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Cadaveric feasibility study. To assess the anatomic and technical feasibility of rotating a clavicular segment on a sternocleidomastoid muscle (SCM) pedicle into the ventral cervical spine using a cadaveric model and to provide the first clinical case description of performing this procedure. Reconstruction of the anterior cervical spine in patients with a high risk of pseudoarthrosis may require the use of a vascularized bone graft (VBG). A vascularized clavicular graft rotated on an SCM pedicle would afford all the benefits of a VBG without the added morbidity of free-tissue transfer; however, this technique has not been described. A multidisciplinary team hypothesized that it would be anatomically and technically feasible to rotate a pedicled clavicular bone graft from the bottom of C2 to the top of T2 via an anterior approach. Five cadavers underwent bilateral anterior neck dissections for a total of 10 clavicular graft assessments. A case report describes the use of a clavicular VBG in a patient with a 3-level corpectomy defect and a history of failed fusion. Ten clavicles were rotated on an SCM pedicle. The grafts were either harvested as an entire segment or as the superior two-thirds of clavicle, leaving the inferior one-third in situ with pectoralis attachments intact. All grafts reached from the bottom of C2 to the top of T2. When the entire length of exposed clavicle was mobilized, it could cover 5–6 levels. The case report highlights technical challenges of this procedure in a living patient and provides clinical context for its potential utility in reconstruction of the ventral cervical spine. This surgical technique is best suited for patients with long-segment cervical defects and an increased risk of pseudarthrosis. Further clinical experience with this technique is required before definitive conclusions can be made. Level of Evidence: 5

Confocal microscopy utilizing fluorescent dyes is widely gaining use in the clinical setting as a diagnostic tool. Reflectance confocal microscopy is a method of visualizing tissue specimens without fluorescent dyes while relying on the natural refractile properties of cellular and subcellular structures. We prospectively evaluated 76 CNS lesions with confocal reflectance microscopy (CRM) to determine cellularity, architecture, and morphological characteristics. A neuropathologist found that all cases showed similar histopathological features when compared to matched hematoxylin and eosin-stained sections. RNA isolated from 7 tissues following CRM imaging retained high RNA integrity, suggesting that CRM does not alter tissue properties for molecular studies. A neuropathologist and surgical pathologist masked to the imaging results independently evaluated a subset of CRM images. In these evaluations, 100% of images reviewed by the neuropathologist and 95.7% of images reviewed by the surgical pathologist were correctly diagnosed as lesional or nonlesional. Furthermore, 97.9% and 91.5% of cases were correctly diagnosed as tumor or not tumor by the neuropathologist and surgical pathologist, respectively, while 95.8% and 85.1% were identified with the correct diagnosis. Our data indicate that CRM is a useful tool for rapidly screening patient biopsies for diagnostic adequacy, molecular studies, and biobanking.

A study was performed on the University Link and Northgate Link projects in Seattle, WA, to investigate the use of apparent density evaluation methods for the identification of air pockets and plugging issues in the chamber of EPB TBMs. Both air pockets and plugging issues can result from improper soil conditioning and the TBM’s inability to mix the soil properly with the conditioning agents. An apparent density below unity indicates the formation of an air pocket in the top part of the chamber and an apparent density above the virgin soil density points to developing plugging issues in the cutterhead bays and pressurized chamber. From the conducted study it can be concluded that the presented apparent density evaluation methods are an effective way to identify issues in the excavation chamber of an EPB TBM and can be used as a mean to improve the soil conditioning process.

Objectives The Hardy classification is used to classify pituitary tumors for clinical and research purposes. The scale was developed using lateral skull radiographs and encephalograms, and its reliability has not been evaluated in the magnetic resonance imaging (MRI) era. Design Fifty preoperative MRI scans of biopsy-proven pituitary adenomas using the sellar invasion and suprasellar extension components of the Hardy scale were reviewed. Setting This study was a cohort study set at a single institution. Participants There were six independent raters. Main Outcome Measures The main outcome measures of this study were interrater reliability, intrarater reliability, and percent agreement. Results Overall interrater reliability of both Hardy subscales on MRI was strong. However, reliability of the intermediate scores was weak, and percent agreement among raters was poor (12–16%) using the full scales. Dichotomizing the scale into clinically useful groups maintained strong interrater reliability for the sellar invasion scale and increased the percent agreement for both scales. Conclusion This study raises important questions about the reliability of the original Hardy classification. Editing the measure to a clinically relevant dichotomous scale simplifies the rating process and may be useful for preoperative tumor characterization in the MRI era. Future research studies should use the dichotomized Hardy scale (sellar invasion Grades 0–III versus Grade IV, suprasellar extension Types 0–C versus Type D).

OBJECTIVEThe goal of this study was to determine the interrater and intrarater reliability of the Knosp grading scale for predicting pituitary adenoma cavernous sinus (CS) involvement.METHODSSix independent raters (3 neurosurgery residents, 2 pituitary surgeons, and 1 neuroradiologist) participated in the study. Each rater scored 50 unique pituitary MRI scans (with contrast) of biopsy-proven pituitary adenoma. Reliabilities for the full scale were determined 3 ways: 1) using all 50 scans, 2) using scans with midrange scores versus end scores, and 3) using a dichotomized scale that reflects common clinical practice. The performance of resident raters was compared with that of faculty raters to assess the influence of training level on reliability.RESULTSOverall, the interrater reliability of the Knosp scale was “strong” (0.73, 95% CI 0.56–0.84). However, the percent agreement for all 6 reviewers was only 10% (26% for faculty members, 30% for residents). The reliability of the middle scores (i.e., average rated Knosp Grades 1 and 2) was “very weak” (0.18, 95% CI −0.27 to 0.56) and the percent agreement for all reviewers was only 5%. When the scale was dichotomized into tumors unlikely to have intraoperative CS involvement (Grades 0, 1, and 2) and those likely to have CS involvement (Grades 3 and 4), the reliability was “strong” (0.60, 95% CI 0.39–0.75) and the percent agreement for all raters improved to 60%. There was no significant difference in reliability between residents and faculty (residents 0.72, 95% CI 0.55–0.83 vs faculty 0.73, 95% CI 0.56–0.84). Intrarater reliability was moderate to strong and increased with the level of experience.CONCLUSIONSAlthough these findings suggest that the Knosp grading scale has acceptable interrater reliability overall, it raises important questions about the “very weak” reliability of the scale's middle grades. By dichotomizing the scale into clinically useful groups, the authors were able to address the poor reliability and percent agreement of the intermediate grades and to isolate the most important grades for use in surgical decision making (Grades 3 and 4). Authors of future pituitary surgery studies should consider reporting Knosp grades as dichotomized results rather than as the full scale to optimize the reliability of the scale.

