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Background: Post-cardiotomy cardiogenic shock (PCCS) remains a life-threatening complication after cardiac surgery. Extracorporeal membrane oxygenation (ECMO) represents the mainstay of mechanical circulatory support for PCCS; however, its availability is limited to larger experienced centers, leading to a mismatch between centers performing cardiac surgery and hospitals offering ECMO management beyond cannulation. We sought to evaluate the outcomes and complications of PCCS patients requiring veno-arterial (V-A) ECMO cannulated at our hospital compared to those cannulated at referral hospitals. Methods: A retrospective analysis of PCCS patients requiring V-A ECMO was conducted between October 2014 to December 2022. Results: A total of 121 PCCS patients required V-A ECMO support, of which 62 (51%) patients were cannulated at the referring institutions and retrieved (retrieved group), and 59 (49%) were cannulated at our hospital (on-site group). The baseline demographics and pre-ECMO variables were similar between groups, except retrieved patients had higher lactic acid levels (retrieved group: 8.5 mmol/L ± 5.8 vs. on-site group: 6.6 ± 5; p = 0.04). Coronary artery bypass graft was the most common surgical intervention (51% in the retrieved group vs. 47% in the on-site group). There was no difference in survival-to-discharge rates between the groups (45% in the retrieved group vs. 51% in the on-site group; p = 0.53) or in the rate of patient-related complications. Conclusions: PCCS patients retrieved on V-A ECMO can achieve similar outcomes as those cannulated at experienced centers. An established network in a hub-and-spoke model is critical for the PCCS patients managed at hospitals without ECMO abilities to improve outcomes.
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Shark skin is composed of denticles, or complex scale-like features, which have been shown to reduce drag in turbulent and laminar flow. The denticle crown features undulating structures called riblets that interact with the turbulent boundary layer to reduce drag. Two mechanisms thought to contribute to the drag-reducing properties of riblets include the lifting of streamwise vortices and the hampering of spanwise vortex interactions to reduce crossflow, which could translate to similar flow mechanisms for denticles. Because of the varied morphologies of dermal denticles on different shark species, which also depend on body location, the impact of these denticle geometries on flow is of interest to the biology community, including related fields such as fluid mechanics and oceanography. This review highlights the past 15 years of manufacturing techniques and experimental measurements of drag over denticle-inspired surface structures, including real shark skin samples and engineered denticles and riblets. State-of-the-art additive manufacturing and other techniques are primarily limited to mm-length denticle scales, which have demonstrated drag reduction in lower flow speeds, under 1 m s-1. New manufacturing approaches can create sub-mm length denticles and nanotextured surface structures, which have achieved reported drag reductions of up to 31%. We synthesize results from the literature to illustrate the drag reduction properties of bioinspired denticles and riblets according to their geometry and flow conditions. Using these trends, we suggest design features and focus areas for future research, such as increasing studies of different denticle morphologies, hydrophobicity, antifouling properties, and acoustic noise reduction. Continued work on bioinspired denticles for drag reduction has wider implications in comparative biology and applications to design more energy-efficient, persistent vehicles for environmental monitoring.
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The objective of this study was to determine whether a novel footbath solution containing stannous fluoride (SnF2) was superior to 5% copper sulfate solution for the treatment and prevention of digital dermatitis (DD) in dairy cattle. Study 1 was conducted over 4 weeks in Missouri and involved 34 lactating Holstein-Friesian cows with hind feet DD lesions. Cows in group SF walked through a footbath containing a proprietary formulation of SnF2 once weekly, whereas cows in group CS walked through a 5% CuSO4 footbath once daily for 5 d each week. Study 2 was conducted over 8 weeks in California and involved 40 lactating Holstein-Friesian cows with hind feet DD lesions. Cows in group SF walked through a SnF2 footbath for 3 consecutive days then once a week for the following 7 weeks. Cows in group CS walked through a 5% CuSO4 footbath 3 times each week for 8 weeks. Data collection included lesion type, lesion area, locomotion score, and pain score. Digital dermatitis was actively transmitted in study 1, and lesion area and locomotion scores were lower in group SF than group CS. In contrast, DD was not actively transmitted in study 2, and lesion area and locomotion scores were similar in groups SF and CS. Stannous fluoride delayed the development of active DD lesions in study 1 compared with copper sulfate, with a lower relative risk (0.57, P < 0.001) of a hind foot developing an active DD lesion over 28 d. However, SnF2 decreased the rate that active DD lesions transitioned to M3, M4, or M0 lesions compared with 5% copper sulfate in both studies, with the relative risk of a hind foot with an active DD lesion transitioning to M3, M4, or M0 in group SF being slightly lower in study 1 (0.83, P = 0.042) and study 2 (0.90, P = 0.020) than group CS. Our findings demonstrated that walking cows through a stannous fluoride footbath once per week in a herd undergoing active transmission of infection was more effective in preventing active DD lesions, but less effective in treating active DD lesions, than walking cows through a copper sulfate footbath 4 times per week. The novel SnF2 footbath solution shows promise for controlling DD in dairy herds that want an alternative footbath solution to CuSO4 and are interested in limiting the environmental accumulation of copper.
