Transabdominal motor evoked potential neuromonitoring of lumbosacral spine surgery.

BACKGROUND CONTEXT: Transcranial Motor Evoked Potentials (TcMEPs) can improve intraoperative detection of femoral plexus and nerve root injury during lumbosacral spine surgery. However, even under ideal conditions, TcMEPs are not completely free of false-positive alerts due to the immobilizing effect of general anesthetics, especially in the proximal musculature. The application of transcutaneous stimulation to activate ventral nerve roots directly at the level of the conus medularis (bypassing the brain and spinal cord) has emerged as a method to potentially monitor the motor component of the femoral plexus and lumbosacral nerves free from the blunting effects of general anesthesia. PURPOSE: To evaluate the reliability and efficacy of transabdominal motor evoked potentials (TaMEPs) compared to TcMEPs during lumbosacral spine procedures. DESIGN: We present the findings of a single-center 12-month retrospective experience of all lumbosacral spine surgeries utilizing multimodality intraoperative neuromonitoring (IONM) consisting of TcMEPs, TaMEPs, somatosensory evoked potentials (SSEPs), electromyography (EMG), and electroencephalography. PATIENT SAMPLE: Two hundred and twenty patients having one, or a combination of lumbosacral spine procedures, including anterior lumbar interbody fusion (ALIF), lateral lumbar interbody fusion (LLIF), posterior spinal fusion (PSF), and/or transforaminal lumbar interbody fusion (TLIF). OUTCOME MEASURES: Intraoperative neuromonitoring data was correlated to immediate post-operative neurologic examinations and chart review. METHODS: Baseline reliability, false positive rate, true positive rate, false negative rate, area under the curve at baseline and at alerts, and detection of pre-operative deficits of TcMEPs and TaMEPs were compared and analyzed for statistical significance. The relationship between transcutaneous stimulation voltage level and patient BMI was also examined. RESULTS: TaMEPs were significantly more reliable than TcMEPs in all muscles except abductor hallucis. Of the 27 false positive alerts, 24 were TcMEPs alone, and 3 were TaMEPs alone. Of the 19 true positives, none were detected by TcMEPs alone, 3 were detected by TaMEPs alone (TcMEPs were not present), and the remaining 16 true positives involved TaMEPs and TcMEPs. TaMEPs had a significantly larger area under the curve (AUC) at baseline than TcMEPs in all muscles except abductor hallucis. The percent decrease in TcMEP and TaMEP AUC during LLIF alerts was not significantly different. Both TcMEPs and TaMEPs reflected three pre-existing motor deficits. Patient BMI and TaMEP stimulation intensity were found to be moderately positively correlated. CONCLUSIONS: These findings demonstrate the high reliability and predictability of TaMEPs and the potential added value when TaMEPs are incorporated into multimodality IONM during lumbosacral spine surgery.

Modeling the hydrodynamic impact on the tool influence function during hemispherical subaperture optical polishing.

To fabricate high-precision and accurate optics relative to the optical design surface, a high level of deterministic control of material removal (i.e., the tool influence function, TIF) during subaperture tool polishing is required. In this study, a detailed analysis of the pressure distribution, which is a key component of the TIF, has been performed using finite element analysis to couple together solid mechanics and fluid dynamics. Modeling experimental parameters of recently published work reveals that, when considering tool deformation, which in turn influences the fluid film thickness between the tool and workpiece, the effective pressure profile has a flat-top distribution. This flat-top pressure profile differs from the parabolic pressure distributions predicted by Hertzian mechanics. Moreover, the shear contribution is shown here to be a key contributor to material removal, inducing the removal at the periphery of the contact edge and even outside the generally accepted contact area. Finally, the simulated fluid velocities provide evidence of mixed-mode contact polishing, supporting recent experimental findings that also suggest that onset of hydroplaning contributions lead to material removal drop-off.

The utility of intraoperative neuromonitoring on simple posterior lumbar fusions-analysis of the National Inpatient Sample.