Internal erosion, a major cause of failure of earthen dams and levees, is often difficult to detect at early stages using traditional visual inspection. The passive seismic-interferometry technique could enable the early detection of internal changes taking place within these structures. We test this technique on a portion of the sea levee of Colijnsplaat, Netherlands, which presents signs of concentrated seepage in the form of sandboils. Applying seismic interferometry to ambient noise collected over a 12-hour period, we retrieve surface waves propagating along the levee. We identify the contribution of two dominant ambient seismic noise sources: the traffic on the Zeeland bridge and a nearby wind turbine. Here, the sea-wave action does not constitute a suitable noise source for seismic interferometry. Using the retrieved surface waves, we compute time-lapse variations of the surface-wave group velocities during the 12-hour tidal cycle for different frequency bands, i.e., for different depth ranges. The estimated group-velocity variations correlate with variations in on-site pore-water pressure measurements that respond to tidal loading. We present lateral profiles of these group-velocity variations along a 180-meter section of the levee, at four different depth ranges (0m–40m). On these profiles, we observe some spatially localized relative group-velocity variations of up to 5% that might be related to concentrated seepage.

Background Surgical resection of brainstem cavernous malformations (BSCMs) is challenging, and patient selection and timing of intervention remain controversial. Objective To evaluate the impact of surgical timing and predictors of neurological outcome after surgical resection of BSCMs. Methods Consecutive adult patients (≥18 years) with BSCMs undergoing surgical resection between 1985 and 2014 by the senior author (RFS) were retrospectively reviewed. Patient demographics, lesion characteristics, imaging results, surgical approach, and perioperative and long-term neurological morbidity were analyzed. Results Data were analyzed for a total of 397 adult patients (160, 40% male). On univariate analysis, a greater proportion of patients treated within 6 weeks of hemorrhage had an improved Glasgow Outcome Scale score (P = .06). On logistic regression analysis, patients treated within 6 weeks of hemorrhage experienced improved clinical outcomes (odds ratio = 1.73; 95% confidence interval = 1.06-2.83; P = .03). Conclusions Although BSCM surgery is associated with significant perioperative morbidity and mortality, favorable long-term hemorrhage rates and symptom resolution can be achieved in a carefully selected group of patients. Overall, patients treated acutely, within 6 weeks, benefited the most from surgical intervention.

The 2017 World Health Organization classification of pituitary tumors redefined pituitary null cell adenomas (NCAs) by restricting this diagnostic category to pituitary tumors that are negative for pituitary transcription factors and adenohypophyseal hormones. The clinical behavior of this redefined entity has not been widely studied, and this is a major shortcoming of the classification. This study evaluated the imaging and clinical features of NCAs from two pituitary centers and compared them with those of gonadotroph adenomas (GAs). Imaging, pathologic, and clinical characteristics of NCAs and GAs were retrospectively reviewed. Tumor immunohistochemistry was performed to confirm absence of adenohypophyseal hormones and pituitary transcription factor expression. Thirty-one NCAs were compared with 38 GAs. NCAs were more likely to invade the cavernous sinus (15/31 [48%] vs. 5/38 [13%], P = .003) and had a higher proliferative index (i.e., MIB-1 > 3%, 11/31 [35%] vs. 5/38 [13%], P = .04). Gross total resection was less likely in the NCA group (19/31 [61%] vs. 33/38 [87], P = .02). Progression-free survival was worse in the NCA cohort (5-year progression-free survival, 0.70 vs. 1.00; P = .011, by log-rank test). Compared with GAs, NCAs are more invasive at the time of presentation and have a more aggressive clinical course. This study provides evidence that NCAs represent a distinct clinicopathologic entity with behavior that differs adversely from that of GAs. This may inform clinical decision-making, including frequency of postoperative tumor surveillance and timing of adjunctive treatments.

Background Falcine meningiomas have unique characteristics including their high rates of recurrence, association with high grade pathology, increased male prevalence, and potential for diffuse involvement of the falx. Objective To address these issues in a substantial series of falcine meningiomas and report on the impact of extent of resection for this distinct meningioma entity. Methods Retrospective analysis of characteristics and outcomes of 59 falcine meningioma patients who underwent surgery with the senior author. A "Grade Zero" category was used when an additional resection margin of 2 to 3 cm from the tumor insertion was achieved. Results For de novo falcine meningiomas, gross total resection (GTR) was associated with significantly decreased recurrence incidence compared with subtotal resection (P ≤ .0001). For recurrent falcine meningiomas, median progression-free survival (PFS) was significantly improved for GTR cases (37 mo vs 12 mo; P = .017, hazard ratio (HR) .243 (.077-.774)). "Grade Zero" resection demonstrated excellent durability for both de novo and recurrent cases, and PFS was significantly improved with "Grade Zero" resection for recurrent cases (P = .003, HR 1.544 (1.156-2.062)). The PFS benefit of "Grade Zero" resection did not achieve statistical significance over Simpson grade 1 during the limited follow-up period (mean 2.8 yr) for these groups. Conclusion The recurrence of falcine meningiomas is related to the diffuse presence of tumor between the leaflets of the falx. Increased extent of resection including, when possible, a clear margin of falx surrounding the tumor base was associated with the best long-term outcomes in our series, particularly for recurrent tumors.

Background We examined the biomechanical performance of a three-dimensional (3D)-printed vertebra on pedicle screw insertional torque (IT), axial pullout (APO), and stiffness (ST) testing. Materials and methods Seventy-three anatomically identical L5 vertebral body models (146 pedicles) were printed and tested for IT, APO, and ST using single-threaded pedicle screws of equivalent diameter (6.5 mm), length (40.0 mm), and thread pitch (2.6 mm). Print properties (material, cortical thickness [number of shells], cancellous density [in-fill], in-fill pattern, print orientation) varied among models. One-way analysis of variance was performed to evaluate the effects of variables on outcomes. Results The type of material significantly affected IT, APO, and ST (P < 0.001, all comparisons). For acrylonitrile butadiene styrene (ABS) models, in-fill density (25-35%) had a positive linear association with APO (P = 0.002), ST (P = 0.008), and IT (P = 0.10); similarly for the polylactic acid (PLA) models, APO (P = 0.001), IT (P < 0.001), and ST (P = 0.14). For the nylon material type, in-fill density did not affect any tested parameter. For a given in-fill density, material, and print orientation, the in-fill pattern significantly affected IT (P = 0.002) and APO (P = 0.03) but not ST (P = 0.23). Print orientation also significantly affected IT (P < 0.001), APO (P < 0.001), and ST (P = 0.002). Conclusions 3D-printed vertebral body models with specific print parameters can be designed to perform analogously to human bone on pedicle screw tests of IT, APO, and ST. Altering the material, in-fill density, in-fill pattern, and print orientation of synthetic vertebral body models could reliably produce a model that mimics bone of a specific bone mineral density.

