Jugular foramen stenosis in external hydrocephalus in infants

OBJECTIVE

To measure the size of jugular foramina in infants affected by external hydrocephalus (EH) and in a control group, to support the hypothesis that a jugular foramen (JF) stenosis may determine dural venous sinus alterations and increased venous outflow resistance as main pathophysiological factor.

METHODS

Minimum, maximum, and mean values of JF areas were measured in a series of phase-contrast magnetic resonance venous angiography (angio MRV PCA3D) performed on 81 infants affected by EH. Results were compared with a group of 54 controls.

RESULTS

Smaller JF area was significantly smaller in patients versus controls (43.1 ± 14.6 vs. 52.7 ± 17.8; p < 0.001) resulting in a significantly smaller mean JF areas in patients vs. controls (51.6 ± 15.8 vs. 57.0 ± 18.3; p = 0.043). In patients, smaller JF areas were significantly associated with higher venous obstruction grading score (VOGS) both on the right (p = 0.018) and on the left side (p = 0.005). Positional plagiocephaly (cranial vault asymmetry index > 3.5%) was more frequent among EH patients than controls (38/17) but the difference was not significant (p = 0.07). In the 38 plagiocephalic patients, JF area was smaller on the flattened side than the contralateral in a significant number of cases both in right (21/7) and left (9/1) plagiocephaly (p < 0.0005) as well as the mean area (48.2 + 16.4 mm2 vs. 57.5 + 20.7 mm2, p = 0.002) and VOGS was significantly higher on the plagiocephalic side than on the contralateral side (1.6 ± 1.1 vs. 1.1 ± 0.9, p = 0.019).

CONCLUSION

In this series of infants affected by EH, the mean size of the ostium of both JF resulted significantly smaller than controls. JF stenosis was significantly associated with higher degrees of venous obstruction on both sides, suggesting a direct extrinsic effect of JF size on dural sinus lumen and possible consequent effect on venous outflow resistance. Positional plagiocephaly, when present, was associated with a decreased JF area and increased VOGS on the flattened side.

Endoscopic ultrasonic aspirator-assisted removal of a third ventricular colloid cyst

BACKGROUND

Colloid cysts are benign tumors usually located on the roof of the third ventricle. Cyst removal is the treatment of choice. It can be accomplished microsurgically through a transcortical- or transcallosal approach, or endoscopically. There is a lack of consensus regarding the best strategy for cyst removal. One of the challenges of the traditional endoscopic technique is dealing with the cyst content density. Hyperdensity on computed tomography scan and low signal on T2-weighted magnetic resonance imaging (MRI) cyst are correlated with high viscosity cystic content.

CASE REPORTS

We present a case of a colloid cyst of the third ventricle in a 15-year-old boy removed through a pure endoscopic transventricular approach. The cyst presented a low signal on T2 MRI; nevertheless, it was easily removed with the help of an endoscopic ultrasonic aspirator.

DISCUSSION AND CONCLUSION

The colloid cyst of the third ventricle can be safely treated by a purely endoscopic approach. The rationale of the use of the ultrasonic aspirator relies on the facilitation of aspiration of the content even when the consistency is extremely firm.

Comprehensive study of Raman optical response of typical substrates for thin-film growth under 633 nm and 785 nm laser excitation

Raman spectroscopy is one of the most efficient and non-destructive techniques for characterizing materials. However, it is challenging to analyze thin films using Raman spectroscopy since the substrates beneath the thin film often obscure its optical response. Here, we evaluate the suitability of fourteen commonly employed single-crystal substrates for Raman spectroscopy of thin films using 633 nm and 785 nm laser excitation systems. We determine the optimal wavenumber ranges for thin-film characterization by identifying the most prominent Raman peaks and their relative intensities for each substrate and across substrates. In addition, we compare the intensity of background signals across substrates, which is essential for establishing their applicability for Raman detection in thin films. The substrates LaAlO3 and Al2O3 have the largest free spectral range for both laser systems, while Al2O3 has the lowest background levels, according to our findings. In contrast, the substrates SrTiO3 and Nb:SrTiO3 have the narrowest free spectral range, while GdScO3, NGO and MgO have the highest background levels, making them unsuitable for optical investigations.

