Evaluation of the Glasgow Coma Scale-Pupils score for predicting inpatient mortality among patients with traumatic subdural hematoma at United States trauma centers

OBJECTIVE

The Glasgow Coma Scale-Pupils (GCS-P) score has been suggested to better predict patient outcomes compared with GCS alone, while avoiding the need for more complex clinical models. This study aimed to compare the prognostic ability of GCS-P versus GCS in a national cohort of traumatic subdural hematoma (SDH) patients.

METHODS

Patient data were obtained from the National Trauma Data Bank (2017-2019). Inclusion criteria were traumatic SDH diagnosis with available data on presenting GCS score, pupillary reactivity, and discharge disposition. Patients with severe polytrauma or nonsurvivable head injury at presentation were excluded. Sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) of GCS-P versus GCS scores for inpatient mortality prediction were evaluated across the entire cohort, as well as in subgroups based on age and traumatic brain injury (TBI) type (blunt vs penetrating). Calibration curves were plotted based on predicted probabilities and actual outcomes.

RESULTS

A total of 196,747 traumatic SDH patients met the study inclusion criteria. Sensitivity (0.707 vs 0.702), specificity (0.821 vs 0.823), and AUC (0.825 vs 0.814, p < 0.001) of GCS-P versus GCS scores for prediction of inpatient mortality were similar. Calibration curve analysis revealed that GCS scores slightly underestimated inpatient mortality risk, whereas GCS-P scores did not. In patients > 65 years of age with blunt TBI (51.9%, n = 102,148), both GCS-P and GCS scores underestimated inpatient mortality risk. In patients with penetrating TBI (2.4%, n = 4,710), the AUC of the GCS-P score was significantly higher (0.902 vs 0.851, p < 0.001). In this subgroup, both GCS-P and GCS scores underestimated inpatient mortality risk among patients with lower rates of observed mortality and overestimated risk among patients with higher rates of observed mortality. This effect was more pronounced in the GCS-P calibration curve.

CONCLUSIONS

The GCS-P score provides better short-term prognostication compared with the GCS score alone among traumatic SDH patients with penetrating TBI. The GCS-P score overestimates inpatient mortality risk among penetrating TBI patients with higher rates of observed mortality. For penetrating TBI patients, which comprised 2.4% of our SDH cohort, a low GCS-P score should not justify clinical nihilism or forgoing aggressive treatment.

Concomitant Traumatic Brain Injury Delays Surgery in Patients With Traumatic Spinal Cord Injury

BACKGROUND AND OBJECTIVES

Growing evidence supports prompt surgical decompression for patients with traumatic spinal cord injury (tSCI). Rates of concomitant tSCI and traumatic brain injury (TBI) range from 10% to 30%. Concomitant TBI may delay tSCI diagnosis and surgical intervention. Little is known about real-world management of this common injury constellation that carries significant clinical consequences. This study aimed to quantify the impact of concomitant TBI on surgical timing in a national cohort of patients with tSCI.

METHODS

Patient data were obtained from the National Trauma Data Bank (2007-2016). Patients admitted for tSCI and who received surgical intervention were included. Delayed surgical intervention was defined as surgery after 24 hours of admission. Multivariable hierarchical regression models were constructed to measure the risk-adjusted association between concomitant TBI and delayed surgical intervention. Secondary outcome included favorable discharge status.

RESULTS

We identified 14 964 patients with surgically managed tSCI across 377 North American trauma centers, of whom 2444 (16.3%) had concomitant TBI and 4610 (30.8%) had central cord syndrome (CCS). The median time to surgery was 20.0 hours for patients without concomitant TBI and 24.8 hours for patients with concomitant TBI. Hierarchical regression modeling revealed that concomitant TBI was independently associated with delayed surgery in patients with tSCI (odds ratio [OR], 1.3; 95% CI, 1.1-1.6). Although CCS was associated with delayed surgery (OR, 1.5; 95% CI, 1.4-1.7), we did not observe a significant interaction between concomitant TBI and CCS. In the subset of patients with concomitant tSCI and TBI, patients with severe TBI were significantly more likely to experience a surgical delay than patients with mild TBI (OR, 1.4; 95% CI, 1.0-1.9).

CONCLUSION

Concomitant TBI delays surgical management for patients with tSCI. This effect is largest for patients with tSCI with severe TBI. These findings should serve to increase awareness of concomitant TBI and tSCI and the likelihood that this may delay time-sensitive surgery.

Pharyngeal oxygen delivery device sustains manikin lung oxygenation longer than high-flow nasal cannula

Purpose

Hypoxemia during a failed airway scenario is life threatening. A dual-lumen pharyngeal oxygen delivery device (PODD) was developed to fit inside a traditional oropharyngeal airway for undisrupted supraglottic oxygenation and gas analysis during laryngoscopy and intubation. We hypothesized that the PODD would provide oxygen as effectively as high-flow nasal cannula (HFNC) while using lower oxygen flow rates.

Methods

We compared oxygen delivery of the PODD to HFNC in a preoxygenated, apneic manikin lung that approximated an adult functional residual capacity. Four arms were studied: HFNC at 20 and 60 liters per minute (LPM) oxygen, PODD at 10 LPM oxygen, and a control arm with no oxygen flow after initial preoxygenation. Five randomized 20-minute trials were performed for each arm (20 trials total). Descriptive statistics and analysis of variance were used with statistical significance of P < 0.05.

Results

Mean oxygen concentrations were statistically different and decreased from 97% as follows: 41 ± 0% for the control, 90 ± 1% for HFNC at 20 LPM, 88 ± 2% for HFNC at 60 LPM, and 97 ± 1% (no change) for the PODD at 10 LPM.

Conclusion

Oxygen delivery with the PODD maintained oxygen concentration longer than HFNC in this manikin model at lower flow rates than HFNC.

Acute Extra-Arachnoid Subdural Hematomas in Patients 50 Years and Older: When Subdurals Act Like Epidurals

BACKGROUND

Some patients with subdural hematoma (SDH) with acute extra-arachnoid lesions and without concomitant subarachnoid blood or contusions may present in similarly grave neurological condition compared with the general population of patients with SDH. However, these patients often make an impressive neurological recovery. This study compared neurological outcomes in patients with extra-arachnoid SDH with all other SDH patients.

METHODS

We compared a prospective series of extra-arachnoid SDH patients without subarachnoid hemorrhage or other concomitant intracranial injury with a Transforming Research and Clinical Knowledge in TBI control group with SDH only. We performed inverse probability weighting for key characteristics and ordinal regression with and without controlling for midline shift comparing neurological outcomes (Extended Glasgow Outcome Scale score) at 2 weeks. We used the Corticosteroid Randomization After Significant Head Injury prognostic model to predict mortality based on age, Glasgow Coma Scale score, pupil reactivity, and major extracranial injury.