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Understanding disordered structure is difficult due to insufficient information in experimental data. Here, we overcome this issue by using a combination of diffraction and simulation to investigate oxygen packing and network topology in glassy (g-) and liquid (l-) MgO-SiO2 based on a comparison with the crystalline topology. We find that packing of oxygen atoms in Mg2SiO4 is larger than that in MgSiO3, and that of the glasses is larger than that of the liquids. Moreover, topological analysis suggests that topological similarity between crystalline (c)- and g-(l-) Mg2SiO4 is the signature of low glass-forming ability (GFA), and high GFA g-(l-) MgSiO3 shows a unique glass topology, which is different from c-MgSiO3. We also find that the lowest unoccupied molecular orbital (LUMO) is a free electron-like state at a void site of magnesium atom arising from decreased oxygen coordination, which is far away from crystalline oxides in which LUMO is occupied by oxygen's 3s orbital state in g- and l-MgO-SiO2, suggesting that electronic structure does not play an important role to determine GFA. We finally concluded the GFA of MgO-SiO2 binary is dominated by the atomic structure in terms of network topology.
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BACKGROUND: Restless legs syndrome (RLS) is a prevalent sensorimotor disorder that can dramatically impair sleep quality, daytime function, and quality of life. Although many patients benefit from standard pharmacological therapy, some patients suffer from insufficient treatment response or medication intolerance. Novel treatment approaches are therefore necessary. OBJECTIVE: Given the overlap between RLS and pain syndromes in both pathophysiological mechanisms and certain treatment options, we aimed to perform a scoping review of the available evidence on spinal cord stimulation (SCS) for RLS and discuss potential mechanistic implications. METHODS: We identified a total of 16 cases of patients with RLS who underwent SCS, all from case reports or case series. DISCUSSION: The published evidence is insufficient to assess SCS efficacy in patients with RLS, but SCS remains a promising investigational therapy in RLS on the basis of its potential mitigatory effects in the central hyperexcitability of the sensorimotor cortex through neuromodulation of spinal, subcortical, and cortical areas. A call for further research in this field is presented, with suggestions for future directions and trial designs.
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Síndrome das Pernas Inquietas , Estimulação da Medula Espinal , Humanos , Qualidade de Vida , Síndrome das Pernas Inquietas/tratamento farmacológico , Síndrome das Pernas Inquietas/etiologiaRESUMO
Deep brain stimulators (DBS) may fail for a multitude of reasons. We present a 79-year-old Parkinson's disease patient who suffered a DBS failure following impulse generator (IPG) replacement surgery due to the IPG flipping within an expanded capsular pocket. This creation of the pocket was unintentional, and the pocket formed around an undiagnosed postoperative hemorrhage. The syndrome could be considered "Twiddler-like" because it resulted in device flipping. There were, however, many characteristic differences between our case and classical Twiddler's syndrome. DBS neurostimulator failure due to hematoma induced device flipping should be suspected when device interrogation is impossible or there are abnormally high impedances across multiple DBS lead contacts. A plain film X-ray series should be ordered and can be useful in providing radiological evidence of device flipping. In cases like ours the extensive braiding encountered in Twiddler's syndrome may be absent. Anchoring the IPG to a deep fascial layer as well as the use of an antimicrobial pouch are two methods that may be employed to prevent or to treat this complication.