Objective Granular cell tumors (GCTs), pituicytomas, and spindle cell oncocytomas are rare, nonfunctioning pituitary tumors sharing positive staining of thyroid transcription factor 1. We present our series, the first single-institutional report with long-term surgical follow-up of all 3 tumor types. Methods Our institutional pathology database was queried for these 3 pathologic diagnoses. Clinical records were assessed for clinical presentation, preoperative and postoperative endocrine status, tumor location on imaging, surgical characteristics, pathology results, and tumor recurrence. Results Data were analyzed for 4 patients with GCTs, 4 with pituicytomas, and 3 with spindle cell oncocytomas. The most common symptoms at presentation were vision changes (64%), headache (55%), endocrine abnormalities (55%), and fatigue (46%). GCTs were the only subtype to present exclusively in the infundibulum and the only subtype in our series to be treated with a transcranial transsylvian approach to resection (n = 2). In our study, in contrast to other reports, estimated blood loss was less than 300 mL in all patients. Imaging confirmed gross total resection in all 11 cases with no known recurrences at a mean (standard deviation) follow-up of 4.7 (3.7) years. Conclusions We present a single-institution series of rare thyroid transcription factor 1–staining posterior pituitary tumors of the sellar region. Key novel findings include gross total resection with no tumor recurrence at nearly 5 years of mean follow-up and no cases of excess or uncontrolled blood loss. Our findings reinforce the observation that GCTs present in the suprasellar space.

Background: The Schwab osteotomy grading scale—a unified osteotomy classification system created in 2014 by Schwab et al .—is one of many concepts in spine surgery that require detailed knowledge of 3-dimensional (3D) anatomy. 3D-printed spine models have demonstrated increasing utility in spine surgery as they more quickly communicate information on complex 3D anatomical relationships than planar imaging or 2-dimensional images. The purpose of this study was to evaluate the utility of a custom, 3D-printed spine model to help surgical trainees understand and perform the Schwab osteotomy grading scale. Methods: Eight participants were randomized into 2 groups: group 1 received written instructional materials about the Schwab osteotomy grading scale, whereas group 2 received both written materials and a 3D-printed model of the spine with osteotomy regions demarcated. All participants were administered written and practical examinations. Results: The group randomized to receive the 3D-printed model performed significantly better on both the written assessment (mean score, 7.75±0.50 vs . 5.75±0.50, P=0.023) and the practical examination (mean score, 1.75±0.32 vs . 1.08±0.09, P=0.025) than the group that received only written instructions. Conclusions: Our results support the conclusion that this 3D-printed spine model is an effective adjunct to help early surgical trainees understand the Schwab osteotomy grading scale. Participants who received the model in addition to the source manuscript demonstrated improved theoretical knowledge and better performance on practical tests of complex spinal osteotomies. Similar models are likely to have utility in surgical training programs and as patient education models.

BACKGROUND Three-dimensional (3D) printing holds great potential for lateral skull base surgical training; however, studies evaluating the use of 3D-printed models for simulating transtemporal approaches are lacking. OBJECTIVE To develop and evaluate a 3D-printed model that accurately represents the anatomic relationships, surgical corridor, and surgical working angles achieved with increasingly aggressive temporal bone resection in lateral skull base approaches. METHODS Cadaveric temporal bones underwent thin-slice computerized tomography, and key anatomic landmarks were segmented using 3D imaging software. Corresponding 3D-printed temporal bone models were created, and 4 stages of increasingly aggressive transtemporal approaches were performed (40 total approaches). The surgical exposure and working corridor were analyzed quantitatively, and measures of face validity, content validity, and construct validity in a cohort of 14 participants were assessed. RESULTS Stereotactic measurements of the surgical angle of approach to the mid-clivus, residual bone angle, and 3D-scanned infill volume demonstrated comparable changes in both the 3D temporal bone models and cadaveric specimens based on the increasing stages of transtemporal approaches (PANOVA

The hydraulic resistance of the filter cake on a tunnel face is an important factor in the stability of slurry-driven shield tunnels. However, the effect of the filter cake is not well understood. The study presented in this paper explores the dynamic and periodic features of the filter cake on the tunnel face through infiltration column tests. A three-dimensional numerical model with a permeable filter cake was developed to investigate the hydraulic head field in sandy soil from which the seepage forces were computed as well as a new calculation approach for the limit excess pressure based on a limit equilibrium analysis. The influences of the hydraulic conductivity of the filter cake on the limit excess pressure were also studied. Our results show that the limit excess pressure increased with an increase in the hydraulic conductivity of the filter cake and also show that the limit excess pressure, when calculated using the current approaches in the literature, was underestimated.

Tunnel Boring Machines (TBMs) are used for tunneling and underground construction, by excavating material and subsequently installing a segmental concrete tunnel liner for support. However, unknown ground conditions pose a significant risk to tunneling operations and any damage to the machine can be disastrous to a project. There is a need for tools which look ahead of the TBM for potential hazards during tunneling, such as water saturated zones, faults, boulders and metal pipes. Geophysical methods offer the capability to image unexcavated material in order to avoid such hazards and thus improve tunneling operations. In particular, the DC resistivity method is useful because it is sensitive to a large range of conductivity variations in geological and man-made materials. The research presented in our paper consists of three parts: (1) a laboratory study of a DC resistivity system mounted on a scale model TBM within a simulated tunneling environment, (2) a series of forward models studying different DC resistivity survey designs, and (3) the inversion and imaging of synthetic DC resistivity data under different constraints. We introduce several new survey designs that attach electrodes on a probe (or probes), which are then pushed into the earth in front of the machine each time excavation stops. Our laboratory data and forward modeling results show that using probes reduces interference caused by the metallic TBM body, and increases the distance ahead of the machine at which a target may be detected. The TBM influence on the data is significantly reduced once the probe is pushed 25% of the TBM diameter ahead of the machine and negligible once the probes are pushed 50% ahead of the machine. Depending on the specific survey design, targets can be detected from up to 70% of the TBM diameter away. Finally, we invert synthetic data to produce ahead-of-tunneling images using different amounts of prior information (e.g. TBM geometry and host resistivity) and also study time-lapse inversion. Numerical results show the target can be imaged with these methods from distances up to 45% TBM diameter.

Proper soil conditioning is critical for effective earth pressure balanced tunnel boring machine (EPBM) operation. Foam as a soil conditioner has been extensively used in EPBM tunneling to modify the excavated soil properties. A critical characteristic of foam-conditioned soil is stability, i.e., the ability to maintain the engineering properties throughout the residency time (30–90 min) in the mixing chamber. A comprehensive suite of experiments on foam-conditioned soil was conducted at both microscale and macroscale to investigate the fundamentals of foam-soil interaction and engineering properties of foam-conditioned soil. A foam-soil capture device and an optical microscope were used to capture bubble-grain images at a microscale under pressure. A pressurized testing chamber (PTC) was used to examine the stability of the mechanical properties of foam-conditioned soil. The compressibility, vane shear strength, pore pressure, and effective stress of foam-conditioned soil with elapsed time were obtained from the PTC test. The bubble-grain image analysis results reveal that foam is more stable when mixed with soil than by itself, indicating that soil particles help stabilize foam bubbles. Soil particles create a barrier to bubble coalescence and coarsening. The PTC test results show that the engineering properties of foam-conditioned soil remained constant over the 60-minute test duration. The results suggest that the accumulated “air bubble” at the top of the mixing chamber during EPBM tunneling is not due to the de-stabilization of foam bubbles when mixed with soil.