RESULTS

Mean midline shift was significantly different between extra-arachnoid SDH and control groups (7.2 mm vs. 2.7 mm, P < 0.001). After weighting for group allocation and controlling for midline shift, extra-arachnoid SDH patients had 5.68 greater odds (P < 0.001) of a better 2-week Extended Glasgow Outcome Scale score than control patients. Mortality in the extra-arachnoid SDH group was less than predicted by the Corticosteroid Randomization After Significant Head Injury prognostic model (10% vs. 21% predicted).

CONCLUSIONS

Patients with extra-arachnoid SDH have significantly better 2-week neurological outcomes and lower mortality than predicted by the Corticosteroid Randomization After Significant Head Injury model. Neurosurgeons should consider surgery for this patient subset even in cases of poor neurological examination, older age, and large hematoma with high degree of midline shift.

Full-endoscopic trans-pars interarticularis approach for far lateral lumbar discectomy

PURPOSE

Surgical management of far lateral disc herniations remains challenging. Current transforaminal full-endoscopic approaches require non-visualized docking in the Kambin's triangle and have been associated with significant risk of inadvertent nerve injury. We develop a full-endoscopic approach based on reliable bony landmarks allowing for visualization of the exiting nerve root prior to the far lateral discectomy.

METHODS

The surgical details of a full-endoscopic trans-pars interarticularis approach for far lateral discectomy are described. These descriptions include high quality intraoperative images and important surgical pearls. A small patient cohort is presented to demonstrate feasibility and safety of the procedure.

RESULTS

We demonstrate the feasibility of this approach in 14 patients with a mean age of 59.5 ± 14.7 years. At a mean follow up of 21.9 ± 6.8 months, improvement of the visual analogue scale (VAS) for leg pain was 4.3 ± 1.0 resulting in minimally clinically important difference in 78.6% of the patients. The mean improvement in VAS for the back pain was 2.6 ± 0.8 and for Oswestry disability index (ODI) was 20.6 ± 5.3. Nuances of the trans-pars surgical techniques are presented in a patient with a right-sided L4-5 far lateral disc herniation. Preoperative imaging studies, steps of the surgical progression, and intraoperative views are described in detail.

CONCLUSION

Using the pars interarticularis as the bony target area allows for safe visualized access to the extraforaminal compartment of the exiting nerve root. This novel surgical technique has the potential benefit of decreasing inadvertent neural injury and subsequent postoperative dysesthesias.

Patellofemoral contact forces and knee gait mechanics 3 months after ACL reconstruction are associated with cartilage degradation 24 months after surgery

OBJECTIVE

Evaluate patellofemoral cartilage health, as assessed by quantitative magnetic resonance imaging (qMRI) T2 relaxation times, 24-months after ACL reconstruction (ACLR) and determine if they were associated with patellofemoral contact forces and knee mechanics during gait 3 months after surgery.

DESIGN

Thirty individuals completed motion analysis during overground walking at a self-selected speed 3 months after ACLR. An EMG-driven neuromusculoskeletal model was used to determine muscle forces, which were then used in a previously described model to estimate patellofemoral contact forces. Biomechanical variables of interest included peak patellofemoral contact force, peak knee flexion angle and moment, and walking speed. These same participants underwent a sagittal bilateral T2 mapping qMRI scan 24-months after surgery. T2 relaxation times were estimated for both patellar and trochlear cartilage. Paired t-tests were used to compare T2 relaxation times between limbs while Pearson correlations and linear regressions were utilized to assess the association between the biomechanical variables of interest and T2 relaxation times.

RESULTS

Prolonged involved limb trochlear T2 relaxation times (vs uninvolved) were present 24-months after surgery, indicating worse cartilage health. No differences were detected in patellar cartilage. Significant negative associations were present within the involved limb for all the biomechanical variables of interest 3 months after ACLR and trochlear T2 relaxation times at 24-months. No associations were found in patellar cartilage or within the uninvolved limb.

CONCLUSIONS

Altered involved limb trochlear cartilage health is present 24-months after ACLR and may be related to patellofemoral loading and other walking gait mechanics 3 months after surgery.

Clopidogrel hyper-response increases peripheral hemorrhagic complications without increasing intracranial complications in endovascular aneurysm treatments requiring dual antiplatelet therapy

Clinical significance of increased clopidogrel response measured by VerifyNow P2Y12 assay is unclear; management guidelines are lacking in the context of neuroendovascular intervention. Our objective was to assess whether increased clopidogrel response predicts complications from endovascular aneurysm treatment requiring dual antiplatelet therapy. A single-institution, 9-year retrospective study of patients undergoing endovascular treatments for ruptured and unruptured aneurysms requiring aspirin and clopidogrel was conducted. Patients were grouped according to preoperative platelet inhibition in response to clopidogrel measured by the VerifyNow P2Y12 assay (VNP; P2Y12 reactivity units, PRU). Demographic and clinical features were compared across groups. Hemorrhagic complication rates (intracranial, major extracranial, minor extracranial) and thromboembolic complications (in-stent stenosis, stroke/transient ischemic attack) were compared, controlling for potential confounders and multiple comparisons. Data were collected from 284 patients across 317 procedures. Pre-operative VNP assays identified 9 % Extreme Responders (PRU ≤ 15), 13 % Hyper-Responders (PRU 16-60), 62 % Therapeutic Responders (PRU 61-214), 16 % Hypo-Responders (PRU ≥ 215). Increased response to clopidogrel was associated with increased risk of any hemorrhagic complication (≤60 PRU vs > 60 PRU; 39 % vs 24 %, P = 0.050); all intracranial hemorrhages occurred in patients with PRU > 60. Thromboembolic complications were similar between therapeutic and subtherapeutic patients (<215 PRU vs ≥ 215 PRU; 15 % vs 16 %, P = 0.835). Increased preoperative clopidogrel response is associated with increased rate of extracranial hemorrhagic complications in endovascular aneurysm treatments. Hyper-responders (16-60 PRU) and Extreme Responders (≤15 PRU) were not associated with intracranial hemorrhagic or thrombotic complications. Hypo-responders who underwent adjustment of antiplatelet therapy and neurointerventions did not experience higher rates of complications.

Racial, ethnic, and gender diversity of applicants and matriculants to neurological surgery residency programs

OBJECTIVE

The aim of this study was to identify trends in the demographic constitution of applicants and matriculants to neurological surgery based on race, ethnicity, and gender.

METHODS

The authors conducted a cross-sectional study using compiled demographic data obtained from the Association of American Medical Colleges. Trends analyzed included proportional changes in race, ethnicity, and gender of applicants and matriculants to neurosurgical residency programs from academic years 2010-2011 to 2018-2019.