BACKGROUND: Several studies have demonstrated the utility of intraoperative neuromonitoring (IOM) including somatosensory evoked potentials (SSEPs), motor-evoked potentials (MEPs), and electromyography (EMG), in decreasing the risk of neurologic injury in spinal deformity procedures. However, there is limited evidence supporting the routine use of IOM in elective posterolateral lumbar fusion (PLF). METHODS: The National Inpatient Sample (NIS) was analyzed for the years 2012-2015 to identify patients undergoing elective PLF with (n=22,404) or without (n=111,168) IOM use. Statistical analyses were conducted to assess the impact of IOM on length of stay, total charges, and development of neurologic complications. These analyses controlled for age, gender, race, income percentile, primary expected payer, number of reported comorbidities, hospital teaching status, and hospital size. RESULTS: The overall use of IOM in elective PLFs was found to have increased from 14.6% in the year 2012 to 19.3% in 2015. The total charge in hospitalization cost for all patients who received IOM increased from $129,384.72 in 2012 to $146,427.79 in 2015. Overall, the total charge of hospitalization was 11% greater in the IOM group when compared to those patients that did not have IOM (P<0.001). IOM did not have a statistically significant impact on the likelihood of developing a neurological complication. CONCLUSIONS: While there may conceivably be benefits to the use of this technology in complex revision fusions or pathologies, we found no meaningful benefit of its application to single-level index PLF for degenerative spine disease.

A wireless spinal stimulation system for ventral activation of the rat cervical spinal cord.

Electrical stimulation of the cervical spinal cord is gaining traction as a therapy following spinal cord injury; however, it is difficult to target the cervical motor region in a rodent using a non-penetrating stimulus compared with direct placement of intraspinal wire electrodes. Penetrating wire electrodes have been explored in rodent and pig models and, while they have proven beneficial in the injured spinal cord, the negative aspects of spinal parenchymal penetration (e.g., gliosis, neural tissue damage, and obdurate inflammation) are of concern when considering therapeutic potential. We therefore designed a novel approach for epidural stimulation of the rat spinal cord using a wireless stimulation system and ventral electrode array. Our approach allowed for preservation of mobility following surgery and was suitable for long term stimulation strategies in awake, freely functioning animals. Further, electrophysiology mapping of the ventral spinal cord revealed the ventral approach was suitable to target muscle groups of the rat forelimb and, at a single electrode lead position, different stimulation protocols could be applied to achieve unique activation patterns of the muscles of the forelimb.

Prone Positioning in Moderate to Severe Acute Respiratory Distress Syndrome Due to COVID-19: A Cohort Study and Analysis of Physiology.

BACKGROUND: Coronavirus disease 2019 (COVID-19) can lead to acute respiratory distress syndrome (ARDS) but it is unknown whether prone positioning improves outcomes in mechanically ventilated patients with moderate to severe ARDS due to COVID-19. METHODS: A cohort study at a New York City hospital at the peak of the early pandemic in the United States, under crisis conditions. The aim was to determine the benefit of prone positioning in mechanically ventilated patients with ARDS due to COVID-19. The primary outcome was in-hospital death. Secondary outcomes included changes in physiologic parameters. Fine-Gray competing risks models with stabilized inverse probability treatment weighting (sIPTW) were used to determine the effect of prone positioning on outcomes. In addition, linear mixed effects models (LMM) were used to assess changes in physiology with prone positioning. RESULTS: Out of 335 participants who were intubated and mechanically ventilated, 62 underwent prone positioning, 199 met prone positioning criteria and served as controls and 74 were excluded. The intervention and control groups were similar at baseline. In multivariate-adjusted competing risks models with sIPTW, prone positioning was significantly associated with reduced mortality (SHR 0.61, 95% CI 0.46-0.80, P < 0.005). Using LMM to evaluate the impact of positioning maneuvers on physiological parameters, the oxygenation-saturation index was significantly improved during days 1-3 (P < 0.01) whereas oxygenation-saturation index (OSI), oxygenation-index (OI) and arterial oxygen partial pressure to fractional inspired oxygen (PaO2: FiO2) were significantly improved during days 4-7 (P < 0.05 for all). CONCLUSIONS: Prone positioning in patients with moderate to severe ARDS due to COVID-19 is associated with reduced mortality and improved physiologic parameters. One in-hospital death could be averted for every 8 patients treated. Replicating results and scaling the intervention are important, but prone positioning may represent an additional therapeutic option in patients with ARDS due to COVID-19.

