High-Frequency versus Low-Frequency Spinal Cord Stimulation in Treatment of Chronic Limb-Threatening Ischemia: Short-Term Results of a Randomized Trial

INTRODUCTION

The objective of the study is to determine if high-frequency (1 kHz) spinal cord stimulation (SCS) is better than low-frequency SCS for pain relief in chronic limb-threatening ischemia (CLTI).

METHODS

HEAL-SCS trial was designed as an open-label, parallel-group, single-center randomized study with a 1:1 allocation ratio. The trial was conducted in Meshalkin National Medical Research Center between August 2018 and February 2020. Total 56 patients underwent screening, 50 were enrolled, 6 were rejected. The participants were randomized into 2 cohorts of 25 patients each by an external coordinator using an online tool. A neurosurgeon and a vascular surgeon both examined all patients and estimated the pain intensity using visual analog scale (VAS), quality of life with short-form-36 health survey (SF-36), and functional status by walking impairment questionnaire (WIQ) at 3 and 12 months. Tissue perfusion was evaluated for 34 patients using transcutaneous oxygen tension measurement (TcPO2) at baseline and in 12 months.

RESULTS

All 50 patients (84% men, median age 66.5 y.o) were available for primary outcome assessment 3 and 12 months after implantation. Intention-to-treat analysis demonstrated comparative advantage of HF-SCS over LF-SCS at 3 months with mean VAS score 2.8 (95% CI, 2.4; 3.2) and 3.3 (95% CI, 3.0; 3.6), respectively (p = 0.031). Clinical superiority of HF-SCS persisted at 12-month follow-up (p < 0.001). HF-SCS produced significantly greater pain relief by WIQ at 3 (p < 0.001) and 12 months (p = 0.009). Despite stair-climbing ability was better in HF-SCS group (p = 0.02), no significant difference between groups was found at 1-year post-op in terms of speed (p = 0.92) and distance scores (p = 0.68). Accordingly, the general and mental health domains of SF-36 were significantly better in HF-SCS at 12 months. Despite a tendency toward better resting oxygen pressure in HF-SCS group, there was no intergroup difference by TcPO2 (p = 0.076). Only 1 patient (2%) required above-the-knee amputation at 10 months after LF-SCS implantation.

CONCLUSION

High-frequency SCS provides better pain relief, life quality, and functional performance in patients with CLTI during short-term follow-up. The lack of perfusion difference between high-frequency and conventional SCS requires further examination to the possible long-term advantages of the method.

Huge cerebral pial arteriovenous fistula in a newborn: illustrative case

BACKGROUND

Pediatric arteriovenous malformations (AVMs) and pial/dural arteriovenous fistulas (AVFs) are rare but life-threatening complications that can lead to congestive heart failure and hemorrhagic stroke in newborns and pediatric patients. The pronounced shunting in these conditions is associated with early complications and necessitates aggressive surgical management. Here, the authors describe endovascular treatment of an atypical cerebral pial AVF in a newborn.

OBSERVATIONS

This AVF formed direct communication between a major cerebral artery (basilar artery) and a large draining vein (dilated deep cerebral vein). The authors performed earlier subtotal embolization of the AVF using 0.020-inch coils, which led to progressive thrombosis of the fistula with restoration of normal arterial blood flow. The patient was discharged 18 days after surgery, examination at 1.5 and 6 months showed magnetic resonance imaging signs of blood flow absence through the fistula and satisfactory condition of the infant without physical and mental developmental delay.

LESSONS

Subtotal coiling of a high-flow pial AVF in a newborn can result in a good clinical outcome.

Prospective comparative study of intraoperative balloon electronic brachytherapy versus resection with multidisciplinary adjuvant therapy for recurrent glioblastoma

Background

Intraoperative balloon electronic brachytherapy (IBEB) may provide potential benefit for local control of recurrent cerebral glioblastomas (GBMs).

