Dorsal root ganglion stimulator-A targeted therapy for post-herpetic neuralgia: The Middle East Experience.

BACKGROUND: Post herpetic neuralgia (PHN) is a chronic neuropathic pain syndrome which presents after an episode of herpes zoster caused by the reactivation of varicella zoster virus. Conservative treatment starts with pharmacological measures using Anti-epileptics and Antidepressants. Some patients also respond well to epidural steroid injections too, but the effect is usually short lasting. Dorsal Root Ganglion Stimulator (DRG-S) has recently been suggested as a new treatment modality for PHN due to its selective targeting of the pathophysiologic focus. CASE SERIES: We are reporting three cases, who were suffering from neuropathic pain after an episode of herpes zoster. Pain and pain related suffering scores were high, even with multiple antiepileptics and opioid medications. They underwent DRG-S implant and appreciated more than 50% reduction of their pain score, meaningful reduction in the dose of medications along with significant improvement of their general well being measured using Generalized Anxiety Disorder Questionnaire (GAD-7), pain disability index (PDI), and 9 Question Patient Health Questionnaire (PHQ-9). To our knowledge this is the first report on DRG stimulator from the Middle East Region. CONCLUSION: DRG-S has potential to be a preferable treatment option in patients with refractory PHN and acts as a specific targeted therapy in the treatment of these patients.

Spontaneous occlusion of a pial arteriovenous fistula after angiography: The role of iodinated contrast media.

Intracranial non-galenic pial arteriovenous fistula (PAVF) is an extremely rare vascular malformation, where one or more pial arteries feeds directly into a cortical vein without any intervening nidus. Though occasionally they can be asymptomatic, neurological symptoms such as headache, seizure, or focal neurological deficit are more common presenting features. Life threatening or fatal hemorrhage is not uncommon, hence needed to be treated more often than not. Spontaneous occlusion of PAVF is reported only four times before. We report a 49-year-old gentleman, who was diagnosed to have a PAVF, possibly secondary to trauma. He presented 5 months and 22 days from initial digital subtraction angiography (DSA) for treatment, and follow-up angiogram showed complete obliteration. He denied any significant event, medication or alternate treatment during this period. His clinical symptoms were stable as well. We postulate iodinated contrast medium induced vasculopathy as a possible cause, which has been described for other vascular pathologies, but never for PAVF.

Enhanced Thermoelectric Performance in the SrTi0.85Nb0.15O3 Oxide Nanocomposite with Fe2O3-Functionalized Graphene.

Doped SrTiO3 is considered one of the potential thermoelectric (TE) candidates but its TE figure of merit, ZT needs to be improved for practical application of electricity generation from high-grade waste-heat. In the present work, enhanced TE performance has been realized for SrTi0.85Nb0.15O3 (STN) perovskite adopting the strategy of composite formation with Fe2O3-functionalized graphene (FGR). We have achieved a maximum electrical conductivity of 1.4 × 105 S m-1 for 1 wt % FGR added to STN, which is around 1185% larger than that of pristine STN. The presence of FGR in the STN matrix acts as a mobility booster of electrons, overcoming the effect of Anderson localization of electrons, which impedes the electron transport in STN. This is evident from the order of magnitude increase in weighted mobility of STN after FGR addition. Furthermore, the incorporation of FGR causes about a 34% decrease in the lattice thermal conductivity. The Debye-Callaway model demonstrates that the phonon-phonon Umklapp scattering is primarily responsible for reduced thermal conductivity. The presence of FGR sheets along the grain boundaries of STN, Fe2O3 nanoparticles, and lattice imperfections gives rise to the glass-like temperature-independent phonon mean-free-path, especially above Debye temperature. The maximum ZT ∼ 0.57 has been obtained at 947 K for the 1 wt % FGR sample, which is around 420% higher than that of pristine STN. Furthermore, we have fabricated a prototype of a four-legged n-type TE module, demonstrating one of the highest power outputs of 18 mW among reported oxide thermoelectrics.

Designing rare earth-free high entropy oxides with a tungsten bronze structure for thermoelectric applications.