RESULTS

A total of 5100 applicants and 2104 matriculants to neurosurgical residency programs were analyzed. No significant change in the percentage of overall women applicants (+0.3%, 95% CI -0.7% to 1.3%; p = 0.77) or in the percentage of women matriculants (+0.3%, 95% CI -2.2% to 2.9%; p = 0.71) was observed. For applicants, no change over time was observed in the percentages of American Indian or Alaska Native (AI/AN) men (0.0%, 95% CI -0.3% to 0.3%; p = 0.65); Asian men (-0.1%, 95% CI -1.2% to 1.1%; p = 0.97); Black or African American men (-0.2%, 95% CI -0.7% to 0.4%; p = 0.91); Hispanic, Latino, or of Spanish Origin men (+0.4%, 95% CI -0.8% to 1.7%; p = 0.26); White men (+0.5%, 95% CI -2.1% to 3.0%; p = 0.27); Asian women (+0.1,% 95% CI -0.9% to 1.1%; p = 0.73); Black or African American women (0.0%, 95% CI -0.6% to 0.5%; p = 0.30); Hispanic, Latino, or of Spanish Origin women (0.0%, 95% CI -0.4% to 0.4%; p = 0.71); and White women (+0.3%, 95% CI -1.1% to 1.7%; p = 0.34). For matriculants, no change over time was observed in the percentages of AI/AN men (0.0%, 95% CI -0.6% to 0.6%; p = 0.56); Asian men (0.0%, 95% CI -2.7% to 2.7%; p = 0.45); Black or African American men (-0.3%, 95% CI -1.4% to 0.8%; p = 0.52); Hispanic, Latino, or of Spanish Origin men (+0.6%, 95% CI -0.8 to 2.0%; p = 0.12); White men (-1.0%, 95% CI -5.3% to 3.3%; p = 0.92); Asian women (+0.1%, 95% CI -1.3% to 1.5%; p = 0.85); Black or African American women (0.0%, 95% CI -0.6% to 0.7%; p = 0.38); Hispanic, Latino, or of Spanish Origin women (-0.1%, 95% CI -0.7% to 0.5%; p = 0.46); and White women (+0.3%, 95% CI -2.4% to 3.0%; p = 0.70).

CONCLUSIONS

Despite efforts to diversify the demographic constitution of incoming neurosurgical trainees, few significant advances have been made in recent years. This study suggests that improved strategies for recruitment and cultivating early interest in neurological surgery are required to further increase the diversification of future cohorts of neurosurgical trainees.

Observation of ultracold atomic bubbles in orbital microgravity

Substantial leaps in the understanding of quantum systems have been driven by exploring geometry, topology, dimensionality and interactions in ultracold atomic ensembles^1-6. A system where atoms evolve while confined on an ellipsoidal surface represents a heretofore unexplored geometry and topology. Realizing an ultracold bubble-potentially Bose-Einstein condensed-relates to areas of interest including quantized-vortex flow constrained to a closed surface topology, collective modes and self-interference via bubble expansion^7-17. Large ultracold bubbles, created by inflating smaller condensates, directly tie into Hubble-analogue expansion physics^18-20. Here we report observations from the NASA Cold Atom Lab²¹ facility onboard the International Space Station of bubbles of ultracold atoms created using a radiofrequency-dressing protocol. We observe bubble configurations of varying size and initial temperature, and explore bubble thermodynamics, demonstrating substantial cooling associated with inflation. We achieve partial coverings of bubble traps greater than one millimetre in size with ultracold films of inferred few-micrometre thickness, and we observe the dynamics of shell structures projected into free-evolving harmonic confinement. The observations are among the first measurements made with ultracold atoms in space, using perpetual freefall to explore quantum systems that are prohibitively difficult to create on Earth. This work heralds future studies (in orbital microgravity) of the Bose-Einstein condensed bubble, the character of its excitations and the role of topology in its evolution.

United States Medicolegal Progress and Innovation in Telemedicine in the Age of COVID-19: A Primer for Neurosurgeons

Telemedicine has received increased attention in recent years as a potential solution to expand clinical capability and patient access to care in many fields, including neurosurgery. Although patient and physician attitudes are rapidly shifting toward greater telemedicine use in light of the COVID-19 pandemic, there remains uncertainty about telemedicine's regulatory future. Despite growing evidence of telemedicine's utility, there remain a number of significant medicolegal barriers to its mass adoption and wider implementation. Herein, we examine recent progress in state and federal regulations in the United States governing telemedicine's implementation in quality of care, finance and billing, privacy and confidentiality, risk and liability, and geography and interstate licensure, with special attention to how these concern teleneurosurgical practice. We also review contemporary topics germane to the future of teleneurosurgery, including the continued expansion of reciprocity in interstate licensure, expanded coverage for homecare services for chronic conditions, expansion of Center for Medicare and Medicaid Services reimbursements, and protections of store-and-forward technologies. Additionally, we discuss recent successes in teleneurosurgery, stroke care, and rehabilitation as models for teleneurosurgical best practices. As telemedicine technology continues to mature and its expanse grows, neurosurgeons' familiarity with its benefits, limitations, and controversies will best allow for its successful adoption in our field to maximize patient care and outcomes.

Prognostic Value of Hemorrhagic Brainstem Injury on Early Computed Tomography: A TRACK-TBI Study

BACKGROUND

Traumatic brainstem injury has yet to be incorporated into widely used imaging classification systems for traumatic brain injury (TBI), and questions remain regarding prognostic implications for this TBI subgroup. To address this, retrospective data on patients from the multicenter prospective Transforming Research and Clinical Knowledge in TBI study were studied.

METHODS

Patients with brainstem and cerebrum injury (BSI+) were matched by age, sex, and admission Glasgow Coma Scale (GCS) score to patients with cerebrum injuries only. All patients had an interpretable head computed tomography (CT) scan from the first 48 hours after injury and a 6-month Glasgow Outcome Scale Extended (GOSE) score. CT scans were reviewed for brainstem lesions and, when present, characterized by location, size, and type (traumatic axonal injury, contusion, or Duret hemorrhage). Clinical, demographic, and outcome data were then compared between the two groups.

RESULTS

Mann-Whitney U-tests showed no significant difference in 6-month GOSE scores in patients with BSI+ (mean 2.7) compared with patients with similar but only cerebrum injuries (mean 3.9), although there is a trend (p = 0.10). However, subclassification by brainstem lesion type, traumatic axonal injury (mean 4.0) versus Duret hemorrhage or contusion (mean 1.4), did identify a proportion of BSI+ with significantly less favorable outcome (p = 0.002). The incorporation of brainstem lesion type (traumatic axonal injury vs. contusion/Duret), along with GCS into a multivariate logistic regression model of favorable outcome (GOSE score 4-8) did show a significant contribution to the prognostication of this brainstem injury subgroup (odds ratio 0.08, 95% confidence interval 0.00-0.67, p = 0.01).

