Outcomes of Staple Line Reinforcement Following Robotic Assisted Sleeve Gastrectomy Based on MBSAQIP Database.

INTRODUCTION: The objective of this study is to evaluate the outcomes for Staple Line Reinforcement (SLR) in RA-SG based on the Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program (MBSAQIP) database for 2019. MATERIALS AND METHODS: We selected patients who underwent RA-SG in the MBSAQIP PUF (Public Utility File) for the year 2019 and grouped them based on their SLR status: Oversewing (OS), Buttressing (BR), both OS and BR and neither. Our primary outcomes were bleeding, organ space infection (OSI), and adverse events (AEs), and our secondary outcomes were operation length, hospital length of stay, readmissions, and conversion to open rates. We conducted separate chi square or one-way analysis of variance (ANOVA) as appropriate and multivariable direct logistic regression models for the categorical outcomes. RESULTS: We found 115,621 patients with complete data of which there were 16,494 who underwent RA-SG. Our results did not show a statistically significant decrease in incidence of postoperative bleeding for BR and OS (Adjusted OR = 0.782, p = 0.2291 and Adjusted OR of 0.482, p = 0.054 for BR and OS respectively). There was a statistically significant effect for SLR status on operation length, with OS patients having the highest operative times (log-transformed mean = 2.03), followed by both BR + OS patients (log-transformed mean = 1.99). BR patients had the shortest operation length. CONCLUSION: SLR did not result in any significant differences related to bleeding, OSI or AEs following RA-SG according to MBSAQIP for the year 2019. However, OS resulted in significantly longer operative time compared to BR alone.

Comparative Analysis of Patients with Robotic Hiatal Hernia Repairs with and without Collis Gastroplasty.

INTRODUCTION: After extensive mediastinal dissection fails to achieve adequate intra-abdominal esophageal length, a Collis gastroplasty(CG) is recommended to decrease axial tension and reduce hiatal hernia recurrence. However, concerns exist about staple line leak, and long-term symptoms of heartburn and dysphagia due to the acid-producing neoesophagus which lacks peristaltic activity. This study aimed to assess long-term satisfaction and GERD-related quality of life after robotic fundoplication with CG (wedge fundectomy technique) and to compare outcomes to patients who underwent fundoplication without CG. Outcomes studied included patient satisfaction, resumption of proton pump inhibitors (PPI), length of surgery (LOS), hospital stay, and reintervention. METHODS: This was a single-center retrospective analysis of patients from January 2017 through December 2018 undergoing elective robotic hiatal hernia repair and fundoplication. 61 patients were contacted for follow-up, of which 20 responded. Of those 20 patients, 7 had a CG performed during surgery while 13 did not. There was no significant difference in size and type of hiatal hernias in the 2 groups. These patients agreed to give their feedback via a GERD health-related quality of life (GERD HRQL) questionnaire. Their medical records were reviewed for LOS, length of hospital stay (LOH), and reintervention needed. Statistical analysis was performed using SPSS v 25. Satisfaction and need for PPIs were compared between the treatment and control groups using the chi-square test of independence. RESULTS: Statistical analysis showed that satisfaction with outcome and PPI resumption was not significantly different between both groups (P > .05). There was a significant difference in the average ranks between the 2 groups for the question on postoperative dysphagia on the follow-up GERD HRQL questionnaire, with the group with CG reporting no dysphagia. There were no significant differences in the average ranks between the 2 groups for the remaining 15 questions (P > .05). The median LOS was longer in patients who had a CG compared to patients who did not (250 vs. 148 min) (P = .01). The LOH stay was not significantly different (P > .05) with a median length of stay of 2 days observed in both groups. There were no leaks in the Collis group and no reoperations, conversions, or blood transfusions needed in either group. CONCLUSION: Collis gastroplasty is a safe option to utilize for short esophagus noted despite extensive mediastinal mobilization and does not adversely affect the LOH stay, need for reoperation, or patient long-term satisfaction.

Decreasing the burden: An unusual GIST presentation, a case report.