Recent extreme weather with heavy rainfall has brought new challenges to the operation of a karst tunnel as a large amount of groundwater flowing toward the tunnel in a short time exceeded the drainage capacity and caused high external water pressure. By evacuating the air in the inner space of the tunnel structure, an apparatus was developed to simulate the external water pressure on the tunnel structure. It was also employed to study the behavior of a highway tunnel structure with a large cross section considering cavities behind the liner. The results showed that the bending moment of the liner increased with the external water pressure, which helps to decrease the nonuniform distribution of the thrust force, and the maximum bending moment and eccentricity were generally located at the knees or side walls. Lower external water pressure contributed to reducing the eccentricity of the liner while higher external water pressure does not further reduce the eccentricity. Under external water pressure, fractures appeared first at the knee, then at the invert and finally at the vault. The air tightness tests under external water pressure also showed that the cavity decreased the bearing capacity of the liner and significantly aggravated the fractures in the liner nearby. The results help to estimate the bearing capacity of the liner under external water pressure, and the method of simulating external water pressure can also be used to study tunnels with different cross section geometries.

Summary Joint inversion and time-lapse inversion techniques of geophysical data are often implemented in an attempt to improve imaging of complex subsurface structures and dynamic processes by minimizing negative effects of random and uncorrelated spatial and temporal noise in the data. We focus on the structural cross-gradient (SCG) approach (enforcing recovered models to exhibit similar spatial structures) in combination with time-lapse inversion constraints applied to surface-based electrical resistivity and seismic traveltime refraction data. The combination of both techniques is justified by the underlying petrophysical models. We investigate the benefits and trade-offs of SCG and time-lapse constraints. Using a synthetic case study, we show that a combined joint time-lapse inversion approach provides an overall improvement in final recovered models. Additionally, we introduce a new approach to reweighting SCG constraints based on an iteratively updated normalized ratio of model sensitivity distributions at each time-step. We refer to the new technique as the Automatic Joint Constraints (AJC) approach. The relevance of the new joint time-lapse inversion process is demonstrated on the synthetic example. Then, these approaches are applied to real time-lapse monitoring field data collected during a quarter-scale earthen embankment induced-piping failure test. The use of time-lapse joint inversion is justified by the fact that a change of porosity drives concomitant changes in seismic velocities (through its effect on the bulk and shear moduli) and resistivities (through its influence upon the formation factor). Combined with the definition of attributes (i.e. specific characteristics) of the evolving target associated with piping, our approach allows localizing the position of the preferential flow path associated with internal erosion. This is not the case using other approaches.

Forced ventilation and recirculation systems are usually used in the construction of long twin tunnels as they offer large amounts of fresh air economically. However, because of the confluence near the cross-aisle, the fluid behavior and gas concentration are very different than in traditional forced ventilation for a single tunnel. A three-dimensional numerical model was built to study the air flow behavior and hazardous gas dispersion near the cross-aisle of a twin-tunnel construction. Field measurements were also carried out to validate the numerical model. The results show that there is a “dead zone” ahead of the cross-aisle which has a much lower air velocity than in other parts of the twin tunnels and where hazardous gases are more concentrated and uniformly distributed. In the cross-aisle and confluence zone of the air flow-out tunnel, methane tends to gather at the top and hydrogen sulfide tends to gather at the bottom. Increasing the recirculation velocity does not eliminate the “dead zone” near the cross-aisle although it consumes a huge amount of energy. Increasing the air velocity of the duct is an effective method to improve the air quality, but it is also expensive, especially when the air duct is long. When a jet fan was placed ahead of the cross-aisle in this study, the “dead zone” was eliminated completely. With respect to the recirculation ventilation system of twin tunnels, local jet fans offer an effective and economical way to eliminate the “dead zone”.

Tunnel excavation by means of tunnel boring machines (TBMs) is susceptible to unknown changes ahead of the tunnel face. Geophysics offers a technique called electrical resistivity that can continuously, in real-time, spatially map the formation in front of the TBM. Electrical resistivity has been successfully established for many applications including vadoze zone hydrology, oil/gas location, mineral location and failure detection in geo-structures. Yet it has not been well-established for TBM excavations. This is in part due to the complexity of the TBM tunneling environment and the uncertain influence this environment may have on the success of TBM-integrated-electrical resistivity to predict changes ahead of the tunnel face. One significant uncertainty lies in the interface region that exists around the TBM created during the modification of the virgin formation by a mechanical mixing action of the rotating cutterhead and the injection of additives used to aid in the extraction of the muck and protect the cutting tools from frictional wear. In this study, we investigate the influence of this interface region on TBM-integrated-electrical resistivity for both hard rock and soft ground tunneling conditions through finite element modeling. Regarding the performance of TBM-integrated-electrical resistivity to detect changes ahead of the cutting face, the interface region holds significant influence for both earth pressure balance (EPB) and open mode tunneling conditions. Electrical resistivity for slurry based tunneling is not influenced by the interface region. Simulations suggest that TBM-integrated-electrical resistivity can be sensitive to a formation change that is located up to five diameters in front of the TBM.

This paper examines the role of slurry TBM operational parameters, namely face, annulus and grout pressures, on ground deformation. The analysis includes both field data and computational modelling. Field data from the very successful Queens bored metro tunnels (6.9 m diameter) project in New York City is employed to illustrate phenomenologically how ground deformation was controlled via slurry TBM parameters. Computational modelling is then employed to support the experimental findings and to further investigate the relative influence of TBM parameters through parametric analysis. The results quantify the importance of the various pressures on controlling ground deformation.

Earthen dams and levees are prone to progressive failure through internal erosion of their structure. Internal erosion is often invisible to current methods of inspection until it manifests itself at the exterior surface. This study focuses on the novel use of passive seismic interferometry to monitor temporal changes in earthen embankments caused by internal erosion. This technique uses the ambient seismic noise – i.e. ambient vibrations – propagating through the structure. Laboratory-scale and field-scale embankment failure experiments are monitored. Seismic impulse responses are reconstructed from the ambient noise and temporal variations in seismic wave velocities are observed throughout each test. The application of seismic interferometry on a canal embankment tested to failure by internal erosion revealed up to 20% reductions in surface wave velocity as internal erosion progressed. The monitoring of a field embankment loaded to partial failure revealed a 30% reduction in averaged surface wave velocity. Some local velocity variations showed good agreement with local pore water pressure responses.

