A New Weibull-G Family of Distributions

Statistical analysis of lifetime data is an important topic in reliability engineering, biomedical and social sciences and others. We introduce a new generator based on the Weibull random variable called the new Weibull-G family. We study some of its mathematical properties. Its density function can be symmetrical, left-skewed, right-skewed, bathtub and reversed-J shaped, and has increasing, decreasing, bathtub, upside-down bathtub, J, reversed-J and S shaped hazard rates. Some special models are presented. We obtain explicit expressions for the ordinary and incomplete moments, quantile and generating functions, Renyi entropy, order statistics and reliability. Three useful characterizations based on truncated moments are also proposed for the new family. The method of maximum likelihood is used to estimate the model parameters. We illustrate the importance of the family by means of two applications to real data sets

The Kumaraswamy Marshal-Olkin Family of Distributions

We introduce a new family of continuous distributions called the Kumaraswamy Marshal-Olkin generalized family of distributions. We study some mathematical properties of this family. Its density function is symmetrical, left-skewed, right-skewed and reversed-J shaped, and has constant, increasing, decreasing, upside-down bathtub, bathtub and S-shaped hazard rate. We present some special models and investigate the asymptotics and shapes of the family. We derive a power series for the quantile function and obtain explicit expressions for the moments, generating function, mean deviations, two types of entropies and order statistics. Some useful characterizations of the family are also proposed. The method of maximum likelihood is used to estimate the model parameters. We illustrate the importance of the family by means of two applications to real data sets

Current State of Neurosurgery Training in Pakistan, Results of a Nationwide Questionnaire Based Survey: Interdepartmental Variations Preclude Standardization

Objective:  To observe inter departmental variation in the availability of resources and academic activities; within various neurosurgery programs of Pakistan. Material and Methods:  This is a proforma based survey of Neurosurgery trainees and young neurosurgeons of Pakistan looking at the academic infrastructure and output of their programs. The proforma was filled by 36 respondents from 11 neurosurgery centers of the countries. All centers are accredited for neurosurgery training in Pakistan. Results:  Out of 36 respondents, 30 were completing fellowship training (FCPS) and 6 were induced for Master in Surgery (MS) program. About 80% participants used Youman’s text book of neurosurgery as reference book. Only 40% candidates had access to more than one indexed neurosurgery journals. Structured academic sessions (journal clubs, neuroradiology meeting, and neuropathology meeting) were lacking in majority of training institutes. 95% trainees had no microsurgical laboratory. Modern neurosurgical tools (frameless neuronavigation system, neuroendoscopy) were in use at few centers only. Conclusion:  Neurosurgery training in Pakistan is not uniform and wide variations exist between centers. We recommend exchange programs between centers at national and international levels to allow the trainees to gain first hand exposures to facilities not available in their own center

A New Weibull–Pareto Distribution: Properties and Applications

Many distributions have been used as lifetime models. In this article, we propose a new three-parameter Weibull–Pareto distribution, which can produce the most important hazard rate shapes, namely, constant, increasing, decreasing, bathtub, and upsidedown bathtub. Various structural properties of the new distribution are derived including explicit expressions for the moments and incomplete moments, Bonferroni and Lorenz curves, mean deviations, mean residual life, mean waiting time, and generating and quantile functions. The Rényi and q entropies are also derived. We obtain the density function of the order statistics and their moments. The model parameters are estimated by maximum likelihood and the observed information matrix is determined. The usefulness of the new model is illustrated by means of two real datasets on Wheaton river flood and bladder cancer. In the two applications, the new model provides better fits than the Kumaraswamy–Pareto, beta-exponentiated Pareto, beta-Pareto, exponentiated Pareto, and Pareto models

The logistic-X family of distributions and its applications

The logistic distribution has a prominent role in the theory and practice of statistics. We introduce a new family of continuous distributions generated from a logistic random variable called the logistic-X family. Its density function can be symmetrical, left-skewed, right-skewed, and reversed-J shaped, and can have increasing, decreasing, bathtub, and upside-down bathtub hazard rates shaped. Further, it can be expressed as a linear combination of exponentiated densities based on the same baseline distribution. We derive explicit expressions for the ordinary and incomplete moments, quantile and generating functions, Bonferroni and Lorenz curves, Shannon entropy, and order statistics. The model parameters are estimated by the method of maximum likelihood and the observed information matrix is determined. We also investigate the properties of one special model, the logistic-Fréchet distribution, and illustrate its importance by means of two applications to real data sets

Children with seizures and radiological diagnosis of focal cortical dysplasia: can drug-resistant epilepsy be predicted earlier?

