Cauda equina syndrome following a lumbar puncture.

Lumbar puncture (LP), a common diagnostic procedure, is usually associated with low morbidity. We describe the case of a 29-year-old woman who underwent a non-traumatic LP in the setting of normal coagulation. Cauda equina syndrome subsequently developed secondary to an extradural spinal haematoma. Avoidance, identification and management of this uncommon complication are discussed. Iatrogenic cauda equina syndrome following LP is rare, but can cause significant morbidity. Our patient's experience and our review of the literature highlight that: (i) normal coagulation and a non-traumatic LP do not exclude this diagnostic possibility; (ii) early recognition determines the management and prognosis, as 50% of patients remain paraplegic if the condition is identified more than 12 hours after symptom onset; and (iii) neurosurgical intervention can be avoided, despite bladder dysfunction, if there are early signs of recovery

Inhibitory Synapse Formation at the Axon Initial Segment

The axon initial segment (AIS) is the site of action potential (AP) initiation in most neurons and is thus a critical site in the regulation of neuronal excitability. Normal function within the discrete AIS compartment requires intricate molecular machinery to ensure the proper concentration and organization of voltage-gated and ligand-gated ion channels; in humans, dysfunction at the AIS due to channel mutations is commonly associated with epileptic disorders. In this review, we will examine the molecular mechanisms underlying the formation of the only synapses found at the AIS: synapses containing γ-aminobutyric type A receptors (GABAARs). GABAARs are heteropentamers assembled from 19 possible subunits and are the primary mediators of fast synaptic inhibition in the brain. Although the total GABAAR population is incredibly heterogeneous, only one specific GABAAR subtype—the α2-containing receptor—is enriched at the AIS. These AIS synapses are innervated by GABAergic chandelier cells, and this inhibitory signaling is thought to contribute to the tight control of AP firing. Here, we will summarize the progress made in understanding the regulation of GABAAR synapse formation, concentrating on post-translational modifications of subunits and on interactions with intracellular proteins. We will then discuss subtype-specific synapse formation, with a focus on synapses found at the AIS, and how these synapses influence neuronal excitation

Does a novel X-ray imaging technology provide a substantial radiation dose reduction for patients in trans-catheter aortic valve implantation procedures?

Purpose: Modern interventional X-ray equipment employs image processing to permit reduction in radiation whilst retaining sufficient image quality. The aim of this study was to investigate whether our recently-installed system (AlluraClarity, Philips Healthcare) which contains advanced real-time image noise reduction algorithms and anatomy-specific X-ray optimization (beam filtering, grid switch, pulse width, spot size, detector and image processing engine), affected patient procedure dose and overall procedure duration in routine trans-catheter aortic valve implantation (TAVI) procedures. Methods: Patient dose for 42 TAVI patients from the AlluraClarity cardiac catheterisation lab and from a reference system (Axiom Artis, Siemens Healthcare) in the same cardiology department was recorded. Median values from the two X-ray systems were compared using the Wilcoxon statistical test. Results: Total patient procedure dose medians were 4016 and 7088 cGy cm2 from the AlluraClarity and reference systems respectively. AlluraClarity median patient doses were 3405 cGy cm2 and 783.5 cGy cm2 from fluoroscopy and digital image acquisition respectively. Reference median patient doses were 4928 cGy cm2 and 2511 cGy cm2 from fluoroscopy and digital image acquisition respectively. All differences in patient dose were significant at the 5% level. Median total fluoroscopy times [min:sec] were 19:57 and 20:20 for the AlluraClarity and reference systems respectively. Conclusion: The AlluraClarity cardiac catheterisation lab had 43% lower total patient procedure dose for TAVI patients than the reference lab; fluoroscopy and digital image acquisition doses were 31% and 69% lower respectively. In terms of total fluoroscopy time, there was no statistically significant difference between the two labs

Image quality based x-ray dose control in cardiac imaging

An automated closed-loop dose control system balances the radiation dose delivered to patients and the quality of images produced in cardiac x-ray imaging systems. Using computer simulations, this study compared two designs of automatic x-ray dose control in terms of the radiation dose and quality of images produced. The first design, commonly in x-ray systems today, maintained a constant dose rate at the image receptor. The second design maintained a constant image quality in the output images. A computer model represented patients as a polymethylmetacrylate phantom (which has similar x-ray attenuation to soft tissue), containing a detail representative of an artery filled with contrast medium. The model predicted the entrance surface dose to the phantom and contrast to noise ratio of the detail as an index of image quality. Results showed that for the constant dose control system, phantom dose increased substantially with phantom size (x5 increase between 20cm and 30 cm thick phantom), yet the image quality decreased by 43% for the same thicknesses. For the constant quality control, phantom dose increased at a greater rate with phantom thickness (>x10 increase between 20 cm and 30 cm phantom). Image quality based dose control could tailor the x-ray output to just achieve the quality required, which would reduce dose to patients where the current dose control produces images of too high quality. However, maintaining higher levels of image quality for large patients would result in a significant dose increase over current practice

