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The ongoing COVID-19 pandemic has forced every radiology set-up to evolve and formulate guidelines for day-to-day functioning. The sub-speciality of neuroradiology, both diagnostic and neuro-intervention, forms a very important part of any radiology or 'neuro-care' set-up. The present document is a consensus statement of the Indian Society of Neuroradiology, prepared after reviewing the available data and working experience. It scientifically tries to answer many questions faced by neuroradiologists everyday in practice. It encompasses simple things such as which patients need to be imaged, what precautions are essential, the work-flows, cleaning of radiology equipment, how to carry out neuro-interventions in COVID-suspect patients, and what procedures/tests to avoid, or their alternatives, to minimise the spread of COVID infection both to the patients and health care personnel. As radiology set-ups can be large, every sub-speciality may have certain precautions which will not be covered in general guidelines, and this document tries to answer those for neuroradiologists. Carefully evolved Standards of Operating Procedure (SOPs) and guidelines are the need of the hour to guide in providing uninterrupted and adequate services to the needy without compromising the safety of the specialised work force and facilities involved. [ABSTRACT FROM AUTHOR]

An anomalous common trunk giving rise to bilateral intercostal arteries at multiple levels is exceedingly rare and its association with spinal filar AVF and low-lying cord has not been reported so far. Here, we report this uncommon anatomical variation in a 60-year-old male who presented with paraplegia and on imaging found to have low-lying spinal cord with filar AVF and venous congestive myelopathy and discuss its embryological basis and associated malformations. Although rare, interventional radiologists should be aware of this entity, as these trunks may be a major source of bleeding in patients with hemoptysis, and also may be involved in vital spinal cord supply. [ABSTRACT FROM AUTHOR]

Fenestrations are rare but well-known arterial anatomic variations in which a segment of artery divides into two parallel channels that reunite distally. Although fenestrations as such are asymptomatic, they have gained clinical significance because of their association with aneurysms and other intracranial vascular pathologies. Here we present a 35-year-old woman with history of sudden severe occipital headache and vomiting. Imaging revealed a ruptured aneurysm in the distal posterior inferior cerebellar artery arising from one of the limbs of the fenestration. The aneurysm was successfully managed by coiling, and the patient made complete recovery without neurological sequelae. [ABSTRACT FROM AUTHOR]

Intracranial dermoid and epidermoid cysts are usually considered to be two different entities in the radiological and surgical literature. Epidermoid cysts are classically off midline in location, isointense to cerebrospinal fluid on T1 and T2-weighted images and have restricted diffusion, whereas dermoid cysts are classically midline in location, have T1-hyperintense regions due to the presence of fat and show facilitated diffusion. We report a case of radiological epidermoid cyst in baseline imaging, which evolved into a radiological dermoid cyst over time, and explain this unique occurrence with a review of the embryology and histopathogenesis of these cysts. [ABSTRACT FROM AUTHOR]

Posterior condylar canal dural arteriovenous fistula (PCC dAVF) is a rare entity with only three cases having been reported so far in the English literature. We describe the clinical presentation, imaging, and endovascular management of an elderly man with left PCC dAVF presenting with subarachnoid haemorrhage (SAH). Endovascular management of such cases requires thorough understanding of the vascular anatomy around the craniovertebral junction (CVJ) and variable bridging vein draining patterns. The fistula in our case was fed by the posterior meningeal branch of the left vertebral artery and was draining through a dilated and tortuous medullary bridging vein into the antero-lateral pontomedullary venous system. Transarterial glue embolisation was performed with complete exclusion of the fistula and venous pouches. The patient developed intractable hiccough and left-sided facial pain on the second post-procedural day, and MRI showed focal diffusion restriction in the left dorso-lateral medulla. He recovered completely after a short course of steroids. [ABSTRACT FROM AUTHOR]