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Despite the prevalence of special interests (SIs) in autistic youth, research on SIs and how they are characterized is limited. Indeed, a significant challenge in identifying and classifying SIs lies in capturing the vast and diverse scope of potential interests in this population. The recently developed Special Interest Survey (SIS) is a caregiver-report measure to improve SI characterization by capturing a broad range of past and current SIs. In the present study, we performed a network analysis of the SIS to examine relations between SIs and identify distinct interest clusters. We analyzed data from 1992 caregivers of autistic youths who completed the SIS. The network of SIs was densely interconnected, characterized by six communities of interests: Fact-seeking, Engineering, Order-seeking, Object Attachment, Entertainment, and Scholarly Pursuits. Findings suggest that the structure of the observed network is likely to generalize to similar samples. Of all the SIs and their respective communities, behaviors related to Fact-seeking were identified as the most central, meaning that endorsement of these interests was most strongly related to co-endorsement of other SIs. These findings lay the groundwork for future work on SIs, such as improved assessment techniques and linkage of SIs to a broad range of demographic variables, youth characteristics, and autism symptoms.
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Transtorno do Espectro Autista , Adolescente , Humanos , Transtorno do Espectro Autista/diagnóstico , Transtorno do Espectro Autista/epidemiologia , Inquéritos e Questionários , Prevalência , CuidadoresRESUMO
OBJECTIVE: The globus pallidus internus (GPI) has been demonstrated to be an effective surgical target for deep brain stimulation (DBS) treatment in patients with medication-refractory Parkinson's disease (PD). The ability of neurosurgeons to define the area of greatest therapeutic benefit within the globus pallidus (GP) may improve clinical outcomes in these patients. The objective of this study was to determine the best DBS therapeutic implantation site within the GP for effective treatment in PD patients. METHODS: The authors performed a retrospective review of 56 patients who underwent bilateral GP DBS implantation at their institution during the period from January 2015 to January 2020. Each implanted contact was anatomically localized. Patients were followed for stimulation programming for at least 6 months. The authors reviewed preoperative and 6-month postsurgery clinical outcomes based on data from the Unified Parkinson's Disease Rating Scale Part III (UPDRS III), dyskinesia scores, and levodopa equivalent daily dose (LEDD). RESULTS: Of the 112 leads implanted, the therapeutic cathode was most frequently located in the lamina between the GPI external segment (GPIe) and the GP externus (GPE) (n = 40). Other common locations included the GPE (n = 24), the GPIe (n = 15), and the lamina between the GPI internal segment (GPIi) and the GPIe (n = 14). In the majority of patients (73%) a monopolar programming configuration was used. At 6 months postsurgery, UPDRS III off medications (OFF) and on stimulation (ON) scores significantly improved (z = -4.02, p < 0.001), as did postsurgery dyskinesia ON scores (z = -4.08, p < 0.001) and postsurgery LEDD (z = -4.7, p < 0.001). CONCLUSIONS: Though the ventral GP (pallidotomy target) has been a commonly used target for GP DBS, a more dorsolateral target may be more effective for neuromodulation strategies. The assessment of therapeutic contact locations performed in this study showed that the lamina between GPI and GPE used in most patients is the optimal central stimulation target. This information should improve preoperative GP targeting.
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Estimulação Encefálica Profunda , Discinesias , Doença de Parkinson , Núcleo Subtalâmico , Humanos , Doença de Parkinson/tratamento farmacológico , Globo Pálido/cirurgia , Núcleo Subtalâmico/cirurgia , Levodopa/uso terapêutico , Resultado do Tratamento , Discinesias/tratamento farmacológico , Eletrodos ImplantadosRESUMO
In order to better evaluate the trade-offs between different simulation options for an electrospray thruster plume, we have developed a multi-scale n-body code to compute the evolution of a single emitter electrospray plume in the pure ionic regime. The electrostatic force computations in the simulation are captured through the use of three different computational algorithms with various degrees of approximation. The results of the simulations for a simple test case are compared in terms of computational speed and accuracy. The test case utilizes a single operating point (323nA) for a stable meniscus solution for the ionic liquid EMI-BF4 firing in the positive pure ion mode. Complex species and probabilistic fragmentation processes are neglected. An overview is provided of the trade-off between accuracy and computational speed for the three algorithms in the context of simulating the electrostatic interactions between particles. For a large number of particles, the faster algorithms show a significant reduction in computational time while maintaining a high level of accuracy with a proper choice of tuning parameters.
