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.

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.

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.

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.

Dural venous sinus anatomy in children with external hydrocephalus: analysis of a series of 97 patients.

PURPOSE: To evaluate the anatomical variations of dural venous sinuses in children with external hydrocephalus, proposing a radiological grading of progressive anatomic restriction to venous outflow based on brain phase-contrast magnetic resonance venography (PC-MRV); to evaluate the correlation between positional plagiocephaly and dural sinuses patency; and to compare these findings with a control group to ascertain the role of anatomical restriction to venous outflow in the pathophysiology of external hydrocephalus. METHODS: Brain MRI and PC MRV were performed in 97 children (76 males, 21 females) diagnosed with external hydrocephalus at an average age of 8.22 months. Reduction of patency of the dural sinuses was graded as 1 (stenosis), 2 (complete stop) and 3 (complete agenesis) for each transverse/sigmoid sinus and sagittal sinus. Anatomical restriction was graded for each patient from 0 (symmetric anatomy of patent dural sinuses) through 6 (bilateral agenesis of both transverse sinuses). Ventricular and subarachnoid spaces were measured above the intercommissural plane using segmentation software. Positional plagiocephaly (PP) and/or asymmetric tentorial insertion (ATI) was correlated with the presence and grading of venous sinus obstruction. These results were compared with a retrospective control group of 75 patients (35 males, 40 females). RESULTS: Both the rate (84.53% vs 25.33%) and the grading (mean 2.59 vs mean 0.45) of anomalies of dural sinuses were significantly higher in case group than in control group. In the case group, sinus anomalies were asymmetric in 59 cases (right-left ratio 1/1) and symmetric in 22. A significant association was detected between the grading of venous drainage alterations and diagnosis of disease and between the severity of vascular anomalies and the widening of subarachnoid space (SAS). Postural plagiocephaly (39.1% vs 21.3%) and asymmetric tentorial insertion (35.4% vs 17.3%) were significantly more frequent in the case group than in the control group. When sinus anomalies occurred in plagiocephalic children, the obstruction grading was significantly higher on the flattened side (p ≤ 0.001). CONCLUSION: Decreased patency of the dural sinuses and consequent increased venous outflow resistance may play a role in the pathophysiology of external hydrocephalus in the first 3 years of life. In plagiocephalic children, calvarial flattening may impact on the homolateral dural sinus patency, with a possible effect on the anatomy of dural sinuses and venous drainage in the first months of life.

Spinal epidural abscess in children: a case-based review.

BACKGROUND: Pediatric spinal epidural abscess is a major suppurative infection of the central nervous system. It is an extremely rare pathology carrying serious risk of permanent neurological sequelae if is not properly treated. METHODS AND RESULTS: All the pertinent literature was analyzed, focused on pediatric cases of spinal epidural abscess and its peculiar features. Two illustrative cases are also presented. The first case is that of a 9-year old girl who took medical attention, when she was already paraplegic. Despite prompt surgical evacuation and good neuroradiological outcome and intensive rehabilitation, motor deficits did not recover after surgery. The second case was that of a 14-year old girl who presented with fever, neck pain, and torticollis. Prompt diagnosis, decompressive surgery, and 6 weeks of antibiotics allowed good neurological outcome. CONCLUSIONS: The management of spinal epidural abscess includes evacuation of the abscess with decompression of the spinal cord and prolonged antibiotic treatment. The presence of neurological deficit and the delay in the initiation of proper treatment are the two factors that more worsen prognosis.

Endoscopic ultrasonic aspiration of brain abscess.

BACKGROUND: Intracerebral abscess is a rare, but very serious complication of neonatal sepsis. Aggressive medical and surgical strategy is warranted in patients with large abscesses. CASE REPORT: A neonate with bilateral large frontal abscesses, caused by Serratia marcescens, was operated using a neuroendoscope coupled with an ultrasonic aspiration device. To our knowledge, this is the first report of such utilization of this new tool. The left abscess was surgically drained through endoscopic aspiration using ultrasonic aspirator. Clinical condition rapidly improved, and postoperative MRI of the brain revealed an almost complete resolution of the left abscess. A second endoscopic procedure was performed 1 week later, and the right abscess was endoscopically drained with the same technique. The remaining clinical course was uneventful. DISCUSSION AND CONCLUSION: Ultrasonic aspiration is effective in obtaining complete removal of the purulent material and of the dense fibrin layer adherent to the capsule. However, further studies are warranted to determine its real effectiveness, compared with the classic technique. In our opinion, it should be considered an option in more difficult cases, such as abscesses caused by aggressive germs in young or immunocompromised patients, or in case of recurrent lesions, in order to avoid craniotomy and open surgery.

Contemporary occurrence of hydrocephalus and Chiari I malformation in sagittal craniosynostosis. Case report and review of the literature.

Chiari malformation type I (CM-I) and hydrocephalus are often associated with complex craniosynostosis. On the contrary, their simultaneous occurrence in monosutural synostosis is extremely rare. The pathophysiological hypothesis is that they may alter posterior fossa growth and lead to cerebellar tonsil herniation also without skull base primary involvement. Hydrocephalus is multifactorial and may be secondary to fourth ventricle outlet obstruction. The management of these cases is quite complex and not well defined. Cranial vault remodeling should be the only treatment when CM-I is asymptomatic and not related to syringomyelia. Suboccipital decompression should be reserved only in complicated CM-I, usually as a second surgical step following the correction of the supratentorial deformity. In our opinion, the associated hydrocephalus should be treated first in order to normalize intracranial hypertension before opening the cranial sutures. We report the case of a 26-month-old child that presented with sagittal craniosynostosis, hydrocephalus, and CM-I. He was managed by performing endoscopic third ventriculostomy (ETV) first and cranial vault remodeling thereafter. Clinico-radiological outcome was very satisfying. Concerning literature is reviewed; physiopathology and surgical management are discussed.

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.

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.

Sodium-Controlled Interfacial Resistive Switching in Thin Film Niobium Oxide for Neuromorphic Applications.

A double layer 2-terminal device is employed to show Na-controlled interfacial resistive switching and neuromorphic behavior. The bilayer is based on interfacing biocompatible NaNbO3 and Nb2O5, which allows the reversible uptake of Na+ in the Nb2O5 layer. We demonstrate voltage-controlled interfacial barrier tuning via Na+ transfer, enabling conductivity modulation and spike-amplitude- and spike-timing-dependent plasticity. The neuromorphic behavior controlled by Na+ ion dynamics in biocompatible materials shows potential for future low-power sensing electronics and smart wearables with local processing.

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.

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.

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.

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.

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.