Virtual reality simulation: basic concepts and use in endoscopic neurosurgery training

Introduction

Virtual reality simulation is a promising alternative to training surgical residents outside the operating room. It is also a useful aide to anatomic study, residency training, surgical rehearsal, credentialing, and recertification.

Discussion

Surgical simulation is based on a virtual reality with varying degrees of immersion and realism. Simulators provide a no-risk environment for harmless and repeatable practice. Virtual reality has three main components of simulation: graphics/volume rendering, model behavior/tissue deformation, and haptic feedback. The challenge of accurately simulating the forces and tactile sensations experienced in neurosurgery limits the sophistication of a virtual simulator. The limited haptic feedback available in minimally invasive neurosurgery makes it a favorable subject for simulation.

Conclusions

Virtual simulators with realistic graphics and force feedback have been developed for ventriculostomy, intraventricular surgery, and transsphenoidal pituitary surgery, thus allowing preoperative study of the individual anatomy and increasing the safety of the procedure. The authors also present experiences with their own virtual simulation of endoscopic third ventriculostomy.     

Cellular neuroanatomy of rat presubiculum

The presubiculum, at the transition from the hippocampus to the cortex, is a key area for spatial information coding but the anatomical and physiological basis of presubicular function remains unclear. Here we correlated the structural and physiological properties of single neurons of the presubiculum in vitro. Unsupervised cluster analysis based on dendritic length and form, soma location, firing pattern and action potential properties allowed us to classify principal neurons into three major cell types. Cluster 1 consisted of a population of small regular spiking principal cells in layers II/III. Cluster 2 contained intrinsically burst firing pyramidal cells of layer IV, with a resting potential close to threshold. Cluster 3 included regular spiking cells of layers V and VI, and could be divided into subgroups 3.1 and 3.2. Cells of cluster 3.1 included pyramidal, multiform and inverted pyramidal cells. Cells of cluster 3.2 contained high‐resistance pyramidal neurons that fired readily in response to somatic current injection. These data show that presubicular principal cells generally conform to neurons of the periarchicortex. However, the presence of intrinsic bursting cells in layer IV distinguishes the presubicular cortex from the neighbouring entorhinal cortex. The firing frequency adaptation was very low for principal cells of clusters 1 and 3, a property that should assist the generation of maintained head direction signals in vivo.     

Making sense of evidence

There is a constant stream of information emanating from psychiatric research. The challenge for the clinician to keep abreast of the latest research findings is huge. However, even more daunting is the task of making sense of the sometimes conflicting data. In this paper, we provide some examples of evidence that seemed to have been accepted with relatively little critical examination. We discuss how evidence may look plausible on the surface either because contextual factors have not been considered or because they fit into a pre-determined world view. We argue that, in the end, the process of making sense of evidence is not straightforward and that professional biases and social prejudices often influence decisions.     

Reversible Vasoconstriction Syndrome with Bilateral Basal Ganglia Hemorrhages

Reversible cerebral vasoconstriction syndrome (RCVS) is an increasingly recognized acute cerebrovascular condition that may produce myriad transient and sustained neurologic deficits as well as a host of radiologic features. We report the case of a woman with RCVS and a severe clinical syndrome with bilateral basal ganglia hemorrhages, cerebral infarctions, and marked vascular abnormalities. The patient made a near complete clinical recovery, representing an extreme and illustrative form of RCVS.     

Transcatheter Arterial Embolization of Spontaneous Soft Tissue Hematomas: A Systematic Review

CardioVascular and Interventional Radiology - Severe spontaneous soft tissue hematomas (SSTH) are usually treated with transcatheter arterial embolization (TAE) although only limited retrospective...     

Bridging Hepatocellular Carcinoma to Transplant: Transarterial Chemoembolization Response,Tumor Biology,and Recurrence after Transplantation in a 12-Year Transplant Cohort

PurposeTo evaluate tumor response to transarterial chemoembolization as well as biologic characteristics of the tumor as predictors of recurrence after transplantation in patients with hepatocellular carcinoma (HCC) who were bridged or down-staged to liver transplantation.Materials and MethodsAn institutional review board-approved, Health Insurance Portability and Accountability Act-compliant, single-institution retrospective analysis was performed on all patients with HCC who were treated with the use of conventional transarterial chemoembolization or transarterial chemoembolization with drug-eluting embolics (DEE) over a 12-year period and who subsequently underwent liver transplantation (n = 142). Treatment response was based on modified Response Evaluation Criteria in Solid Tumors (mRECIST) imaging criteria and then correlated with tumor characteristics and recurrence. Of the 142 patients followed after transplantation, 127 had imaging after transarterial chemoembolization but before transplantation. Imaging response and post-transplantation recurrence were correlated with patient demographics, liver function, and tumor morphology. HCC recurred in 9 patients (mean time from transplantation, 526 days). Recurrence was analyzed with the use of univariate and multivariate statistics. Kaplan-Meier recurrence-free survival curves were calculated based on immediate imaging response before transplantation with the use of the log-rank test.ResultsBefore transplantation, 57% of patients (72/127) demonstrated complete response (CR) and 24% (31/127) showed partial response (PR). Complete pathologic necrosis occurred in 54% (39/72) of CR patients and 20% (6/31) of PR patients. Poor treatment response, defined as stable disease (SD) or progressive disease (PD), occurred in 18% of patients (24/127) before transplantation and was present in 67% of cases of recurrence (6/9; P < .001). Post-transplantation recurrence was present in 1.4% of patients (1/71) with CR and in 6.5% of patients (2/31) with PR. In patients with SD after transarterial chemoembolization, HCC recurred in 18.8% of transplant patients (3/16) and in 43% of patients (3/7) with PD. Larger pretreatment tumor size (P = .05), higher Child-Pugh score (P = .002), higher tumor grade at explantation (P = .04), and lymphovascular invasion at explantation (P = .008) also were associated with increased incidence of post-transplantation recurrence.ConclusionsPoor tumor response to transarterial chemoembolization before transplantation identifies patients at increased risk for post-transplantation recurrence.