Measuring sectoral/geographic concentration risk

This article focuses on the application of the Pykhtin model to the Italian banking system to measure concentration risk by industry sector and geographic region. The proposed approach generalizes the portfolio model used in Pillar 1 for the calculation of the capital requirement, removing the assumptions of the existence of one systematic risk factor and of an infinitely granular portfolio. The difference between the unexpected loss stemming from the Pykhtin model and that calculated using the supervisory formula can be interpreted as a measure of concentration risk. The Pykhtin model is consistent with the Basel II framework. It accordingly generates an unexpected loss measure that is in line with the IRB capital requirements. The proposed model therefore has the advantage of “speaking the language of supervisors”. This approach makes it possible to interpret the difference between regulatory and economic capital. It also enables concentration risk to be broken down into its two components: single-name and sectoral/geographic concentration risk. The empirical results show the model’s ability to generate internally coherent rankings that are close to the economic intuition: exposure to sectoral/geographic concentration risk is negatively correlated to banks’size.Basel 2, concentration risk, economic capital, VaR

Dynamic provisioning: rationale, functioning, and prudential treatment

Current policy debate has renewed interest in countercyclical provisioning policies; dynamic provisions are regarded as a valuable device for pursuing this goal. Last July, Ecofin supported “the introduction of forward-looking provisioning, which consists in constituting provisions deducted from profits in good times for expected losses on loan portfolios, and which would contribute to limiting procyclicalityâ€. This paper describes: i) how dynamic provisions work in a general framework based on expected losses; ii) how they work according to the Spanish system, which is the only real example of countercyclical provisioning; iii) the differences and similarities between the expected loss model and the Spanish approach. Building on proposals currently under discussion in the international community, it also suggests a possible way forward for introducing a system of dynamic provisions that, while meeting the prudential goal of having more conservative provisioning policies, would not clash with accounting standards.dynamic provisions, capital buffers, Basel 2, credit risk, procyclicality

Emergency decompressive craniectomy after removal of convexity meningiomas

BACKGROUND: Convexity meningiomas are benign brain tumors that are amenable to complete surgical resection and are associated with a low complication rate. The aim of this study was to identify factors that result in acute postoperative neurological worsening after the removal of convexity meningiomas. METHODS: Clinical evaluation and neuroradiological analysis of patients who underwent removal of a supratentorial convexity meningioma were reviewed. Patients were selected when their postoperative course was complicated by acute neurological deterioration requiring decompressive craniectomy. RESULTS: Six patients (mean age: 43.3 years) underwent surgical removal of a supratentorial convexity meningioma. Brain shift (mean: 9.9 mm) was evident on preoperative imaging due to lesions of varying size and perilesional edema. At various times postoperatively, patient consciousness worsened (up to decerebrate posture) with contralateral paresis and pupillary anisocoria. Computed tomography revealed no postoperative hematoma, however, did indicate increased brain edema and ventricular shift (mean: 12 mm). Emergency decompressive craniectomy and brief ventilator assistance were performed in all patients. Ischemia of the ipsilateral posterior cerebral artery occurred in 3 patients and hydrocephalus occurred in 2 patients. Outcome was good in 2, fair in 2, 1 patient had severe disability, and 1 patient died after 8 months. CONCLUSIONS: Brain shift on preoperative imaging is a substantial risk factor for postoperative neurological worsening in young adult patients after the removal of convexity meningiomas. Emergency decompressive craniectomy must be considered because it is effective in most cases. Other than consciousness impairment, there is no reliable clinical landmark to guide the decision to perform decompressive craniectomy; however, brain ischemia may have already occurred

A mouse model for creatine transporter deficiency reveals early onset cognitive impairment and neuropathology associated with brain aging.

Mutations in the creatine (Cr) transporter (CrT) gene lead to cerebral creatine deficiency syndrome-1 (CCDS1), an X-linked metabolic disorder characterized by cerebral Cr deficiency causing intellectual disability, seizures, movement and autistic-like behavioural disturbances, language and speech impairment. Since no data are available about the neural and molecular underpinnings of this disease, we performed a longitudinal analysis of behavioural and pathological alterations associated with CrT deficiency in a CCDS1 mouse model. We found precocious cognitive and autistic-like defects, mimicking the early key features of human CCDS1. Moreover, mutant mice displayed a progressive impairment of short and long-term declarative memory denoting an early brain aging. Pathological examination showed a prominent loss of GABAergic synapses, marked activation of microglia, reduction of hippocampal neurogenesis and the accumulation of autofluorescent lipofuscin. Our data suggest that brain Cr depletion causes both early intellectual disability and late progressive cognitive decline, and identify novel targets to design intervention strategies aimed at overcoming brain CCDS1 alterations

Endoscope-assisted resection of calcified thoracic disc herniations

PURPOSE: Resection of calcified thoracic disc herniations carries significant risks of neurological worsening, particularly in case of concomitant central location. Transthoracic approaches are a first-choice option to avoid spinal cord manipulation but entail drawbacks such as postoperative pain and the risk of bronchopulmonary complications. The purpose of this report is to describe a novel approach to resect calcified herniations, even centrally located, from a posterior perspective. METHODS: Unilateral lamino-arthrectomy is performed, uncovering few millimeters of the disc space beside the dura. Following discectomy and drilling of the vertebral endplates, an angled endoscope is introduced allowing resection of the calcified herniation through an anterior perspective. The spinal cord can now be decompressed with a no-touch technique. Each maneuver aimed at resecting the calcified mass up to the contralateral side can be done under visual control. RESULTS: The technique was used in two patients. The first was a 38-year-old man with a calcified mediolateral T9-T10 disc herniation and mild myelopathic symptoms. The second patient was a 73-year-old obese woman, with a T6-T7 central, calcified disc herniation and severe compression myelopathy. In both cases, complete decompression of the spinal cord could be achieved and rapid neurological recovery was observed postoperatively. No surgery-related complications were observed. CONCLUSIONS: The endoscope-assisted posterior approach afforded safe and complete resection of calcified discs. The technique is particularly useful for central disc herniations, where transthoracic approaches are normally deemed mandatory

Symptomatic spinal cord bending after meningioma resection: a technical case report

Resection of intradural tumors is often followed by bending of the spinal cord within the surgical cave. This event is known to be innocuous. We report a case where the position assumed by the spinal cord at the end of surgery was associated with significant MEP decline. The patient, a 44-year-old woman with a meningioma of the cranio-cervical junction, underwent tumor resection aided by intraoperative neurophysiological monitoring. At the time of dural closure, the motor evoked potentials were completely lost on the left side and reduced on the right side . Intraoperative maneuvers showed that worsening was related to the spinal cord position. MEPs were restored by tethering the cord posteriorly, back to its original site. This report underlines the usefulness of maintaining intraoperative monitoring until the end of surgery and provides a technical nuance to manage a rare complication

Cluster analysis for portfolio optimization

We consider the problem of the statistical uncertainty of the correlation matrix in the optimization of a financial portfolio. We show that the use of clustering algorithms can improve the reliability of the portfolio in terms of the ratio between predicted and realized risk. Bootstrap analysis indicates that this improvement is obtained in a wide range of the parameters N (number of assets) and T (investment horizon). The predicted and realized risk level and the relative portfolio composition of the selected portfolio for a given value of the portfolio return are also investigated for each considered filtering method.