The Western giants of the neuroanatomical past: an ode to yesterday. Part II

"The history of the world is the biography of the great man. And I said: the great man always acts like a thunder. He storms the skies, while others are waiting to be stormed," said Thomas Carlyle. In this historical vignette, we study the contribution to neuroanatomy, of greats from the past. What led them to find the basis of topography and anatomical localization? How did they unravel the pathways of cerebrospinal fluid and cortical structure of the human brain? To understand this, we study the paths of Pierre Paul Broca, Richard L. Heschl, Hubert von Luschka, Carl Wernicke, Hans Chiari, Ludwig Edinger, and Carl Westphal, Korbinian Brodmann, and Walter Dandy.

The western giants of neuroanatomical past: an ode to yesterday - Part I

"The only history is a mere question of one's struggle inside oneself. But that is the joy of it. One need neither discover Americas nor conquer nations, and yet one has as great a work as Columbus or Alexander to do," said David H. Lawrence. In this historical vignette, we look at the lives of certain western giants of neuroanatomy from the past. To understand the origin of today's advancements and successes in neurosurgery, a strong foothold on the path taken by anatomical greats is necessary. What curiosity inspired them to search the meaning of the human nervous system? Learning this from the paths of Herophilus, Galen, Franciscus Sylvius, Thomas Willis, Alexander Monro secundus, Luigi Rolando, François Magendie, and Martin Rathke, will propel us to create a better future for our successors.

Flow Diversion for Treatment of Anterior Inferior Cerebellar Artery Aneurysms: Mechanism and Pitfalls from a Novel Management Strategy

BACKGROUND

Anterior inferior cerebellar artery (AICA) aneurysms present a challenge for neurosurgeons and neurointerventionalists alike.

METHODS

Cases of AICA aneurysms managed with endovascular flow diversion at our institute are reviewed with their angiographic outcomes.

RESULTS

Both direct and indirect flow diversion provide complete aneurysm occlusion at follow-up. We propose a stratified method of approaching AICA aneurysms based on location, rupture status, and neck size.

CONCLUSIONS

Careful evaluation of preoperative parameters is paramount in deciding between a surgical or a neuroendovascular approach. Low-profile stents in the future may assist in direct flow diversion of AICA trunk aneurysms. In addition, neurosurgeons need to be well versed in endovascular approaches.

Radially adjustable stent retriever for mechanical thrombectomy in acute ischemic stroke: Improved first-pass effect with rapid-inflation deflation technique

INTRODUCTION

Evidence for improved first-pass effect with the novel radially adjustable radio-opaque stent retriever Tigertriever is lacking.

OBJECTIVE

To compare improvement in first pass success with Tigertriever using two different techniques-rapid inflation deflation (RID) and suction thrombectomy (ST).

METHODS

Retrospective analysis of patients with acute ischemic stroke who underwent mechanical thrombectomy with Tigertriever at a single comprehensive stroke center.

RESULTS

Thirty patients were included. Mean age was 72.8 years. Twelve patients (48%) experienced successful first passes with Tigertriever. Successful revascularization (modified thrombolysis in cerebral infarction (mTICI) 2b/3) was achieved in all (100%) patients who received RID or ST technique for thrombectomy. Good clinical outcome (modified Rankin score = 0-2) was noted in 40% (n = 10). Total mortality in the cohort was 8% (n = 2). RID and ST groups comprised of 10 and 15 patients, respectively. Five patients underwent MT with Tigertriever as a rescue device.

RID VS ST

No difference was noted in mean age (p = 0.27), gender (p = 0.29), location of occlusion (p = 0.46), and device used for first pass (p = 0.57). A 70% first-pass success rate in RID group and 37.5% in ST group was noticed (p = 0.06). Mean time from groin puncture to reperfusion (TICI 2b//3) was statistically similar (p = 0.29, RID: 19.9 min vs ST: 25 min). Both groups noted a 100% complete recanalization rate. The rate of mortality between the two groups were not statistically different (p = 0.46).