Background External ventricular drains (EVDs) are routinely placed as part of the management of intracranial hypertension. Pseudoaneurysm formation after EVD placement is a rare complication that can occur as a result of direct trauma to the cerebral vasculature. Prompt recognition and treatment may prevent future rupture. Objective To present our management strategy of a unique case of pseudoaneurysm formation in the context of the medical literature on these rare complications. Methods An EVD was placed in a 58-year-old female patient who presented with intracranial hypertension after subarachnoid hemorrhage secondary to a ruptured posterior communicating artery aneurysm before coiling of the aneurysm. On postbleed day 10, a pseudoaneurysm was identified in the distal anterior cerebral artery adjacent to the EVD tract. Results The pseudoaneurysm was successfully treated with surgical resection. Conclusion Pseudoaneurysm formation after EVD placement is a rare but serious complication. We do not recommend routine screening for this complication; however, further investigation may be warranted when a delayed EVD tract hemorrhage is encountered. Prompt treatment of pseudoaneurysms is necessary to prevent future hemorrhage.

BackgroundThe Pipeline Flex embolization device has several advantages over the first-generation Pipeline embolization device (Covidien, Dublin, Republic of Ireland). Despite these advantages, we have observed frequent difficulty in recapturing the device's delivery wire.ObjectiveTo prospectively document the incidence of failure to recapture the delivery wire.MethodsWe tracked our experience in patients undergoing endovascular treatment with a flow-diverting stent for cerebral aneurysms between 1 May and 30 September 2016. Patient and lesion characteristics, device dimensions, and technical outcomes of delivery wire recapture were prospectively recorded for each device.ResultsEighteen devices were deployed in 15 patients by the senior author (FCA) during this period. Failure to recapture the delivery wire occurred in 10 of 18 (56%) cases. No adverse outcomes of delivery wire recapture failure were encountered in this series.ConclusionsThe incidence of delivery wire recapture failure with the Pipeline Flex device is high. Failure to recapture the delivery wire carries a theoretical risk of stent displacement when re-navigating across the device, and endovascular surgeons should be aware of this limitation. Authors are encouraged to report delivery wire recapture failure rates in future clinical series in which the Pipeline Flex device is used.

While meningiomas are commonly benign brain tumors, as many as 30% may be classified as atypical, or WHO Grade 2. Patients are at risk of recurrence following resection and often are prescribed adjuvant radiation therapy (RT)-although most data on this treatment is retrospective and has shown mixed RESULTS: In this study we assessed the influence of adjuvant RT following gross total resection (GTR) in patients with newly diagnosed atypical meningiomas at our institution and sought to determine predictors of tumor recurrence. All patients who underwent GTR (Simpson Grade I and II) at their index operation from 1994-2014 were retrospectively reviewed. Patients then either underwent observation or adjuvant RT (Intensity-Modulated Radiation Therapy (IMRT) or stereotactic radiosurgery (SRS)). A total of 145 patients had documented GTR at the time of initial resection, including 88 females (61%) and 57 males (39%), with a mean age of 58 +/- 15.7 years. 118 patients were followed with observation after surgery while 27 (18.6%) patients received adjuvant RT prior to known recurrence (IMRT for 15 patients (55.5%) and SRS in 12 patients (44.4%)). Patients receiving adjuvant RT had significantly larger tumors, as well as a higher incidence of spontaneous necrosis and small cell phenotype on histopathology. Overall 5-year PFS in our cohort was 71.6% (CI 60.6%-84.7%) and was unchanged by adjuvant RT (p = 0.52). 23 patients (15.8%) had a recurrence with a mean follow up of 42.9 months (17.1-53.5 months). Male gender (HR=1.02, p=0.019), tumor size (HR=1.17, p= 0.002) and MIB-1 > 4 (HR=8.50, p=0.04) were associated with increased recurrence risk. There was no association between radiation type (SRS vs. IMRT) and risk of recurrence (p= 0.154). In our patients, adjuvant RT following GTR of atypical meningiomas did not improve PFS. Risk factors for recurrence included male gender, larger tumor size, and MIB-1 > 4.

Earth pressure balance shield tunnel boring machines (EPBM) are widely used in tunneling practice yet the mechanics that define ground-EPBM interaction, specifically the advance rate, are not well understood. In the study presented here, machine learning techniques including feature selection, support vector regression (SVR) and partial dependence plots (PDP), were successfully applied to EPBM data to develop and explain EPBM advance rate modeling through five widely varying soil types. The geotechnical conditions were implicitly incorporated into the analysis by developing soil formation-specific SVR models. The SVR models were highly successful in capturing AR behavior, exhibiting R2 values of 0.88–0.95 when independently evaluated with test data. Automatic feature selection revealed the same EPBM parameters of notable influence on AR across all ESUs, including net thrust, cutterhead torque, foam flow rate and screw conveyor torque. The SVR models, however, revealed considerably different relationships between these key parameters and AR, indicating that the soil plays a significant role in AR behavior. PDP analysis captured the sensitivity of AR to each key parameter as a function of parameter magnitude. The PDP results show that AR is positively correlated (increasing AR with increasing parameter value) and/or negatively correlated (decreasing AR with increasing parameter value) to varying degrees as a function of parameter value, all of which is strongly soil dependent.

This paper presents a simplified excavation chamber pressure model for earth pressure balance shield tunnel boring machine (EPBM) tunneling in granular soils, capable of predicting chamber pressure response during both excavation and standstill periods. Two physical processes, (1) compressible material flow, and (2) chamber fluid seepage, are modeled. The chamber pressure model is physics-based and is built upon chamber muck mass conservation. The model assumes muck behavior to be pressure-dependent and quasi-static. Given recorded EPBM operations, including advance rate, chamber additive injection rates and screw conveyor rotation speed, the model can predict the chamber pressure fluctuation with good accuracy, both during excavation and standstill periods. A case study using tunneling project data is included, where the model’s capability to simulate chamber pressure evolution during excavation of a single ring and multiple consecutive rings is demonstrated.

This paper addresses the elastic net modeling of earth pressure balance shield machine (EPBM) advance rate for which there is no published physical model. Elastic net polynomial regression is employed to model the advance rate using data collected during the excavation of Sound Transit Northgate Link tunnels (N125) in Seattle, Washington, USA. The EPBM data was partitioned based on the geological profile to examine the influence of the soil type through which the EPBM was tunneling. The feature set for regression analyses included net thrust force, cutterhead rotation speed, conditioning foam flow rate, cutterhead torque, screw conveyor torques, as well as depths below ground surface and groundwater table. Third order polynomial models were able to model over 75% of the advance rate response on independent test data with normalized RMSE less than 20%. Using stratified sampling, only 10% of the EPBM data is required for model training to achieve these levels of accuracy and efficacy. Advance rate models were found to be considerably different across soil units indicating the soil type plays a significant role in EPBM response. The most influential parameters varied across soil types. Conditioning foam flow rate was the most important parameter in three of five soil units, while net thrust force and screw conveyor torque were the most influential features in two of five soil units. Partial dependence and individual conditional expectation analysis revealed that advance rate is positively related (increasing advance rate with increasing parameter value) and/or negatively related (decreasing advance rate with increasing parameter value) to varying degrees as a function of parameter value, all of which is strongly soil dependent.

