. METHODS In 3 cadaver heads, bilateral supraorbital keyhole minicraniotomies were performed to expose the ipsilateral and contralateral optic nerves. The extent of exposure of the medial optic nerve was assessed. In 2 patients, a contralateral supraorbital keyhole approach was used to remove pathology of the contralateral medial optic nerve and tract. RESULTS The supraorbital keyhole craniotomy provided better exposure of the contralateral superomedial nerve than it did of the same portion of the ipsilateral nerve. In both patients gross-total resections of the pathology was achieved. CONCLUSIONS The authors demonstrate the suitability of the contralateral supraorbital keyhole approach for lesions involving the superomedial optic nerve.

Introduction: We describe the feasibility of using minimally invasive robotic laser interstitial thermotherapy (LITT) for achieving an anterior two-thirds as well as a complete corpus callosotomy., Methods: Ten probe trajectories were plotted on normal magentic resonance imaging (MRI) scans using the Brainlab Stereotactic Planning Software (Brainlab, Munich, Germany). The NeuroBlate® System (Monteris Medical, MN, USA) was used to conform the thermal burn to the corpus callosum along the trajectory of the probe. The distance of the ideal entry site from either the coronal suture and the torcula or nasion and the midline was calculated. The distance of the probe tip from the dorsal and ventral limits of the callosotomy in the sagittal plane were also calculated., Results: Anterior two-thirds callosotomy was possible in all patients using a posterior parieto-occipital paramedian trajectory through the non-dominant lobe. The average entry point was 3.64 cm from the midline, 10.6 cm behind the coronal suture, and 9.2 cm above the torcula. The probe tip was an average of 1.4 cm from the anterior commissure. For a total callosotomy, an additional contralaterally placed frontal probe was used to target the posterior one-third of the corpus callosum. The average entry site was 3.3 cm from the midline and 9.1 cm above the nasion. The average distance of the probe tip from the base of the splenium was 0.94 cm., Conclusion: The directional thermoablation capability of the NeuroBlate® system allows for targeted lesioning of the corpus callosum, to achieve a two-thirds or complete corpus callosotomy. A laser distance of < 2 cm is sufficient to reach the entire corpus callosum through one trajectory for an anterior two-thirds callosotomy and two trajectories for a complete callosotomy., Competing Interests: The authors have declared that no competing interests exist.

We propose a method for the automated identification of key white matter fiber tracts for neurosurgical planning, and we apply the method in a retrospective study of 18 consecutive neurosurgical patients with brain tumors. Our method is designed to be relatively robust to challenges in neurosurgical tractography, which include peritumoral edema, displacement, and mass effect caused by mass lesions. The proposed method has two parts. First, we learn a data-driven white matter parcellation or fiber cluster atlas using groupwise registration and spectral clustering of multi-fiber tractography from healthy controls. Key fiber tract clusters are identified in the atlas. Next, patient-specific fiber tracts are automatically identified using tractography-based registration to the atlas and spectral embedding of patient tractography. Results indicate good generalization of the data-driven atlas to patients: 80% of the 800 fiber clusters were identified in all 18 patients, and 94% of the 800 fiber clusters were found in 16 or more of the 18 patients. Automated subject-specific tract identification was evaluated by quantitative comparison to subject-specific motor and language functional MRI, focusing on the arcuate fasciculus (language) and corticospinal tracts (motor), which were identified in all patients. Results indicate good colocalization: 89 of 95, or 94%, of patient-specific language and motor activations were intersected by the corresponding identified tract. All patient-specific activations were within 3mm of the corresponding language or motor tract. Overall, our results indicate the potential of an automated method for identifying fiber tracts of interest for neurosurgical planning, even in patients with mass lesions.

Transsphenoidal microscopic pituitary surgery has long been considered the gold standard in surgical treatment of pituitary tumors. Endonasal endoscopic pituitary surgery has come into prominence over the last two decades as an alternative to microscopic surgery. In this review, we use recent literature to discuss the advantages and disadvantages of each approach. Our review shows that for small intrasellar tumors, both approaches appear equally effective in experienced hands. For larger tumors with extrasellar extension, the endoscopic approach offers several advantages and may improve outcomes associated with the extent of resection and postoperative complications.