CONCLUSIONS

These findings suggest two groups of patients with brainstem injuries may exist with divergent recovery potential after TBI. These data support the notion that newer CT imaging classification systems may augment traditional clinical measures, such as GCS in identifying those patients with TBI and brainstem injuries that stand a higher chance of favorable outcome.

Cellular allograft for multilevel stand-alone anterior cervical discectomy and fusion

OBJECTIVE

Anterior cervical discectomy and fusion (ACDF) is the most common treatment for degenerative disease of the cervical spine. Given the high rate of pseudarthrosis in multilevel stand-alone ACDF, there is a need to explore the utility of novel grafting materials. In this study, the authors present a single-institution retrospective study of patients with multilevel degenerative spine disease who underwent multilevel stand-alone ACDF surgery with or without cellular allograft supplementation.

METHODS

In a prospectively collected database, 28 patients who underwent multilevel ACDF supplemented with cellular allograft (ViviGen) and 25 patients who underwent multilevel ACDF with decellularized allograft between 2014 and 2020 were identified. The primary outcome was radiographic fusion determined by a 1-year follow-up CT scan. Secondary outcomes included change in Neck Disability Index (NDI) scores and change in visual analog scale scores for neck and arm pain.

RESULTS

The study included 53 patients with a mean age of 53 ± 0.7 years who underwent multilevel stand-alone ACDF encompassing 2.6 ± 0.7 levels on average. Patient demographics were similar between the two cohorts. In the cellular allograft cohort, 2 patients experienced postoperative dysphagia that resolved by the 3-month follow-up. One patient developed cervical radiculopathy due to graft subsidence and required a posterior foraminotomy. At the 1-year CT, successful fusion was achieved in 92.9% (26/28) of patients who underwent ACDF supplemented with cellular allograft, compared with 84.0% (21/25) of patients who underwent ACDF without cellular allograft. The cellular allograft cohort experienced a significantly greater improvement in the mean postoperative NDI score (p < 0.05) compared with the other cohort.

CONCLUSIONS

Cellular allograft is a low-morbidity bone allograft option for ACDF. In this study, the authors determined favorable arthrodesis rates and functional outcomes in a complex patient cohort following multilevel stand-alone ACDF supplemented with cellular allograft.

The Kempe incision for decompressive craniectomy, craniotomy, and cranioplasty in traumatic brain injury and stroke

OBJECTIVE

Decompressive craniectomy (DC) is an effective, lifesaving option for reducing intracranial pressure (ICP) in traumatic brain injury (TBI), stroke, and other pathologies with elevated ICP. Most DCs are performed via a standard trauma flap shaped like a reverse question mark (RQM), which requires sacrificing the occipital and posterior auricular arteries and can be complicated by wound dehiscence and infections. The Ludwig Kempe hemispherectomy incision (Kempe) entails a T-shaped incision, one limb from the midline behind the hairline to the inion and the other limb from the root of the zygoma to the coronal suture. The authors' objective in this study was to define their implementation of the Kempe incision for DC and craniotomy, report clinical outcomes, and quantify the volume of bone removed compared with the RQM incision.

METHODS

A retrospective review of a single-surgeon experience with DC in TBI and stroke was performed. Patient demographics, imaging, and outcomes were collected for all DCs from 2015 to 2020, and the incisions were categorized as either Kempe or RQM. Preoperative and postoperative CT scans were obtained and processed using a combination of automatic segmentation (in Python and SimpleITK) with manual cleanup and further subselection in ITK-SNAP. The volume of bone removed was quantified, and the primary outcome was percentage of hemicranium removed. Postoperative surgical wound infections, estimated blood loss (EBL), and length of surgery were compared between the two groups as secondary outcomes. Cranioplasty data were collected.

RESULTS

One hundred thirty-six patients were included in the analysis; there were 57 patients in the craniotomy group (44 patients with RQM incisions and 13 with Kempe incisions) and 79 in the craniectomy group (41 patients with RQM incisions and 38 Kempe incisions). The mean follow-up for the entire cohort was 251 ± 368 days. There was a difference in the amount of decompression between approaches in multivariate modeling (39% ± 11% of the hemicranium was removed via the Kempe incision vs 34% ± 10% via the RQM incision, p = 0.047), although this did not achieve significance in multivariate modeling. Wound infection rates, EBL, and length of surgery were comparable between the two incision types. No wound infections in either cohort were due to wound dehiscence. Cranioplasty outcomes were comparable between the two incision types.

CONCLUSIONS

The Kempe incision for craniectomy or craniotomy is a safe, feasible, and effective alternative to the RQM. The authors advocate the Kempe incision in cases in which contralateral operative pathology or subsequent craniofacial/skull base repair is anticipated.

Re-examining decompressive craniectomy medial margin distance from midline as a metric for calculating the risk of post-traumatic hydrocephalus

Decompressive craniectomy (DC) is a life-saving procedure in severe traumatic brain injury, but is associated with higher rates of post-traumatic hydrocephalus (PTH). The relationship between the medial craniectomy margin's proximity to midline and frequency of developing PTH is controversial. The primary study objective was to determine whether average medial craniectomy margin distance from midline was closer to midline in patients who developed PTH after DC for severe TBI compared to patients that did not. The secondary objective was to determine if a threshold distance from midline could be identified, at which the risk of developing PTH increased if the DC was performed closer to midline than this threshold. A retrospective review was performed of 380 patients undergoing DC at a single institution between March 2004 and November 2014. Clinical, operative and demographic variables were collected, including age, sex, DC parameters and occurrence of PTH. Statistical analysis compared mean axial craniectomy margin distance from midline in patients with versus without PTH. Distances from midline were tested as potential thresholds. No significant difference was identified in mean axial craniectomy margin distance from midline in patients developing PTH compared with patients with no PTH (n = 24, 12.8 mm versus n = 356, 16.6 mm respectively, p = 0.086). No significant cutoff distance from midline was identified (n = 212, p = 0.201). This study, the largest to date, was unable to identify a threshold with sufficient discrimination to support clinical recommendations in terms of DC margins with regard to midline, including thresholds reportedly significant in previously published research.

Laser interstitial thermal therapy for pediatric atypical teratoid/rhabdoid tumor: case report

Herein, the authors describe the successful use of laser interstitial thermal therapy (LITT) for management of metastatic craniospinal disease for biopsy-proven atypical teratoid/rhabdoid tumor in a 16-month-old boy presenting to their care. Specifically, LITT was administered to lesions of the right insula and left caudate. The patient tolerated 2 stages of LITT to the aforementioned lesions without complication and with evidence of radiographic improvement of lesions at the 2- and 6-month follow-up appointments. To the authors' knowledge, this represents the first such published report of LITT for management of atypical teratoid/rhabdoid tumor.

