Dysphagia after anterior cervical spine surgery: incidence and risk factors. Kalb S., Reis MT, Cowperthwaite MC, Fox DJ, Lefevre R, Theodore N, Papadopoulos SM, Sonntag Vk. World Neurosurgery (2011): in press
The authors report results from a retrospective analysis of cervical spine patients undergoing anterior cervical discectomy and fusion.
Model-driven, probabilistic level set based segmentation of magnetic resonance images of the brain. Verma N, Muralidhar GS, Bovik AC, Cowperthwaite MC, Markey MK. 33rd Annual International Conference of the IEEE Engineering in Medicine and Biology Society (2011).
Abstract—Accurate segmentation of magnetic resonance (MR) images of the brain to differentiate features such as soft tissue, tumor, edema and necrosis is critical for both diagnosis and treatment purposes. Region-based formulations of geometric active contour models are popular choices for segmentation of MR and other medical images. Most of the traditional region-based formulations model local region intensity by assuming a piecewise constant approximation. However, the piecewise constant approximation rarely holds true for medical images such as MR images due to the presence of noise and bias field, which invariably results in a poor segmentation of
the image. To overcome this problem, we have developed a probabilistic region-based active contour model for automatic segmentation of MR images of the brain. In our approach, a mixture of Gaussian distributions is used to accurately model the arbitrarily shaped local region intensity distribution. Prior spatial information derived from probabilistic atlases is also integrated into the level set evolution framework for guiding the segmentation process. Our experiments with a series of publicly available brain MR images show that the proposed active contour model gives stable and accurate segmentation results when compared to the traditional region based formulations.
Treatment course and outcomes following drug and alcohol-related traumatic injuries. Cowperthwaite MC, Burnett MG. J Trauma Manag Outcomes (2011);5(1):3.
Abstract: Alcohol and drug use is known to be a major factor affecting the incidence of traumatic injury. However, the ways in which immediate pre-injury substance use affects patients’ clinical care and outcomes remains unclear. The goal of the present study is to determine the associations between pre-injury use of alcohol or drugs and patient injury severity, hospital course, and clinical outcome.
Laser Speckle Contrast Imaging of Cerebral Blood Flow in humans during neurosurgery: A pilot clinical study. Parthasarathy AB, Weber EL, Richards LM, Fox DJ, Dunn AK. J Biomed Opt (2010);15(6):066030.
Abstract: Monitoring cerebral blood flow (CBF) during neurosurgery can provide important physiological information for a variety of surgical procedures. CBF measurements are important for assessing whether blood flow has returned to pre-surgical baseline levels and for assessing post-surgical tissue viability. Existing techniques for intraoperative monitoring of CBF based on magnetic resonance imaging are expensive and often impractical, while techniques like indocyanine green angiography cannot produce quantitative measures of blood flow. Laser Speckle Contrast Imaging (LSCI) is an optical technique that has been widely used to quantitatively image relative CBF in animal models in vivo. In this pilot clinical study, we adapted an existing neurosurgical operating microscope to obtain LSCI images in humans in real-time during neurosurgery under baseline conditions and after bipolar cautery. Simultaneously recorded ECG waveforms from the patient were used to develop a filter that helped reduce measurement variabilities due to motion artifacts. Results from this study demonstrate the feasibility of using LSCI to obtain blood flow images during neurosurgeries and its capability to produce full field CBF image maps with excellent spatial resolution in real-time with minimal disruption to the surgical procedure.
Does the weather influence stroke?: An analysis of admissions from 155 United States Hospitals. Cowperthwaite MC, Burnett, MG. Journal of Clinical Neuroscience (2011); 18(5):618:23.
Abstract: 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 United States. We consider admissions to 155 United States hospitals 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 analysis methods, no significant association was observed between any weather variable and any subtype of stroke over the five-year study period. 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 associated between specific weather patterns and stroke should be interpreted with caution.