INTRODUCTION: Gastrointestinal stromal tumours (GIST) are notoriously one of the most common mesenchymal tumours of the alimentary canal. Most commonly originating from the gastric stroma, they are recognized by their mass effects on the abdominal cavity. Recurrence frequently occurs with GIST and these tumours may become refractory to tyrosine kinase inhibitors (TKIs). Therefore, resection may be indicated for improved outcomes. PRESENTATION OF CASE: We present a 52-year-old African American male with a surgical history of GIST resection with recurrence that came to the emergency room with worsening diffuse abdominal pain. The tumour was refractory to two TKIs, Imatinib and Sunitinib. Computed tomography (CT) of the abdomen and pelvis was done which showed severe metastatic disease with carcinomatosis, multiple dilated loops of small bowel in the left hemiabdomen without discrete transition point. After seventeen days on nasogastric tube, antiemetics, the patient worsened, and it was decided to go to surgery. In this report, attention is focused on the surgical approach of tumour debulking with subsequent Regorafenib therapy for decreased obstructive symptoms and improved quality of life. CONCLUSION: This case serves as an example of the importance of surgical debulking in addition to molecular therapy for patients with severely extensive GISTs. Tumour debulking is important to decrease tumour burden, improve chemotherapeutic response and improve quality of life especially in persons refractory to pharmacological therapy.

Fatal Subarachnoid Hemorrhage From Ruptured Intracerebral Aneurysm After Carotid Endarterectomy.

Concomitant carotid stenosis with cerebral aneurysm is a rare entity with an incidence reported to be about 1.9-3.2%. The effect of carotid revascularization on pre-existing cerebral aneurysm, along with risk factors for aneurysmal rupture, is not fully understood. We report a 61-year-old man who underwent carotid endarterectomy (CEA) for symptomatic carotid stenosis, and 6 days post-operatively the patient suffered a fatal subarachnoid hemorrhage from the rupture of a known basilar artery aneurysm. This rare but potentially fatal complication of a ruptured cerebral aneurysm after CEA warrants a discussion on the management of concomitant pathology.

Visual-vestibular estimation of the body's curvilinear motion through the world: A computational model.

Motion along curved paths (curvilinear self-motion) introduces a rotation component to the radial expanding patterns of visual motion generated in the eyes of moving animals with forward-facing eyes. The resultant image motion (vector flow field) is no longer purely radial, and it is difficult to infer the heading direction from such combined translation-plus-rotation flow fields. The eye need not rotate relative to the head or body during curvilinear self-motion, and so there is an absence of efference signals directing and indicating the rotation. Yet the eye's rotation relative to the world needs to be measured accurately and its effect removed from the combined translation-rotation image motion in order for successful navigation to occur. I demonstrate that to be able to account for human heading-estimation performance, the precision of the eye-in-world rotation velocity signal needs to be at least 0.2°/s. I show that an accurate estimate of the eye's curvilinear motion path through the world can be achieved by combining relatively imprecise vestibular estimates of the rotation rate and direction with visual image-motion velocities distributed across the retina. Combined visual-vestibular signals produce greater accuracy than each on its own. The model can account for a wide range of existing human heading- and curvilinear-estimation psychophysical data.

The Effect of Differences in Day and Night Lighting Distributions on Drivers' Speed Perception.

Previous research has shown that changes to contrast levels in the visual environment caused by fog can affect drivers' perceptions of speed. It is not easy, however, to extrapolate these results to other driving scenarios in which contrast is affected, such as during nighttime driving, because the measure of contrast is more complex when considering factors such as the illumination provided by headlights. Therefore, we investigated the differences in lighting distribution patterns between day- and nighttime driving on speed perception using prerendered 3D scenarios representing driving on a rural road. A two-alternative forced-choice design based on the method of constant stimuli was utilised, with 32 participants viewing a series of pairs of scenarios (day vs. night driving) from a driver's perspective while indicating for each pair whether the second scenario was faster or slower than the first scenario. Our results indicated that speed discrimination accuracy was minimally affected by changes in lighting distribution patterns between day and night.

Fixating on the size-speed illusion of approaching railway trains: What we can learn from our eye movements.

Railway level crossing collisions have recently been linked to a size-speed illusion where larger objects such as trains appear to move slower than smaller objects such as cars. An explanation for this illusion has centred on observer eye movements - particularly in relation to the larger, longer train. A previous study (Clark et al., 2016) found participants tend to make initial fixations to locations around the visual centroid of a moving vehicle; however individual eye movement patterns tended to be either fixation-saccade-fixation type, or smooth pursuit. It is therefore unknown as to which type of eye movement contributes to the size-speed illusion. This study isolated fixation eye movements by requiring participants to view computer animated sequences in a laboratory setting, where a static fixation square was placed in the foreground at one of two locations on a train (front and centroid). Results showed that even with the square placed around the front location of a vehicle, participants still underestimated the speed of the train relative to the car and underestimation was greater when the square was placed around the visual centroid of the train. Our results verify that manipulation of eye movement behaviour can be effective in reducing the magnitude of the size-speed illusion and propose that interventions based on this manipulation should be designed and tested for effectiveness.