CONCLUSION

The preliminary first-pass success rates of RID technique with Tigertriever compared to ST technique, are encouraging. Longitudinal studies with longer follow up are needed to elucidate the smaller learning curve with this device.

Exoscope-assisted resection of a recurrent left frontal pilocytic astrocytoma

An exoscope strengthens the armamentarium of a neurosurgeon by improving visualization and surgeon ergonomics, reducing surgeon discomfort, and improving coordination among the surgical team. A 23-year-old male patient developed focal seizures and weakness affecting his right arm that was attributable to a recurrent left frontal lesion. Despite two craniotomies at an 8-year interval, chemotherapy, and radiation, the tumor continued to progress. In this video, the authors demonstrate resection of a recurrent left frontal pilocytic astrocytoma with the assistance of an exoscope, neuronavigation, and neuromonitoring. The exoscope can enhance surgical resectability while smoothening the surgical workflow. The video can be found here: https://stream.cadmore.media/r10.3171/2023.10.FOCVID23158.

Management Strategies of Plasma Cell Granuloma Involving the Central Nervous System: A Systematic Review of the Literature

BACKGROUND

Plasma cell granuloma (PCG) is a rare clinical entity seen in the neurosurgical literature. It has often been referred to as inflammatory myofibroblastic tumor or inflammatory pseudotumor. No well-defined management guidelines exist in the literature.

METHODS

Using PRISMA guidelines, we systematically reviewed the literature in PubMed and Google Scholar using MeSH terms: intracranial plasma cell granuloma, myofibroblastic tumor, intracranial pseudotumor, spinal plasma cell granuloma. We analyzed the clinical presentation, treatment strategies, clinical outcomes, and follow-up across different studies.

RESULTS

Eighty-three studies were included presenting 108 cases. Primary extracranial disease was seen in 4 patients and primary central nervous system (CNS) disease in 104. In the combined cohort, multicompartmental disease was seen in 22 (20.8%) patients. Headache (n=40, 42.59%) was the most common clinical symptom. Surgical excision (n=86, 79.6%) was the most common primary treatment used. Radiation therapy, steroids, and chemotherapy (methotrexate/6-mercaptopurine/rituximab) were also used. Disease recurrence was noted in 25 (33.3%) patients and residual disease in 33 (30.5%). Mortality was seen in 4 (3.7%) patients. In the cranial PCG subgroup (n=87), 81 (93.1%) patients had solitary lesions, and 6 (6.8%) had multiple lesions. Recurrence after primary surgery was noted in 27.58% (n=24). In the spinal PCG subgroup (n=17), the thoracic spine was the most common location (n=9, 52.9%) and recurrence was seen in 5.84% (n=1).

CONCLUSIONS

Combination of multiple treatment modalities is needed when approaching this complex disease. Spinal PCGs respond favorably to gross total excision, with a low recurrence rate. Cranial PCGs warrant intense follow-up with secondary chemotherapy/radiation/steroids in recurrent cases.

Tension Pneumocranium Following Transsphenoidal Surgeries-A Case Report and Systematic Review of Literature with Analysis of Predisposing Factors and Treatment Regimens: Is Early Skull Base Repair Better than Conservative Treatment?

BACKGROUND

Conclusive evidence describing the outcomes following different treatment strategies for tension pneumocranium (TP) is lacking. Impact of predisposing conditions like multiple transnasal transsphenoidal (TNTS) procedures, intraoperative cerebrospinal fluid leak, obstructive sleep apnea, continuous positive airway pressure, violent coughing, nose blowing, positive pressure ventilation on TP outcomes is also unknown.

METHODS

PubMed, Embase, Cochrane, and Google Scholar were searched for articles using Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines. Multivariate logistic regression analysis was done using STATA/ BE ver 17.0.