Fully Optical in Operando Investigation of Ambient Condition Electrical Switching in MoS2 Nanodevices

MoS₂ nanoswitches have shown superb ultralow switching energies without excessive leakage currents. However, the debate about the origin and volatility of electrical switching is unresolved due to the lack of adequate nanoimaging of devices in operando. Here, three optical techniques are combined to perform the first noninvasive in situ characterization of nanosized MoS₂ devices. This study reveals volatile threshold resistive switching due to the intercalation of metallic atoms from electrodes directly between Mo and S atoms, without the assistance of sulfur vacancies. A "semi-memristive" effect driven by an organic adlayer adjacent to MoS₂ is observed, which suggests that nonvolatility can be achieved by careful interface engineering. These findings provide a crucial understanding of nanoprocess in vertically biased MoS₂ nanosheets, which opens new routes to conscious engineering and optimization of 2D electronics.

Endoscopic aqueductoplasty and stenting in the treatment of isolated fourth ventricle in children: 20-year institutional experience

BACKGROUND

Endoscopic aqueductoplasty with aqueductal stenting is an effective surgical procedure for the treatment of isolated fourth ventricle (IFV). Due to the rarity of the underlying pathology, it can be considered a rare procedure that can be performed with different surgical techniques and approaches.

OBJECTIVES

To assess long-term functioning of permanent aqueductal stents implanted in children affected by hydrocephalus and IFV and to describe some variations of the same procedure.

METHODS

We reviewed retrospectively all the patients presenting at our institution in the years 1999-2019 for symptoms of isolated fourth ventricle who underwent a surgical procedure of endoscopic aqueductoplasty and/or aqueductal stent. Surgical reports, radiological images, and surgical videos were retrospectively analyzed.

RESULTS

Thirty-three patients with symptomatic isolated fourth ventricle (IFV) underwent fifty (50) neuroendoscopic procedures in the period observed. The median age of the patients at the time of first surgery was 7 months, with 22 premature babies. In twenty-nine patients (87.8%), a precoronal approach was performed, while four patients received a suboccipital burr hole. Ten patients were never reoperated since. Twenty-three patients underwent further surgeries: a new aqueductoplasty with aqueductal stent was performed in 13 cases. The remaining 10 patients required a combination of other procedures for management of hydrocephalus. Long-term follow-up showed a permanent stent functioning rate of 87% at 2 years and 73% at 4 years, remaining stable afterwards at very long term (20 years).

CONCLUSION

Endoscopic aqueductoplasty and stenting is a reliable procedure in the long-term management of isolated fourth ventricle.

Optical probes of molecules as nano-mechanical switches

Molecular electronics promises a new generation of ultralow-energy information technologies, based around functional molecular junctions. Here, we report optical probing that exploits a gold nanoparticle in a plasmonic nanocavity geometry used as one terminal of a well-defined molecular junction, deposited as a self-assembled molecular monolayer on flat gold. A conductive transparent cantilever electrically contacts individual nanoparticles while maintaining optical access to the molecular junction. Optical readout of molecular structure in the junction reveals ultralow-energy switching of ∼50 zJ, from a nano-electromechanical torsion spring at the single molecule level. Real-time Raman measurements show these electronic device characteristics are directly affected by this molecular torsion, which can be explained using a simple circuit model based on junction capacitances, confirmed by density functional theory calculations. This nanomechanical degree of freedom is normally invisible and ignored in electrical transport measurements but is vital to the design and exploitation of molecules as quantum-coherent electronic nanodevices.

The development of molecular electronics at single molecule level calls for new tools beyond electrical characterisation. Kos et al. show an optical probe of molecular junctions in a plasmonic nanocavity geometry, which supports in situ interrogation of molecular configurations.

Subtemporal Transtentorial Approach in Mesencephalic and Perimesencephalic Lesions in Children-A Series of 20 Patients

BACKGROUND

Midbrain and surrounding areas are among the most difficult regions to surgically approach in neurosurgery. The subtemporal approach is a well-known neurosurgical approach that is rarely described in children.

OBJECTIVE

To assess the feasibility, advantages, and disadvantages of subtemporal approach in children.

METHODS

A total of 20 pediatric patients with intra-axial tumors involving the lateral midbrain or superior cerebellar peduncle or with extra-axial tumors in the middle incisural space/Meckel cave underwent subtemporal transtentorial approaches with the aim to remove (16 cases) or biopsy (4 cases) their lesions. These cases were retrospectively reviewed and the surgical approach described.