Methods

This is a preliminary report of an open-label, prospective, comparative cohort study conducted in two neurosurgical centers with ongoing follow-up. At recurrence, patients at one center (n = 15) underwent reresection with IBEB while, at the second center (n = 15), control subjects underwent re-resection with various accepted second-line adjuvant chemoradiotherapy options. A comparative analysis of overall survival (OS) and local progression-free survival (LPFS) following re-resection was performed. Exploratory subgroup analysis based on postoperative residual contrast-enhanced volume status was also done.

Results

In the IBEB group, median LPFS after re-resection was significantly longer than in the control group (8.0 vs. 6.0 months; log rank χ² = 4.93, P = 0.026, P < 0.05). In addition, the median OS after second resection in the IBEB group was also significantly longer than in the control group (11.0 vs. 8.0 months; log rank χ² = 4.23, P = 0.04, P < 0.05).

Conclusion

These hypothesis-generating results from a small cohort of subjects suggest putative clinical benefit in OS and LPFS associated with maximal safe re-resection of recurrent GBM with IBEB versus re-resection and standard adjuvant therapy, a hypothesis that deserves further testing in an appropriately powered clinical trial.

Comparability of Raman Spectroscopic Configurations: A Large Scale Cross-Laboratory Study

The variable configuration of Raman spectroscopic platforms is one of the major obstacles in establishing Raman spectroscopy as a valuable physicochemical method within real-world scenarios such as clinical diagnostics. For such real world applications like diagnostic classification, the models should ideally be usable to predict data from different setups. Whether it is done by training a rugged model with data from many setups or by a primary-replica strategy where models are developed on a 'primary' setup and the test data are generated on 'replicate' setups, this is only possible if the Raman spectra from different setups are consistent, reproducible, and comparable. However, Raman spectra can be highly sensitive to the measurement conditions, and they change from setup to setup even if the same samples are measured. Although increasingly recognized as an issue, the dependence of the Raman spectra on the instrumental configuration is far from being fully understood and great effort is needed to address the resulting spectral variations and to correct for them. To make the severity of the situation clear, we present a round robin experiment investigating the comparability of 35 Raman spectroscopic devices with different configurations in 15 institutes within seven European countries from the COST (European Cooperation in Science and Technology) action Raman4clinics. The experiment was developed in a fashion that allows various instrumental configurations ranging from highly confocal setups to fibre-optic based systems with different excitation wavelengths. We illustrate the spectral variations caused by the instrumental configurations from the perspectives of peak shifts, intensity variations, peak widths, and noise levels. We conclude this contribution with recommendations that may help to improve the inter-laboratory studies.

Intra-operative radiation therapy as salvage treatment option for recurrent glioblastoma multiforme

2535

Background: Glioblastoma multiforme (GBM) is an extremely aggressive cerebral tumor with poor prognosis. The majority of patients relapse after the initial surgery plus adjuvant radiation and chemotherapy. In case of recurrence there is no established standard therapy. The optimal techniques for salvage re-irradiation are unclear, so that procedure poses a challenge. In contrast to traditional external beam radiotherapy (EBRT) intra-operative radiotherapy (IORT) may improve patient’s outcome at the cost of minimal side effects and short treatment duration. Methods: A total of 30 patients were treated with recurrent GBM between August 2016 and June 2019. All patients underwent maximal safe resection; patients were divided into IORT and EBRT groups. 15 patients were included in each group with similar clinical characteristics. All patients in IORT group underwent maximal safe microsurgical resection with subsequent intraoperative balloon electronic brachytherapy (IBEB) and no further adjuvant treatment. IBEB was performed using Axxent electronic brachytherapy device (Xoft Electronic Brachytherapy (eBx) System, USA. Patients in EBRT group underwent same surgery followed by external beam radiotherapy. Contrast-enhanced brain MRI with perfusion was performed within 24 hours of surgery +/- brain PET-CT with 18-FDOPA and then every 3 months. Both groups were also assigned to subgroups (≤ 2.5cm3 and > 2.5cm3) based on post-operative contrast-enhancing volume (POCEV). Median overall survival (OS) since diagnosis and local progression-free survival (locPFS) following the second surgery were analyzed. Possible toxicities and prognostic factors were also evaluated. Results: Median OS was 27 months in IORT group and 21 months in EBRT group. The locPFS range between 3.5 to 39 months in IORT group and only 2 to 10 months in group with EBRT. Kaplan-Meier OS curves in patients with POCEV ≤ 2.5cm3 showed more favorable outcomes for patients in the IORT group (p < 0.05). In patients with POCEV > 2.5cm3 the median OS was 17 months in IORT group and 13.5 months in EBRT group. Conclusions: IORT of recurrent GBM is feasible and provides encouraging local progression-free and overall survival; no high-grade radiation induced toxicities occur and further studies to establish this method are mandatory. The toxicity profile of additional IBEB was manageable. Maximal safe microsurgical resection is the most important prognostic factor and could determine the effectiveness of post-surgical IBEB.

