Reliability of CT Angiography in Cerebral Vasospasm: A Systematic Review of the Literature and an Inter- and Intraobserver Study

BACKGROUND AND PURPOSE

Computed tomography angiography offers a non-invasive alternative to DSA for the assessment of cerebral vasospasm following subarachnoid hemorrhage but there is limited evidence regarding its reliability. Our aim was to perform a systematic review (Part I) and to assess (Part II) the inter- and intraobserver reliability of CTA in the diagnosis of cerebral vasospasm.

MATERIALS AND METHODS

In Part I, articles reporting the reliability of CTA up to May 2018 were systematically searched and evaluated. In Part II, 11 raters independently graded 17 arterial segments in each of 50 patients with SAH for the presence of vasospasm using a 4-category scale. Raters were additionally asked to judge the presence of any moderate/severe vasospasm (≥ 50% narrowing) and whether findings would justify augmentation of medical treatment or conventional angiography ± balloon angioplasty. Four raters took part in the intraobserver reliability study.

RESULTS

In Part I, the systematic review revealed few studies with heterogeneous vasospasm definitions. In Part II, we found interrater reliability to be moderate at best (κ ≤ 0.6), even when results were stratified according to specialty and experience. Intrarater reliability was substantial (κ > 0.6) in 3/4 readers. In the per arterial segment analysis, substantial agreement was reached only for the middle cerebral arteries, and only when senior raters' judgments were dichotomized (presence or absence of ≥50% narrowing). Agreement on the medical or angiographic management of vasospasm based on CTA alone was less than substantial (κ ≤ 0.6).

CONCLUSIONS

The diagnosis of vasospasm using CTA alone was not sufficiently repeatable among observers to support its general use to guide decisions in the clinical management of patients with SAH.

Cospeciation vs host-shift speciation: methods for testing, evidence from natural associations and relation to coevolution

Hosts and their symbionts are involved in intimate physiological and ecological interactions. The impact of these interactions on the evolution of each partner depends on the time-scale considered. Short-term dynamics - 'coevolution' in the narrow sense - has been reviewed elsewhere. We focus here on the long-term evolutionary dynamics of cospeciation and speciation following host shifts. Whether hosts and their symbionts speciate in parallel, by cospeciation, or through host shifts, is a key issue in host-symbiont evolution. In this review, we first outline approaches to compare divergence between pairwise associated groups of species, their advantages and pitfalls. We then consider recent insights into the long-term evolution of host-parasite and host-mutualist associations by critically reviewing the literature. We show that convincing cases of cospeciation are rare (7%) and that cophylogenetic methods overestimate the occurrence of such events. Finally, we examine the relationships between short-term coevolutionary dynamics and long-term patterns of diversification in host-symbiont associations. We review theoretical and experimental studies showing that short-term dynamics can foster parasite specialization, but that these events can occur following host shifts and do not necessarily involve cospeciation. Overall, there is now substantial evidence to suggest that coevolutionary dynamics of hosts and parasites do not favor long-term cospeciation.

Fitness effects of derived deleterious mutations in four closely related wild tomato species with spatial structure

A key issue in evolutionary biology is an improved understanding of the genetic mechanisms by which species adapt to various environments. Using DNA sequence data, it is possible to quantify the number of adaptive and deleterious mutations, and the distribution of fitness effects of new mutations (its mean and variance) by simultaneously taking into account the demography of a given species. We investigated how selection functions at eight housekeeping genes of four closely related, outcrossing species of wild tomatoes that are native to diverse environments in western South America (Solanum arcanum, S. chilense, S. habrochaites and S. peruvianum). We found little evidence for adaptive mutations but pervasive evidence for strong purifying selection in coding regions of the four species. In contrast, the strength of purifying selection seems to vary among the four species in non-coding (NC) regions (introns). Using F(ST)-based measures of fixation in subdivided populations, we suggest that weak purifying selection has affected the NC regions of S. habrochaites, S. chilense and S. peruvianum. In contrast, NC regions in S. arcanum show a distribution of fitness effects with mutations being either nearly neutral or very strongly deleterious. These results suggest that closely related species with similar genetic backgrounds but experiencing contrasting environments differ in the variance of deleterious fitness effects.