The role of eye movements in the size-speed illusion of approaching trains.

Recent research on the perceived speed of large moving objects, compared to smaller moving objects, has revealed the presence of a size-speed illusion. This illusion, where a large object seems to be moving more slowly than a small object travelling at the same speed may account for collisions between motor cars and trains at level crossings, which is a serious safety issue in New Zealand and worldwide. One possible reason for the perceived size-speed difference may be related to the movement of our eyes when we track moving vehicles. In order to investigate this, we tested observers' relative speed perception of moving objects (both abstract and more detailed objects) moving in depth towards the observer, presented on a computer display and eye movements recorded with an eyetracker. Experiment 1 confirmed first the size-speed illusion when the observers were situated further away (18, 36m) from the simulated rail crossing or intersection. It also revealed that the eye movement behaviour of our participants was different when they judged the speeds of the small and large objects; eye fixations were localised around the visual centroid of longer objects and hence were further from the front of the moving large objects than the smaller ones. Experiment 2 found that manipulating eye movements could reduce the magnitude of the illusion. When observers tracked targets (dots) that were placed at corresponding locations at the front of the small object and the long object respectively, they perceived the speeds of the two objects as equal. When target dots were placed closer to the visual centroid, observers perceived the larger object to be moving slower. These results demonstrate that there is a close relationship between eye movement behaviour and our perceived judgement of an approaching train's speed.

Redundancy reduction explains the expansion of visual direction space around the cardinal axes.

Motion direction discrimination in humans is worse for oblique directions than for the cardinal directions (the oblique effect). For some unknown reason, the human visual system makes systematic errors in the estimation of particular motion directions; a direction displacement near a cardinal axis appears larger than it really is whereas the same displacement near an oblique axis appears to be smaller. Although the perceptual effects are robust and are clearly measurable in smooth pursuit eye movements, all attempts to identify the neural underpinnings for the oblique effect have failed. Here we show that a model of image velocity estimation based on the known properties of neurons in primary visual cortex (V1) and the middle temporal (MT) visual area of the primate brain produces the oblique effect. We also provide an explanation for the unusual asymmetric patterns of inhibition that have been found surrounding MT neurons. These patterns are consistent with a mechanism within the visual system that prevents redundant velocity signals from being passed onto the next motion-integration stage, (dorsal Medial superior temporal, MSTd). We show that model redundancy-reduction mechanisms within the MT-MSTd pathway produce the oblique effect.

Simulating component-to-pattern dynamic effects with a computer model of middle temporal pattern neurons.

Some primate motion-sensitive middle temporal (MT) neurons respond best to motion orthogonal to a contour's orientation (component types) whereas another class (pattern type) responds maximally to the overall pattern motion. We have previously developed a model of the pattern-type neurons using integration of the activity generated in speed- and direction-tuned subunits. However, a number of other models have also been able to replicate MT neuron pattern-like behavior using a diverse range of mechanisms. This basic property does not really challenge or help discriminate between the different model types. There exist two sets of findings that we believe provide a better yardstick against which to assess MT pattern models. Some MT neurons have been shown to change from component to pattern behavior over brief time intervals. MT neurons have also been observed to switch from component- to pattern-like behavior when the intensity of the intersections in a plaid pattern stimulus changes. These properties suggest more complex time- and contrast-sensitive internal mechanisms underlying pattern motion extraction, which provide a real challenge for modelers. We have now replicated these two component-to-pattern effects using our MT pattern model. It incorporates two types of V1 neurons (sustained and transient), and these have slightly different time delays; this initially favors the component response, thus mimicking the temporal effects. We also discovered that some plaid stimuli contain a contrast asymmetry that depends on the plaid direction and the intensity of the intersections. This causes the model MT pattern units to act as component units.

An illusory size-speed bias and railway crossing collisions.

Collisions between motor vehicles and trains at railway level crossings have been a high-profile issue for many years in New Zealand and other countries. Errors made in judging a train's speed could possibly be attributed to motorists being unknowingly subjected to a size-speed illusion and this could put them at considerable risk. Leibowitz (1985) maintained that a large object seems to be moving slower than a small object travelling at the same speed. Support has been provided for Leibowitz's theory from studies using simple shapes on a screen. However, the reasons behind the size-speed illusion remain unknown and there is no experimental evidence that it applies to an approaching train situation. To investigate these issues, we tested observers' relative speed estimation performance for a train and a car approaching at a range of speeds and distances, in a simulated environment. The data show that participants significantly underestimated the speed of the train, compared to the car. A size-speed illusion seems to be operating in the case of the approaching train in our simulation and may therefore be a risk factor in some railway level crossing collisions.

