Juergen Meixensberger

Validation of Knowledge Acquisition for Surgical Process Models

OBJECTIVE Surgical Process Models (SPMs) are models of surgical interventions. The objectives of this study are to validate acquisition methods for Surgical Process Models and to assess the performance of different observer populations. DESIGN The study examined 180 SPM of simulated Functional Endoscopic Sinus Surgeries (FESS), recorded with observation software. About 150,000 single measurements in total were analyzed. MEASUREMENTS Validation metrics were used for assessing the granularity, content accuracy, and temporal accuracy of structures of SPMs. RESULTS Differences between live observations and video observations are not statistically significant. Observations performed by subjects with medical backgrounds gave better results than observations performed by subjects with technical backgrounds. Granularity was reconstructed correctly by 90%, content by 91%, and the mean temporal accuracy was 1.8 s. CONCLUSION The study shows the validity of video as well as live observations for modeling Surgical Process Models. For routine use, the authors recommend live observations due to their flexibility and effectiveness. If high precision is needed or the SPM parameters are altered during the study, video observations are the preferable approach.

The navigation-controlled drill in temporal bone surgery: a feasibility study.

Background: This study examines the feasibility of a navigation‐controlled (NC) drill for surgery on the petrosal bone in an experimental environment. According to the principle of NC, the drill is to be switched off automatically once the borders of the workspace are exceeded during a mastoidectomy.

Evaluation of a navigation system for ENT with surgical efficiency criteria

The aim of this study is the evaluation of a navigation system (NaviBase) for ENT surgery. For this purpose, a new methodology for the evaluation of surgical and ergonomic system properties has been developed. The practicability of the evaluation instruments will be examined using the example of the overall assessment of the system in comparison with the current surgical standard and with other systems using clinical efficiency criteria. The evaluation is based on 102 ENT surgical applications; of these, 89 were functional endoscopic sinus surgeries (FESS). The evaluation of surgical and ergonomic performance factors was performed by seven ENT surgeons. To evaluate surgical system properties, the Level of Quality (LOQ) in 89 cases of the FESS was determined. It compares the existing information of the surgeon with that of the navigation system on a scale of 0 to 100 and with a mean value of 50 and places it in a relationship to the clinical impact. The intraoperative change of the planned surgical strategy (Change of Surgical Strategy) was documented. The ergonomic factors of the system with the categories of Overall Confidence (Trust), awareness of the situation (Situation Awareness), influence on the operating team, requirements for specific skills (Skill Set Requirement), and cognitive load (Workload Shift) were recorded for all surgical procedures as Level of Reliance (LOR). In the evaluation of the surgical system properties, an average evaluation of the quality of the information, as an LOQ of 63.59, resulted. Every second application of the navigation system (47.9%), on average, led to a change in the surgical strategy. An extension/enhancement of the indication of the endonasal approach through the use of the navigation system was shown in 7 of 102 (6.8%) cases. The completion of the resection in the FESS was rated by 74% of group I and 11% of group II as better in comparison with the standard approach. Total confidence shows a positive evaluation of 3.35 in the LOR. To supplement the evaluation of the navigation system, the technical parameters were included. The maximum deviation, Amax, of the displayed position of the reference value amounted to 1.93 mm. The average deviation was at 1.29 mm with an SD above all values, sd, of 0.29. The subsequent economic evaluation resulted in an effective average extra expenditure of time of 1.35 minutes per case. The overall evaluation of the system imparts application‐relevant information beyond the technical details and permits comparability between different assistance systems.

Clinical cerebral microdialysis: brain metabolism and brain tissue oxygenation after acute brain injury.

Abstract While continuous monitoring of brain tissue oxygenation (ptiO2) is known as a practicable, safe and reliable monitoring technology supplementing traditional ICP-CPP-monitoring, the impact of cerebral microdialysis, now available bedside, is not proven extensively. Therefore our studies focused on the practicability, complications and clinical impact of microdialysis during long term monitoring after acute brain injury, especially the analysis of the correlation between changes of local brain oxygenation and metabolism. Advanced neuromonitoring including ICP-CPP-ptiO2 was performed in 20 patients suffering from acute brain injury. Analysis of the extracellular fluid metabolites (glucose, lactate, pyruvate, glutamate) were performed bedside hourly. No catheter associated complications, like infection and bleeding, occurred. However, longterm monitoring was limited in 5 out of 20 patients caused by obliteration of the microdialysis catheter after 3-4 days. In the individual patients partly a correlation between increased lactate levels as well as lactate pyruvate ratios and hypoxic brain tissue oxygenation could be found. Analysing the data sets of all patients only a low correlation was detected indicating physiological and increased lactate and lactate/pyruvate ratio during sufficient brain oxygenation. Additionally, concentrations of excitatory amino acid glutamate were found in normal and elevated range during periods of hypoxic oxygenation (ptiO2 < 10 mmHg) and intracranial hypertension. Our data strongly suggest partly evidence of correlation between hypoxic oxygenation and metabolic disturbances after brain injury. On the other hand brain metabolism is altered without changes of cerebral oxygenation. Further studies are indicated to improve our pathophysiological knowledge before microdialysis is routinely useful in neurointensive care. [Neurol Res 2001; 23: 801-806]

Automation in surgery: the impact of navigated-control assistance on performance, workload, situation awareness, and acquisition of surgical skills.