In recent years, forming high entropy oxides has emerged as one of the promising approaches to designing oxide thermoelectrics. Entropy engineering is an excellent strategy to improve thermoelectric performance by minimizing the thermal conductivity arising from enhanced multi-phonon scattering. In the present work, we have successfully synthesized a rare-earth-free single phase solid solution of novel high entropy niobate (Sr0.2Ba0.2Li0.2K0.2Na0.2)Nb2O6, with a tungsten bronze structure. This is the first report on the thermoelectric properties of high entropy tungsten bronze-type structures. We have obtained a maximum Seebeck coefficient of -370 µV K-1 at 1150 K, which is the highest among tungsten bronze-type oxide thermoelectrics. The minimum thermal conductivity of 0.8 W m-1 K-1 is obtained at 330 K, which is so far the lowest reported value among rare-earth-free high entropy oxide thermoelectrics. This synergistic combination of large Seebeck and record low thermal conductivity gives rise to a maximum ZT of 0.23 which is so far the highest among rare-earth free high entropy oxide-based thermoelectrics.

Enhanced Thermoelectric Performance of Rare-Earth-Free n-Type Oxide Perovskite Composite with Graphene Analogous 2D MXene.

Here, the first experimental demonstration on the effect of incorporating new generation 2D material, MXene, on the thermoelectric performance of rare-earth-free oxide perovskite is reported. The charge localization phenomenon is predominant in the electron transport of doped SrTiO3 perovskites, which deters from achieving a higher thermoelectric power factor in these oxides. In this work, it is shown that incorporating Ti3 C2 Tx MXene in a matrix of SrTi0.85 Nb0.15 O3 (STN) facilitates the delocalization of electrons resulting in better than single-crystal-like electron mobility in polycrystalline composites. A 1851% increase in electrical conductivity and a 1000% enhancement in power factor are attained. Besides, anharmonicity caused by MXene in the STN matrix has led to enhanced Umklapp scattering giving rise to lower lattice thermal conductivity. Hence, 700% ZT enhancement is achieved in this composite. Further, a prototype of thermoelectric generator (TEG) using only n-type STN + MXene is fabricated and a power output of 38 mW is obtained, which is higher than the reported values for oxide TEG.

Two-Stage Resection of a Giant Trigeminal Schwannoma in a Non-Neurofibromatosis Type 2 Pediatric Patient: A Case Report, Systematic Review, and Intraoperative Video.

BACKGROUND: Trigeminal schwannoma is an uncommon tumor in pediatric patients. Several surgical approaches have been described in the literature. METHODS: The case of an 11-year-old boy with a giant dumbbell-shaped trigeminal schwannoma removed through a 2-stage approach was presented with an intraoperative video. Using PubMed and Scopus, the literature on trigeminal schwannoma in pediatric patients was searched according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. RESULTS: The search strategy yielded 312 titles, of which 13 were included in the review. Cases of trigeminal schwannoma were described, with a highly variable clinical presentation and anatomical arrangement in cranial fossae. Two-stage approaches were reported, although most studies described single-stage approaches. Common postoperative outcomes were a range of disturbances of cranial nerve V. CONCLUSIONS: The surgical approach varies based on the tumor conformation. However, a 2-stage pterional subtemporal and semisitting retrosigmoid approach is a safe, practical, and effective strategy for the removal of dumbbell-shaped trigeminal schwannoma in a pediatric patient.

Low Lattice Thermal Conductivity in a Wider Temperature Range for Biphasic-Quaternary (Ti,V)CoSb Half-Heusler Alloys.

Intrinsically high lattice thermal conductivity has remained a major bottleneck for achieving a high thermoelectric figure of merit (zT) in state-of-the-art ternary half-Heusler (HH) alloys. In this work, we report a stable n-type biphasic-quaternary (Ti,V)CoSb HH alloy with a low lattice thermal conductivity κL ≈ 2 W m-1 K-1 within a wide temperature range (300-873 K), which is comparable to the reported nanostructured HH alloys. A solid-state transformation driven by spinodal decomposition upon annealing is observed in Ti0.5V0.5CoSb HH alloy, which remarkably enhances phonon scattering, while electrical properties correlate well with the altering electronic band structure and valence electron count (VEC). A maximum zT ≈ 0.4 (±0.05) at 873 K was attained by substantial lowering of κL and synergistic enhancement of the power factor. We perform first-principles density functional theory calculations to investigate the structure, stability, electronic structure, and transport properties of the synthesized alloy, which rationalize the reduction in the lattice thermal conductivity to the increase in anharmonicity due to the alloying. This study upholds the new possibilities of finding biphasic-quaternary HH compositions with intrinsically reduced κL for prospective thermoelectric applications.