RESULTS

Total resection was achieved in 11 patients. In the 4 patients who underwent biopsies, a diagnosis was obtained. A total of 5 patients presented non-neoplastic lesions (dermoid tumors or cavernomas). A total of 9 patients harbored low-grade tumors and 6 high-grade tumors. Patients with low-grade tumors and non-neoplastic lesions are all alive with no evidence of disease or stable residue. Four patients affected by high grade tumors died. No patient suffered permanent neurological deficits related to the surgical approach. Three patients presented temporary neurological deficits following the procedure: one case of strabismus, one case of aphasia and hemiparesis, secondary to delayed, transient thrombosis of the Labbé vein, and 1 case of trigeminal neuralgia.

CONCLUSION

The subtemporal approach represents a feasible approach for mesencephalic and perimesencephalic lesions in children. It provides an ample and direct access, with excellent outcomes and acceptable postoperative morbidity.

Electrically Controlled Nano and Micro Actuation in Memristive Switching Devices with On-Chip Gas Encapsulation

Nanoactuators are a key component for developing nanomachinery. Here, an electrically driven device yielding actuation stresses exceeding 1 MPa withintegrated optical readout is demonstrated. 10 nm thick Al₂ O₃ electrolyte films are sandwiched between graphene and Au electrodes. These allow reversible room-temperature solid-state redox reactions, producing Al metal and O₂ gas in a memristive-type switching device. The resulting high-pressure oxygen micro-fuel reservoirs are encapsulated under the graphene, swelling to heights of up to 1 µm, which can be dynamically tracked by plasmonic rulers. Unlike standard memristors where the memristive redox reaction occurs in single or few conductive filaments, the mechanical deformation forces the creation of new filaments over the whole area of the inflated film. The resulting on-off resistance ratios reach 10⁸ in some cycles. The synchronization of nanoactuation and memristive switching in these devices is compatible with large-scale fabrication and has potential for precise and electrically monitored actuation technology.

Initial experience with endoscopic ultrasonic aspirator in purely neuroendoscopic removal of intraventricular tumors

OBJECTIVE Neuroendoscopic removal of intraventricular tumors is difficult and time consuming because of the lack of an effective decompression system that can be used through the working channel of the endoscope. The authors report on the utilization of an endoscopic ultrasonic aspirator in the resection of intraventricular tumors. METHODS Twelve pediatric patients (10 male, 2 female), ages 1-15 years old, underwent surgery via a purely endoscopic approach using a Gaab rigid endoscope and endoscopic ultrasonic aspirator. Two patients presented with intraventricular metastases from high-grade tumors (medulloblastoma, atypical teratoid rhabdoid tumor), 2 with subependymal giant cell astrocytomas (associated with tuberous sclerosis), 2 with low-grade intraparaventricular tumors, 4 with suprasellar tumors (2 craniopharyngiomas and 2 optic pathway gliomas), and 2 with pineal tumors (1 immature teratoma, 1 pineal anlage tumor). Hydrocephalus was present in 5 cases. In all patients, the endoscopic trajectory and ventricular access were guided by electromagnetic neuronavigation. Nine patients underwent surgery via a precoronal bur hole while supine. In 2 cases, surgery was performed through a frontal bur hole at the level of the hairline. One patient underwent surgery via a posterior parietal approach to the trigone while in a lateral position. The endoscopic technique consisted of visualization of the tumor, ventricular washing to dilate the ventricles and to control bleeding, obtaining a tumor specimen with biopsy forceps, and ultrasonic aspiration of the tumor. Bleeding was controlled with irrigation, monopolar coagulation, and a thulium laser. RESULTS In 7 cases, the resection was total or near total (more than 90% of lesion removed). In 5 cases, the resection was partial. Histological evaluation of the collected material (withdrawn using biopsy forceps and aspirated with an ultrasonic aspirator) was diagnostic in all cases. The duration of surgery ranged from 30 to 120 minutes. One case was complicated by subdural hygroma requiring a subduro-peritoneal shunt implant. CONCLUSIONS In this preliminary series, endoscopic ultrasonic aspiration proved to be a safe and reliable method for achieving extensive decompression or complete removal in the management of intra- and/or paraventricular lesions in pediatric patients.