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Background: Adult lead encephalopathy is a rare but critical condition to recognize in modern healthcare settings. Few reports have described the medical and neurosurgical management of severe adult lead encephalopathy. Case Presentation: A 22 year old woman presented with severe headache, anemia, vomiting, 40-lb weight loss, and constipation. At the time of presentation, she had extensive colonic radiopaque material and a serum lead concentration of 87 mcg/dl (normal <10). She rapidly developed anisocoria requiring emergent ventriculostomy insertion. Following CSF diversion, ICP mitigation, and lead chelation, she considerably improved in <2 weeks. Conclusion: We report one of the few instances of successful surgical and medical management of adult lead encephalopathy. Dedicated neurocritical care and neurosurgical teams are necessary in conjunction with toxicology in order to manage the advanced sequalae of severe lead poisoning.
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How is the orientation of molecular liquids ordered on cooling? What are the basic structures of molecular glasses, e.g., close to the crystalline structure or some special structures such as icosahedral cluster? These are long-standing questions in liquid and glass physics. We have constructed a novel cryostat to prepare simple molecular glasses by vapor deposition and performed in situ synchrotron radiation x-ray diffraction experiments. The glassy state of a simple molecule CS2, which cannot be vitrified by normal liquid quenching, was successfully prepared with this instrument, and its diffraction data were collected in a wide Q-range of 0.16-25.7 Å-1 with a high-energy diffractometer at BL04B2, SPring-8. The diffraction data of liquid CS2 were also recorded in a wide temperature range of 160-300 K. These diffraction data were analyzed with molecular dynamics simulations and reverse Monte Carlo modelings to investigate orientational correlation. From the obtained 3D structure models, the orientational correlation between neighboring CS2 molecules was investigated quantitatively as a function of temperature. At room temperature, the parallel and T-shaped arrangements are preferred for the nearest neighbor correlation. On cooling, these arrangements are developed gradually, and its rate became prominent below the melting temperature (162 K). In the glassy state, the slipped-parallel arrangement is dominant as well as the T-shaped arrangement. Both arrangements appear in the CS2 crystal, indicating that the structure of glassy CS2 is close to that of crystalline CS2.
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Dental caries (cavities), one of the most common infectious diseases, is caused by a number of factors. Oral microbes, dietary practices, sociodemographic factors, and dental hygiene all inform caries risk. Assessing the impact of diet is complicated as individuals eat foods in combinations, and the interactions among the foods may alter caries risk. Our study aimed to prospectively assess the association between dietary patterns and caries risk in the postpartum period, a potentially sensitive period for caries development. We analyzed in-person dental assessments and telephone food frequency questionnaires (FFQs) from 879 Caucasian women participating in the Center for Oral Health Research in Appalachia Cohort 2 (COHRA2) that were collected biannually for up to 6 y. One-week recall of food intake frequency was assessed using a Likert scale. We used principal component analysis to summarize the FFQ data; the top 2 components described 15% and 12% of the variance in FFQ data. The first component was characterized by high consumption of fruits and vegetables, while the second component was heavily influenced by desserts and crackers. We used a modified Poisson model to predict the risk of an increase in the number of decayed, missing, and filled teeth in the postpartum period by 1) dietary patterns and 2) individual foods and beverages at the previous study visit, after controlling for other known risk factors, including history of carious lesions. Eating a dietary pattern high in desserts and crackers was associated with a 20% increase in the number of decayed, missing, and filled teeth in the postpartum period (95% confidence interval, 1.03-1.39). However, this effect was attenuated among those who also consumed a dietary pattern high in fruits and vegetables. Dietary patterns should be considered when devising interventions aimed at preventing dental caries.
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Cárie Dentária , Estudos de Coortes , Estudos Transversais , Cárie Dentária/epidemiologia , Cárie Dentária/etiologia , Cárie Dentária/prevenção & controle , Dieta/efeitos adversos , Feminino , Humanos , Saúde Bucal , Período Pós-PartoRESUMO
This study examined differences in observed mealtime behaviors between children preparing to transition to oral feeding and children with various other chronic illnesses using a standardized measure of mealtime beaviors. The parent-child mealtime relationship can become strained due to problematic mealtime behaviors that limit food intake, as well as inadvertent reinforcement of disruptive behavior by caregivers. Frequency/rate of behaviors were compared between children with tube feeding (CwTF) and from previous studies of children with chronic illnesses using the Dyadic Interactive Nomenclature for Eating (DINE). Parents of CwTF used more coaxing, physical prompts, and reinforcement during meals, while parents of children with chronic illnesses used more direct commands and engaged in more parent talk. Findings support differences in parent-child mealtime interactions and eating behaviors across pediatric illness subgroups.