Rapid acquisition of mean Raman spectra of eukaryotic cells for a robust single cell classification

Raman spectroscopy has previously been used to identify eukaryotic and prokaryotic cells. While prokaryotic cells are small in size and can be assessed by a single Raman spectrum, the larger size of eukaryotic cells and their complex organization requires the acquisition of multiple Raman spectra to properly characterize them. A Raman spectrum from a diffraction-limited spot at an arbitrary location within a cell results in spectral variations that affect classification approaches. To probe whole cells with Raman imaging at high spatial resolution is time consuming, because a large number of Raman spectra need to be collected, resulting in low cell throughput and impairing statistical analysis due to low cell numbers. Here we propose a method to overcome the effects of cellular heterogeneity by acquiring integrated Raman spectra covering a large portion of a cell. The acquired spectrum represents the mean macromolecular composition of a cell with an exposure time that is comparable to acquisition of a single Raman spectrum. Data sets were collected from T lymphocyte Jurkat cells, and pancreatic cell lines Capan1 and MiaPaca2. Cell classification by support vector machines was compared for single spectra, spectra of images and integrated Raman spectra of cells. The integrated approach provides better and more stable prediction for individual cells, and in the current implementation, the mean macromolecular information of a cell can be acquired faster than with the acquisition of individual spectra from a comparable region. It is expected that this approach will have a major impact on the implementation of Raman based cell classification.

High-bit rate ultra-compact light routing with mode-selective on-chip nanoantennas

Optical nanoantennas provide a promising pathway toward advanced manipulation of light waves, such as directional scattering, polarization conversion, and fluorescence enhancement. Although these functionalities were mainly studied for nanoantennas in free space or on homogeneous substrates, their integration with optical waveguides offers an important "wired" connection to other functional optical components. Taking advantage of the nanoantenna's versatility and unrivaled compactness, their imprinting onto optical waveguides would enable a marked enhancement of design freedom and integration density for optical on-chip devices. Several examples of this concept have been demonstrated recently. However, the important question of whether nanoantennas can fulfill functionalities for high-bit rate signal transmission without degradation, which is the core purpose of many integrated optical applications, has not yet been experimentally investigated. We introduce and investigate directional, polarization-selective, and mode-selective on-chip nanoantennas integrated with a silicon rib waveguide. We demonstrate that these nanoantennas can separate optical signals with different polarizations by coupling the different polarizations of light vertically to different waveguide modes propagating into opposite directions. As the central result of this work, we show the suitability of this concept for the control of optical signals with ASK (amplitude-shift keying) NRZ (nonreturn to zero) modulation [10 Gigabit/s (Gb/s)] without significant bit error rate impairments. Our results demonstrate that waveguide-integrated nanoantennas have the potential to be used as ultra-compact polarization-demultiplexing on-chip devices for high-bit rate telecommunication applications.

Data transmission in long-range dielectric-loaded surface plasmon polariton waveguides

We demonstrate the data transmission of 10 Gbit/s on-off keying modulated 1550 nm signal through a long-range dielectric-loaded surface plasmon polariton waveguide structure with negligible signal degradation. In the experiment the bit error rate penalties do not exceed 0.6 dB over the 15 nm wavelength range and received optical power between -7 and 3 dBm.