RESULTS

Thirty-five studies with 49 cases of endoscopic TNTS surgeries were included. Tension pneumocephalus was seen in 77.5% (n = 38), tension pneumosella in 7 (14.28%), and tension pneumoventricle in 4 (8.16%). Nonfunctional pituitary adenomas (40.81%) were most common lesions associated with TP. The need of mechanical ventilation was significantly higher in patients who received conservative management (odds ratio, 1.34; confidence interval, 0.65-2.74) (P < 0.01). However, incidence of meningitis or mortality were not influenced by factors like age, gender, pathological diagnosis, initial conservative management or early skull base repair, use of adjuvant radiation, intraoperative cerebrospinal fluid leak, multiple TNTS explorations, or presence of precipitating factors.

CONCLUSIONS

Nonfunctional pituitary adenomas were the most common lesions associated with TP. Multiple TNTS procedures did not increase incidence of meningitis or mortality. Conservative management increased the need for mechanical ventilation but did not worsen the mortality outcomes.

Network analysis of neurosurgical literature: an increased focus on training during the COVID-19 pandemic

The COVID-19 pandemic led to stringent guidelines to restrict the conduct of non-emergent surgical procedures. Consequently, neurosurgery departments experienced a decline in case volumes and greater educational time being spent on virtual research projects. In our report, we reveal how neurosurgical research has changed during the pandemic compared to the pre-pandemic phase. The WebOfScience database was searched for neurosurgical articles published between 2012-2019 (pre-pandemic) and 2020-2022 (pandemic). From this data, the keywords, terms, and countries were analyzed using networks formed by the VOS Viewer software. In addition, the analysis was repeated for neurosurgical articles specific to COVID-19. Network analyses of terms and keywords revealed an increased popularity of virtual research projects, including case reports, meta-analyses, reviews, surveys, and database studies. Additionally, there was increased interest in research pertaining to neurosurgical education during the post-pandemic era, including topics regarding virtual training modalities, mental health, and telemedicine. Our bibliometrics analysis suggests that the impact of COVID-19 restrictions on hospital systems affected neurosurgical training programs. Future investigations should explore the effects of the trainee experience during the COVID-19 pandemic on the outlook for neurosurgical education.

Surpass embolization of intracranial aneurysms: Perspective from a 2-year longitudinal follow-up study across high volume comprehensive stroke centers

BACKGROUND

Surpass Streamline (SS; Stryker^©) is an over-the-wire first-generation flow diverter (FD). There is a scarcity of data on real-world outcomes and complications of this FD.

METHODS

A retrospective review of consecutive cases between January 2019 and July 2021 at two high-volume comprehensive stroke centers, involving SS was conducted.

RESULTS

Fifty-five patients harbored 69 treated aneurysms, of which 96% were in the internal carotid petrous to terminus segments and 88% were <10 mm in size, and 12% measuring 10-24 mm. Raymond Roy Grade 1 occlusion was noted in 55 aneurysms (79.7%) at 1 year. Median follow-up duration was 26 months (mean = 26.06). Major complications were seen in eight patients (14.5%; 95% CI 6.5-26.7) and mortality attributable to SS stenting complications occurred in two (4.3%) patients. Four (7.2%) had ophthalmologic thromboembolic complications and two had (3.6%) ischemic complications. Procedural complications occurred in 10 patients (18.18%; 95% CI 9.1-30.9). Technical complications during procedure (n = 3, 5.3%) were: "confirmed" distal middle cerebral artery (MCA) guidewire perforation; "suspected" distal MCA guidewire perforation causing post-procedural subarachnoid hemorrhage and internal carotid artery dissection causing ischemic stroke. Seizures were seen in 5 (9.09%) and carotid-cavernous fistula in 1 (1.8%). Multivariate regression analysis showed technical challenges significantly predicted occurrence of major complications (p = 0.001; R²= 0.39, F(13,43) = 2.15, p = 0.029). Univariate analysis showed technical challenges significantly predicted ophthalmological complications (R²= 0.06, F(1,55) = 4.04, p = 0.049) and major complications (R²= 0.21, F(1,55) = 15.11, p = 0.0002).

