Large-Scale Assessment of Polygon-Edge Boulder Clustering in the Martian Northern Lowlands

Two features evident in many images of the martian northern low-lands are polygonal fractures (especially northwards of 60N) and meter-scale surface boulders. Since their first observation, several attempts have been made to classify and study these polygons as well as how the forces that form these polygons may modify the surface. Surface boulders have been used as a potential indicator of such modification, though current studies find evidence both for and against their association with the underlying polygons. Both these investigations are limited by the same fundamental challenge: map-ping the location of surface boulders manually is not practical at large scales. Here, we use the Martian Boulder Automatic Recognition System (MBARS) to provide image-wide assessments of boulder location and size, enabling large-scale assessment of boulder populations. To compare these boulder locations with the underlying polygons, we modified the 2-D Fourier analysis described by Orloff in 2013 to analyze boulder locations. When compared with Orloffs observations of polygon scales, this provides an avenue for large-scale comparison of boulder-cluster scale and polygon scale

High incidence of tumor dissemination in myxopapillary ependymoma in pediatric patients

Journal ArticleP Myxopapillary ependymomas (MPEs) have historically been thought to be benign tumors occurring most frequently in adults. Only 8 to 20% of these tumors occur in the first two decades of life, making this tumor a rarity in pediatric neurosurgery. Five patients with intraspinal MPEs were treated by the authors between 1992 and 2003. Four (80%) of these five patients suffered from disseminated disease of the central nervous system (CNS) at the time of presentation; this incidence is much higher than that reported in the combined adult and pediatric literature. Combining five pediatric case series reported in the literature with the present series, the authors review a total of 26 cases of pediatric patients with intraspinal MPEs. In nine cases (35%) CNS metastases occurred. In those cases in which patients underwent screening for CNS tumor dissemination, however, the incidence of disseminated disease was 58% (seven of 12 patients). In pediatric patients MPEs may spread throughout the CNS via cerebrospinal fluid pathways; therefore, MR imaging of the entire CNS axis is recommended at both presentation and follow-up review to detect tumor dissemination

High incidence of tumor dissemination in myxopapillary ependymoma in pediatric patients

Journal ArticleP Myxopapillary ependymomas (MPEs) have historically been thought to be benign tumors occurring most frequently in adults. Only 8 to 20% of these tumors occur in the first two decades of life, making this tumor a rarity in pediatric neurosurgery. Five patients with intraspinal MPEs were treated by the authors between 1992 and 2003. Four (80%) of these five patients suffered from disseminated disease of the central nervous system (CNS) at the time of presentation; this incidence is much higher than that reported in the combined adult and pediatric literature. Combining five pediatric case series reported in the literature with the present series, the authors review a total of 26 cases of pediatric patients with intraspinal MPEs. In nine cases (35%) CNS metastases occurred. In those cases in which patients underwent screening for CNS tumor dissemination, however, the incidence of disseminated disease was 58% (seven of 12 patients). In pediatric patients MPEs may spread throughout the CNS via cerebrospinal fluid pathways; therefore, MR imaging of the entire CNS axis is recommended at both presentation and follow-up review to detect tumor dissemination

Cervical spine deformity associated with resection of spinal cord tumors

Journal ArticlePostoperative sagittal-plane cervical spine deformities are a concern when laminectomy is performed for tumor resection in the spinal cord. These deformities appear to occur more commonly after resection of intramedullary spinal cord lesions, compared with laminectomy for stenosis caused by degenerative spinal conditions. Postlaminectomy deformities are most common in pediatric patients with an immature skeletal system, but are also more common in young adults (, 25 years of age) in comparison with older adults. The extent of laminectomy and facetectomy, number of laminae removed, location of laminectomy, preoperative loss of lordosis, and postoperative radiation therapy in the spine have all been reported to influence the risk of postlaminectomy spinal deformities. When these occur, patients should be monitored closely with serial imaging studies, because a significant percentage will have progressive deformities. These can range from focal kyphosis to more complicated swan-neck deformities. General indications for surgical intervention include progressive deformity, axial pain in the area, and neurological symptoms attributable to the deformity. Surgical options include anterior, posterior, and combined anterior-posterior procedures. The authors have reviewed the literature on postlaminectomy kyphosis as it relates to resection of cervical spinal cord tumors, and they summarize some general factors to consider when treating these patients

Spinal epidural lipomatosis: a review of its causes and recommendations for treatment

Journal ArticleSpinal epidural lipomatosis is most commonly observed in patients receiving long-term exogenous steroid therapy, but can also be seen in patients with endogenous steroid overproduction, obesity, or idiopathic disease. With this condition, there is hypertrophy of the epidural adipose tissue, causing a narrowing of the spinal canal and compression of neural structures. A majority of patients will present with progressive myelopathy, but radicular symptoms are also common. Conservative treatment-weaning from steroids or weight loss-can reverse the hypertrophy of the adipose tissue and relieve the neural compression. If conservative management fails, surgery with decompressive laminectomy is also very successful at improving the patient's neurological symptoms