Intraspinal mesenchymal chondrosarcoma: An argument for aggressive local resection and adjuvant therapy based on review of the literature.

BACKGROUND: Mesenchymal chondrosarcoma is a rare cartilaginous neoplasm that typically involves the axial skeleton. Despite a well-circumscribed appearance, this tumor has a tendency to recur both locally and with distant metastases. CASE DESCRIPTION: A 17-year-old patient presented with numbness and paresthesias in the lower extremities attributed to a T10-T11 intradural extramedullary mesenchymal chondrosarcoma. The patient was treated with aggressive local resection and adjuvant therapy. Here, this case and present literature are appropriately reviewed. CONCLUSION: Although uncommon, intraspinal mesenchymal chondrosarcomas warrant both radical local resection and aggressive adjuvant therapy with chemoradiation to provide the greatest chance of progression-free survival.

A Ketogenic & Low-Protein Diet Slows Retinal Degeneration in rd10 Mice.

Purpose: Treatments that delay retinal cell death regardless of genetic causation are needed for inherited retinal degeneration (IRD) patients. The ketogenic diet is a high-fat, low-carbohydrate diet, used to treat epilepsy, and has beneficial effects for neurodegenerative diseases. This study aimed to determine whether the ketogenic diet could slow retinal degeneration. Methods: Early weaned, rd10 and wild-type (WT) mice were placed on either standard chow, a ketogenic diet, or a ketogenic & low-protein diet. From postnatal day (PD) 23 to PD50, weight and blood ß-hydroxybutyrate levels were recorded. Retinal thickness, retinal function, and visual performance were measured via optical coherence tomography, electroretinography (ERG), and optokinetic tracking (OKT). At PD40, serum albumin, rhodopsin protein, and phototransduction gene expression were measured. Results: Both ketogenic diets elicited a systemic induction of ketosis. However, rd10 mice on the ketogenic & low-protein diet had significant increases in photoreceptor thickness, ERG amplitudes, and OKT thresholds, whereas rd10 mice on the ketogenic diet showed no photoreceptor preservation. In both rd10 and WT mice, the ketogenic & low-protein diet was associated with abnormal weight gain and decreases in serum albumin levels, 27% and 56%, respectively. In WT mice, the ketogenic & low-protein diet was also associated with an ∼20% to 30% reduction in ERG amplitudes. Conclusions: The ketogenic & low-protein diet slowed retinal degeneration in a clinically relevant IRD model. In WT mice, the ketogenic & low-protein diet was associated with a decrease in phototransduction and serum albumin, which could serve as a protective mechanism in the rd10 model. Although ketosis was associated with protection, its role remains unclear. Translational Relevance: Neuroprotective mechanisms associated with the ketogenic & low-protein diet have potential to slow retinal degeneration.

Prone Positioning in Moderate to Severe Acute Respiratory Distress Syndrome due to COVID-19: A Cohort Study and Analysis of Physiology.

BACKGROUND: Coronavirus disease 2019 (COVID-19) can lead to acute respiratory distress syndrome (ARDS) but it is unknown whether prone positioning improves outcomes in mechanically ventilated patients with moderate to severe ARDS due to COVID-19. METHODS: A cohort study at a New York City hospital at the peak of the early pandemic in the United States, under crisis conditions. The aim was to determine the benefit of prone positioning in mechanically ventilated patients with ARDS due to COVID-19. The primary outcome was in-hospital death. Secondary outcomes included changes in physiologic parameters. Fine-Gray competing risks models with stabilized inverse probability treatment weighting (sIPTW) were used to determine the effect of prone positioning on outcomes. In addition, linear mixed effects models (LMM) were used to assess changes in physiology with prone positioning. RESULTS: Out of 335 participants who were intubated and mechanically ventilated, 62 underwent prone positioning, 199 met prone positioning criteria and served as controls and 74 were excluded. The intervention and control groups were similar at baseline. In multivariate-adjusted competing risks models with sIPTW, prone positioning was significantly associated with reduced mortality (SHR 0.61, 95% CI 0.46-0.80, P < 0.005). Using LMM to evaluate the impact of positioning maneuvers on physiological parameters, the oxygenation-saturation index was significantly improved during days 1-3 ( P < 0.01) whereas oxygenation-saturation index (OSI), oxygenation-index (OI) and arterial oxygen partial pressure to fractional inspired oxygen (P a O 2 :FiO 2 ) were significantly improved during days 4-7 ( P < 0.05 for all). CONCLUSIONS: Prone positioning in patients with moderate to severe ARDS due to COVID-19 is associated with reduced mortality and improved physiologic parameters. One in-hospital death could be averted for every eight patients treated. Replicating results and scaling the intervention are important, but prone positioning may represented an additional therapeutic option in patients with ARDS due to COVID-19.