Progress in diffuse intrinsic pontine glioma: advocating for stereotactic biopsy in the standard of care

Diffuse intrinsic pontine glioma (DIPG) is a universally fatal pediatric brainstem tumor affecting approximately 300 children in the US annually. Median survival is less than 1 year, and radiation therapy has been the mainstay of treatment for decades. Recent advances in the biological understanding of the disease have identified the H3K27M mutation in nearly 80% of DIPGs, leading to the 2016 WHO classification of diffuse midline glioma H3K27M-mutant, a grade IV brainstem tumor. Developments in epigenetic targeting of transcriptional tendencies have yielded potential molecular targets for clinical trials. Chimeric antigen receptor T cell therapy has also shown preclinical promise. Recent clinical studies, including prospective trials, have demonstrated the safety and feasibility of pediatric brainstem biopsy in the setting of DIPG and other brainstem tumors. Given developments in the ability to analyze DIPG tumor tissue to deepen biological understanding of this disease and develop new therapies for treatment, together with the increased safety of stereotactic brainstem biopsy, the authors present a case for offering biopsy to all children with suspected DIPG. They also present their standard operative techniques for image-guided, frameless stereotactic biopsy.

Towards an understanding of the chemo-mechanical influences on kidney stone failure via the material point method

This paper explores the use of the meshfree computational mechanics method, the Material Point Method (MPM), to model the composition and damage of typical renal calculi, or kidney stones. Kidney stones are difficult entities to model due to their complex structure and failure behavior. Better understanding of how these stones behave when they are broken apart is a vital piece of knowledge to medical professionals whose aim is to remove these stone by breaking them within a patient’s body. While the properties of individual stones are varied, the common elements and proportions are used to generate synthetic stones that are then placed in a digital experiment to observe their failure patterns. First a more traditional engineering model of a Brazil test is used to create a tensile fracture within the center of these stones to observe the effect of stone consistency on failure behavior. Next a novel application of MPM is applied which relies on an ultrasonic wave being carried by surrounding fluid to model the ultrasonic treatment of stones commonly used by medical practitioners. This numerical modeling of Extracorporeal Shock Wave Lithotripsy (ESWL) reveals how these different stones failure in a more real-world situation and could be used to guide further research in this field for safer and more effective treatments.

Trends in Race/Ethnicity Among Applicants and Matriculants to US Surgical Specialties, 2010-2018

IMPORTANCE

Surgical programs across the US continue to promote and invest in initiatives aimed at improving racial/ethnic diversity, but whether this translates to changes in the percentage of applicants or matriculants from racial/ethnic minority groups remains unclear.

OBJECTIVE

To examine trends in the percentage of applicants and matriculants to US surgical specialties who identified as part of a racial/ethnic group underrepresented in medicine from the 2010-2011 to 2018-2019 academic years.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional study examined trends in self-reported racial/ethnic identity among applicants and matriculants to US residency programs to evaluate demographic changes among surgical programs from 2010 to 2018. Data were obtained from the Association of American Medical Colleges.

RESULTS

The study population consisted of a total of 737 034 applicants and 265 365 matriculants to US residency programs, including 134 158 applicants and 41 347 matriculants to surgical programs. A total of 21 369 applicants (15.9%) and 5704 matriculants (13.8%) to surgical specialties identified as underrepresented in medicine. There was no statistically significant difference in the percentage of applicants underrepresented in medicine based on race/ethnicity for all surgical specialties combined in 2010 vs 2018 (15.3% [95% CI, 14.7%-15.9%] vs 17.5% [95% CI, 16.9%-18.1%]; P = .63). Thoracic surgery was the only surgical specialty in which there was a statistically significant change in the percentage of applicants (8.1% [95% CI, 4.9%-13.2%] vs 14.6% [95% CI, 10.2%-20.4%]; P = .02) or matriculants (0% [95% CI, 0%-19.4%] vs 10.0% [95% CI, 4.0%-23.1%]; P = .01) underrepresented in medicine based on race/ethnicity. Obstetrics and gynecology had the highest mean percentage of applicants (20.2%; 95% CI, 19.4%-20.8%) and matriculants (19.0%; 95% CI, 18.2%-19.8%) underrepresented in medicine among surgical specialties. Thoracic surgery had the lowest mean percentage of applicants (12.5%; 95% CI, 9.46%-15.4%) and otolaryngology the lowest mean percentage of matriculants (8.5%; 95% CI, 7.2%-9.9%) underrepresented in medicine.

CONCLUSIONS AND RELEVANCE

In this cross-sectional study, overall US surgical programs had no change in the percentage of applicants or matriculants who self-identified as underrepresented in medicine based on race/ethnicity, but the proportion remained higher than in nonsurgical specialties. Reevaluation of current strategies aimed at increasing racial/ethnic representation appear to be necessary to help close the existing gap in medicine and recruit a more racially/ethnically diverse surgical workforce.

Pediatric functional hemispherectomy: operative techniques and complication avoidance

Functional hemispherectomy/hemispherotomy is a disconnection procedure for severe medically refractory epilepsy where the seizure foci diffusely localize to one hemisphere. It is an improvement on anatomical hemispherectomy and was first performed by Rasmussen in 1974. Less invasive surgical approaches and refinements have been made to improve seizure freedom and minimize surgical morbidity and complications. Key anatomical structures that are disconnected include the 1) internal capsule and corona radiata, 2) mesial temporal structures, 3) insula, 4) corpus callosum, 5) parietooccipital connection, and 6) frontobasal connection. A stepwise approach is indicated to ensure adequate disconnection and prevent seizure persistence or recurrence. In young pediatric patients, careful patient selection and modern surgical techniques have resulted in > 80% seizure freedom and very good functional outcome. In this report, the authors summarize the history of hemispherectomy and its development and present a graphical guide for this anatomically challenging procedure. The use of the osteoplastic flap to improve outcome and the management of hydrocephalus are discussed.

Multiple Sclerosis Performance Test: validation of self-administered neuroperformance modules

BACKGROUND AND PURPOSE

The purpose was to determine the test-retest reliability, practice effects, convergent validity and sensitivity to multiple sclerosis (MS) disability of neuroperformance subtests from the patient self-administered Multiple Sclerosis Performance Test (MSPT) designed to assess low contrast vision (Contrast Sensitivity Test, CST), upper extremity motor function (Manual Dexterity Test, MDT) and lower extremity motor function (Walking Speed Test, WST) and to introduce the concept of regression-based norms to aid clinical interpretation of performance scores using the MSPT cognition test (Processing Speed Test, PST) as an example.

METHODS

Substudy 1 assessed test-retest reliability, practice effects and convergent validity of the CST, MDT and WST in 30 MS patients and 30 healthy controls. Substudy 2 examined sensitivity to MS disability in over 600 MS patients as part of their routine clinic assessment. Substudy 3 compared performance on the PST in research volunteers and clinical samples.