Nanoscale Plasmon-Enhanced Spectroscopy in Memristive Switches

Resistive switching memories are nonvolatile memory cells based on nano-ionic redox processes and offer prospects for high scalability, ultrafast write and read access, and low power consumption. In two-terminal cation based devices a nanoscale filament is formed in a switching material by metal ion migration from the anode to the cathode. However, the filament growth and dissolution mechanisms and the dynamics involved are still open questions, restricting device optimization. Here, a spectroscopic technique to optically characterize in situ the resistive switching effect is presented. Resistive switches arranged in a nanoparticle-on-mirror geometry are developed, exploiting the high sensitivity to morphological changes occurring in the tightly confined plasmonic hotspot within the switching material. The focus is on electrochemical metallization and the optical signatures detected over many cycles indicate incomplete removal of metal particles from the filament upon RESET and suggest that the filament can nucleate from different positions from cycle to cycle. The technique here is nondestructive and the measurements can be easily performed in tunable ambient conditions and with realistic cell geometries.

Posterior fossa tumors in infants and neonates

INTRODUCTION

Management of posterior fossa tumors in infants and neonates is challenging. The characteristics of the young babies make surgery very difficult, sometimes precluding a safe complete removal.

METHODS

A review of the literature was undertaken to examine the incidence, histology, surgical aspects, and prognosis of posterior fossa tumors in the first year of life. Therapeutical strategies of the most frequent tumor types are also discussed in detail.

RESULTS

Histology is dominated by tumors with aggressive behavior, such as medulloblastomas, atypical teratoid/rhabdoid tumors, and anaplastic ependymomas. The most important surgical considerations in small children are the small circulating blood volume; the poor thermoregulation; and incomplete maturation of the brain, of the skull, and of the soft tissue. Treatment toxicity is inversely related to the age of the patients. Radiation therapy is usually considered as contraindicated in young children, with few exceptions. Proton therapy is a promising tool, but access to this kind of treatment is still limited. The therapeutic limitations of irradiation render resection of this tumor and adjuvant chemotherapy often the only therapeutic strategy in many cases.

CONCLUSIONS

The overall prognosis remains dismal because of the prevalent aggressive histologies, the surgical challenges, and the limitations of adjuvant treatment. Nevertheless, the impressive improvements in anesthesiology and surgical techniques allow, in the vast majority of the cases, complete removal of the lesions with minor sequelae in high-volume referral pediatric centers.

Directional fluorescence emission by individual V-antennas explained by mode expansion

Specially designed plasmonic antennas can, by far-field interference of different antenna elements or a combination of multipolar antenna modes, scatter light unidirectionally, allowing for directional light control at the nanoscale. One of the most basic and compact geometries for such antennas is a nanorod with broken rotational symmetry, in the shape of the letter V. In this article, we show that these V-antennas unidirectionally scatter the emission of a local dipole source in a direction opposite the undirectional side scattering of a plane wave. Moreover, we observe high directivity, up to 6 dB, only for certain well-defined positions of the emitter relative to the antenna. By employing a rigorous eigenmode expansion analysis of the V-antenna, we fully elucidate the fundamental origin of its directional behavior. All findings are experimentally verified by measuring the radiation patterns of a scattered plane wave and the emission pattern of fluorescently doped PMMA positioned in different regions around the antenna. The fundamental interference effects revealed in the eigenmode expansion can serve as guidelines in the understanding and further development of nanoscale directional scatterers.

Unidirectional side scattering of light by a single-element nanoantenna

Unidirectional side scattering of light by a single-element plasmonic nanoantenna is demonstrated using full-field simulations and back focal plane measurements. We show that the phase and amplitude matching that occurs at the Fano interference between two localized surface plasmon modes in a V-shaped nanoparticle lies at the origin of this effect. A detailed analysis of the V-antenna modeled as a system of two coherent point-dipole sources elucidates the mechanisms that give rise to a tunable experimental directivity as large as 15 dB. The understanding of Fano-based directional scattering opens a way to develop new directional optical antennas for subwavelength color routing and self-referenced directional sensing. In addition, the directionality of these nanoantennas can increase the detection efficiency of fluorescence and surface enhanced Raman scattering.