Recurrent drug-eluting stent restenosis (DES ISR) can be challenging to treat. Vascular brachytherapy (VBT) has been used with encouraging results. We report the long-term outcomes of patients with recurrent DES ISR treated with VBT from January 2014 to September 2018 [target lesion failure (TLF)

BACKGROUND: World Health Organization (WHO) Grade III meningiomas are associated with poor clinical outcomes due to high rates of recurrence and limited adjuvant treatment options. The Forkhead Box M1 (FOXM1) transcription factor is a phosphorylation target of CDK4/6 that protects cancer cells from senescence and is upregulated in Grade III meningiomas. We sought to investigate FOXM1 and phosphorylated FOXM1 (pFOXM1) expression in WHO Grade III meningiomas in relation to proliferative index, CDK4/6 cytogenetic profile, and clinical history. METHODS: We examined 38 tissue specimens from 27 patients with Grade III meningiomas. CDK4, CDK6, and CDKN2A cytogenetic profiles were studied using fluorescence in situ hybridization. FOXM1 and pFOXM1 were identified with immunohistochemistry and quantified using imaging analysis software. RESULTS: pFOXM1 nuclear staining (positive nuclei/mm2) correlated with tumor proliferative index in Grade III meningiomas (mitotic rate > 20, 115.5 vs. mitotic rate < 20, 34.7, P=0.02). Cytogenetic loss of CDK4/6 was associated with significantly decreased pFOXM1 staining (30.8 vs. 111.1, P=0.017). No significant differences in FOXM1 or pFOXM1 staining were observed with gain/amplification of CDK4/6 or with loss of CDKN2A. Grade I/II meningiomas that transformed to Grade III were accompanied by an increase in pFOXM1 staining compared to their de novo counterparts (138.3 vs. 45.9, P < 0.05). CONCLUSIONS: pFOXM1 expression correlated with tumor proliferative rate, CDK4/6 cytogenetic status, and prior Grade I/II meningiomas, suggesting a role of FOXM1 signaling in the transformation of lower-grade meningiomas to Grade III lesions. These findings support the potential role for selective CDK4/6 inhibitors as an adjuvant therapy for Grade III meningiomas.

Importance Despite evidence that therapeutic hypothermia improves patient outcomes for out-of-hospital cardiac arrest, use of this therapy remains low. Objective To determine whether the use of therapeutic hypothermia and patient outcomes have changed after publication of the Targeted Temperature Management trial on December 5, 2013, which supported more lenient temperature management for out-of-hospital cardiac arrest. Design, Setting, and Participants A retrospective cohort was conducted between January 1, 2013, and December 31, 2016, of 45 935 US patients in the Cardiac Arrest Registry to Enhance Survival who experienced out-of-hospital cardiac arrest and survived to hospital admission. Exposures Calendar time by quarter year. Main Outcomes and Measures Use of therapeutic hypothermia and patient survival to hospital discharge. Results Among 45 935 patients (17 515 women and 28 420 men; mean [SD] age, 59.3 [18.3] years) who experienced out-of-hospital cardiac arrest and survived to admission at 649 US hospitals, overall use of therapeutic hypothermia during the study period was 46.4%. In unadjusted analyses, the use of therapeutic hypothermia dropped from 52.5% in the last quarter of 2013 to 46.0% in the first quarter of 2014 after the December 2013 publication of the Targeted Temperature Management trial. Use of therapeutic hypothermia remained at or below 46.5% through 2016. In segmented hierarchical logistic regression analysis, the risk-adjusted odds of use of therapeutic hypothermia was 18% lower in the first quarter of 2014 compared with the last quarter of 2013 (odds ratio, 0.82; 95% CI, 0.71-0.94; P = .006). Similar point-estimate changes over time were observed in analyses stratified by presenting rhythm of ventricular tachycardia or ventricular fibrillation (odds ratio, 0.89; 95% CI, 0.71-1.13, P = .35) and pulseless electrical activity or asystole (odds ratio, 0.75; 95% CI, 0.63-0.89; P = .001). Overall risk-adjusted patient survival was 36.9% in 2013, 37.5% in 2014, 34.8% in 2015, and 34.3% in 2016 (P, This cohort study examines whether the use of therapeutic hypothermia and patient survival have changed after publication of the Targeted Temperature Management trial, which supported more lenient temperature management for out-of-hospital cardiac arrest., Key Points Question Did the use of therapeutic hypothermia for out-of-hospital cardiac arrest change after publication of a trial that supported more lenient temperature goals? Findings In a cohort study of 45 935 US patients who experienced out-of-hospital cardiac arrest and survived to hospital admission, the risk-adjusted odds of the use of therapeutic hypothermia decreased 18% in the first quarter of 2014 after publication of the Targeted Temperature Management trial, compared with the last quarter of 2013. Risk-adjusted patient survival also decreased during the study period, but was not mediated by trends in hypothermia use. Meaning In a US registry of patients who experienced out-of-hospital cardiac arrest, the use of guideline-recommended active cooling decreased after publication of the Targeted Temperature Management trial.

Jugular foramen schwannomas (JFSs) are relatively rare, benign lesions that account for 10% to 30% of all tumors in the region of the jugular foramen. Given their slow-growing nature, JFSs can become quite large before causing symptoms of lower cranial nerve (LCN) dysfunction, making microsurgical resection a challenge. Successful resection of any JFS is dependent on the identification and preservation of the adjacent, uninvolved LCNs to alleviate nerve compression and preserve function. We report a transmastoid, high cervical approach to a dumbbell-shaped, extracranial JFS that was causing symptomatic LCN compression. The patient presented with dysphagia and was found to have left vocal cord paralysis on video laryngoscopy and intermittent aspiration on a swallowing evaluation. The transmastoid, high cervical exposure allowed for early identification of the tumor as well as the adjacent LCNs. Neurophysiological monitoring included somatosensory evoked potentials; brainstem auditory evoked responses; and cranial nerve VII, X, XI, and XII electromyographic monitoring. Endoscopic assistance allowed for improved LCN visualization from the high cervical exposure and gross-total resection of the tumor. The patient's dysphagia improved both subjectively and objectively following the resection. The patient gave written informed consent for surgery and publication of the case report. Institutional review board approval was not required for this case report. Used with permission from Barrow Neurological Institute.

Introduction Nationwide databases are frequently used resources for assessing practice patterns and clinical outcomes. However, analyses based on billing codes may be limited by the inconsistent application of current procedural terminology (CPT) codes to specific operations. We investigated the variability among commonly used CPT codes for vestibular schwannomas resection and sought to identify factors that underlie this variation. Methods The surgical procedure for 274 cases of vestibular schwannoma resections from two institutions was reviewed and classified as retrosigmoid, translabyrinthine, or middle fossa approaches. We then assessed the CPT codes assigned to each case and analyzed their association with surgical approach, surgeons involved, the coding specialty, and year of surgery. We further compared the incidence of CPT codes assigned for vestibular schwannoma surgeries in the American College Surgeons National Surgical Quality Improvement Program (NSQIP) database from 2010 to 2014. Results The majority (65%) of vestibular schwannoma resections within the institutional cohort were billed with skull base approach and/or excision codes, whereas 76% of cases in NSQIP were associated with a single craniotomy for tumor code. The use of skull base codes over the past decade increased within our institutional cohort but remained relatively stable within NSQIP. CPT codes did not consistently reflect the operative approaches for vestibular schwannomas. Conclusion We observed significant variability in coding patterns for vestibular schwannoma surgeries within institutions, surgical practices, and national databases. These results call for discretion in interpretation of data from aggregated billing code-based nationwide databases and suggests a role for institutional standardization of CPT assignments for the same approaches.