Vertebral artery injuries associated with cervical spine injuries: a review of the literature

Journal ArticleObjective: To determine the incidence of vertebral artery injuries (VAIs) in association with cervical spine trauma and investigate the optimum diagnostic and treatment protocols. Summary of Background Data: VAIs may result from cervical spine trauma and have the potential to cause cerebral, brainstem, and even spinal cord ischemia. Screening and treatment for traumatic VAI are very controversial, with conflicting recommendations within the trauma and spine literature. Methods: A literature review was performed to identify publications pertaining to VAIs associated with cervical spine trauma. These publications were evaluated to determine the incidence, radiographic evaluation, and treatment options of VAIs. Results: Approximately 0.5% of all trauma patients will have a VAI, and 70% of all traumatic VAIs will have an associated cervical spine fracture. Cervical spine translation injuries and transverse foramen fractures are most commonly cited as having a significant association with VAIs. The incidence of neurologic deficits secondary to VAI ranges from 0% to 24% in published series that incorporate a screening protocol for asymptomatic patients. Catheter angiography has been the gold standard for the diagnosis of VAIs; however, new 16-slice computed tomography angiography seems to have sensitivity and specificity close to that of catheter angiography. Treatment options include observation, antiplatelet agents, anticoagulation, and endovascular treatments. Although some authors have advocated antithrombotic therapy for most asymptomatic VAIs, there is a lack of class I evidence to support any strong guidelines for treatment. Conclusions: VAIs can occur in association with cervical spine trauma and have the potential for neurological ischemic events. Screening for and treatment of asymptomatic VAIs may be considered, but it is unclear based on the current literature whether these strategies improve outcomes

Hemorrhage from moyamoya-like vessels associated with a cerebral arteriovenous malformation

Journal ArticleThe authors describe a case of subarachnoid hemorrhage from moyamoya-like vessels associated with an arteriovenous malformation (AVM) in a 44-year-old Hispanic man who presented with severe headache. The AVM was located in the left parietal lobe and the ipsilateral middle cerebral artery was occluded. Although the patient was initially neurologically intact, he began to experience neurological deficits from mild vasospasm, illustrating the sensitivity of the underperfused portion of brain surrounding an AVM. His neurological deficits improved with aggressive hydration and elevated blood pressure. After a 3-week period, the AVM was resected without complication and all of the patient's neurological deficits resolved. The authors review radiographic findings of this unique case

Cholesteatoma of the clivus case report

ManuscriptObjective: Cholesteatomas (CNS epidermoids) can be found intradurally or extradurally in the central nervous system. Extradural intraosseous lesions are most commonly found in the petrous bone. Design: Case report Clinical Presentation: The authors describe a unique case of a clival cholesteatoma occurring in a 64-year-old woman who presented with headaches. No other neurological complaints or physical examination findings were noted. Magnetic resonance imaging showed an expansile lesion centered in the middle portion of clivus with erosion of a large portion of the clivus. Results: This lesion was explored via a transnasal transsphenoidal approach and granular debris was evacuated. The cystic lining was stripped from the surrounding bone and the bone opening was widely fenestrated. Pathological examination showed keratinous debris with macrophages and an outer lining of benign epithelial tissue consistent with a cholesteatoma (epidermoid cyst). Conclusions: The authors review the radiographic, surgical, and pathological findings of this unique case

Boulder Bands on Lobate Debris Aprons: Does Spatial Clustering Reveal Accumulation History for Martian Glaciations?

Glacial landforms such as lobate debris aprons (LDA) and Concentric Crater Fill (CCF) are the dominant debris-covered glacial landforms on Mars. These landforms represent a volumetrically significant component of the Amazonian water ice budget, however, because small craters (diameter D 0.5-1 km) are poorly retained glacial brain terrain surfaces, and, since the glacial landforms are geologically young, it is challenging to reliably constrain either individual glacial deposit ages or formational sequences in order to determine how quickly the glaciers accumulated. A fundamental question remaining is whether ice deposition and flow that formed LDA occurred episodically during a few, short instances, or whether glacial flow was quasi-continuous over a long period (~108 yr). Because glaciation is thought to be controlled largely by obliquity excursions, a larger question is whether glacial deposits on Mars exhibit regional to global characteristics that can be used to infer synchronicity of flow or degradation

Research issues in Elderly patients: gaps in knowledge and suggested directions.

There has been an increase of over 400% in the number of elderly and very elderly patients on dialysis in Australia and New Zealand over the past 2 decades (1). This rapid increase has generated considerable debate resulting in wide variation in attitude towards referral and acceptance of elderly patients for dialysis (2-4). One major reason for this is that there is uncertainty about the outcome from dialysis treatment in this population (5)