CONCLUSION

Large-scale future registry should focus on national data regarding SS safety, technical challenges, and procedural complications. We present one of the longest follow-ups for SS in literature.

Trends in Global Research for Treating Intracranial Aneurysms: A Bibliographic Analysis

INTRODUCTION

Although significant advancements have been made in the detection, surveillance, and treatment of intracranial aneurysms, research and care can differ vastly based on location. Currently, there is a lack of knowledge regarding the trends in the literature and how the field is evolving with new technology.

OBJECTIVE

Here, we use bibliographic analysis to visualize the knowledge structure of the field and identify global research trends in intracranial aneurysm treatment.

METHODS

The Web of Science Core Collection was queried for primary research and review articles related to intracranial aneurysm treatment. 4,702 relevant documents were collected and publications over time on different treatment types and publications and citations of journals were collected. VOSviewer was used to: 1) identify relationships between keywords, 2) identify co-authorship patterns among organizations and countries, and 3) analyze citation patterns of countries, organizations, and journals.

RESULTS

Our results show that research in flow diversion increased at a rapid rate but tended to have low link strength with keywords related to evaluating patient risk and mortality. The highest publication producing countries were the USA, Japan, and China, although China had less citations relative to its peers. Korean organizations showed less international collaboration. The USA has been the leader in terms of productivity and collaboration in the field, as have several US-based journals such as Journal of Neurosurgery, Neurosurgery, and World Neurosurgery.

CONCLUSION

Evaluating the safety of flow diversion treatment remains a pressing area of research. Chinese and Korean organizations may be of interest for global collaborations.

Management paradigms of persistent primitive trigeminal artery aneurysms: A systematic review and analysis of techniques and complications from 1960s to 2022: From conservative to surgical to endovascular, how far along the right path are we?

INTRODUCTION

Aneurysms of persistent primitive trigeminal artery (PPTAAs) are increasingly reported and commonly managed by endovascular (EN) techniques. There are no systematic reviews or meta-analyses which analyse outcomes and complications of treatment modalities for PPTAAs. We aim to highlight the change in trend of management of PPTAAs and to identify clinical and radiological parameters which may influence management paradigms.

METHODOLOGY

A systematic search of literature was done in PubMed, Embase, Google Scholar, Cochrane library and Medline using keywords 'persistent primitive trigeminal artery', 'aneurysms', 'embolization', 'surgical clipping', etc. Only cases reporting aneurysms of PPTA were included. Three subgroups, such as conservative, open surgical (OS) and EN interventional, were studied for outcome evaluation. In the EN subgroup, relation of clinical and radiological parameters with outcome (complete/partial occlusion) was analysed using Microsoft Excel Data Analysis ToolPak.

RESULTS

Of the 101 articles found eligible for assessment, 54 were analysed quantitatively. Mortality in the conservative group was 12.5% and OS group was 9.09%. After EN treatment, complete angiographic occlusion was seen in 88.89% PPTAAs and 5.5% warranted retreatment. In the EN subgroup, location (p=0.17), shape (p=0.69), Saltzman circulation (p=0.26) or status of rupture (p=0.08) did not significantly impact angiographic occlusion outcome. Multivariate regression analysis showed 6.6% influence of independent variables, that is, age, gender, aneurysm location, side, shape (saccular/fusiform), rupture status and type of Saltzman circulation on aneurysm occlusion outcome [F(7,27) =1.34] (p=0.27). Total mortality reported in the EN group was 8.57%.

CONCLUSION

Clinical or radiological parameters do not influence angiographic occlusion outcome. Although EN techniques are successful, meticulous reporting of outcomes and complications is important.

Correspondence - Further reflections of the role of artificial intelligence in acute medicine

We read with great interest the article "Artificial Intelligence: its Future and Impact on Acute Medicine". Regarding the historical perspective on artificial intelligence (AI) origins, we believe the role of John von Neumann (1903-1957) also deserves emphasis.