Confocal laser endomicroscopy (CLE) is an advanced optical fluorescence imaging technology that has the potential to increase intraoperative precision, extend resection, and tailor surgery for malignant invasive brain tumors because of its subcellular dimension resolution. Despite its promising diagnostic potential, interpreting the gray tone fluorescence images can be difficult for untrained users. In this review, we provide a detailed description of bioinformatical analysis methodology of CLE images that begins to assist the neurosurgeon and pathologist to rapidly connect on-the-fly intraoperative imaging, pathology, and surgical observation into a conclusionary system within the concept of theranostics. We present an overview and discuss deep learning models for automatic detection of the diagnostic CLE images and discuss various training regimes and ensemble modeling effect on the power of deep learning predictive models. Two major approaches reviewed in this paper include the models that can automatically classify CLE images into diagnostic/nondiagnostic, glioma/nonglioma, tumor/injury/normal categories and models that can localize histological features on the CLE images using weakly supervised methods. We also briefly review advances in the deep learning approaches used for CLE image analysis in other organs. Significant advances in speed and precision of automated diagnostic frame selection would augment the diagnostic potential of CLE, improve operative workflow and integration into brain tumor surgery. Such technology and bioinformatics analytics lend themselves to improved precision, personalization, and theranostics in brain tumor treatment., Comment: See the final version published in Frontiers in Oncology here: https://www.frontiersin.org/articles/10.3389/fonc.2018.00240/full

Introduction The Barrow Biomimetic Spine project is an ongoing effort to develop a three-dimensional (3D)-printed synthetic spine model with high anatomical and biomechanical fidelity to human tissue. The purpose of this study was to evaluate the biomechanical performance of an L4-L5 3D-printed synthetic spine model in a lordotic correction test after Schwab grade 2 osteotomies as compared to human cadaveric spines that have undergone the same osteotomies and lordotic correction. Methods Ten different L4-L5 synthetic spine models were 3D printed. Each print varied in either the material used for the soft tissue components, the infill density of the bony and soft tissue structures, the pre-correction disc height, or the model orientation on the print bed. Each print was instrumented with pedicle screws and underwent a Schwab grade 2 osteotomy. Changes in disc height measurements and end-plate angle were compared against cadaveric data acquired using the same study method. Results A simple linear correlation analysis demonstrated that for horizontally printed models using PolyFlex (Polymaker, New York, NY, USA)(models 1-3, 8, 10), the pre-correction posterior disc height and lordotic correction were moderately correlated (r = 0.56), but this correlation did not achieve statistical significance (P = 0.12). Regression analysis demonstrated a very strong correlation between lordotic correction and change in posterior disc height (r = 0.92, P < 0.001). Models printed either vertically (models 4-6) or with low bone density and high soft tissue density (model 10) appeared to perform the most similarly to the cadaveric tissue. Discussion The 3D-printed synthetic spine models demonstrated predictable and reliable performance in a lordotic correction test based on their respective material qualities and print densities. The print variables tested further demonstrated that this model is capable of achieving high biomechanical fidelity to cadaveric tissue when subjected to the same lordotic correction test after Schwab grade 2 osteotomies.

BACKGROUND Styloidogenic jugular venous compression syndrome (SJVCS) is a rare cause of idiopathic intracranial hypertension (IIH). OBJECTIVE To elucidate the pathophysiology and the hemodynamics of SJVCS. METHODS We conducted a retrospective review of medical records, clinical images, dynamic venography, and manometry for consecutive patients with SJVCS undergoing microsurgical decompression from April 2009 to October 2017. Patients with IIH with normal venography and manometry findings served as controls. RESULTS Data were analyzed for 10 patients with SJVCS who presented with headaches. Neck flexion exacerbated headaches in 7 patients. Eleven patients with IIH provided control data for normal intracranial venous pressure and styloid process anatomy. Patients with SJVCS had bilateral osseous compression of venous outflow. The styloid processes were significantly longer in patients with SJVCS than in those with IIH (mean [standard deviation (SD)] distance, 31.0 [10.6] vs 19.0 [14.1] mm; P

Objective Patients with hydrocephalus secondary to third ventricular colloid cysts can require bilateral external ventricular drain (EVD) placement while awaiting surgery. However, some patients could develop auto-fenestration of the septum pellucidum (AFSP) and only require 1 EVD. We evaluated our experience with bedside iohexol ventriculography and staged EVD placement for patients with obstructive hydrocephalus. Methods We retrospectively identified 34 patients who had been treated for third ventricular colloid cysts (2013–2016). The preoperative and postoperative data, including age, sex, colloid cyst size, preoperative hydrocephalus, preoperative EVD placement, preoperative iohexol ventriculography, operative approach, intraoperative findings, and postoperative ventriculoperitoneal shunt requirements, were reviewed. Results Hydrocephalus was found in 23 patients (68%) on initial presentation. Nine patients (26%) had EVDs placed before surgery. Six patients (18%) underwent iohexol ventriculography after insertion of a right-sided EVD. Five patients (15%) demonstrated no evidence of ventricular communication. Four patients (67%) required left-sided EVD placement. One patient (17%) had robust communication between the lateral ventricles after intraventricular iohexol injection, which was managed with a single EVD. AFSP was observed during surgical resection of this patient’s colloid cyst. One other patient who did not undergo preoperative EVD placement was noted to have AFSP intraoperatively, resulting in 2 of 34 patients (6%) with AFSP in our series. Conclusions A subset of patients with obstruction at the foramina of Monro can develop AFSP. Iohexol ventriculography after unilateral EVD placement allows clinicians to assess for the presence of AFSP and identify patients who can be treated with a single EVD before surgery.

Background: Many surgeons utilize assistants to perform procedures in more than one operating room at a given time using a practice known as overlapping surgery. Debate has continued as to whether overlapping surgery improves the efficiency and access to care or risks patient safety and outcomes. Objective: To examine effects of overlapping surgery in deep brain stimulation (DBS) for movement disorders. Methods: In this retrospective analysis of overlapping and non-overlapping cases, we evaluated stereotactic accuracy, operative duration, length of hospital stay, and the presence of hemorrhage, wound-related complications, and hardware-related complications requiring revision in adults with movement disorders undergoing DBS. Results: Of 324 cases, 141 (43.5%) were overlapping and 183 (56.5%) non-overlapping. Stereotactic error, number of brain penetrations, and postoperative length of hospitalization did not differ significantly (p ≥ 0.08) between the overlapping and non-overlapping groups. Mean operative duration was significantly longer for overlapping (81/141 [57.4%], 189.5 ± 10.8 min) than for non-overlapping cases (79/183 [43.2%], 169.9 ± 7.6 min; p = 0.004). There were no differences in rates of wound-related complications or hemorrhages, but overlapping cases had a significantly higher rate of hardware-related complications requiring revision (7/141 [5.0%] vs. 0/183 [0%]; p = 0.002). Conclusions: Overlapping and non-overlapping cases had comparable DBS lead placement accuracy. Overlapping cases had a longer operative duration and had a higher rate of hardware-related complications requiring revision.