Enthalpies of Combustion and Formation of Severely Crowded Methyl-Substituted 1,3-dioxanes. The Magnitudes of 2,4- and 4,6-diaxial Me,Me-Interactions and the Chair-2,5-twist Energy Difference.

Enthalpies of combustion of 2,2-trans-4,6- (1) and 4,4,6,6-tetramethyl- (2) and 2,4,4,6,6- (3) and 2,2,4,4,6-pentamethyl-1,3-dioxanes (4) were determined to estimate their enthalpies of formation in the gas phase. By comparing the latter with the corresponding enthalpies estimated based on the various bond-bond interactions allowed to determine the chair-2,5-twist energy difference (ΔHCT = 29.8 kJ mol-1) for 1 since C-13 shift correlations indicate that it escapes to the 2,5-twist form where the 2-methyl groups are isoclinal and 4- and 6-methyl groups pseudoequatorial to avoid syn-axial interactions. Compounds 2 and 3 in turn give the values 21.0 and 21.6 kJ mol-1 for the 4,6-diaxial Me,Me-interaction. Finally compound 4, which retains the chair conformation to avoid pseudoaxial interactions in the twist forms gives the value 19.5 kJ mol-1 for the 2,4-diaxial Me,Me-interaction indicating that its chair form appears to be somewhat deformed.

Variability in the size of the retroperitoneal oblique corridor: A magnetic resonance imaging-based analysis.

BACKGROUND: A minimally invasive approach to the L2-S1 disc spaces through a single, left-sided, retroperitoneal oblique corridor has been previously described. However, the size of this corridor varies, limiting access to the disc space in certain patients. Here, the authors retrospectively reviewed lumbar spine magnetic resonance imaging (MRI) in 300 patients to better define the size and variability of the retroperitoneal oblique corridor. METHODS: Lumbar spine MRI from 300 patients was reviewed. The size of the retroperitoneal oblique corridor from L2-S1 was measured. It was defined as the (1) distance between the medial aspect of the aorta and the lateral aspect of the psoas muscle from L2-L5 and (2) the distance between the midpoint of the L5-S1 disc and the medial aspect of the nearest major vessel on the left at L5-S1. In addition, the rostral-caudal location of the iliac bifurcation was measured. RESULTS: The size of the retroperitoneal oblique corridor at L2/3, L3/4, L4/5, and L5/S1 was, respectively, 17.3 ± 6.4 mm, 16.2 ± 6.3 mm, 14.8 ± 7.8 cm, and 13.0 ± 8.3 mm. The incidence of corridor size <1 cm at L2/3, L3/4, L4/5, and L5/S1 was 10.3%, 16.0%, 30.0%, and 39.3%, respectively. The iliac bifurcation was most commonly found behind the L4 vertebral body (n = 158, 52.67%) followed by the L4/5 disc space (n = 74, 24.67%). CONCLUSION: The size of the retroperitoneal oblique corridor diminishes in a rostral-caudal direction, often limiting access to the L4/5 and L5/S1 disc spaces.

Contemporary Management of Increased Intraoperative Intracranial Pressure: Evidence-Based Anesthetic and Surgical Review.