Closed-form formulations of two-dimensional (2D) higher-order shear deformation theories (HOSTs) for the free vibration analysis of simply supported cross-ply laminated composite and sandwich doubly curved shells are presented. The formulation includes the Sander's theory for doubly curved shells. Two of the HOSTs account for the effects of both transverse shear strains/stresses and the transverse normal strain/stress, while the third includes only the effects of transverse shear deformation. In these developments a realistic parabolic distribution of transverse shear strains through the shell thickness is assumed. The equations of motion are obtained using Hamilton's principle. Solutions are obtained in closed-form using Navier's technique and by solving the eigenvalue equations. Numerical results are presented for the natural frequencies of laminated composite and sandwich shallow shells. The closed-form solutions presented herein for laminated composite plates and shells are compared with the available 3D elasticity and analytical solutions and it is believed that the solutions for sandwich laminates using various higher-order displacement models will serve as benchmark in future. [ABSTRACT FROM AUTHOR]

A simple C° isoparametric finite element model, based on a higher-order shear deformation theory is presented for the free vibration analysis of isotropic, orthotropic, and layered anisotropic composite and sandwich skew laminates. This theory incorporates a realistic nonlinear variation of displacements through the laminate thickness, and eliminates the use of shear correction coefficients. The boundary conditions on the skew edges are imposed through the suitable transformation of element matrices. The accuracy of the present model is demonstrated by comparing with alternative solutions available in the literature. Extensive numerical results are presented for natural frequencies of cross-ply and angle-ply skew laminates with various lamination parameters, skew angles, boundary conditions, and width-to-thickness ratios. New results on skew sandwiches are obtained for different lamination parameters and skew angles. [ABSTRACT FROM AUTHOR]

Closed-form formulations of 2D higher-order shear deformation theories for the thermomechanical and free vibration analysis of simply supported, cross-ply laminated sandwich, doubly curved thick shells are presented. One of the higher-order shear deformation theories accounts for the effects of both transverse shear strains/stresses and the transverse normal strain/stress, while the other includes only the effects of the transverse shear deformation. Numerical results for thermal and mechanical load cases of laminated composite and sandwich thick shell panels are compared with the available analytical solutions, and it is believed that solutions for thermal loading will serve as benchmarks in future. Natural frequencies of laminated sandwich shells are also presented. [ABSTRACT FROM AUTHOR]

Two higher-order shear deformable finite element models using a higher-order facet shell element are presented for the free vibration analysis of layered anisotropic sandwich laminates. One of the higher-order shear deformation models accounts for the effects of both transverse shear strains/stresses and the transverse normal strain/stress, while the other includes only the effects of the transverse shear deformation. The accuracy of the present models is demonstrated by comparing the results of laminated sandwich plates with the available closed- form solutions. Benchmark solutions with the parametric study for the laminated sandwich cylindrical and spherical shell panels are also presented. [ABSTRACT FROM AUTHOR]

Although intracranial aneurysms are rare in the paediatric population, the proportion of those involving posterior circulation is higher than that of adults (approximately 25% vs. 8%, respectively). Moreover, posterior circulation aneurysms in kids tend to be larger in size, many of them being giant dissecting types, and treatment of them is often challenging. Treatment of giant dissecting aneurysms, especially involving the Basilar artery is difficult due to strategic location and haemodynamic factors. Use of reconstructive techniques viz. flow-diverters and braided stents is difficult in children because of the lack of standard protocol for use of antiplatelet therapy and the need for prolonged use of the same. Continuous growth of parent vessel is also suggested as a pitfall for the use of a flow diverter/ braided stent which has a fixed caliber. Carefully planned endovascular parent or feeder branch artery occlusion (FAO) is a time-tested method to achieve flow reversal or favourable flow modifications in an arterial segment harbouring dissecting aneurysm. Here, in this case report, we describe a case of a ruptured distal giant basilar artery dissecting aneurysm in a 10-year-old boy treated with flow diversion by FAO. The dominant left vertebral artery was occluded, thereby diverting flow from the right vertebral artery towards the left posterior inferior cerebellar artery and decreasing flow through the aneurysm. On 1-year follow-up, the patient was asymptomatic and on check angiography, there was complete involution of the aneurysm with increased flow through bilateral posterior communicating arteries to distal posterior circulation which proved our hypothesis correct. [ABSTRACT FROM AUTHOR]