Mark G. Burnett

Diffuse optical measurement of blood flow, blood oxygenation, and metabolism in a human brain during sensorimotor cortex activation

We combine diffuse optical and correlation spectroscopies to simultaneously measure the oxyhemoglobin and deoxyhemoglobin concentration and blood flow in an adult human brain during sensorimotor stimulation. The observations permit calculation of the relative cerebral metabolic rate of oxygen in the human brain, for the first time to our knowledge, by use of all-optical methods. The feasibility for noninvasive optical measurement of blood flow through the skull of an adult brain is thus demonstrated, and the clinical potential of this hybrid, all-optical noninvasive, methodology can now be explored.

Spatiotemporal Quantification of Cerebral Blood Flow during Functional Activation in Rat Somatosensory Cortex using Laser-Speckle Flowmetry

Laser-speckle flowmetry was used to characterize activation flow coupling after electrical somatosensory stimulation of forepaw and hindpaw in the rat. Quantification of functional activation was made with high transverse spatial (μm) and temporal (msec) resolution. Different activation levels and duration of stimulation were quantitatively investigated, and were in good agreement with previous laser-Doppler measurements. Interestingly, the magnitude but not the overall shape of the response was found to scale with stimulus amplitude and the distance from the activation centroid. The results provide new insights about the spatial characteristics of cerebral blood flow response to functional activation, and the method should lead to improved understanding of the coupling of neuronal activity and hemodynamics under normal and pathologic conditions.

Differentiating tumor recurrence from treatment necrosis: a review of neuro-oncologic imaging strategies

Differentiating treatment-induced necrosis from tumor recurrence is a central challenge in neuro-oncology. These 2 very different outcomes after brain tumor treatment often appear similarly on routine follow-up imaging studies. They may even manifest with similar clinical symptoms, further confounding an already difficult process for physicians attempting to characterize a new contrast-enhancing lesion appearing on a patients follow-up imaging. Distinguishing treatment necrosis from tumor recurrence is crucial for diagnosis and treatment planning, and therefore, much effort has been put forth to develop noninvasive methods to differentiate between these disparate outcomes. In this article, we review the latest developments and key findings from research studies exploring the efficacy of structural and functional imaging modalities for differentiating treatment necrosis from tumor recurrence. We discuss the possibility of computational approaches to investigate the usefulness of fine-grained imaging characteristics that are difficult to observe through visual inspection of images. We also propose a flexible treatment-planning algorithm that incorporates advanced functional imaging techniques when indicated by the patients routine follow-up images and clinical condition.

Prophylaxis for deep venous thrombosis in craniotomy patients: A decision analysis

OBJECTIVE: We sought to determine the most efficient perioperative prophylactic strategy for deep venous thrombosis (DVT) in craniotomy patients by use of a decision analysis model. METHODS: We conducted a structured review of the relevant literature and compiled the reported incidences of DVT, pulmonary embolism, and postoperative intracranial hemorrhage (ICH) in craniotomy patients. We also obtained from the literature estimates of the likelihood and the impact of various outcomes of these complications. Data from 810 craniotomies performed at our own institution were also examined. The decision analytic model was then used to compare the effectiveness of pneumatic compression boots with pneumatic compression boots combined with either unfractionated or low-molecular-weight heparin. The model dealt with variability by using both sensitivity analysis and Monte Carlo simulation. RESULTS: As expected, the addition of heparin lowered the incidence of both DVT and pulmonary embolism, but at the cost of increasing ICH. Because the deleterious effects of ICH were so much greater than the benefits from heparinization, overall outcomes were best with mechanical prophylaxis alone. This was especially true for low-molecular-weight heparin, which is associated with a relatively high risk of ICH. Our own institutional data support the findings in the literature. Although the differences are modest, they reach statistical significance in the case of low-molecular-weight heparin. CONCLUSION: Using decision analytic modeling, we have shown that mechanical prophylaxis yields outcomes in craniotomy patients superior to those of either unfractionated or low-molecular-weight heparin.

Cost-effectiveness of current treatment strategies for lumbar spinal stenosis: nonsurgical care, laminectomy, and X-STOP

OBJECT Standard treatment options for patients with lumbar spinal stenosis include nonoperative therapies as well as decompressive laminectomy. The introduction of interspinous decompression devices such as the X-STOP has broadened treatment options, but data comparing these treatment strategies are lacking. The object of this study was to provide a cost-effectiveness analysis of laminectomy, interspinous decompression, and nonoperative treatment for patients with lumbar stenosis. METHODS The authors performed a structured literature review of lumbar stenosis and constructed a cost-effectiveness model. Using conservative treatment, decompressive laminectomy, and placement of X-STOP as the treatment arms, their primary analysis evaluated the optimal treatment strategy for a patient with lumbar stenosis at a 2-year time horizon. Secondary analyses were done to compare cases in which patients required single-level procedures with those in which multilevel procedures were required as well as to examine the outcomes for a 4-year time horizon. Outcomes were calculated using quality-adjusted life years and costs were considered from the perspective of society. RESULTS Laminectomy was found to be the most effective treatment strategy, followed by X-STOP and then conservative treatment at a 2-year time horizon. Both surgical procedures were more costly than conservative treatment. Because laminectomy was both more effective and less costly than X-STOP, it is said to dominate overall. When single level procedures were considered alone, laminectomy was more effective but also more costly than X-STOP. CONCLUSIONS Lumbar laminectomy appears to be the most cost-effective treatment strategy for patients with symptomatic lumbar spinal stenosis.

