COVID-19 nasopharyngeal swab and cribriform fracture

Since the start of the pandemic, over 400 million COVID-19 swab tests have been conducted in the UK with a non-trivial number associated with skull base injury. Given the continuing use of nasopharyngeal swabs, further cases of swab-associated skull base injury are anticipated. We describe a 54-year-old woman presenting with persistent colourless nasal discharge for 2 weeks following a traumatic COVID-19 nasopharyngeal swab. A β2-transferrin test confirmed cerebrospinal fluid (CSF) rhinorrhoea and a high-resolution sinus computed tomography (CT) scan demonstrated a cribriform plate defect. Magnetic resonance imaging showed radiological features of idiopathic intracranial hypertension (IIH): a Yuh grade V empty sella and thinned anterior skull base. Twenty-four hour intracranial pressure (ICP) monitoring confirmed raised pressures, prompting insertion of a ventriculoperitoneal shunt. The patient underwent CT cisternography and endoscopic transnasal repair of the skull base defect using a fluorescein adjuvant, without complications. A systematic search was performed to identify cases of COVID-19 swab-related injury. Eight cases were obtained, of which three presented with a history of IIH. Two cases were complicated by meningitis and were managed conservatively, whereas six required endoscopic skull base repair and one had a ventriculoperitoneal shunt inserted. A low threshold for high-resolution CT scanning is suggested for patients presenting with rhinorrhoea following a nasopharyngeal swab. The literature review suggests an underlying association between IIH, CSF rhinorrhoea and swab-related skull base injury. We highlight a comprehensive management pathway for these patients, including high-resolution CT with cisternography, ICP monitoring, shunt and fluorescein-based endoscopic repair to achieve the best standard of care.

Historical and future trends in emergency pituitary referrals: a machine learning analysis

PURPOSE

Acute pituitary referrals to neurosurgical services frequently necessitate emergency care. Yet, a detailed characterisation of pituitary emergency referral patterns, including how they may change prospectively is lacking. This study aims to evaluate historical and current pituitary referral patterns and utilise state-of-the-art machine learning tools to predict future service use.

METHODS

A data-driven analysis was performed using all available electronic neurosurgical referrals (2014-2021) to the busiest U.K. pituitary centre. Pituitary referrals were characterised and volumes were predicted using an auto-regressive moving average model with a preceding seasonal and trend decomposition using Loess step (STL-ARIMA), compared against a Convolutional Neural Network-Long Short-Term Memory (CNN-LSTM) algorithm, Prophet and two standard baseline forecasting models. Median absolute, and median percentage error scoring metrics with cross-validation were employed to evaluate algorithm performance.

RESULTS

462 of 36,224 emergency referrals were included (referring centres = 48; mean patient age = 56.7 years, female:male = 0.49:0.51). Emergency medicine and endocrinology accounted for the majority of referrals (67%). The most common presentations were headache (47%) and visual field deficits (32%). Lesions mainly comprised tumours or haemorrhage (85%) and involved the pituitary gland or fossa (70%). The STL-ARIMA pipeline outperformed CNN-LSTM, Prophet and baseline algorithms across scoring metrics, with standard accuracy being achieved for yearly predictions. Referral volumes significantly increased from the start of data collection with future projected increases (p < 0.001) and did not significantly reduce during the COVID-19 pandemic.

CONCLUSION

This work is the first to employ large-scale data and machine learning to describe and predict acute pituitary referral volumes, estimate future service demands, explore the impact of system stressors (e.g. COVID pandemic), and highlight areas for service improvement.

Whole-brain mapping of structural connectivity in infants reveals altered connection strength associated with growth and preterm birth

Cerebral white-matter injury is common in preterm-born infants and is associated with neurocognitive impairments. Identifying the pattern of connectivity changes in the brain following premature birth may provide a more comprehensive understanding of the neurobiology underlying these impairments. Here, we characterize whole-brain, macrostructural connectivity following preterm delivery and explore the influence of age and prematurity using a data-driven, nonsubjective analysis of diffusion magnetic resonance imaging data. T1- and T2-weighted and -diffusion MRI were obtained between 11 and 31 months postconceptional age in 49 infants, born between 25 and 35 weeks postconception. An optimized processing pipeline, combining anatomical, and tissue segmentations with probabilistic diffusion tractography, was used to map mean tract anisotropy. White-matter tracts where connection strength was related to age of delivery or imaging were identified using sparse-penalized regression and stability selection. Older children had stronger connections in tracts predominantly involving frontal lobe structures. Increasing prematurity at birth was related to widespread reductions in connection strength in tracts involving all cortical lobes and several subcortical structures. This nonsubjective approach to mapping whole-brain connectivity detected hypothesized changes in the strength of intracerebral connections during development and widespread reductions in connectivity strength associated with premature birth.