BACKGROUND A simple, reliable grading scale to better characterize nonfunctioning pituitary adenomas (NFPAs) preoperatively has potential for research and clinical applications. OBJECTIVE To develop a grading scale from a prospective multicenter cohort of patients that accurately and reliably predicts the likelihood of gross total resection (GTR) after transsphenoidal NFPA surgery. METHODS Extent-of-resection (EOR) data from a prospective multicenter study in transsphenoidal NFPA surgery were analyzed (TRANSSPHER study; ClinicalTrials.gov NCT02357498). Sixteen preoperative radiographic magnetic resonance imaging (MRI) tumor characteristics (eg, tumor size, invasion measures, tumor signal characteristics, and parameters impacting surgical access) were evaluated to determine EOR predictors, to calculate receiver-operating characteristic curves, and to develop a grading scale. A separate validation cohort (n = 165) was examined to assess the scale's performance and inter-rater reliability. RESULTS Data for 222 patients from 7 centers treated by 15 surgeons were analyzed. Approximately one-fifth of patients (18.5%; 41 of 222) underwent subtotal resection (STR). Maximum tumor diameter > 40 mm; nodular tumor extension through the diaphragma into the frontal lobe, temporal lobe, posterior fossa, or ventricle; and Knosp grades 3 to 4 were identified as independent STR predictors. A grading scale (TRANSSPHER grade) based on a combination of these 3 features outperformed individual variables in predicting GTR (AUC, 0.732). In a validation cohort, the scale exhibited high sensitivity and specificity (AUC, 0.779) and strong inter-rater reliability (kappa coefficient, 0.617). CONCLUSION This simple, reliable grading scale based on preoperative MRI characteristics can be used to better characterize NFPAs for clinical and research purposes and to predict the likelihood of achieving GTR.

Objective and subjective fluoroscopic assessments of a new synthetic spine model.The aim of this study was to analyze the fluoroscopic performance and fidelity to human tissue of a new synthetic spine model.The Barrow Biomimetic Spine project aims to develop a 3-dimensional (3D) printed, synthetic spine model that will one day replace cadaveric tissue in spine biomechanical research. A crucial component to any biomimetic spine model is that it performs similarly to cadaveric tissue on standard diagnostic imaging modalities.Numerous L5 vertebral bodies (VBs) were 3D printed with variable shell thicknesses and internal densities, and fluoroscopic images were taken of these models to measure cortical thickness and gray-scale density. An L3-L5 spinal segment was then printed, and fluoroscopic films were obtained at variable C-arm angles. Three spine surgeons subjectively scored these images for human fidelity. Pedicle screws were then placed into the L3-L5 segment to demonstrate successful or breached placement. Standard anteroposterior (AP) and lateral films were taken, and three spine surgeons were tested and scored on correctly identifying screw placement.Cortical thickness and gray-scale density testing demonstrated an upward trend with increases in relevant print settings. Subjective scoring demonstrated nearly perfect fidelity for the L3-L5 model. Surgeon identification of screw placement on the AP and lateral fluoroscopic views also demonstrated nearly perfect fidelity.This study is the first to demonstrate that 3D-printed VB and segmental spine models accurately mimic human tissue on C-arm fluoroscopy, not only in respect to their anatomical appearance in standard views but also in their response to surgical manipulation and the variations in C-arm angle that commonly occur in the operating room. As such, these spine models have the potential to serve as an excellent platform for future research and surgical education programs.N/A.

Background and importance Although posterior petrosal approaches are utilized less frequently in many practices today, they continue to provide distinct surgical advantages in carefully selected cases. Here, we report a case of a recurrent cerebellopontine angle (CPA) hemangioblastoma that had failed a prior, more conservative, surgical approach. We provide cadaveric dissections of variations of posterior petrosal approaches to illustrate the advantages of the selected approach. Clinical presentation A 70-yr-old female presented with a growing left CPA hemangioblastoma. The lesion had undergone a prior subtotal resection from a retrosigmoid approach and subsequent adjuvant radiation treatment. The patient had worsening left facial strength, progressive balance difficulty, and absent left auditory function. Preoperative angiogram demonstrated arterial blood supply from the left anterior inferior cerebellar artery (AICA) that was deemed unsafe for embolization due to significant arteriovenous shunting. A posterior petrosal transotic approach was performed in order to optimize the working angle to the anterior brainstem and afford the ability to occlude the vascular supply from AICA prior to surgical resection of the lesion. Conclusion The posterior petrosal transotic approach offers an improved surgical working angle to the anterior brainstem compared to the translabyrinthine approach. This advantage can be particularly important with vascular tumors that receive blood supply anteriorly, as in this case from AICA, and can improve the safety of the resection.

OBJECTIVEWith drastic changes to the health insurance market, patient cost sharing has significantly increased in recent years. However, the patient financial burden, or out-of-pocket (OOP) costs, for surgical procedures is poorly understood. The goal of this study was to analyze patient OOP spending in cranial neurosurgery and identify drivers of OOP spending growth.METHODSFor 6569 consecutive patients who underwent cranial neurosurgery from 2013 to 2016 at the authors’ institution, the authors created univariate and multivariate mixed-effects models to investigate the effect of patient demographic and clinical factors on patient OOP spending. The authors examined OOP payments stratified into 10 subsets of case categories and created a generalized linear model to study the growth of OOP spending over time.RESULTSIn the multivariate model, case categories (craniotomy for pain, tumor, and vascular lesions), commercial insurance, and out-of-network plans were significant predictors of higher OOP payments for patients (all p < 0.05). Patient spending varied substantially across procedure types, with patients undergoing craniotomy for pain ($1151 ± $209) having the highest mean OOP payments. On average, commercially insured patients spent nearly twice as much in OOP payments as the overall population. From 2013 to 2016, the mean patient OOP spending increased 17%, from $598 to $698 per patient encounter. Commercially insured patients experienced more significant growth in OOP spending, with a cumulative rate of growth of 42% ($991 in 2013 to $1403 in 2016).CONCLUSIONSEven after controlling for inflation, case-mix differences, and partial fiscal periods, OOP spending for cranial neurosurgery patients significantly increased from 2013 to 2016. The mean OOP spending for commercially insured neurosurgical patients exceeded $1400 in 2016, with an average annual growth rate of 13%. As patient cost sharing in health insurance plans becomes more prevalent, patients and providers must consider the potential financial burden for patients receiving specialized neurosurgical care.