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Advancements in ultrafast electron microscopy have allowed elucidation of spatially selective structural dynamics. However, as the spatial resolution and imaging capabilities have made progress, quantitative characterization of the electron pulse trains has not been reported at the same rate. In fact, inexperienced users have difficulty replicating the technique because only a few dedicated microscopes have been characterized thoroughly. Systems replacing laser driven photoexcitation with electrically driven deflectors especially suffer from a lack of quantified characterization because of the limited quantity. The primary advantages to electrically driven systems are broader frequency ranges, ease of use and simple synchronization to electrical pumping. Here, we characterize the technical parameters for electrically driven UEM including the shape, size and duration of the electron pulses using low and high frequency chopping methods. At high frequencies, pulses are generated by sweeping the electron beam across a chopping aperture. For low frequencies, the beam is continuously forced off the optic axis by a DC potential, then momentarily aligned by a countering pulse. Using both methods, we present examples that measure probe durations of 2 ns and 10 ps for the low and high frequency techniques, respectively. We also discuss how the implementation of a pulsed probe affects STEM imaging conditions by adjusting the first condenser lens., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Published by Elsevier B.V.)

Objective: Red blood cell (RBC) transfusion is commonly indicated in brain tumor surgery due to risk of blood loss. Current transfusion guidelines are based on evidence derived from critically ill patients and may not be optimal for brain tumor surgeries. Our study is the first to synthesize available evidence to suggest RBC transfusion thresholds in brain tumor patients undergoing surgery., Methods: A systematic review was conducted using PubMed, EMBASE, and Google Scholar databases in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines to critically assess RBC transfusion thresholds in adult patients with brain tumors and complications secondary to transfusion following blood loss in the operating room or perioperative period., Results: Seven articles meeting our search criteria were reviewed. Brain tumor patients who received blood transfusions were older, had greater rates of American Society of Anesthesiologists class 3 or 4, and presented with increased number of comorbidities including diabetes, hypertension, and cardiovascular diseases. In addition, transfused patients had a prolonged surgical time. Transfusions were associated with multiple postoperative major and minor complications, including longer hospital length of stay, increased return to the operating room, and elevated 30-day mortality. Analysis of transfusion thresholds showed that a restrictive hemoglobin threshold of 8 g/dL is safe in patients, as evidenced by a reduction in length of stay, mortality, and complications (level C class IIa)., Conclusions: A restrictive Hb threshold of 8 g/dL appears to be safe and minimizes potential complications of transfusion in brain tumor patients., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Objective: Optic pathway gliomas (OPGs) typically occur in the first decade of life and 40%-50% are not associated with neurofibromatosis 1 (NF1) (sporadic). Management strategies are often patient specific because of the variable and unpredictable course. No study has summarized the effect of treatment strategies on visual outcomes in the subset of pediatric patients with sporadic OPG., Methods: We conducted a systematic review to determine the nature of visual outcomes in pediatric patients with sporadic, non-NF1-associated OPG using the PubMed, Embase, Scopus, Cochrane, and CINAHL Plus databases. Visual outcomes were categorized as improved, unchanged, or deteriorated., Results: Of 1316 results, 31 articles were included. Treatment indications are unknown with full clinical detail. A total of 45.2% (14/31) reported deteriorated outcomes after treatment, 35.5% (11/31) no change, and 19.4% (6/31) improvement. Of radiotherapy studies, 50.0% (4/8) found no change, 37.5% (3/8) deterioration, and 12.5% (1/8) improvement. Of chemotherapy studies, 35.7% (5/14) each showed improvement and deterioration, whereas 28.6% (4/14) showed no change. Of surgical studies, 62.5% (5/8) indicated deterioration, and 37/5% (3/8) indicated no change. The singular study examining observation reported deterioration in visual outcomes. Factors associated with poor visual outcomes included signs and symptoms of visual decline at presentation, involvement of the intraorbital optic nerve, and intracranial hypertension requiring surgery. Causality cannot be determined from systematic review., Conclusions: Most studies showed that vision in pediatric patients with sporadic OPG is stable to poor after observation, chemotherapy, radiotherapy, or surgery. Chemotherapy may be associated with most favorable visual outcomes., (Copyright © 2022 Elsevier Inc. All rights reserved.)

The development of ultrafast electron microscopy (UEM), specifically stroboscopic imaging, has brought the study of structural dynamics to a new level by overcoming the spatial limitations of ultrafast spectroscopy and the temporal restrictions of traditional TEM simultaneously. Combining the concepts governing both techniques has enabled direct visualization of dynamics with spatiotemporal resolutions in the picosecond-nanometer regime. Here, we push the limits of imaging using a pulsed electron beam via RF induced transverse deflection based on the newly developed 200 keV frequency-tunable strip-line pulser. We demonstrate a 0.2 nm spatial resolution and elucidation of magnetic spin induction maps using the phase-microscopy method. We also present beam coherence measurements and expand our study using the breathing modes of a silicon interdigitated comb under RF excitation which achieves improved temporal synchronization between the electron pulse-train and electric field. A new RF holder has also been developed with impedance matching to the RF signal to minimize transmission power loss to samples and its performance is compared with a conventional sample holder., (Published by Elsevier B.V.)