A neural-based code for computing image velocity from small sets of middle temporal (MT/V5) neuron inputs.

It is still not known how the primate visual system is able to measure the velocity of moving stimuli such as edges and dots. Neurons have been found in the Medial Superior Temporal (MST) area of the primate brain that respond at a rate proportional to the speed of the stimulus but it is not clear how this property is derived from the speed-tuned Middle Temporal (MT) neurons that precede area MST along the visual motion pathway. I show that a population code based on the outputs from a number of MT neurons is susceptible to errors if the MT neurons are tuned to a broad range of spatial frequencies and have receptive fields that span a wide range of sizes. I present a solution that uses the activity of just three MT units within a velocity channel to estimate the velocity using a weighted vector average (centroid) technique. I use a range of velocity channels (1, 2, 4, and 8°/s) with inhibition between them so that only a single channel passes the velocity estimate onto the next stage of processing (MST). I also include a contrast-dependent redundancy-removal stage which provides tighter spatial resolution for the velocity estimates under conditions of high contrast but which trades off spatial compactness for greater sensitivity at low contrast. The new model produces an output signal proportional to the stimulus input velocity (consistent with MST neurons) and its input stages have properties closely tied to those of neurons in areas V1 and MT.

Spatial integration by MT pattern neurons: a closer look at pattern-to-component effects and the role of speed tuning.

The primate visual system faces a difficult problem whenever it encounters the motion of an object moving over a patch of the retina. Objects typically contain a number of edges at different orientations and so a range of image velocities are generated within the receptive field of a neuron processing the object movement. It is still a mystery as to how these different velocities are combined into one unified and correct velocity. Neurons in area MT (V5) are considered to be the neural substrate for this motion integration process. Some MT neurons (pattern type) respond selectively to the correct global motion of an object, whereas others respond primarily to the individual components making up the pattern (component type). Recent findings from MT pattern cells tested with small patches of motion (N. J. Majaj, M. Carandini, & J. A. Movshon, 2007) have put further constraints on the possible mechanisms underlying MT pattern motion integration. We tested and refined an existing model of MT pattern neurons (J. A. Perrone, 2004) using these same small patch stimuli and found that it can accommodate these new findings. We also discovered that the speed of the test stimuli may have had an impact on the N. J. Majaj et al. (2007) results and that MT direction and speed tuning may be more closely linked than previously thought.

The role of looming and attention capture in drivers' braking responses.

This study assessed the ability of drivers to detect the deceleration of a preceding vehicle in a simulated vehicle-following task. The size of the preceding vehicles (car, van, or truck) and following speeds (50, 70, or 100 km/h) were systematically varied. Participants selected a preferred following distance by engaging their vehicle's cruise control and when the preceding vehicle began decelerating (no brake lights were illuminated), the participant's braking latency and distances to the lead vehicle were recorded. The experiment also employed a secondary task condition to examine how the attention-capturing properties of a looming vehicle were affected by driver distraction. The results indicated that a looming stimulus is capable of redirecting a driver's attention in a vehicle following task and, as with detection of brake lights, a driver's detection of a looming vehicle is compromised in the presence of a distracting task. Interestingly, increases in vehicle size had the effect of decreasing drivers' braking latencies and drivers engaged in the secondary task were significantly closer to the lead vehicle when they began braking, regardless of the size of the leading vehicle. Performance decrements resulting from the secondary task were reflected in a time-to-collision measure but not in optic expansion rate, lending support to earlier arguments that time-to-collision estimates require explicit cognitive judgements while perception of optic expansion may function in a more automatic fashion to redirect a driver's attention when cognitive resources are low or collision is imminent.

Vector subtraction using visual and extraretinal motion signals: a new look at efference copy and corollary discharge theories.