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Nutrição Enteral , Refeições , Criança , Ingestão de Alimentos , Comportamento Alimentar , Humanos , Relações Pais-Filho , PaisRESUMO
Extreme body mass index (BMI) values (i.e., above the 97th and below the 3rd percentiles) are inaccurately represented on the Centers for Disease Control and Prevention's growth curves, which may limit the utility of BMI percentile and BMI z-score for capturing changes in clinical outcomes for patients at extreme weights. Modeling child obesity severity based upon the percentage of BMI in excess of the 95th percentile (BMI95pct) has been proposed as an improved metric to better capture variability in weight at extreme ends of growth curves, which may improve our understanding of relationships between weight status and changes in clinical outcomes. However, few studies have evaluated whether the use of BMI95pct would refine our understanding of differences in clinical psychosocial constructs compared to previous methods for categorization. This cross-sectional study evaluated child obesity severity based on BMI95pct to examine potential group differences in a validated, obesity-specific measure of Health-Related Quality of Life (HRQoL). Four hundred and sixty-five children with obesity completed Sizing Me Up, a self-report measure of HRQoL. Children were classified into categories based on BMI95pct (i.e., class I: ≥100% and <120%; class II: ≥120% and <140%; class III: ≥140%). The results indicate that children with class III obesity reported lower HRQoL than children with class I and class II obesity; however, there were no differences between Class II and Class I. In much of the previous literature, children with class II and class III obesity are often combined under the category "Severe Obesity" based upon BMI above the 99th percentile. This study suggests that grouping children from various classes together would neglect to capture critical differences in HRQoL. Future research including children with severe obesity should consider obesity classes to best account for functioning and clinical outcomes.
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The total scattering method is the simultaneous study of both the real- and reciprocal-space representations of diffraction data. While conventional Bragg-scattering analysis (employing methods such as Rietveld refinement) provides insight into the average structure of the material, pair distribution function (PDF) analysis allows for a more focused study of the local atomic arrangement of a material. Generically speaking, a PDF is generated by Fourier transforming the total measured reciprocal-space diffraction data (Bragg and diffuse) into a real-space representation. However, the details of the transformation employed and, by consequence, the resultant appearance and weighting of the real-space representation of the system can vary between different research communities. As the worldwide total scattering community continues to grow, these subtle differences in nomenclature and data representation have led to conflicting and confusing descriptions of how the PDF is defined and calculated. This paper provides a consistent derivation of many of these different forms of the PDF and the transformations required to bridge between them. Some general considerations and advice for total scattering practitioners in selecting and defining the appropriate choice of PDF in their own research are presented. This contribution aims to benefit people starting in the field or trying to compare their results with those of other researchers.
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BACKGROUND: The centromedian-parafascicular (Cm-Pf) complex of the thalamus is a common deep brain stimulation (DBS) target for treatment of Tourette syndrome (TS). Currently, there are no standardized functional intraoperative neurosurgical targeting approaches. Collectively, these issues have led to variability in DBS lead placement. Therefore, more defined methods are needed to improve targeting accuracy. OBJECTIVE: The objective of this observational study was to develop and to verify a functional mapping task capable of differentiating the Cm-Pf region from the nearby ventral intermediate (Vim) nucleus region of the thalamus. The overarching goal was to improve the reproducibility of DBS targeting in the Cm-Pf region. METHODS: Seven TS patients completed a modified Go/NoGo task (five in the post-operative setting and two in the intra-operative setting). Post-operative neural signals from Cm-Pf region were collected using sensing-enabled implanted neural stimulators, and intraoperative neural signals from the Cm-Pf region were collected using an external amplifier. Event-related potential (ERP) features were identified by using the grand-average of stimulus onset signals derived from the postoperative participants. These features were correlated with anatomical locations for the specific electrode recordings. The same features were extracted from the intraoperative patients in order to verify electrode positions in the operating room environment. RESULTS: Two features - a positive and a negative deflection - were identified in the average ERP from the post-operative participants. The peak amplitudes of both features were significantly correlated with the electrode depth position (p = 0.025 for positive deflection and p = 0.039 for negative deflection). The same result was reproduced intra-operatively in the two most recent patients, where more ventral electrode contacts revealed stronger peak amplitudes in comparison to the dorsal electrode contacts. CONCLUSION: This process was used to physiologically confirm accurate lead placement in the operating room setting. The modified Go/NoGo task elicited robust neural responses in the Cm-Pf region however the signal was not present in the Vim nucleus region of thalamus along the DBS electrode trajectory. We conclude that the differences in ERP responses may be a potentially novel LFP based functional approach for future targeting of the Cm-Pf complex for TS DBS.