Lifeguard--a personal physiological monitor for extreme environments

Monitoring vital signs in applications that require the subject to be mobile requires small, lightweight, and robust sensors and electronics. A body-worn system should be unobtrusive, noninvasive, and easy-to-use. It must be able to log vital signs data for several hours as well as transmit it on demand in real-time using secure wireless technologies. The NASA Ames Research Center (Astrobionics) and Stanford University (National Center for Space Biological Technologies) are currently developing a wearable physiological monitoring system for astronauts, called LifeGuard, that meets all of the above requirements and is also applicable to clinical, home-health monitoring, first responder and military applications.

Antagonistic pleiotropy may help population-level selection in maintaining genetic polymorphism for transmission rate in a model phytopathogenic fungus

It has been shown theoretically that the conditions for the maintenance of polymorphism at pleiotropic loci with antagonistic effects on fitness components are rather restrictive. Here, we use a metapopulation model to investigate whether antagonistic pleiotropy could help maintain polymorphism involving common deleterious alleles in the phytopathogenic fungus Microbotryum violaceum. This fungus causes anther smut disease of the Caryophyllaceae. A previous model has shown that the sex-linked deleterious alleles can be maintained under a metapopulation structure, when intra-tetrad selfing (mating between products of the same meiosis) is high, due to founder effects and selection at the population level. Here, we add two types of pleiotropic advantages to the metapopulation model. A competitive advantage for strains carrying the sex-linked deleterious alleles did not facilitate their maintenance because competitive situations were too rare. In contrast, higher spore production did facilitate the maintenance of the deleterious alleles at low intra-tetrad mating rates and with a large advantage for spore production. These results show that antagonistic pleiotropy may promote the persistence of genetic variation, in combination with other selective forces.

Mild head injury: a misnomer

Despite controversy surrounding the concept of mild head injury (MHI), it is becoming evident that even a head trauma termed 'mild' may result in significant behavioural sequelae. The present study was an attempt at documenting structural cerebral damage, by way of computerized tomography, in a group of patients having suffered a MHI as defined by the Glasgow Coma Scale (GCS) score. A 1-year retrospective chart review identified 80 MHI patients who presented to the Emergency department of a lead hospital for trauma. Sixty-six per cent of these MHI patients were scanned. Evidence of intracranial abnormalities was obtained in 31% of the overall sample. Patients with a lower GCS score had a higher percentage of abnormal scans than those with a GCS score of either 14 or 15. The present findings suggest that a MHI can be associated with significant morbidity, and that a MHI group does not constitute a homogeneous pool of patients.

Long-term effects of severe penetrating head injury on psychosocial adjustment

The long-term effects of severe penetrating head injury on adjustment levels were studied. Forty-one World War II veterans who suffered penetrating injury to the brain were interviewed 40 years after their initial injury using the Washington Psycho-Social Seizure Inventory (WPSI). The results support a comparable behavioral impact of right and left hemispheric lesions. Similarly, no significant relations were found between anterior and posterior locus of damage and psychosocial difficulties, although the results pertaining to the right-anterior group could be interpreted as suggestive of much greater maladjustment in all life dimensions assessed by the WPSI. Findings are discussed in terms of theoretical positions on hemispheric specialization and long-term expectancies that hold implications for planning rehabilitation programs for such patients.

Long-term effects of severe penetrating head injury on psychosocial adjustment

The long-term effects of severe penetrating head injury on adjustment levels were studied. Forty-one World War II veterans who suffered penetrating injury to the brain were interviewed 40 years after their initial injury using the Washington Psycho-Social Seizure Inventory (WPSI). The results support a comparable behavioral impact of right and left hemispheric lesions. Similarly, no significant relations were found between anterior and posterior locus of damage and psychosocial difficulties, although the results pertaining to the right-anterior group could be interpreted as suggestive of much greater maladjustment in all life dimensions assessed by the WPSI. Findings are discussed in terms of theoretical positions on hemispheric specialization and long-term expectancies that hold implications for planning rehabilitation programs for such patients.