The question as to how the visual motion generated during eye movements can be 'canceled' to prevent an apparent displacement of the external world has a long history. The most popular theories (R. W. Sperry, 1950; E. von Holst & H. Mittelstaedt, 1950) lack specifics concerning the neural mechanisms involved and their loci. Here we demonstrate that a form of vector subtraction can be implemented in a biologically plausible way using cosine distributions of activity from visual motion sensors and from an extraretinal source such as a pursuit signal. We show that the net result of applying an 'efference copy/corollary discharge signal' in the form of a cosine distribution is a motion signal that is equivalent to that produced by vector subtraction. This vector operation provides a means of 'canceling' the effect of eye movements. It enables the extraretinal generated image motion to be correctly removed from the combined retinal-extraretinal motion, even in cases where the two motions do not share the same direction. In contrast to the established theories (efference copy and corollary discharge), our new model makes specific testable predictions concerning the location (the MT-MST/VIP areas) and nature of the eye-rotation cancellation stage (neural-based vector subtraction).

A single mechanism can explain the speed tuning properties of MT and V1 complex neurons.

A recent study by Priebe et al., (2006) has shown that a small proportion (27%) of primate directionally selective, complex V1 neurons are tuned for the speed of image motion. In this study, I show that the weighted intersection mechanism (WIM) model, which was previously proposed to explain speed tuning in middle temporal neurons, can also explain the tuning found in complex V1 neurons. With the addition of a contrast gain mechanism, this model is able to replicate the effects of contrast on V1 speed tuning, a phenomenon that was recently discovered by Priebe et al., (2006). The WIM model simulations also indicate that V1 neuron spatiotemporal frequency response maps may be asymmetrical in shape and hence poorly characterized by the symmetrical two-dimensional Gaussian fitting function used by Priebe et al., (2006) to classify their cells. Therefore, the actual proportion of speed tuning among directional complex V1 cells may be higher than the 27% estimate suggested by these authors.

Economy of scale: a motion sensor with variable speed tuning.

We have previously presented a model of how neurons in the primate middle temporal (MT/V5) area can develop selectivity for image speed by using common properties of the V1 neurons that precede them in the visual motion pathway (J. A. Perrone & A. Thiele, 2002). The motion sensor developed in this model is based on two broad classes of V1 complex neurons (sustained and transient). The S-type neuron has low-pass temporal frequency tuning, p(omega), and the T-type has band-pass temporal frequency tuning, m(omega). The outputs from the S and T neurons are combined in a special way (weighted intersection mechanism [WIM]) to generate a sensor tuned to a particular speed, v. Here I go on to show that if the S and T temporal frequency tuning functions have a particular form (i.e., p(omega)/(m(omega) = k/omega), then a motion sensor with variable speed tuning can be generated from just two V1 neurons. A simple scaling of the S- or T-type neuron output before it is incorporated into the WIM model produces a motion sensor that can be tuned to a wide continuous range of optimal speeds.

A visual motion sensor based on the properties of V1 and MT neurons.

The motion response properties of neurons increase in complexity as one moves from primary visual cortex (V1), up to higher cortical areas such as the middle temporal (MT) and the medial superior temporal area (MST). Many of the features of V1 neurons can now be replicated using computational models based on spatiotemporal filters. However until recently, relatively little was known about how the motion analysing properties of MT neurons could originate from the V1 neurons that provide their inputs. This has constrained the development of models of the MT-MST stages which have been linked to higher level motion processing tasks such as self-motion perception and depth estimation. I describe the construction of a motion sensor built up in stages from two spatiotemporal filters with properties based on V1 neurons. The resulting composite sensor is shown to have spatiotemporal frequency response profiles, speed and direction tuning responses that are comparable to MT neurons. The sensor is designed to work with digital images and can therefore be used as a realistic front-end to models of MT and MST neuron processing; it can be probed with the same two-dimensional motion stimuli used to test the neurons and has the potential to act as a building block for more complex models of motion processing.

A model of speed tuning in MT neurons.

We have shown previously that neurons in the middle temporal (MT) area of primate cortex have inseparable spatiotemporal receptive fields-their response profiles exhibit a ridge that is oriented in the spatiotemporal frequency domain, and this orientation predicts the neurons' preferred speed. When measured in spatiotemporal frequency space, such MT spectral receptive field (SRF) properties are closely matched to the spectrum generated by a moving edge. In contrast, V1 neurons have SRF properties that are poorly matched to moving edge spectra, indicating that V1 neurons are not tuned to a particular image speed but rather to specific spatial and temporal frequencies. Here we describe a neural mechanism based directly on the properties of V1 neurons that is able to explain the SRF change that occurs between V1 and MT. We outline the theory behind this transformation and posit an explanation for how the visual system extracts true speed (independent of spatial frequency) from retinal image motion. We tested this speed model against our MT neuron data and found that it provides an excellent account of speed tuning in MT.