RESULTS

The CST, MDT and WST were shown to be reliable, valid and sensitive to MS outcomes. Performance was comparable to technician-administered testing. PST performance was poorer in the clinical sample compared with the research volunteer sample.

CONCLUSIONS

The self-administered MSPT neuroperformance modules produce reliable, objective metrics that can be used in clinical practice and support outcomes research. Published studies which require patient voluntary consent may underestimate the rate of cognitive dysfunction observed in a clinical setting.

Blossoming contusions: identifying factors contributing to the expansion of traumatic intracerebral hemorrhage

Here, the authors examined the factors involved in the volumetric progression of traumatic brain contusions. The variables significant in this progression are identified, and the expansion rate of a brain bleed can now effectively be predicted given the presenting characteristics of the patient.

Reversible, Position-Dependent Midbrain Compression in a Patient with Spontaneous Intracranial Hypotension

BACKGROUND

Intracranial hypotension is an underrecognized cause of spontaneous subdural hematoma. Failure to identify this entity and treat the underlying etiology can result in profoundly dangerous clinical consequences, prolonged and costly hospitalization, and caregiver fatigue, as seen in the case presented here.

CASE DESCRIPTION

We present a case of intracranial hypotension associated with a spontaneous cerebrospinal fluid (CSF) leak in the cervical spine leading to consistently reproducible herniation syndrome with head of bed elevation, and bilateral subdural hematomas as a result of a pressure gradient favoring downward migration of intracranial contents resulting in traction on bridging veins. This gradient promoted transtentorial herniation with resultant brainstem compression, leading to a prolonged intensive care unit stay, recurrent respiratory failure, and severe deconditioning. An exhaustive diagnostic workup uncovered a cervical root CSF leak with a nuclear medicine CSF flow study, which was successfully treated with nerve root ligation and dural closure. The patient recovered well postprocedurally and was able to return to baseline level of function.

CONCLUSIONS

This case demonstrates the importance of considering intracranial hypotension in cases of positional herniation syndrome and the necessity for early and aggressive attempts at identifying and treating the underlying cause to prevent unnecessary neurologic dysfunction and protracted medical care.

Variation in hospital charges in patients with external ventricular drains: comparison between the intensive care and surgical floor settings

OBJECTIVE

Placement of an external ventricular drain (EVD) is a common and potentially life-saving neurosurgical procedure, but the economic aspect of EVD management and the relationship to medical expenditure remain poorly studied. Similarly, interinstitutional practice patterns vary significantly. Whereas some institutions require that patients with EVDs be monitored strictly within the intensive care unit (ICU), other institutions opt primarily for management of EVDs on the surgical floor. Therefore, an ICU burden for patients with EVDs may increase a patient's costs of hospitalization. The objective of the current study was to examine the expense differences between the ICU and the general neurosurgical floor for EVD care.

METHODS

The authors performed a retrospective analysis of data from 2 hospitals within a single, large academic institution-the University of Washington Medical Center (UWMC) and Seattle Children's Hospital (SCH). Hospital charges were evaluated according to patients' location at the time of EVD management: SCH ICU, SCH floor, or UWMC ICU. Daily hospital charges from day of EVD insertion to day of removal were included and screened for days that would best represent baseline expenses for EVD care. Independent-samples Kruskal-Wallis analysis was performed to compare daily charges for the 3 settings.

RESULTS

Data from a total of 261 hospital days for 23 patients were included in the analysis. Ten patients were cared for in the UWMC ICU and 13 in the SCH ICU and/or on the SCH neurosurgical floor. The median values for total daily hospital charges were $19,824.68 (interquartile range [IQR] $12,889.73-$38,494.81) for SCH ICU care, $8,620.88 (IQR $6,416.76-$11,851.36) for SCH floor care, and $10,002.13 (IQR $8,465.16-$12,123.03) for UWMC ICU care. At SCH, it was significantly more expensive to provide EVD care in the ICU than on the floor (p < 0.001), and the daily hospital charges for the UWMC ICU were significantly greater than for the SCH floor (p = 0.023). No adverse clinical event related to the presence of an EVD was identified in any of the settings.

CONCLUSIONS

ICU admission solely for EVD care is costly. If safe EVD care can be provided outside of the ICU, it would represent a potential area for significant cost savings. Identifying appropriate patients for EVD care on the floor is multifactorial and requires vigilance in balancing the expenses associated with ICU utilization and optimal patient care.

Nitrogen use efficiency and nitrous oxide emissions from five UK fertilised grasslands

Intensification of grasslands is necessary to meet the increasing demand of livestock products. The application of nitrogen (N) on grasslands affects the N balance therefore the nitrogen use efficiency (NUE). Emissions of nitrous oxide (N₂O) are produced due to N fertilisation and low NUE. These emissions depend on the type and rates of N applied. In this study we have compiled data from 5 UK N fertilised grassland sites (Crichton, Drayton, North Wyke, Hillsborough and Pwllpeiran) covering a range of soil types and climates. The experiments evaluated the effect of increasing rates of inorganic N fertiliser provided as ammonium nitrate (AN) or calcium ammonium nitrate (CAN). The following fertiliser strategies were also explored for a rate of 320 kg N ha^-1: using the nitrification inhibitor dicyandiamide (DCD), changing to urea as an N source and splitting fertiliser applications. We measured N₂O emissions for a full year in each experiment, as well as soil mineral N, climate data, pasture yield and N offtake. N₂O emissions were greater at Crichton and North Wyke whereas Drayton, Hillsborough and Pwllpeiran had the smallest emissions. The resulting average emission factor (EF) of 1.12% total N applied showed a range of values for all the sites between 0.6 and 2.08%. NUE depended on the site and for an application rate of 320 kg N ha^-1, N surplus was on average higher than 80 kg N ha^-1, which is proposed as a maximum by the EU Nitrogen Expert Panel. N₂O emissions tended to be lower when urea was applied instead of AN or CAN, and were particularly reduced when using urea with DCD. Finally, correlations between the factors studied showed that total N input was related to Nofftake and Nexcess; while cumulative emissions and EF were related to yield scaled emissions.