Concurrent intracranial infarct and intraventricular hemorrhage with spontaneous nontraumatic extradural hemorrhage in follow-up: An enigma of COVID-19-associated intracranial vasculopathy

Background:

Several neurological manifestations have been described in the literature, in patients affected with COVID-19 infection. Some common forms include ischemic stroke, cardioembolic stroke, intraparenchymal hemorrhage, and multicompartmental hemorrhage. Concurrent brain infarct and intraventricular hemorrhage (IVH) have not been described in the literature previously.

Case Description:

A 35-year hypertensive and COVID-19-positive patient developed sudden-onset spontaneous IVH with concurrent infarct in the left internal capsule. In spite of undergoing an initial CSF drainage procedure, he had persistent worsening sensorium and increasing midline shift on CT imaging, so he underwent a left-sided decompressive craniectomy. One month after discharge, he developed spontaneous extradural hemorrhage at the operative site. In view of impending cerebral herniation, emergency hematoma evacuation was done, which restored his neurological status.

Conclusion:

This is the first reported detailed case of concurrent intracranial infarct and IVH in a patient affected with COVID-19 infection. We also report a rare phenomenon of nontraumatic noncoagulopathic extradural hemorrhage on the decompressive craniectomy site, in this patient 1 month after surgery.

157 Non-Surgical Management of an Acute Isolated Volar Dislocation of the Distal Radio-Ulnar Joint

Isolated distal radio-ulnar joint dislocations are rare and commonly missed on radiographs. A young male presented with severe pain and deformity of the left wrist, following a collision whilst playing rugby. This was easily diagnosed using plain radiographs, and the initial attempted reduction methods in the Emergency Department failed. The patient was subsequently anaesthetised in theatre, yet reduction by an accepted method of palmar to dorsal pressure over the interosseous membrane with simultaneous distraction of the wrist failed. A further attempt to manipulate the dislocated ulnar head was successful, with the same force applied whilst the wrist was maximally flexed and pronated – thereby avoiding an open reduction. The patient was asymptomatic at final follow-up, over one year later. This technique has not previously been described in the literature and may be used in similar injuries in the future.

Is Twice-weekly Maintenance Hemodialysis Justified?

Background:

The benefits of twice-weekly dialysis at initiation are significant with respect to access longevity, preservation of residual renal function, economic factors, and patient quality of life. It is widely practiced in developing countries due to resource and financial constraints. We present a 3-year follow-up of patients on twice-weekly dialysis and their outcomes.

Material and Methods:

This was a 3-year observational follow-up study of patients initiated on twice-weekly hemodialysis. Adequacy and basic cost-effective hematological and biochemical parameters were studied monthly. In case of complications, the patient was shifted to thrice-weekly hemodialysis.

Results:

88 incident hemodialysis patients were followed up. Total sessions of hemodialysis (HD) studied were 16,406. The mean hemoglobin level was 9.53 g/dl with hyperphosphatemia in 74.88% patients. The mean residual renal function (RRF) at initiation was 5.71 +/- 3.70 ml/min. The mean interdialytic weight gain was 1.91 +/- 1.26 kg with a mean ultrafiltration of 2600 ± 410 ml. The spKt/V and eKt/V were adequate in 68.54% and 48.34% patients; however, the standard Kt/V of 2 was achieved in only 10.51% patients. Emergency HD was done in 41 sessions (0.24%). There were 24 deaths (27.27%) during this period with the mean time to mortality being 503.12 +/- 296.62 days.

Conclusion:

Initiation at twice-weekly schedules for patients on maintenance hemodialysis is a viable option with increments in case of requirement, more so in patients with good urine output and residual renal function. The biochemical and hematological parameters were stable and within KDOQI guidelines and do not worsen with time.