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Estimulação Encefálica Profunda , Síndrome de Tourette , Humanos , Reprodutibilidade dos Testes , Tálamo , Síndrome de Tourette/terapiaRESUMO
OBJECTIVES: Despite the initial characterization of night eating syndrome (NES) in 1955, the definition and operationalization of its symptoms has varied considerably. To standardize the definition of NES and its symptoms, Allison et al. developed research diagnostic criteria. Even so, conceptualization and intervention of NES remains guided by medical models, which assume that pathology is driven by a distinct, underlying causal mechanism. Conversely, recent work on other eating disorders (EDs) has used network analysis to reconceptualize ED psychopathology and treatment by identifying (a) unique relationships between key symptoms, and (b) the symptoms most central to specific EDs. The present study examined NES symptoms through network analysis to identify the most central symptoms within the NES network. METHOD: Regularized partial correlation networks were estimated using 144 individuals in a community sample diagnosed with NES. Participants completed semi-structured interviews, self-report measures, and food/sleep diaries to measure NES symptoms, nonspecific health domains (e.g., sleep disturbance, overall mood, stress, and circadian rhythm functioning), and transdiagnostic ED symptoms. RESULTS: Depressed mood, poor sleep quality, and a strong urge to eat upon awakening at night were highly central to the psychopathology network for NES and were significantly more central than most other NES symptoms and nonspecific health domains. DISCUSSION: This study provides insight on the unique symptomological relationships of NES and sets the stage for future work that can identify causal linkages among NES symptoms. These symptoms represent key elements of the core psychopathology of NES and should represent primary targets for intervention.
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Transtornos da Alimentação e da Ingestão de Alimentos , Síndrome do Comer Noturno , Afeto , Ritmo Circadiano , Comportamento Alimentar , Transtornos da Alimentação e da Ingestão de Alimentos/diagnóstico , Humanos , SonoRESUMO
BACKGROUND: Optical neuronavigation has been established as a reliable and effective adjunct to many neurosurgical procedures. Operations such as asleep deep brain stimulation (aDBS) benefit from the potential increase in accuracy that these systems offer. Built into these technologies is a degree of tolerated error that may exceed the presumed accuracy resulting in suboptimal outcomes. OBJECTIVE: The objective of this study was to identify an underlying source of error in neuronavigation and determine strategies to maximize accuracy. METHODS: A Medtronic Stealth system (Stealth Station 7 hardware, S8 software, version 3.1.1) was used to simulate an aDBS procedure with the Medtronic Nexframe system. Multiple configurations and orientations of the Nexframe-Nexprobe system components were examined to determine potential sources of, and to quantify navigational error, in the optical navigation system. Virtual entry point and target variations were recorded and analyzed. Finally, off-plan error was recorded with the AxiEM system and visual observation on a phantom head. RESULTS: The most significant source of error was found to be the orientation of the reference marker plate configurations to the camera system, with the presentation of the markers perpendicular to the camera line of site being the most accurate position. Entry point errors ranged between 0.134 ± 0.048 and 1.271 ± 0.0986 mm in a complex, reproducible pattern dependent on the orientation of the Nexprobe reference plate. Target errors ranged between 0.311 ± 0.094 and 2.159 ± 0.190 mm with a similarly complex, repeatable pattern. Representative configurations were tested for physical error at target with errors ranging from 1.2 mm to 1.4 mm. Throughout data acquisition, no orientation was indicated as outside the acceptable tolerance by the Stealth software. CONCLUSIONS: Use of optical neuronavigation is expected to increase in frequency and variety of indications. Successful implementation of this technology depends on understanding the tolerances built into the system. In situations that depend on extremely high precision, surgeons should familiarize themselves with potential sources of error so that systems may be optimized beyond the manufacturer's built-in tolerances. We recommend that surgeons align the navigation reference plate and any optical instrument's reference plate spheres in the plane perpendicular to the line of site of the camera to maximize accuracy.