Increased intracranial pressure (ICP) is frequently encountered in the neurosurgical setting. A multitude of tactics exists to reduce ICP, ranging from patient position and medications to cerebrospinal fluid diversion and surgical decompression. A vast amount of literature has been published regarding ICP management in the critical care setting, but studies specifically tailored toward the management of intraoperative acute increases in ICP or brain bulk are lacking. Compartmentalizing the intracranial space into blood, brain tissue, and cerebrospinal fluid and understanding the numerous techniques available to affect these individual compartments can guide the surgical team to quickly identify increased brain bulk and respond appropriately. Rapidly instituting measures for brain relaxation in the operating room is essential in optimizing patient outcomes. Knowledge of the efficacy, rapidity, feasibility, and risks of the various available interventions can aid the team to properly tailor their approach to each individual patient. In this article, we present the first evidence-based review of intraoperative management of ICP and brain bulk.

Scalable Light-Printing of Substrate-Engraved Free-Form Metasurfaces.

A key challenge for metasurface research is locally controlling at will the nanoscale geometric features on meter-scale apertures. Such a technology is expected to enable large aperture meta-optics and revolutionize fields such as long-range imaging, lasers, laser detection and ranging (LADAR), and optical communications. Furthermore, these applications are often more sensitive to light-induced and environmental degradation, which constrains the possible materials and fabrication process. Here, we present a relatively simple and scalable method to fabricate a substrate-engraved metasurface with locally printed index determined by induced illumination, which, therefore, addresses both the challenges of scalability and durability. In this process, a thin metal film is deposited onto a substrate and transformed into a mask via local laser-induced dewetting into nanoparticles. The substrate is then dry-etched through this mask, and selective mask removal finally reveals the metasurface. We show that masking by the local nanoparticle distribution, and, therefore, the local index, is dependent on the local light-induced dewetting temperature. We demonstrate printing of a free-form pattern engraved into a fused silica glass substrate using a laser raster scan. Large-scale spatially controlled engraving of metasurfaces has implications on other technological fields beyond optics, such as surface fluidics, acoustics, and thermomechanics.

Minimally Invasive Tubular Tethered Cord Release in the Pediatric Population.

BACKGROUND: Tethered cord syndrome (TCS) refers to a clinical constellation of signs and symptoms associated with tension in the spinal cord and associated with pathologies related to abnormally low-lying conus medullaris. As minimally invasive spinal operations have become more prevalent in the past decade, we applied expanding indications to selected intradural procedures, such as tethered cord release (TCR). We present the first series of minimally invasive muscle-sparing TCR in the pediatric population. METHODS: A retrospective review of the Texas Children's Hospital, Houston, neurosurgical database was conducted for patients who underwent TCR between 2010 and 2017. Charts were reviewed to determine the source of TCS and whether surgery was conducted in a minimally invasive fashion. To establish a cohort of control population, age-matched cases of open TCR were selected in the same. Exclusion criterion was non-fatty filum sources of TCS. The length of stay, operative time, estimated blood loss, and postoperative complications were recorded. RESULTS: Eleven patients underwent minimally invasive TCR. Mean age of the patients was 10.1 years. All patients underwent L4-5 tubular laminotomy and cord detethering by 2 pediatric neurosurgeons at Texas Children's Hospital. The average length of stay in the hospital was 2.6 days. The average operative time was 167 minutes and average estimated blood loss was 8.2 mL. Ten patients reported clinical improvement and 1 patient was lost to follow-up. CONCLUSIONS: Minimally invasive TCR is a safe and represents a viable alternative to the open approach with advantages such as minimal estimated blood loss, shortened length of stay, and postoperative pain control.

A study on Chinese consumer preferences for food traceability information using best-worst scaling.