Enhanced Thermoelectric Performance in Oxide Composites of La and Nb Codoped SrTiO3 by Using Graphite as the Electron Mobility Booster.

Inherent insulating nature of oxides makes it challenging for use in thermoelectric applications that warrant reasonable electrical conductivity. In the present work, we have used graphite (G) to improve the electron transport in La0.07Sr0.93Ti0.93Nb0.07O3 (LSTN) by making composites. Graphite acts as the electron momentum booster in the LSTN matrix, which otherwise suffers from Anderson localization of electrons, causing an order of magnitude increase in weighted mobility and electrical conductivity. As a result, the thermoelectric power factor increases more than 6 times due to graphite incorporation in LSTN. Furthermore, the lattice thermal conductivity is suppressed due to enhanced Umklapp scattering, as derived from the Debye-Callaway model. Hence, we have recorded ∼423% increment in the figure of merit (ZT) in LSTN + G composites. The maximum ZT obtained is 0.68 at 980 K for the LSTN with 1 wt % graphite composite. Furthermore, we have fabricated a four-legged n-type thermoelectric power generator demonstrating a milliwatt level power output, which hitherto remained unattainable for oxide thermoelectrics.

Temperature-dependent excitonic emission characteristics of lead-free inorganic double perovskites and their third-order optical nonlinearities.

We report temperature-dependent photoluminescence (PL) in the temperature range between 77 K and 300 K, and room temperature nonlinear optical (NLO) properties of solution processed lead-free Cs2NaBiI6 (CNBI) and Cs2KBiI6 (CKBI) perovskite films. The de-convolution analysis of temperature-dependent PL spectra showed thermal quenching behavior of free-exciton (FX) emission, an unusual blue-shift of PL emission, and line broadening with increasing temperature as a consequence of strong exciton-phonon interaction. The nonlinear refractive index (n2) and nonlinear absorption coefficient (ß) of both the CNBI and CKBI films are determined using a closed aperture (CA) and open aperture (OA) Z-scan technique, respectively. Both the CNBI and CKBI perovskites exhibited features of saturable absorption (SA) with ß âˆ¼ -6.23 × 10-12 cm W-1, and -1.14× 10-12 cm W-1, respectively. The CA measurements depicted a self-defocusing effect in both the samples with n2 values ∼-1.06 × 10-14 cm2 W-1 and -1.337× 10-14 cm2 W-1, respectively. With such emission and NLO characteristics, CNBI and CKBI perovskite films can be used for designing eco-friendly optoelectronic and NLO devices.

The analysis of charge transport mechanism in mixed ionic electronic conductor composite of Sr2TiCoO6double perovskite with yttria stabilized zirconia.

In this investigation, the ionic conduction mechanism in mixed ionic electronic conductors composites of Sr2TiCoO6/YSZ has been studied with the help of universal dynamic response. 3 mol% and 8 mol% yttria stabilized ZrO2have been mixed with Sr2TiCoO6(STC) double perovskite in 1:1 ratio to prepare STC/3YSZ and STC/8YSZ composites via solid-state reaction route. AC Impedance spectroscopy has been carried out to examine the charge transport mechanism, which has been modeled using the microstructural networks of resistors and capacitors. Grain boundaries are more resistive and capacitive compared to the bulk. Modulus spectroscopy analysis demonstrates the non-Debye character of conductivity relaxation with frequency. Complex frequency-dependent AC conductivity is found to obey Almond West power law and reveals that ion migration occurs through the correlated hopping mechanism. Further, the DC conductivity and relaxation time have been found to follow the Barton Nakajima and Namikawa relation, which is correlated with AC to DC conduction. The time-temperature superposition principle has been used to explain the conductivity scaling in the intermediate frequency range. At low temperatures, the ions are localized in the asymmetric potential well, while at high temperatures, hopping behavior starts dominating. Further Kramers-Kronig transformation connects the dielectric strength with conductivity relaxation and verifies the impedance data.

Use of Temporary Rod and Intraoperative Neuroimaging for Correction of Adolescent Idiopathic Scoliosis: 2-Dimensional Operative Video.