The contribution of cattle urine and dung to nitrous oxide emissions: Quantification of country specific emission factors and implications for national inventories

Urine patches and dung pats from grazing livestock create hotspots for production and emission of the greenhouse gas, nitrous oxide (N₂O), and represent a large proportion of total N₂O emissions in many national agricultural greenhouse gas inventories. As such, there is much interest in developing country specific N₂O emission factors (EFs) for excretal nitrogen (EF_3, pasture, range and paddock) deposited during gazing. The aims of this study were to generate separate N₂O emissions data for cattle derived urine and dung, to provide an evidence base for the generation of a country specific EF for the UK from this nitrogen source. The experiments were also designed to determine the effects of site and timing of application on emissions, and the efficacy of the nitrification inhibitor, dicyandiamide (DCD) on N₂O losses. This co-ordinated set of 15 plot-scale, year-long field experiments using static chambers was conducted at five grassland sites, typical of the soil and climatic zones of grazed grassland in the UK. We show that the average urine and dung N₂O EFs were 0.69% and 0.19%, respectively, resulting in a combined excretal N₂O EF (EF₃), of 0.49%, which is <25% of the IPCC default EF₃ for excretal returns from grazing cattle. Regression analysis suggests that urine N₂O EFs were controlled more by composition than was the case for dung, whilst dung N₂O EFs were more related to soil and environmental factors. The urine N₂O EF was significantly greater from the site in SW England, and significantly greater from the early grazing season urine application than later applications. Dycandiamide reduced the N₂O EF from urine patches by an average of 46%. The significantly lower excretal EF₃ than the IPCC default has implications for the UK's national inventory and for subsequent carbon footprinting of UK ruminant livestock products.

Weak-link Josephson Junctions Made from Topological Crystalline Insulators

We report on the fabrication of Josephson junctions using the topological crystalline insulator Pb_{0.5}Sn_{0.5}Te as the weak link. The properties of these junctions are characterized and compared to those fabricated with weak links of PbTe, a similar material yet topologically trivial. Most striking is the difference in the ac Josephson effect: junctions made with Pb_{0.5}Sn_{0.5}Te exhibit a rich subharmonic structure consistent with a skewed current-phase relation. This structure is absent in junctions fabricated from PbTe. A discussion is given on the origin of this effect as an indication of novel behavior arising from the topologically nontrivial surface state.

The potential impact of the demographic transition in the Senegal-Gambia region of sub-Saharan Africa on the burden of infectious disease and its potential synergies with control programmes: the case of hepatitis B

BACKGROUND

Sub-Saharan Africa (SSA) continues to suffer high communicable disease burdens as its demographic transition (DT) proceeds. Although the consequent changes in population structures influence age-specific contact patterns relevant for transmission, the age distribution of immunity, and the disease burden, investigation of the potential of DT to affect infectious disease epidemiology in regions of SSA has hitherto been overlooked. With a substantial disease burden and complex epidemiology, hepatitis B virus (HBV) represents a prime example of an infection whose epidemiology may be significantly influenced by the DT.

METHODS

An age-structured mathematical model for HBV in the Senegal and Gambia (SG) region was set within a demographic framework with varying vital rates mirroring the entire course of the DT there over 1850-2100, to investigate the effects of the DT on HBV epidemiology, with and without the combined action of vaccination. The model was run from its reconstructed ancien régime (old order) demo-epidemiologic equilibrium and calibrated against SG 1950 age-distribution estimates and Gambian pre-vaccination HBV age-prevalence data.

RESULTS

The model, which reproduced well demographic and HBV age-prevalence data, predicted a complex transition of HBV epidemiology over the course of the DT. This included a prolonged epoch of expansion alongside population growth and rejuvenation until 1990-2000, followed by a dramatic retreat, mainly reflecting projected fertility decline during the twenty-first century. This transitional pattern was mostly explained by the underlying demographically driven changes in horizontal transmission resulting from the changes in the age structure of the population. During 2000-2150 the HBV burden is predicted to decline by more than 70% even in the absence of vaccination.

CONCLUSIONS

Demographic change alone may strongly affect HBV disease burden and shape HBV endemicity. The onset of the demographically driven decline in HBV prevalence, aligned with the expansion of HBV vaccination, forms a synergy potentially boosting effectiveness of control. Such a synergy currently appears to be presenting a "window of opportunity" facilitating HBV elimination which it would be important to exploit and which underlines the importance of taking demographic change into account when assessing the potential longer term impact of vaccination and other control measures.

Nutrient composition and retention in whole turkeys with and without added solution

Whole turkeys sold in retail outlets are typically processed with added solutions to improve their taste and tenderness. The purpose of this study was to evaluate the nutrient composition of whole turkeys with and without added solution, and to update the nutrient profile of turkey for the USDA National Nutrient Database for Standard Reference. Eleven pairs of turkeys with added solution were obtained from statistically representative retail outlets using a nationwide sampling plan developed for USDA's National Food and Nutrient Analysis Program; 4 pairs of turkeys without added solution were purchased from local food outlets. Turkeys were roasted to an internal temperature of 165°F (74°C). Values of selected nutrients in light and dark meat, including skin, were determined by USDA approved laboratories using quality assurance protocols. Both raw and cooked turkeys, with and without added solution, were compared by one-way and 2-way factorial ANOVA. The results showed a significant interaction for fat (P < 0.0001) and zinc (P = 0.0070) between turkeys that were raw and cooked and those prepared with or without added solution. Fat was higher in raw turkeys with added solution compared to without added solution. Similarly, sodium, phosphorus, and calcium values were significantly higher in turkeys with added solution (P < 0.05) than in turkeys without added solution. Data from this study will be useful for developing strategies to address sodium-related health issues, nutrition monitoring, consumption surveys, and policy development.

Synthesis of a C1-C23 fragment of the archazolids and evidence for V-ATPase but not COX inhibitory activity

A convergent synthesis of a C1-C23 fragment of the archazolids has been completed based on a high yielding Stille coupling to costruct the substituted Z,Z,E-conjugated triene. After removal of the protecting groups, the resulting tetrol exhibited evidence for inhibition of the vacuolar-type ATPase (V-ATPase) but not cyclooxygenase (COX) inhibitory activity.

Safety and clinical response of intraventricular caspofungin for Scedosporium apiospermum complex central nervous system infection

We present a 71-year old woman treated with 14 days of 5 mg intraventricular caspofungin for Scedosporium apiospermum complex meningoencephalitis diagnosed after spinal fusion and instrumentation. Cerebrospinal fluid studies improved during therapy and intraventricular administration was well tolerated. Within weeks of discontinuation, the patient experienced clinical deterioration with disease progression. There are sparse data on the efficacy and safety of administering intraventricular caspofungin. While apparently safe, intraventricular caspofungin was insufficient for disease control in this case.