A starting point in the evaluation of the outcome of care: an example using cancer registry information

Many health services worldwide are paying increasing attention to the evaluation of care. However, most studies in the past have concentrated on structure and process instead of outcome. The objective of this paper is to show how a fairly simple technique can provide a possible feedback loop to a health service system. A study on patients with lung cancer in East Anglia, UK is used as an example. Using information which was more or less routinely collected in cancer registration, the study showed that there was no significant difference between the survival of patients seen in the eight districts in East Anglia. Adjustment by the use proportional hazard modelling for prognostic factors including age, sex, histological type, stage and whether active treatment was given did not alter the outcome. This finding was slightly unexpected in view of the presumed (yet not documented) variation in enthusiasm and expertise among the districts. Such a result should be seen as a starting point for studies designed to examine the effects of the level of care provided and resource use on the length and quality of survival. While the methodology requires refinement and substantial local difficulties may arise, development of similar researches on the outcome of care should be encouraged in Hong Kong.published_or_final_versio

Can homogeneous nucleation resolve the inner core nucleation paradox?

The formation of Earth's solid inner core is thought to mark a profound change in the evolution of the deep Earth and the power that is available to generate the geomagnetic field. Previous studies generally find that the inner core nucleated around 0.5–1 billion years ago, but neglect the fact that homogeneous liquids must be cooled far below their melting point in order for solids to form spontaneously. The classical theory of nucleation predicts that the core must be undercooled by several hundred K, which is incompatible with estimates of the core's present-day temperature. This “inner core nucleation paradox” therefore asserts that the present inner core should not have formed, leaving a significant gap in our understanding of deep Earth evolution. In this paper we explore the nucleation process in as yet untested iron-rich systems which may comprise the Earth's early core. We find that 1 mol.% Si and S increase the supercooling required to freeze the inner core compared to pure iron by 400 K and 1000 K respectively. 10 mol.% O reduces the required inner core nucleation supercooling to 730 K and 3 mol.% C to only 612 K, which is close to resolving the paradox but still requires that the inner core formed recently

Temporal trends in safety of carotid endarterectomy in asymptomatic patients

Objective: To systematically review temporal changes in perioperative safety of carotid endarterectomy (CEA) in asymptomatic individuals in trial and registry studies. Methods: The MEDLINE and EMBASE databases were searched using the terms “carotid” and “endarterectomy” and “asymptomatic” from 1947 to August 23, 2014. Articles dealing with 50%–99% stenosis in asymptomatic individuals were included and low-volume studies were excluded. The primary endpoint was 30-day stroke or death and the secondary endpoint was 30-day all-cause mortality. Statistical analysis was performed using random-effects meta-regression for registry data and for trial data graphical interpretation alone was used. Results: Six trials (n = 4,431 procedures) and 47 community registries (n = 204,622 procedures) reported data between 1983 and 2013. Registry data showed a significant decrease in postoperative stroke or death incidence over the period 1991–2010, equivalent to a 6% average proportional annual reduction (95% credible interval [CrI] 4%–7%; p < 0.001). Considering postoperative all-cause mortality, registry data showed a significant 5% average proportional annual reduction (95% CrI 3%–9%; p < 0.001). Trial data showed a similar visual trend. Conclusions: CEA is safer than ever before and high-volume registry results closely mirror the results of trials. New benchmarks for CEA are a stroke or death risk of 1.2% and a mortality risk of 0.4%. This information will prove useful for quality improvement programs, for health care funders, and for those re-examining the long-term benefits of asymptomatic revascularization in future trials

Examining the power supplied to Earth's dynamo by magnesium precipitation and radiogenic heat production

We examine magnesium and potassium solubility in liquid Fe mixtures, representative of Earth's core composition, in equilibrium with liquid silicate mixtures representative of an early magma ocean. Our study is based on the calculation of the chemical potentials of MgO and K2O in both phases, using density functional theory. For MgO, we also study stability against precipitation of the solid phase. We use thermal evolution models of the core and mantle to assess whether either radiogenic heating from 40K decay or Mg precipitation from the liquid core can resolve the new core paradox by powering the geodynamo prior to inner core formation. Our results for K show that concentrations in the core are likely to be small and the effect of 40K decay on the thermal evolution of the core is minimal, making it incapable of sustaining the early geodynamo alone. Our results also predict small concentrations of Mg in the core which might be sufficient to power the geodynamo prior to inner core formation, depending on the process by which it is transported across the core mantle boundary