Competing effects of social balance and influence

We study a three-state (leftist, rightist, centrist) model that couples the dynamics of social balance with an external deradicalizing field. The mean-field analysis shows that there exists a critical value of the external field p_{c} such that for a weak external field (p<p_{c}), the system exhibits a metastable fixed point and a saddle point in addition to a stable fixed point. However, if the strength of the external field is sufficiently large (p>p_{c}), there is only one (stable) fixed point, which corresponds to an all-centrist consensus state (absorbing state). In the weak-field regime, the convergence time to the absorbing state is evaluated using the quasistationary distribution and is found to be in agreement with the results obtained by numerical simulations.

Minimum Dominating Sets in Scale-Free Network Ensembles

We study the scaling behavior of the size of minimum dominating set (MDS) in scale-free networks, with respect to network size N and power-law exponent γ, while keeping the average degree fixed. We study ensembles generated by three different network construction methods, and we use a greedy algorithm to approximate the MDS. With a structural cutoff imposed on the maximal degree we find linear scaling of the MDS size with respect to N in all three network classes. Without any cutoff (k_max = N – 1) two of the network classes display a transition at γ ≈ 1.9, with linear scaling above, and vanishingly weak dependence below, but in the third network class we find linear scaling irrespective of γ. We find that the partial MDS, which dominates a given z < 1 fraction of nodes, displays essentially the same scaling behavior as the MDS.

Threshold-limited spreading in social networks with multiple initiators

A classical model for social-influence-driven opinion change is the threshold model. Here we study cascades of opinion change driven by threshold model dynamics in the case where multiple initiators trigger the cascade, and where all nodes possess the same adoption threshold ϕ. Specifically, using empirical and stylized models of social networks, we study cascade size as a function of the initiator fraction p. We find that even for arbitrarily high value of ϕ, there exists a critical initiator fraction pc(ϕ) beyond which the cascade becomes global. Network structure, in particular clustering, plays a significant role in this scenario. Similarly to the case of single-node or single-clique initiators studied previously, we observe that community structure within the network facilitates opinion spread to a larger extent than a homogeneous random network. Finally, we study the efficacy of different initiator selection strategies on the size of the cascade and the cascade window.

Use of prednisolone to aid propagation of Toxoplasma gondii in mice

AIM

To determine the usefulness of prednisolone in increasing the number of Toxoplasma (T.) gondii tachyzoites and bradyzoites in mice.

MATERIALS AND METHODS

The mice were water-fasted prior to being immunosuppressed with oral inoculation of prednisolone. Tachyzoites of 7T gondii RH strain were inoculated into mice and the number of the parasites in the intraperitoneal fluids was then determined at 96 hs post-infection. In addition, tachyzoites of T. gondii ME49 strains were orally introduced into mice and the number of brain cysts formed was observed by microscopic observation at 45 days post-infection.

RESULTS

T. gondii propagation was found to be significantly improved by introduction of the prednisolone (p = 0.0004); and the number of parasite showed positive correlation with the increment in dosage of prednisolone (r = 0.9051).

CONCLUSIONS

The use of prednisolone greatly improved the number of parasite formed in mice: both tachyzoite and cyst forms.

Accelerating consensus on coevolving networks: the effect of committed individuals

Social networks are not static but, rather, constantly evolve in time. One of the elements thought to drive the evolution of social network structure is homophily-the need for individuals to connect with others who are similar to them. In this paper, we study how the spread of a new opinion, idea, or behavior on such a homophily-driven social network is affected by the changing network structure. In particular, using simulations, we study a variant of the Axelrod model on a network with a homophily-driven rewiring rule imposed. First, we find that the presence of rewiring within the network, in general, impedes the reaching of consensus in opinion, as the time to reach consensus diverges exponentially with network size N. We then investigate whether the introduction of committed individuals who are rigid in their opinion on a particular issue can speed up the convergence to consensus on that issue. We demonstrate that as committed agents are added, beyond a critical value of the committed fraction, the consensus time growth becomes logarithmic in network size N. Furthermore, we show that slight changes in the interaction rule can produce strikingly different results in the scaling behavior of consensus time, T(c). However, the benefit gained by introducing committed agents is qualitatively preserved across all the interaction rules we consider.