Quantum statistics of surface plasmon polaritons in metallic stripe waveguides

Heralded single surface plasmon polaritons are excited using photons generated via spontaneous parametric down conversion. The mean excitation rates, intensity correlations, and Fock state populations are studied. The observed dependence of the second-order coherence in our experiment is consistent with a linear uncorrelated Markovian environment in the quantum regime. Our results provide important information about the effect of loss for assessing the potential of plasmonic waveguides for future nanophotonic circuitry in the quantum regime.

Plasmonic-photonic arrays with aperiodic spiral order for ultra-thin film solar cells

We report on the design, fabrication and measurement of ultra-thin film Silicon On Insulator (SOI) Schottky photo-detector cells with nanostructured plasmonic arrays, demonstrating broadband enhanced photocurrent generation using aperiodic golden angle spiral geometry. Both golden angle spiral and periodic arrays of various center-to-center particle spacing were investigated to optimize the photocurrent enhancement. The primary photocurrent enhancement region is designed for the spectral range 600nm-950nm, where photon absorption in Si is inherently poor. We demonstrate that cells coupled to spiral arrays exhibit higher photocurrent enhancement compared to optimized periodic gratings structures. The findings are supported through coupled-dipole numerical simulations of radiation diagrams and finite difference time domain simulations of enhanced absorption in Si thin-films.

Directional excitation of surface plasmon polaritons via nanoslits under varied incidence observed using leakage radiation microscopy

Surface Plasmon Polaritons (SPPs) are excited at the interface between a thin gold film and air via the illumination of nanoslits etched into the film. The coupling efficiency to the two propagation directions away from the slits is determined by leakage radiation microscopy, when the angle of incidence of the pump beam is changed from 0° to 20°. We find that preferential coupling of SPPs into one direction can be achieved for non-normal incidence in the case of single slits and slit pairs. The proportion of SPP excited into one direction can be in excess of 90%. We further provide a simple model of the process, and directly compare the performances of the two approaches.

Meningiomas of the transverse--sigmoid sinus junction area

Meningiomas with exclusive or prevalent dural attachment over the transverse-sigmoid sinus junction area represent a well-defined subgroup of posterior fossa meningiomas. This study reports 13 cases of this localisation (10.8% of all infratentorial meningiomas). In this series, six patients (46%) were discovered as an incidental MR finding. One patient with a small (1.5 cm) meningioma presented with an intracranial hypertension syndrome due to severe obstruction of the unique transverse-sigmoid sinus junction. A MR angiography was performed in 11 patients; it showed intraluminal tumour in two cases with dominant and unique transverse sinus, respectively. Tumour removal with excision of the outer dural layer and coagulation of the dural attachment (Simpson II) was performed in 11 cases; in two others with focal sinus invasion, removal of the small intravenous tumour fragment was not performed (Simpson III). No post-operative complications occurred. Remission of pre-operative symptoms was obtained in all symptomatic cases. The management of the transverse-sigmoid sinus junction is the main problem of meningiomas of this region. Excision of the outer dural layer and coagulation of the dural attachment are in our opinion sufficient in most cases, even when there is tumour invasion of the patent venous lumen. The resection of the sinus wall should be reserved to cases with a totally obstructed segment and symmetrical or asymmetrical but present transverse and sigmoid sinuses.

Dexamethasone in hyperdynamic sepsis in children

Background

A recent study analysed the usefulness of dexamethasone (DX) in hyperdynamic sepsis in children. This prospective study was performed in order to confirm or refute the conclusions obtained previously.

Methods

A prospective, randomized and sequential study was performed in 38 patients of both sexes with a mean age of 10 years. Patients had at least five of the following clinical features to be included in the study: hyperthermia, oliguria, tachycardia, tachypnoea, cyanosis or another sign of hypoxaemia, impaired consciousness (confusion, meningeal signs, psychomotor excitation, delirium) and digestive disturbance (haemorrhage, vomiting, diarrhoea). Criteria for exclusion were: previous organ failure (adrenal or renal insufficiency), diabetes, tuberculosis, systemic mycosis, corticosteroid sensibility and immunodeficiency. Patients were divided into two equal groups: placebo control and DX, the latter with forward contribution to the dose of 3 mg kg−1 each time, repeated at 12 and 24 h. In all cases, clinic and laboratory variables used commonly in intensive care were monitored. The evaluations were immediately before, and at 48 and 72 h after, the first dose of DX.

Results

There was no significant difference between the two groups.

Conclusion

The application of macrodoses of DX in hyperdynamic sepsis in children is not indicated.