Adolescent idiopathic scoliosis (AIS) is an abnormal lateral curvature of the spine that arises during the pubescent growth spurt. AIS mainly affects females in the age group of 10 to 16 yr, with a prevalence of about 1% to 3% in the at-risk population.1 Treatment options vary depending on disease presentation and severity. Mild curvature mainly requires periodic observation for disease progression, whereas more moderate curvature can necessitate bracing or corrective surgery.2 Here, we present the use of a temporary rod and neuroimaging for the correction of Lenke type 1 spinal curvature in an AIS patient. An inferior facetectomy is performed, and a Lenke probe is used for entry into the pedicle and vertebral body. The channel is sounded before and after tapping to check for adequate walls prior to insertion of the pedicle screw. The ARTIS pheno is brought into the field, which uses fluoroscopy to create a 3-dimensional (3D) representation of the instrumentation within the spine. A temporary rod is placed in the concavity, and a combination of corrective techniques, including a rod roll, apical translation, and reduction, is performed to bring up the concavity, derotate the spine, and translate the spine. The permanent rod is then placed in the convexity, and compression is performed to bring down the scapular prominence. The temporary rod is then removed, and a final rod is placed to complete the 3D correction. The patient consented to the procedure, and an informed written consent was obtained from the patient to use her photographs and video recordings for publication.

Endoscopic-assisted resection of vestibular schwannomas in high-riding jugular bulb.

The present surgical video demonstrates safe opening of the internal auditory canal (IAC) during vestibular schwannoma surgery via a retrosigmoid approach in the sitting position. Resection of the intrameatal portion of a tumor is important for progression-free survival. Preoperative thin-sliced CT revealed a high-riding jugular bulb obscuring the trajectory. After dural opening, the IAC was approached anteriorly and superiorly. The posterior margin of IAC drilling was above the Tubingen line. Drilling was performed under continuous jugular compression. The vein was pushed down to augment visibility. An angled endoscope was helpful. IAC can be drilled safely in a high-riding jugular bulb with the technique mentioned in the video. The video can be found here: https://stream.cadmore.media/r10.3171/2021.7.FOCVID2198.

Foramen magnum meningiomas.

The foramen magnum meningioma (FMM) is one of most challenging tumors among all the meningiomas because of its distinctive location, clinical course, insidious onset, and the relative large size of the tumor during presentation. These tumors are slow-growing and clinical symptoms vary according to involvement of different structures including the spinal cord, vertebral artery, lower cranial nerves, and medulla oblongata. Controversies regarding appropriate surgical approach for resection of tumor in this unique location continue. Tumors in the posterior or posterolateral region of the foramen magnum is accessible by midline suboccipital approach. The anterior and anterolateral tumors are encountered by various modifications of the far lateral approach. Drilling of condylar fossa is adequate in most of the cases as tumors often create a surgical corridor. However, an anterior tumor with significant extension on both sides of midline may require variable amounts of condyle resection. Here we review the FMMs with an emphasis on surgical approaches.

Surgical Outcomes with Midline versus Lateral Approaches for Cranial Base Chordomas: A Systematic Review and Meta-Analysis.

BACKGROUND: Cranial base chordomas are complex lesions centered on the clivus that surgically can be approached from either a midline or a lateral corridor. OBJECTIVE: To compare the surgical outcomes from midline versus lateral approaches by conducting a meta-analysis of the literature. METHODS: Studies were identified between 2000 and 2018. The primary outcome was gross total resection (GTR) rate. The secondary outcomes were recurrence rate and rates of cerebrospinal fluid (CSF) leak and new cranial nerve palsy. Odds ratios were calculated with a random-effect model using studies describing both approaches. An indirect (proportion) meta-analysis was performed pooling studies describing either of the approaches. Individual patient data were analyzed for differences in GTR or recurrence rate with different tumor extensions. RESULTS: Thirty-three studies were found suitable for indirect meta-analysis and 10 studies for direct meta-analysis. The overall odds of GTR with a midline approach compared with a lateral approach was 0.83 (95% confidence interval [CI], -0.43 to 1.62). The odds ratios for recurrence, CSF leak, and new cranial nerve palsy were 0.82 (95% CI, 0.26-2.56), 1.49 (95% CI, 0.14-15.5), and 0.14 (95% CI, 0.04-0.56), respectively. With individual patient data analysis, no statistically significant difference was observed in GTR or recurrence rates between the 2 approaches with different tumor extensions. CONCLUSIONS: The meta-analysis did not show any significant difference in GTR or recurrence rates between the midline versus lateral approaches. Tumor extension to different compartments did not affect the GTR or recurrence rates with either approach. In terms of complications, CSF leak rate was higher in midline approaches and cranial nerve palsy was higher in lateral approaches.