A study of adverse drug reactions in pediatric patients

Aim:

To study the adverse drug reaction (ADR) pattern in a pediatric population in a tertiary care hospital.

Materials and Methods:

An observational study was done in the department of pediatrics in a tertiary care hospital. The ADRs occurring in the inpatient wards and outpatient department of pediatrics were actively monitored. The collected reports were analyzed for ADR pattern, drug groups, demographic profile, causality, severity, and preventability of the ADR.

Results:

A total of 30 ADRs were documented during the mid period of 2009 among pediatric patients. Most of the ADRs (60%) occurred below the age of 1 year. Antibiotics comprised the major group of drugs causing ADRs (67%). Rashes and urticaria were the most common type of ADR (37%) followed by fever, anaphylactic shock, vomiting, chills, and rigors. A single case of death had been reported in the study period. There were more occurrences of ADRs with multiple drugs compared to single drug therapy. About 80% of the ADRs were of probable causality and 87% were of probable preventability. There were no mild reactions, with 77% of reactions being moderate and 23% of reactions being severe in the severity scale.

Conclusions:

ADRs occur more among infants and antibiotics were more commonly implicated. Most of the reactions were of moderate severity. This indicates the need for a rigid ADR monitoring among pediatric patients to ensure safety of drug therapy.

Social consensus through the influence of committed minorities

We show how the prevailing majority opinion in a population can be rapidly reversed by a small fraction p of randomly distributed committed agents who consistently proselytize the opposing opinion and are immune to influence. Specifically, we show that when the committed fraction grows beyond a critical value p(c) ≈ 10%, there is a dramatic decrease in the time T(c) taken for the entire population to adopt the committed opinion. In particular, for complete graphs we show that when p < pc, T(c) ~ exp [α(p)N], whereas for p>p(c), T(c) ~ ln N. We conclude with simulation results for Erdős-Rényi random graphs and scale-free networks which show qualitatively similar behavior.

Social influencing and associated random walk models: Asymptotic consensus times on the complete graph

We investigate consensus formation and the asymptotic consensus times in stylized individual- or agent-based models, in which global agreement is achieved through pairwise negotiations with or without a bias. Considering a class of individual-based models on finite complete graphs, we introduce a coarse-graining approach (lumping microscopic variables into macrostates) to analyze the ordering dynamics in an associated random-walk framework. Within this framework, yielding a linear system, we derive general equations for the expected consensus time and the expected time spent in each macro-state. Further, we present the asymptotic solutions of the 2-word naming game and separately discuss its behavior under the influence of an external field and with the introduction of committed agents.

Child and adolescent suicide in a large, urban area: psychological, demographic, and situational factors

We examined all completed suicides by children and adolescents in Los Angeles County who died during 1996 and 1997. There were 46 subjects, aged 11 through 16. The majority of the decedents were males and over age 14. The predominant racial group was Hispanic. There was an almost even split between firearms and hanging as the means of death. Females had a statistically significantly higher rate of prior suicide attempts than males. Over one-third left a suicide note, almost one-half were noted to be depressed, and 22% tested positive for alcohol or illicit drugs. Less than one-quarter were in mental health treatment. Eighty-seven percent had difficulty transitioning to or during adolescence; e.g., problems at home, legal and school difficulties, and relationship losses. These findings are discussed in terms of Eriksonian developmental theory. We offer recommendations for intervention and prevention of suicide.

The future of criminal violence: juveniles tried as adults

Juveniles tried as adults (JTA) represent a select and small subsample of juvenile offenders. This study seeks to provide a profile of habitually violent JTAs transferred to the adult penal system and to compare them with their adult counterparts. Twenty-nine incarcerated violent male juveniles tried as adults were compared with a sample of 27 incarcerated violent male offenders across demographic, neuropsychological, criminal history, psychopathy, and substance abuse variables. The JTAs were characterized by a high rate of gang membership (96%), substance abuse (alcohol, marijuana, and phenylcyclidene), and use of guns. In the juvenile sample, 65 percent used guns in violence not leading to arrest, and 93 percent used guns in a violent crime leading to arrest. Juvenile offenders were similar to their adult counterparts in patterns of criminality, although adult offenders had higher psychopathy scores. Both groups revealed generally intact neuropsychological functioning with the exception of a higher rate of perseverative responses in the adult sample. The results are discussed in terms of the implication of the degree of violence in a young offender population.