Divorced pearlite in steels

Steels containing large carbon concentrations are used particularly when a high hardness is required, for example, in the manufacture of components such as bearings. This, however, makes it difficult to shape or machine the alloys during the process of component manufacture unless they are first heat-treated into a softened condition. One method of achieving this economically is to generate a microstructure known as divorced pearlite, in which ferrite and cementite grow from the austenite in a non-cooperative manner, leading to a final microstructure that consists of coarse, spherical particles of cementite dispersed in a matrix of ferrite. This is in contrast to the harder lamellar pearlite which normally develops when high-carbon steels are cooled. The theoretical framework governing the transition from the divorced to the lamellar form is developed and validated experimentally.

Diffusion-controlled growth of pearlite in ternary steels

A theory for the diffusion-controlled growth of pearlite in steels containing manganese is presented and assessed in the light of experimental data. Given the overwhelmingly rapid diffusivity that a substitutional solute has within the transformation front, the growth rate is found to be dominated by diffusion parallel to the interface with austenite as the rate controlling step. The relevant interfacial diffusion parameters have been derived by fitting experimental data to kinetic theory. All reported measurements of pearlite growth where the full set of necessary parameters have been listed, are shown to be inconsistent with mechanisms that do not involve the partitioning of substitutional solutes. The method adopted here, which is based on the local equilibrium at the transformation interface with the long-range partitioning of substitutional solutes by migration within the interface, has been shown to reasonably explain experimental data over a range of temperatures and chemical compositions.

Mixed diffusion-controlled growth of pearlite in binary steel

A kinetic theory for the diffusion-controlled growth of pearlite is presented, which accounts simultaneously for diffusion through the austenite and via the transformation front. The simplified method abandons the need for mechanical equilibrium at the phase junctions and yet is able to explain experimental data on the growth rate of pearlite. Furthermore, unlike previous analyses, the deduced value for the activation energy for the interfacial diffusion of carbon is found to be realistic when compared with corresponding data for volume diffusion.

Reference Models for Mitral Valve Tissue Engineering Based on Valve Cell Phenotype and Extracellular Matrix Analysis

The advance of mitral valve repair techniques through tissue engineering is impeded by the lack of information regarding the cellular and extracellular components of the mitral valve. The present study aims to expand our understanding of the mitral valve structure by analysing the synthesis of extracellular matrix (ECM) proteins and the expression of nitric oxide synthase (NOS). Valvular endothelial cells (VECs) and valvular interstitial cells (VICs) were isolated from porcine mitral valves. Immunochemical staining of ECM components, including type I, II, III, IV and V collagen, laminin, fibronectin, elastin and chondroitin sulphate (CS), was performed on both mitral valve tissue and cell cultures. Reverse transcription polymerase chain reaction and immunochemistry were used to analyse NOS expression in native valve and in culture. Both VECs and VICs synthesised the basement membrane components, laminin and type IV collagen both in vivo and in vitro, amongst other fibrous ECM proteins. Synthesis of type I collagen and CS was absent in VEC cultures. Each cell type had a characteristic profile of NOS expression. VECs synthesised endothelial NOS both in vivo and in vitro, with a minority of VICs expressing neuronal NOS in vitro. The present study reports newly recognised aspects of the mitral valve structure and the in vitro behaviour of mitral valve cell populations based on ECM synthesis and NOS expression. The presented profiles can be used as base tools for the generation of data necessary for the selection of ideal cell sources and for the design of appropriate scaffolds for the development of effective tissue-engineered mitral valves.