The Association Between Weather and Spontaneous Subarachnoid Hemorrhage: An Analysis of 155 United States Hospitals. Cowperthwaite MC, Burnett, MG. Neurosurgery (2011). 68:132-139.
Abstract: A seasonal and meteorological influence on the incidence of spontaneous subarachnoid hemorrhage (SAH) has been suggested, but a consensus within the literature has yet to emerge. The present study examines the impact of weather patterns on the incidence of SAH utilizing a geographically broad analysis of hospital admissions and represents the largest study of the topic to date.
Cost-effectiveness of current treatment strategies for lumbar spinal stenosis: nonsurgical care, laminectomy, and X-STOP. Burnett, MG, Stein, SC, Bartels, RH. Journal of Neurosurgery Spine. (2010) Jul; 13(1), 36-8.
Abstract: 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.
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Genome-wide association studies: a powerful tool for neurogenomics. Cowperthwaite MC, Mohanty D, Burnett MG. Neurosurg Focus (2010). 28(1):E2.
Abstract: As their power and utility increase, genome-wide association (GWA) studies are poised to become an important element of the neurosurgeon's toolkit for diagnosing and treating disease. In this paper, the authors review recent findings and discuss issues associated with gathering and analyzing GWA data for the study of neurological diseases and disorders, including those of neurosurgical importance. Their goal is to provide neurosurgeons and other clinicians with a better understanding of the practical and theoretical issues associated with this line of research. A modern GWA study involves testing hundreds of thousands of genetic markers across an entire genome, often in thousands of individuals, for any significant association with a particular disease. The number of markers assayed in a study presents several practical and theoretical issues that must be considered when planning the study. Genome-wide association studies show great promise in our understanding of the genes underlying common neurological diseases and disorders, as well as in leading to a new generation of genetics tests for clinicians.
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Textbook of Interventinoal Neurology, Chapter 21. Vertebroplasty and Kyphoplasty. Kim, SH, Patel, AI, Conrad LK, Gruiell, N, Yu, YI. Cambridge University Press (2010).
Bioinformatic analysis of the contribution of primer sequences to aptamer structures. Cowperthwaite MC, Ellington AD. J Mol Evol (2008). 67(1):95-102.
Abstract: Aptamers are nucleic acid molecules selected in vitro to bind a particular ligand. While numerous experimental studies have examined the sequences, structures, and functions of individual aptamers, considerably fewer studies have applied bioinformatics approaches to try to infer more general principles from these individual studies. We have used a large Aptamer Database to parse the contributions of both random and constant regions to the secondary structures of more than 2000 aptamers. We find that the constant, primer-binding regions do not, in general, contribute significantly to aptamer structures. These results suggest that (a) binding function is not contributed to nor constrained by constant regions; (b) in consequence, the landscape of functional binding sequences is sparse but robust, favoring scenarios for short, functional nucleic acid sequences near origins; and (c) many pool designs for the selection of aptamers are likely to prove robust
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The ascent of the abundant: how mutational networks constrain evolution. Cowperthwaite MC, Economo EP, Harcombe WR, Miller EL, Meyers LA. PLoS Comput Biol (2008). 4(7): e1000110.
Abstract: Evolution by natural selection is fundamentally shaped by the fitness landscapes in which it occurs. Yet fitness landscapes are vast and complex, and thus we know relatively little about the long-range constraints they impose on evolutionary dynamics. Here, we exhaustively survey the structural landscapes of RNA molecules of lengths 12 to 18 nucleotides, and develop a network model to describe the relationship between sequence and structure. We find that phenotype abundance--the number of genotypes producing a particular phenotype--varies in a predictable manner and critically influences evolutionary dynamics. A study of naturally occurring functional RNA molecules using a new structural statistic suggests that these molecules are biased toward abundant phenotypes. This supports an "ascent of the abundant" hypothesis, in which evolution yields abundant phenotypes even when they are not the most fit. PMID: 18636097
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