Food safety is a global public health issue, which often arises from asymmetric information between consumers and suppliers. With the development of information technology in human life, building a food traceability information sharing platform is viewed as one of the best ways to overcome the trust crisis and resolve the problem of information asymmetry in China. However, among the myriad information available from the food supply chain, there is a lack of knowledge on consumer preference. Based on the best-worst scaling approach, this paper investigated consumer preferences for vegetable, pork, and dairy product traceability information. Specifically, this paper measured the relative importance that consumers place on the traceable information. The results indicate that consumers have varying priorities for information in different cases. "Pesticide/veterinary use," "picking/slaughtering date," and "fertilizer/feed use" are the most preferred traceable information for Chinese consumers in the case of vegetables, while "picking/slaughtering date" and "history of illness and taking protective measures" are the most preferred information in the case of pork. In the case of dairy products, consumers prefer "processing information," "environmental information of the origin," and "traceable tag certification information" most. The results of this study call for the direct involvement of the Chinese government in the food safety information sharing system as following. First, given consumers' diverse preferences, different types of traceable information should be recorded into the information sharing platform depending on food types. Second, the government could promote the step-by-step construction of such a platform based on the priority of consumers' preferences. Third, new technology should be applied to guarantee the reliability of traceable information. Finally, local preferences in terms of the way consumers receive and understand information should be taken into consideration.

Videoexoscopic real-time intraoperative navigation for spinal neurosurgery: a novel co-adaptation of two existing technology platforms, technical note.

Image-guided approaches to spinal instrumentation and interbody fusion have been widely popularized in the last decade [1-5]. Navigated pedicle screws are significantly less likely to breach [2, 3, 5, 6]. Navigation otherwise remains a point reference tool because the projection is off-axis to the surgeon's inline loupe or microscope view. The Synaptive robotic brightmatter drive videoexoscope monitor system represents a new paradigm for off-axis high-definition (HD) surgical visualization. It has many advantages over the traditional microscope and loupes, which have already been demonstrated in a cadaveric study [7]. An auxiliary, but powerful capability of this system is projection of a second, modifiable image in a split-screen configuration. We hypothesized that integration of both Medtronic and Synaptive platforms could permit the visualization of reconstructed navigation and surgical field images simultaneously. By utilizing navigated instruments, this configuration has the ability to support live image-guided surgery or real-time navigation (RTN). Medtronic O-arm/Stealth S7 navigation, MetRx, NavLock, and SureTrak spinal systems were implemented on a prone cadaveric specimen with a stream output to the Synaptive Display. Surgical visualization was provided using a Storz Image S1 platform and camera mounted to the Synaptive robotic brightmatter drive. We were able to successfully technically co-adapt both platforms. A minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) and an open pedicle subtraction osteotomy (PSO) were performed using a navigated high-speed drill under RTN. Disc Shaver and Trials under RTN were implemented on the MIS TLIF. The synergy of Synaptive HD videoexoscope robotic drive and Medtronic Stealth platforms allow for live image-guided surgery or real-time navigation (RTN). Off-axis projection also allows upright neutral cervical spine operative ergonomics for the surgeons and improved surgical team visualization and education compared to traditional means. This technique has the potential to augment existing minimally invasive and open approaches, but will require long-term outcome measurements for efficacy.

Creutzfeldt Cell Rich Glioblastoma: A Diagnostic Dilemma.

Differentiating demyelinating conditions from neoplastic conditions can pose a significant challenge. There are a number of reports in the literature of large ring-enhancing, space-occupying lesions that were initially considered neoplastic or infectious but, on further review, were deemed demyelinating. Creutzfeldt-Peters cells (CPC) are reactive astrocytes with fragmented nuclear inclusions that are routinely seen in multiple sclerosis (MS) and generally exclude the diagnosis of glioblastoma (GB). The patient is a 78-year-old man with a history of prostate cancer, which was treated with radiation therapy, who presented with altered mental status. A magnetic resonance imaging (MRI) scan of the brain revealed a 4.6 x 3.1 cm mass lesion in the right posterior temporal lobe with minimal mass effect and heterogeneous contrast enhancement. The patient underwent an open biopsy of the mass, which on histology was rich with Creutzfeldt-Peters cells. Frozen histology was unclear and full resection of the mass was delayed. A molecular and immunohistochemical analysis confirmed glioblastoma. The patient returned four weeks later for a subtotal resection of the tumor. The case presented demonstrates an example of a challenging diagnosis. Differentiating between demyelinating and neoplastic conditions is critical since the management and prognosis differ greatly. More importantly, we present a case of glioblastoma rich with Creutzfeldt-Peters cells, which has previously not been reported in the literature.