Fibrin scaffold as an effective vehicle for the delivery of acidic fibroblast growth factor (FGF-1)

The effect of wound healing by fibrin and acidic fibroblast growth factor (FGF-1) in an in vivo model was evaluated in this study. Four full-thickness wounds were made on the dorsum of each rabbit (n = 5). Each of these wounds had different treatment groups: control, topical FGF-1 (100 microg/9 cm2), fibrin (2.0 mL at 60 mg/mL fibrinogen), and FGF-1 (100 microg/9 cm2)/fibrin. The animals were sacrificed at the end of 2 weeks. Histomorphometric analysis and mechanical testing were conducted to assess the healing response. FGF-1/fibrin treatment improved the mechanical properties of the healed tissue. Fibrin scaffold exhibited the desired tissue response, as demonstrated by the lack of inflammation, and was deemed an effective carrier for FGF-1.

In vivo wound healing response to a modified degradable fibrin scaffold

Pooled donor fibrin with an ultimate fibrinogen concentration of 60 mg/ml was used to study its effect on wound healing of surgically created ulcers in a rabbit ear. Water soluble polymer (PEG Mw = 20 KD) beads of 100-150 microns were added (12% by volume) to the fibrinogen to obtain a porous and rough structure. Five 6 mm-diameter ulcers to the depth of bare cartilage were created on each rabbit ear. There were two periods of study (4 and 8 days), with 15 ulcers in each time period, 5 of which were treated with a modified fibrin scaffold, 5 with a non-modified fibrin scaffold, and 5 served as control ulcers. The ulcer sites were subjected to routine histological processing and histomorphometrical quantification. Data analysis revealed significant increases in volume fraction of fibroblast and number of blood vessels in the modified fibrin scaffold treated ulcers over control and non-modified fibrin scaffold treated groups.

Stimulation of angiogenesis by FGF-1 delivered through a modified fibrin scaffold

A few studies have indicated that repeated dosing of acidic fibroblast growth factor (FGF-1) is essential to be effective in modulating the wound-healing response. However, little investigation has been done to determine the effective dosing regimen of FGF-1 or the appropriate carrier vehicle for this growth factor. The main objective of this study was to determine the effective angiogenic stimulatatory dose of FGF-1 delivered through a modified fibrin matrix, using a rabbit ear ulcer model. Specifically, the aim was to test the effects of FGF-1 on the angiogenic, fibroblastic, and epithelial responses in a wound model. Five 6-mm diameter ulcers to the depth of bare cartilage were created on each rabbit ear. Four different combinations (0.8, 8, 80, and 800 micrograms/ml) of the growth factor were examined across two periods of study. Pooled modified fibrin was used to deliver the growth factor. Histomorphometrical quantification was conducted after routine histological processing of the ulcers sites. Data analysis indicated a strong correlation between concentration and the histomorphometric response. In general, the growth factor treatments affected the healing response and exhibited a dose-dependent behavior. The addition of FGF-1 led to an increase in the angiogenic and fibroblastic responses, as well as an increase in the epithelialization rate. The preferred dose of 8 micrograms initiated a high epithelialization rate, fibroblastic, and angiogenic responses, and was the lowest dose required to initiate these responses.

Effect of oxygen treatment and dressing oxygen permeability on wound healing

Although it has been shown that both the level of tissue oxygen and its gradient are critical factors in the healing process, optimal conditions for oxygen therapy have not been determined. In this study, both the oxygen level and oxygen gradient for a full-thickness defect were modified on the basis of preceding in vitro studies to determine the effect on the healing process. The goal of this study was to help determine the optimal clinical oxygen treatment protocol. Specifically, the healing of full-thickness defects in a rabbit model as determined by histomorphometric analyses (cell and tissue volume fraction, epithelialization, and contraction) under two types of dressings with or without oxygen treatment (70% O(2)) was investigated. One of the dressings was more oxygen permeable than the other. No significant differences were found in the histomorphometric response between the wounds covered with the oxygen-permeable and oxygen-impermeable dressings in the group without supplemental oxygen. Oxygen treatment, however, seemed to enhance the healing response significantly. According to the histomorphometric response, the wounds covered with the oxygen-impermeable dressings were significantly better than those with the oxygen-permeable dressing in the oxygen-treated group after 1 week, but the wounds covered by the oxygen-permeable dressings were better healed at 3 weeks. Therefore, oxygen-impermeable dressings may be useful only in the early stages of healing, before granulation tissue formation.