Electrical Forepaw Stimulation During Reversible Forebrain Ischemia Decreases Infarct Volume

Background and Purpose— Functional stimulation is accompanied by increases in regional cerebral blood flow which exceed metabolic demands under normal circumstances, but it is unknown whether functional stimulation is beneficial or detrimental in the setting of acute ischemia. The aim of this study was to determine the effect of forepaw stimulation during temporary focal ischemia on neurological and tissue outcome in a rat model of reversible focal forebrain ischemia. Methods— Sprague-Dawley rats were prepared for temporary occlusion of the right middle cerebral artery (MCA) using the filament model. Cerebral blood flow in the MCA territory was continuously monitored with a laser-Doppler flowmeter. Subdermal electrodes were inserted into the dorsal forepaw to stimulate either the forepaw ipsilateral or contralateral to the occlusion starting 1 minute into ischemia and continuing throughout the ischemic period. A neurological evaluation was undertaken after 24 hours of reperfusion, and animals were then euthanized and brain slices stained with 2,3,5-triphenyltetrazolium chloride. Cortical and striatal damage was measured separately. Results— The cortical and striatal infarct volumes were both significantly reduced in the contralateral stimulated group compared with the ipsilateral stimulated group (48% total reduction). There were no statistically significant differences in the neurobehavioral scores between the 2 groups, or in the laser-Doppler flow measurements from the MCA core. Conclusions— Functional stimulation of ischemic tissue may decrease tissue damage and improve outcome from stroke. Although the precise mechanism of this effect remains to be determined, functional stimulation could readily be translated to clinical practice.

An analysis of admissions from 155 United States hospitals to determine the influence of weather on stroke incidence

Weather is the most frequently proposed factor driving apparent seasonal trends in stroke admissions. Here, we present the largest study of the association between weather and ischemic stroke in the USA to date. We consider admissions to 155 United States hospitals in 20 states during the five-year period from 2004 to 2008. The data set included 196,439 stroke admissions, which were classified as ischemic (n=98,930), hemorrhagic (n=18,960), or transient ischemic attack (n=78,549). Variations in stroke admissions were tested to determine if they tracked seasonal and transient weather patterns over the same time period. Using autocorrelation analyses, no significant seasonal changes in stroke admissions were observed over the study period. Using time-series analyses, no significant association was observed between any weather variable and any stroke subtype over the five-year study. This study suggests that seasonal associations between weather and stroke are highly confounded, and an association between weather and stroke is virtually non-existent. Therefore, previous studies reporting an association between specific weather patterns and stroke should be interpreted with caution.

The association between weather and spontaneous subarachnoid hemorrhage: An analysis of 155 US hospitals

BACKGROUND:A seasonal and meteorological influence on the incidence of spontaneous subarachnoid hemorrhage (SAH) has been suggested, but a consensus in the literature has yet to emerge. OBJECTIVE:This study examines the impact of weather patterns on the incidence of SAH using a geographically broad analysis of hospital admissions and represents the largest study of the topic to date. METHODS:We retrospectively analyzed SAH admissions to 155 US hospitals during the calendar years 2004 to 2008 (N = 7758). Daily weather readings for temperature, pressure, and humidity were obtained for the same period from National Oceanic and Atmospheric Administration weather stations located near each hospital. The daily values of each weather variable were associated with the daily volume of SAH admissions using a combination of correlation and time-series analyses. RESULTS:No seasonal trends were observed in the monthly volume of SAH admissions during the study period. No significant correlation was detected between the daily SAH admission volume and the days weather, the previous days weather, or the 24-hour weather change. CONCLUSION:This study represents the most comprehensive investigation of the association between weather and spontaneous SAH to date. The results suggest that neither season nor weather significantly influences the incidence of SAH.

Cost-effectiveness of Intraoperative Imaging in Carotid Endarterectomy

OBJECTIVE: There has never been a large, randomized controlled trial to assess the impact of intraoperative imaging on the success of carotid endarterectomy (CEA). This comparison involves cost-effectiveness analysis. METHODS: We constructed a decision-analytic model to compare effectiveness and costs of intraoperative ultrasound (IUS) and completion angiography as adjuncts to CEA. Data on procedural mortality, morbidity, and costs were obtained from the English-language literature. The review included a total of 52 reports, encompassing more than 22,000 patients. The main components of costs were those of the monitoring interventions and the care of perioperative stroke. RESULTS: Mean perioperative outcome without completion imaging is approximately 96.7% of what it would be in the absence of perioperative stroke or death. IUS and completion angiography each result in approximately 2% improvement in expected outcome. Mean perioperative costs are

Identification of the mouse calcium-binding proteins, MRP 8 and MRP 14, in Schistosoma mansoni-induced granulomas: biochemical and functional characterization.

396.50 for IUS,