Metal Hypersensitivity After Spinal Instrumentation: When to Suspect and How to Treat.

BACKGROUND: Metal hypersensitivity is a rare complication after spinal implant placement but is related to significant clinical challenges including implant failure and poor wound healing. The incidence is likely underreported secondary to challenges with diagnosis and retreatment options. CASE DESCRIPTION: We present the case of a 41-year-old woman with metal hypersensitivity 6 years status post anterior lumbar interbody fusion after a previously failed revision procedure who presented with low back pain and abdominal pain with food intolerance. Diagnostics revealed presacral fluid collection, which was negative for infection. A detailed workup ruled out other possible differential diagnoses and confirmed hypersensitivity to nickel. Intraoperatively, the interbody was loose but difficult to remove secondary to scar tissue. Ultimately, it was successfully replaced with a polyetheretherketone interbody, which did not contain nickel. CONCLUSIONS: Metal hypersensitivity is likely an underreported complication in spine literature that is associated with poor outcomes. Further research to create evidence-based guidelines on diagnosis and retreatment options will facilitate diagnosis, reduce time to revision surgery, and ultimately decrease patient suffering.

Effect of B-site cation ordering on high temperature thermoelectric behavior of Ba x Sr2-x TiFeO6 double perovskites.

Here, we have reported the detailed structural analysis in correlation with thermoelectric properties of Ba doped Sr2TiFeO6 (BSTF) double perovskites in the temperature range from 300 K to 1100 K. BSTF compositions exhibit single phase cubic structure with [Formula: see text] crystal symmetry from room temperature to 523 K and also at temperature beyond 923K. Rietveld refinement of high temperature XRD data suggests the coexistence of two cubic phases with [Formula: see text] space group having same composition in the intermediate temperature region. Correlation of the phase-fraction with electrical conductivity data posits the possibility of high temperature cubic phase being conductive compared to the insulator-like cubic phase observed at room temperature. The experimental analysis alone seems insufficient to explain the conductivity behavior demonstrating semiconductor [Formula: see text] to metal like [Formula: see text] transition. Hence DFT framework has been adopted for computational analysis coupled with the Boltzmann transport equations to understand their thermoelectric properties based on the electronic restructuring occurred due to octahedral arrangements in these double perovskites. It has been shown that clustering of FeO6 octahedra may lead to the formation of a conduction path in the cubic phase of BSTF, which induces metallic behavior in these double perovskites.

Use of Pheno Room, Augmented Reality, and 3-Rod Technique for 3-Dimensional Correction of Adolescent Idiopathic Scoliosis.

This is a surgical video that showcases the surgical repair of a young male patient with idiopathic scoliosis in a hybrid operating room with the utilization of a new imaging modality Advanced Radar Target Identification System (ARTIS) PHENO (Siemens Medical Solutions, Pennsylvania, USA) and augmented reality (Video 1). A 17-year-old male patient with idiopathic scoliosis underwent scoliosis repair in a hybrid operating room with segment reality surgical planning. The use of augmented reality helped in visualization of proper screw trajectory, and the use of ARTIS PHENO helped in identification of correct screw placement and rod fixation. Intraoperative use of new imaging modalities as augmented reality imaging and ARTIS PHENO can decrease surgical complication and time.

Surgical correction of proximal junctional kyphosis.

This 3D video showcases the surgical techniques for patients with proximal junctional kyphosis. The surgical repair for patients with proximal junctional kyphosis is an individualized approach depending on patient history and imaging with adequate surgical measurements. This video will shed light on two cases with proximal junctional kyphosis and the method taken for their repair. The first case is of an 11-year-old female known to have osteogenesis imperfecta and status post T5-L3 posterior spinal fusion with segmental instrumentation. The patient underwent change of older instruments and scoliosis repair, with full correction on postoperative x-ray. The second patient is a 16-year-old male known to have cerebral palsy and kyphoscoliosis status post spinal fusion. The patient underwent scoliosis repair surgery with replacement of old instrumentation and scoliosis correction. The video can be found here: https://youtu.be/f5iLwqbU26Q.