Objective: Human performance consequences of a new technology of image-guided navigation (IGN) support for surgeons are investigated. Background: Navigated control (NC) represents an advancement of IGN technology. In contrast to currently available pointer-based systems, it represents a higher degree of automation that supports processes not only of information analysis and integration but also of intraoperative decision making. Method: In the first experiment, 14 surgical novices performed a simulated mastoidectomy with and without NC support. Effects of provision of the system were analyzed with respect to different measures of surgical performance and outcome, workload, and situation awareness. In the second experiment, 21 advanced medical students were trained to perform a mastoidectomy by practicing it either with or without NC support. It was investigated to what extent the provision of the system during practice would affect the acquisition of surgical skills. Results: The results reveal that NC support can reduce both the risk of intraoperative injuries and complications as well as the physiological effort of surgeons. “Cost effects” compared to a conventional (i.e., not supported) surgery emerged with respect to the time needed for the surgery, increased subjective workload, reduced spare capacity, and a reduced level of situation awareness. However, no significant effects on processes of skill acquisition were found. Conclusion: NC systems can contribute to improved patient safety. Most of the cost effects seem to be related not to the basic principle of NC but to its current technological implementation. Application: The results have consequences for the design and clinical use of automated navigation support.

Bortezomib Sensitizes Primary Meningioma Cells to TRAIL-Induced Apoptosis by Enhancing Formation of the Death-Inducing Signaling Complex

Abstract A meningioma is the most common primary intracranial tumor in adults. Here, we investigated the therapeutic potential of the tumor necrosis factor–related apoptosis-inducing ligand (TRAIL) in 37 meningiomas. Freshly isolated primary meningioma cells were treated with TRAIL with or without different sensitizing protocols, and apoptotic cell death was then quantified. Mechanisms of TRAIL sensitization were determined by a combination of Western blotting, flow cytometry, receptor complex immunoprecipitation, and siRNA-mediated knockdown experiments. Tumor necrosis factor–related apoptosis-inducing ligand receptor expression was analyzed using immunohistochemistry and quantified by an automated software-based algorithm. Primary tumor cells from 11 (29.7%) tumor samples were sensitive to TRAIL-induced apoptosis, 12 (32.4%) were intermediate TRAIL resistant, and 14 (37.8%) were completely TRAIL resistant. We tested synergistic apoptosis-inducing cotreatment strategies and determined that only the proteasome inhibitor bortezomib potently enhanced expression of the TRAIL receptors TRAIL-R1 and/or TRAIL-R2, the formation of the TRAIL death-inducing signaling complex, and activation of caspases; this treatment resulted in sensitization of all TRAIL-resistant meningioma samples to TRAIL-induced apoptosis. Bortezomib pretreatment induced NOXA expression and downregulated c-FLIP, neither of which caused the TRAIL-sensitizing effect. Native TRAIL receptor expression could not predict primary TRAIL sensitivity. This first report on TRAIL sensitivity of primary meningioma cells demonstrates that TRAIL/bortezomib cotreatment may represent a novel therapeutic option for meningiomas.

Induction of Gliosarcoma and Atypical Meningeoma 13 Years after Radiotherapy of Residual Pilocytic Astrocytoma in Childhood

Background: Malignant transformation of pilocytic astrocytomas in children is rare and often linked to previous radiotherapy. Methods and Results: We report a patient who underwent subtotal resection of a right temporal and insular pilocytic astrocytoma at age 8 in 1988 followed by high-dose radiation therapy. A local recurrence, grade WHO III, with signs of focal sarcomatous transformation, was subtotally resected 13 years later in 2001. A new and fast growing right frontal meningeoma, grade WHO II, was removed in 2003. In 2004 a second glioma recurrence was partially resected, this time graded gliosarcoma WHO IV. The patient was treated thereafter with repeated courses of temozolamide. Another tumor mass reduction in 2005 was followed by stereotactic radiotherapy. Nevertheless, he deceased 3 months later. Conclusion: Most of the reported cases of malignant transformation of pilocytic astrocytomas received radiation therapy beforehand. Irradiation-induced meningeomas in children are known to occur, however not following radiotherapy of low-grade hemispheric gliomas. The presented case illustrates why adjuvant radiotherapy of residual pilocytic astrocytoma in children is not recommended anymore. For children who underwent radiotherapy in the past, we recommend MRI surveillance on a yearly basis far beyond 10 years, even in those who seem to have achieved total remission.

Two cases of atypical meningioma with pulmonary metastases: A comparative cytogenetic analysis of chromosomes 1p and 22 and a review of the literature

We present two cases of atypical meningioma WHO grade II with a history of multiple local recurrences and late pulmonary metastases. Comparative cytogenetic analyses on 1p and 22q confirmed clonal origin of the primary intracranial meningiomas and the pulmonary metastases in both cases. These cases illustrate the importance of close neuroradiological follow‐up to detect tumor recurrence in patients with atypical meningiomas WHO grade II even with clinically stable disease and should sensitize clinicians to late extracranial metastases of these tumors, especially to the lung. In an effort to elucidate common clinical features of metastatic meningiomas, especially to the lung, the literature was reviewed from 1995 to 2014, identifying a total of 45 published cases.

Automation in Surgery: The Impact of Navigated-Control Assistance on the Performance, Workload and Situation Awareness of Surgeons

The present study investigates performance consequences of a new approach of automated support for surgeons. “Navigated-Control” (NC) represents an advancement of image-guided navigation that does not only support the surgeon in navigating through a patients anatomy, but also can stop the surgical device if it comes too close to risk structures which need to be protected to ensure patient safety. It is explored, how NC affects different aspects of surgical outcome, workload and stress, and situation awareness. Fourteen advanced students of medicine performed a simulated Mastoidectomy with and without NC support. The results reveal that NC support can reduce both, the risk of intra-operative injuries, as well as the physiological stress level of surgeons. However, “cost effects” emerged with respect to subjective workload, and a reduced spare capacity compared to unsupported surgeries. These latter effects do not seem to be related to the principle of NC but technical constraints of current implementations.