Experimental Protocol for Biodiesel Production with Isolation of Alkenones as Coproducts from Commercial Isochrysis Algal Biomass

The need to replace petroleum fuels with alternatives from renewable and more environmentally sustainable sources is of growing importance. Biomass-derived biofuels have gained considerable attention in this regard, however first generation biofuels from edible crops like corn ethanol or soybean biodiesel have generally fallen out of favor. There is thus great interest in the development of methods for the production of liquid fuels from domestic and superior non-edible sources. Here we describe a detailed procedure for the production of a purified biodiesel from the marine microalgae Isochrysis. Additionally, a unique suite of lipids known as polyunsaturated long-chain alkenones are isolated in parallel as potentially valuable coproducts to offset the cost of biodiesel production. Multi-kilogram quantities of Isochrysis are purchased from two commercial sources, one as a wet paste (80% water) that is first dried prior to processing, and the other a dry milled powder (95% dry). Lipids are extracted with hexanes in a Soxhlet apparatus to produce an algal oil ("hexane algal oil") containing both traditional fats (i.e., triglycerides, 46-60% w/w) and alkenones (16-25% w/w). Saponification of the triglycerides in the algal oil allows for separation of the resulting free fatty acids (FFAs) from alkenone-containing neutral lipids. FFAs are then converted to biodiesel (i.e., fatty acid methyl esters, FAMEs) by acid-catalyzed esterification while alkenones are isolated and purified from the neutral lipids by crystallization. We demonstrate that biodiesel from both commercial Isochrysis biomasses have similar but not identical FAME profiles, characterized by elevated polyunsaturated fatty acid contents (approximately 40% w/w). Yields of biodiesel were consistently higher when starting from the Isochrysis wet paste (12% w/w vs. 7% w/w), which can be traced to lower amounts of hexane algal oil obtained from the powdered Isochrysis product.

Enamel and dentin mineralization in familial hypophosphatemic rickets: a micro-CT study

OBJECTIVES

The aim of the present study was to analyse the mineralization pattern of enamel and dentin in patients affected by X-linked hypophosphatemic rickets (XLHR) using micro-CT (µCT), and to associate enamel and dentin mineralization in primary and permanent teeth with tooth position, gender and the presence/absence of this disease.

METHODS

19 teeth were collected from 5 individuals from the same family, 1 non-affected by XLHR and 4 affected by XLHR. Gender, age, tooth position (anterior/posterior) and tooth type (deciduous/permanent) were recorded for each patient. Following collection, teeth were placed in 0.1% thymol solution until µCT scan. Projection images were reconstructed and analysed. A plot profile describing the greyscale distance relationship in µCT images was achieved through a line bisecting each tooth in a region with the presence of enamel and dentin. The enamel and dentin mineralization densities were measured and compared. Univariate ANOVA and post hoc Tukey tests were used for all comparisons.

RESULTS

Teeth of all affected patients presented dentin with a different mineralization pattern compared with the teeth of healthy patients with dentin defects observed next to the pulp chambers. Highly significant differences were found for gray values between anterior and posterior teeth (p < 0.05), affected and non-affected (p < 0.05), as well as when position and disease status were considered (p < 0.05).

CONCLUSIONS

In conclusion, the mineralization patterns of dentin differed when comparing teeth from patients with and without FHR, mainly next to pulp chambers where areas with porosity and consequently lower mineral density and dentin defects were found.

Effects of agricultural conservation practices on N loads in the Mississippi-atchafalaya river basin

A modeling framework consisting of a farm-scale model, Agricultural Policy Environmental Extender (APEX); a watershed-scale model, Soil and Water Assessment Tool (SWAT); and databases was used in the Conservation Effects Assessment Project to quantify the environmental benefits of conservation practices on cropland. APEX is used to simulate conservation practices on cultivated cropland and Conservation Reserve Program land to assess the edge-of-field water-quality benefits. Flow and pollutant loadings from APEX are input to SWAT. SWAT simulates the remaining noncultivated land and routes flow and loads generated from noncultivated land, point sources, and cropland to the basin outlet. SWAT is used for assessing the effects of practices on local and in-stream water-quality benefits. Each river basin is calibrated and validated for streamflow and loads at multiple gauging stations. The objectives of the current study are to estimate the effects of currently existing and additional conservation practices on total N (TN) loads in the Mississippi-Atchafalaya River Basin (MARB) and draw insights on TN load reductions necessary for reducing the hypoxic zone in the Gulf of Mexico. The effects of conservation practice scenarios on local and in-stream (riverine) water quality are evaluated. Model results indicate that conservation practices currently on cropland have reduced the TN losses to local waters between 20 and 59% in the six river basins within MARB and the TN load discharged to the Gulf by 17%. Further water-quality improvement can be obtained in the MARB with additional conservation treatment.

Temperature measurements of shocked silica aerogel foam

We present recent results of equation-of-state (EOS) measurements of shocked silica (SiO_{2}) aerogel foam at the OMEGA laser facility. Silica aerogel is an important low-density pressure standard used in many high energy density experiments, including the novel technique of shock and release. Due to its many applications, it has been a heavily studied material and has a well-known Hugoniot curve. This work then complements the velocity and pressure measurements with additional temperature data providing the full EOS information within the warm dense matter regime for the temperature interval of 1-15 eV and shock velocities between 10 and 40 km/s corresponding to shock pressures of 0.3-2 Mbar. The experimental results were compared with hydrodynamic simulations and EOS models. We found that the measured temperature was systematically lower than suggested by theoretical calculations. Simulations provide a possible explanation that the emission measured by optical pyrometry comes from a radiative precursor rather than from the shock front, which could have important implications for such measurements.

Positive impact of increases in condom use among female sex workers and clients in a medium HIV prevalence epidemic: modelling results from Project SIDA1/2/3 in Cotonou, Benin

BACKGROUND

A comprehensive, HIV prevention programme (Projet Sida1/2/3) was implemented among female sex workers (FSWs) in Cotonou, Benin, in 1993 following which condom use among FSWs increased threefold between 1993 and 2008 while FSW HIV prevalence declined from 53.3% to 30.4%.

OBJECTIVE

Estimate the potential impact of the intervention on HIV prevalence/incidence in FSWs, clients and the general population in Cotonou, Benin.

METHODS AND FINDINGS

A transmission dynamics model parameterised with setting-specific bio-behavioural data was used within a Bayesian framework to fit the model and simulate HIV transmission in the high and low-risk population of Cotonou and to estimate HIV incidence and infections averted by SIDA1/2/3. Our model results suggest that prior to SIDA1/2/3 commercial sex had contributed directly or indirectly to 93% (84-98%) of all cumulative infections and that the observed decline in FSWs HIV prevalence was more consistent with the self-reported post-intervention increase in condom use by FSWs than a counterfactual assuming no change in condom use after 1993 (CF-1). Compared to the counterfactual (CF-1), the increase in condom use may have prevented 62% (52-71%) of new HIV infections among FSWs between 1993 and 2008 and 33% (20-46%) in the overall population.

CONCLUSIONS

Our analysis provides plausible evidence that the post-intervention increase in condom use during commercial sex significantly reduced HIV prevalence and incidence among FSWs and general population. Sex worker interventions can be effective even in medium HIV prevalence epidemics and need to be sustained over the long-term.