Objective: Surgical management of aneurysmal subarachnoid hemorrhage (SAH) often involves red blood cell (RBC) transfusion, which increases the risk of postoperative complications. RBC transfusion guidelines report on chronically critically ill patients and may not apply to patients with SAH. Our study aims to synthesize the evidence to recommend RBC transfusion thresholds among adult patients with SAH undergoing surgery., Methods: A systematic review was conducted using PubMed, Google Scholar, and Web of Science electronic databases according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines to critically assess primary articles discussing RBC transfusion thresholds and describe complications secondary to RBC transfusion in adult patients with SAH in the perioperative period., Results: Sixteen articles meeting our search strategy were reviewed. Patients with SAH who received blood transfusion were older, female, had World Federation of Neurosurgical Societies grade IV-V and modified Fisher grade 3-4 scores, and presented with more comorbidities such as hypertension, diabetes, and cardiovascular and pulmonary diseases. In addition, transfusion was associated with multiple postoperative complications, including higher rates of vasospasms, surgical site infections, cardiovascular and respiratory complications, increased postoperative length of stay, and 30-day mortality. Analysis of transfused patients showed that a higher hemoglobin (>10 g/dL) goal after SAH was safe and that patients may benefit from a higher whole hospital stay hemoglobin nadir, as shown by a reduction in risk of cerebral vasospasm and improvement in clinical outcomes (level B class II)., Conclusions: Among patients with SAH, the benefits of reducing cerebral ischemia and anemia are shown to outweigh the risks of transfusion-related complications., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Background: Serum biomarkers have gained significant popularity as an adjunctive measure in the evaluation and prognostication of traumatic brain injury (TBI). However, a concise and clinically oriented report of the major markers in function of TBI severity is lacking. This systematic review aims to report current data on the diagnostic and prognostic utility of blood-based biomarkers across the spectrum of TBI., Methods: A literature search of the PubMed/Medline electronic database was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. We excluded systematic reviews and meta-analyses that did not provide novel data. The American College of Cardiology/American Heart Association criteria were used to assess levels of evidence., Results: An initial 1463 studies were identified. In total, 115 full-text articles reporting on 94 distinct biomarkers met the inclusion criteria. Glasgow Coma Scale scores, computed tomography/magnetic resonance imaging abnormalities, and injury severity scores were the most used clinical diagnostic variables. Glasgow Outcome Scores and 1-, 3-, and 6-month mortality were the most used clinical prognostic variables. Several biomarkers significantly correlated with these variables and had statistically significant different levels in TBI subjects when compared with healthy, orthopedic, and polytrauma controls. The biomarkers also displayed significant variability across mild, moderate, and severe TBI categories, as well as in concussion cases., Conclusions: This review summarizes existing high-quality evidence that supports the use of severity-specific biomarkers in the diagnostic and prognostic evaluation of TBI. These data can be used as a launching platform for the validation of upcoming clinical studies., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Objective: We investigated whether a sex-related difference exists in the postoperative complication risk and health-related quality of life measures after surgery for adult spinal deformity., Methods: We performed a retrospective study of 156 adult patients with a diagnosis of adult spinal deformity who had undergone spinal surgery. The primary outcome variables included the postoperative complication rates and changes in the health-related quality of life measures. Adjusted odds ratios were estimated by multivariate logistic regression with the inclusion of covariate terms for sex, smoking, preoperative optimization, American Society of Anesthesiologists grade, depression, osteoporosis, invasiveness of surgery (number of vertebral levels fused), and baseline functional disability., Results: At presentation, the women were more likely to be smokers (74 women [71.15%]; 23 men [42.31%]; P = 0.01) and to have a greater prevalence of depression (36 women [34.62%]; 10 men [19.23%]; P = 0.06). The women had also presented with more severe baseline pain (visual analog scale for back pain score, 7.24 vs. 6.00 [P = 0.02]; visual analog scale for leg pain score, 5.87 vs. 5.59 [P = 0.07]) and worse functional disability (patient-reported outcomes measurement information system score, 6.82 vs. 5.65 [P = 0.01]; Oswestry disability index, 45.42 vs. 37.07 [P = 0.01]). However, postoperatively, the women experienced greater improvement in pain and disability compared with the men. The unadjusted odds of a postoperative complication was greater for the women (odds ratio, 1.14; 95% confidence interval, 0.55-2.33). On multivariate logistic regression analysis, the association between sex and postoperative complications was attenuated after controlling for other baseline variables., Conclusions: In the present study, after adjustment for important baseline prognostic factors, no differences were found in the postoperative complication rates or extent of functional improvement when stratified by sex. Both sexes responded equally well to corrective surgery for symptomatic adult spinal deformity., (Copyright © 2020 Elsevier Inc. All rights reserved.)

For two decades, time-resolved transmission electron microscopes (TEM) have relied on pulsed-laser photoemission to generate electron bunches to explore sub-microsecond to sub-picosecond dynamics. Despite the vast successes of photoemission time-resolved TEMs, laser-based systems are inherently complex, thus tend not to be turn-key. In this paper, we report on the successful retrofit of a commercial 200 keV TEM, without an external laser, capable of producing continuously tunable pulsed electron beams with repetition rates from 0.1 GHz up to 12 GHz and a tunable bunch length from tens of nanoseconds down to 10 ps. This innovation enables temporal access into previously inaccessible regimes: i.e., high repetition rate stroboscopic experiments. Combination of a pair of RF-driven traveling wave stripline elements, quadrupole magnets, and a variable beam aperture enables operation of the instrument in (1) continuous waveform (CW) mode as though the instrument was never modified (i.e. convention TEM operation mode, where the electrons from the emission cathode randomly arrive at the sample without resolvable time information), (2) stroboscopic (pump-probe) mode, and (3) pulsed beam mode for dose rate sensitive materials. To assess the effect of a pulsed beam on image quality, we examined Au nanoparticles using bright field, high-resolution TEM imaging and selected area diffraction in both continuous and pulsed-beam mode. In comparison of conventional TEMs, the add-on beam pulser enables the observation of ultrafast dynamic behavior in materials that are reversible under synchronized excitation., (Copyright © 2019 Elsevier B.V. All rights reserved.)