Psychological factors in the determination of suicide in self-inflicted gunshot head wounds

Self-inflicted contact gunshot wounds to the head have usually been considered presumptive of suicide. This study evaluates whether sufficient psychological data are gathered in such cases to support a manner of death determination of suicide. We suggest that law enforcement agencies and coroner's departments do not fully explore the decedent's state of mind at the time of death. We studied the first 50 consecutive deaths in 1993 in a major metropolitan county due to self-inflicted gunshot wounds to the head. The sample consists primarily of unmarried, white males, with a median age of 35 years, who displayed psychiatric disturbance, primarily depression, before their death. Younger individuals were often under the influence of alcohol and/or drugs at the time of death. Stressors, such as the loss of a loved one, are common among young and middle-aged persons, while serious health problems are found among the majority of middle-aged and elderly individuals. Many of the findings of this study are consistent with the literature regarding individuals who commit suicide. Although data on many important psychological risk factors are missing in most cases, sufficient psychological material is gathered about the decedent's mental condition at the time of death to support a suicide determination.

Actuarial risk assessment models: a review of critical issues related to violence and sex-offender recidivism assessments

Risk assessment in the area of identification of violence has been dichotomized by several prominent researchers as the "clinical approach" versus the "actuarial method". The proponents of the actuarial approach argue for actuarially derived decisions to replace existing clinical practice. The actuarial method requires no clinical input, just a translation of the relevant material from the records to calculate the risk score. A risk appraisal approach based upon a sole actuarial method raises several questions: those of public safety, peer-accepted standards of practice, liability issues, and concordance with evidence-based medicine practice. We conclude that the sole actuarial approach fails to satisfy these critical issues.

Neuropsychological assessment of competency to stand trial evaluations: a practical conceptual model

Competency for adjudication is a complex concept that, despite judicial efforts to articulate functional criteria, has presented conscientious clinicians with the need to filter through multiple levels of psychological data to adequately evaluate and describe the germane functional capacities and deficits of a given defendant. Practitioners are confronted with preparing evaluations that are either psychologically inclusive and too broad to be judicially useful or too brief (opinions with inadequate descriptions of how a specific defendant's abilities and impediments affect the legal criteria). The trend toward harsh sentencing guidelines has further increased defendants' incentives either to postpone adjudication or to attempt to establish a foundation for an insanity plea. Therefore, accurate identification of malingered deficits has become a more significant problem in evaluating competency to stand trial than it previously was. When neuropsychological factors are introduced, competency assessment becomes complex. This article presents a methodology for managing these complexities. Strategies for preparing concise competency evaluations for defendants presenting neuropsychological symptoms are provided along with examples that help illustrate the evaluation process.

Extended civil commitment for dangerous psychiatric patients

Mental health clinicians are increasingly held civilly liable for the dangerous acts of their psychiatric patients. One area of liability is the negligent release of involuntarily committed patients who engage in dangerous acts after their hospital discharge. All states have provisions for extended involuntary commitment for mentally ill dangerous patients. We examined extended civil commitment petitions in Los Angeles County, California, and found that the great majority were rejected. While the standard for extended civil commitment in California includes verbal threats of substantial physical harm, deputy district attorneys tended to reject petitions initiated by clinicians when verbal threats were the sole criterion of dangerousness. This tendency by deputy district attorneys can be quite confusing for clinicians. Mental health professionals' liability has sensitized them to the legal implications of patients' verbal threats of harm; attorneys do not incur the same legal liability and are not so sensitized.