Variation in Psoas Muscle Location Relative to the Safe Working Zone for L4/5 Lateral Transpsoas Interbody Fusion: A Morphometric Analysis.

BACKGROUND: The safe working zone for lateral access to the L4/5 disc space has been said to lie in the anteroposterior (AP) midpoint of the disc space due to the location of the femoral nerve at that level. However, the AP location of the psoas muscle (and thus the lumbosacral plexus within) at L4/5 is variable. A psoas muscle lying excessively anteriorly at the L4/5 disc space may preclude safe access to the L4/5 disc space from a lateral transpsoas approach. METHODS: Lumbar spine magnetic resonance imaging (MRI) for 300 consecutive patients at the authors' institution were reviewed retrospectively. The AP distance between the ventral aspect of the thecal sac and the dorsal aspect of the psoas muscle at L4/5 was measured, as was the AP diameter of the L4/5 disc space. RESULTS: The dorsal aspect of the psoas muscle at L4/5 was most commonly found dorsal to the ventral aspect of the thecal sac (zone P, N = 145; 48.3%), whereas it was found at the junction of zones IV/P in 37 patients (12.3%), in zone IV in 85 patients (28.3%), in zone III in 29 patients (9.7%), and in zone II in 4 patients (1.3%). CONCLUSIONS: The location of the psoas muscle in relation to the L4/5 disc space is somewhat variable. In 11% of patients, the dorsal-most aspect of the psoas muscle was located within zones II or III, likely precluding safe access to the L4/5 disc space from a lateral transpsoas approach.

Monitoring for a specific management objective: protection of shorebird foraging habitat adjacent to a waste water treatment plant.

Intertidal invertebrates are often used in environmental monitoring programs as they are good indicators of water quality and an important food source for many species of fish and birds. We present data from a monitoring program where the primary aim is to report on the condition of the potential invertebrate prey abundance, biomass and diversity for migrating shorebirds on mudflats adjacent to a waste water treatment plant in a Ramsar listed wetland in Victoria, Australia. A key threat to the foraging habitat at this site has been assessed as a reduction in potential prey items as a result of the changes to the waste water treatment processes. We use control charts, which summarise data from intertidal mudflats across the whole shoreline of the adjacent waste water treatment plant, to elicit a management response when trigger levels are reached. We then examine data from replicate discharge and control sites to determine the most appropriate management response. The monitoring program sits within an adaptive management framework where management decisions are reviewed and the data is examined at different scales to evaluate and modify our models of the likely outcomes of management actions. This study provides a demonstration of the process undertaken in a year when trigger levels were reached and a management decision was required. This highlights the importance of monitoring data from a range of scales in reducing uncertainty and improving decision making in complex systems.

Diagnostic Dilemma: Cerebellopontine Angle Lipoma Versus Dermoid Cyst.

Both lipomas and dermoid cysts of the cerebellopontine angle are rare tumors. These tumors differ in their embryological origin but share similar features on imaging. Both of these congenital lesions can be found in the cerebellopontine angle (CPA), and symptomatic clinical presentation is dictated by the location of the lesion. This paper demonstrates a unique case in which a CPA lipoma was misidentified as a dermoid cyst, leading to surgical intervention. Further, the paper provides a literature review of CPA lipomas and dermoid cysts to aid readers in further differentiating between these two unique tumors.

Spinal Schwannoma and Meningioma Mimicking a Single Mass at the Craniocervical Junction Subsequent to Remote Radiation Therapy for Acne Vulgaris.

BACKGROUND: Schwannomas and meningiomas are relatively common tumors of the nervous system. They have been reported in the literature as existing concurrently as a single mass, but very rarely have they been shown to present at the craniocervical junction. CASE DESCRIPTION: We present a rare and interesting case of a patient previously treated with radiation therapy for acne vulgaris and who presented to us with a concurrent schwannoma and meningioma of the craniocervical junction mimicking a single mass. CONCLUSIONS: These tumors can be solitary or mixed masses, and are known to be associated with certain disease processes such as long-term sequelae of radiation therapy and neurofibromatosis type 2. The precise mechanism behind the formation of these tumors is unknown; however, molecular cues in the tumor microenvironment may play a role.