Objective: Focal cortical dysplasia (FCD) is a malformation of cortical development and is associated with drug-resistant epilepsy. Standard indication for epilepsy surgery is drug resistance (as defined by the ILAE). Given the high incidence of drug resistance in these children, this delay may not be warranted. The aim of the study was to determine the proportion of patients with a presumed FCD who develop drug resistance, and evaluate post-operative outcomes. Methods: This study incorporated a survey within a regional paediatric epilepsy network and a retrospective database review of a paediatric epilepsy center serving the network to identify children with epilepsy and a presumed FCD on MRI. Results: The survey revealed that 86% of the patients with epilepsy and presumed FCD on MRI within the network were referred to our centre. Of 139 pediatric patients included in the study, 131 (94.2%) had drug-resistant epilepsy. One hundred and ten (83.9%) patients were referred to epilepsy surgery, of whom 97 underwent surgery. Of 92 with one-year postoperative follow-up, 59.8% had an Engel Class 1 (seizure-free) outcome. Concordance of location between MRI and ictal EEG was strongly associated with Engel Class 1 outcome ( p <0.001), as was older age at seizure onset ( p =0.03). Time from diagnosis to surgery, number of medications, type of surgery and histology were not associated with improved outcome. Significance: Our data suggest that most children presenting with seizures and a radiological diagnosis of FCD will develop drug-resistant epilepsy and are candidates for epilepsy surgery. The main outcome predictors are the correlation between MRI and ictal EEG localization and age at onset. This suggests that patients with FCD and epilepsy may be considered for surgery before traditional criteria of drug resistance are met. This change in practice has the potential to improve quality of life and cognitive function, and reduce burden on epilepsy services

Proportion of resected seizure onset zone contacts in pediatric stereo-EEG-guided resective surgery does not correlate with outcome

Objective: We aimed to determine whether the proportion of putative seizure onset zone (SOZ) contacts resected associates with seizure outcome in a cohort of children undergoing stereoelectroencephalography (SEEG)-guided resective epilepsy surgery. / Methods: Patients who underwent SEEG-guided resective surgery over a six-year period were included. The proportion of SOZ contacts resected was determined by co-registration of pre- and post-operative imaging. Outcome was classified as seizure free (SF, Engel class I) or not seizure-free (NSF, Engel class II-IV) at last clinical follow-up. / Results: Twenty-nine patients underwent resection of whom 22 had sufficient imaging data for analysis (median age at surgery of 10 years, range 5–18). Fifteen (68.2%) were SF at median follow-up of 19.5 months (range 12–46). On univariate analysis, histopathology, was the only significant factor associated with SF (p < 0.05). The percentage of defined SOZ contacts resected ranged from 25-100% and was not associated with SF (p = 0.89). In a binary logistic regression model, it was highly likely that histology was the only independent predictor of outcome. / Conclusions: The percentage of SOZ contacts resected was not associated with SF in children undergoing SEEG-guided resective epilepsy surgery. / Significance: Factors such as spatial organisation of the epileptogenic zone, neurophysiological biomarkers and the prospective identification of pathological tissue may therefore play an important role

Lesion detection in epilepsy surgery: Lessons from a prospective evaluation of a machine learning algorithm

AIM: To evaluate a lesion detection algorithm designed to detect focal cortical dysplasia (FCD) in children undergoing stereoelectroencephalography (SEEG) as part of their presurgical evaluation for drug-resistant epilepsy. METHOD: This was a prospective, single-arm, interventional study (Idea, Development, Exploration, Assessment, and Long-Term Follow-Up phase 1/2a). After routine SEEG planning, structural magnetic resonance imaging sequences were run through an FCD lesion detection algorithm to identify putative clusters. If the top three clusters were not already sampled, up to three additional SEEG electrodes were added. The primary outcome measure was the proportion of patients who had additional electrode contacts in the SEEG-defined seizure-onset zone (SOZ). RESULTS: Twenty patients (median age 12 years, range 4-18 years) were enrolled, one of whom did not undergo SEEG. Additional electrode contacts were part of the SOZ in 1 out of 19 patients while 3 out of 19 patients had clusters that were part of the SOZ but they were already implanted. A total of 16 additional electrodes were implanted in nine patients and there were no adverse events from the additional electrodes. INTERPRETATION: We demonstrate early-stage prospective clinical validation of a machine learning lesion detection algorithm used to aid the identification of the SOZ in children undergoing SEEG. We share key lessons learnt from this evaluation and emphasize the importance of robust prospective evaluation before routine clinical adoption of such algorithms