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Svetlana Kvint, James Schuster and Monisha A. Kumar

Patients taking antithrombotic agents are very common in neurosurgical practice. The perioperative management of these patients can be extremely challenging especially as newer agents, with poorly defined laboratory monitoring and reversal strategies, become more prevalent. This is especially true with emergent cases in which rapid reversal of anticoagulation is required and the patient’s exact medical history is not available. With an aging patient population and the associated increase in diseases such as atrial fibrillation, it is expected that the use of these agents will continue to rise in coming years. Furthermore, thromboembolic complications such as deep venous thrombosis, pulmonary embolism, and myocardial infarction are common complications of major surgery. These trends, in conjunction with a growing understanding of the hemostatic process and its contribution to the pathophysiology of disease, stress the importance of the complete evaluation of a patient’s hemostatic profile in guiding management decisions. Viscoelastic hemostatic assays (VHAs), such as thromboelastography and rotational thromboelastometry, are global assessments of coagulation that account for the cellular and plasma components of coagulation. This FDA-approved technology has been available for decades and has been widely used in cardiac surgery and liver transplantation. Although VHAs were cumbersome in the past, advances in software and design have made them more accurate, reliable, and accessible to the neurosurgeon. VHAs have demonstrated utility in guiding intraoperative blood product transfusion, identifying coagulopathy in trauma, and managing postoperative thromboprophylaxis. The first half of this review aims to evaluate and assess VHAs, while the latter half seeks to appraise the evidence supporting their use in neurosurgical populations.

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James M. Schuster and M. Sean Grady

Metastatic spinal tumors are an increasingly common and difficult problem encountered by neurosurgeons and orthopedic surgeons. To improve therapies and increase life expectancy for patients with tumors such as those of the breast and prostate, a global, systematic approach is required to maximize the preservation of neurological function, maintenance of spinal stability, and relief of pain, all with the ultimate goal of improved functional capacity and quality of life (QOL). Although radiotherapy and surgery are still the primary therapeutic options, several new adjuvant therapies initially implemented to control pain more effectively have also been shown to reduce overall skeleton-related complications (pathological fractures and hypercalcemia) and may ultimately improve and extend QOL. This more global approach to spinal metastases also includes optimizing each patient's overall medical condition and potential for healing (that is, nutrition), as well as avoiding potential complications associated with metastatic disease (such as deep vein thrombosis), including excessive blood loss in the case of renal metastasis. A thorough knowledge and understanding of these therapeutic adjuvants is required to optimize care and to respond to our increasingly medically knowledgable patient population whose access to prevalent medical information has been increased because of the internet.

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Shabbar F. Danish, Jessica A. Wilden and James Schuster

✓The authors describe 2 cases of intraoperative thoracic vertebral body extension fractures in morbidly obese patients with ankylosing spondylitis (AS), undergoing total hip arthroplasty, with resultant acute traumatic paraplegia. The pathophysiology with regard to the surgical positioning and the associated risks of obesity and AS are reviewed. Additionally, strategies for avoiding these types of injuries are discussed.

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Saurabh Sinha, Eric Hudgins, James Schuster and Ramani Balu

Acute brain injuries are a major cause of death and disability worldwide. Survivors of life-threatening brain injury often face a lifetime of dependent care, and novel approaches that improve outcome are sorely needed. A delayed cascade of brain damage, termed secondary injury, occurs hours to days and even weeks after the initial insult. This delayed phase of injury provides a crucial window for therapeutic interventions that could limit brain damage and improve outcome.

A major barrier in the ability to prevent and treat secondary injury is that physicians are often unable to target therapies to patients’ unique cerebral physiological disruptions. Invasive neuromonitoring with multiple complementary physiological monitors can provide useful information to enable this tailored, precision approach to care. However, integrating the multiple streams of time-varying data is challenging and often not possible during routine bedside assessment.

The authors review and discuss the principles and evidence underlying several widely used invasive neuromonitors. They also provide a framework for integrating data for clinical decision making and discuss future developments in informatics that may allow new treatment paradigms to be developed.

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James Schuster, Jun Zhang and Maria Longo

Object

One of the major difficulties of conducting bone metastasis research is the lack of adequate models for studying the bone–tumor microenvironment. The limitations of current in vivo models include the following: non-human tumor or bone, variable reproducibility, limited supply, and an inability to be easily manipulated. The objective of the present study was to develop a uniform and reproducible model of bone/spine metastasis by utilizing bone derived from human osteoblasts grown subcutaneously in severe combined immunodeficiency (SCID) mice with subsequent introduction of human carcinoma cell lines.

Methods

Human osteoblasts were serially passed in culture and induced to differentiate into mature osteoblasts. They were subsequently loaded on hydroxyapatite-coated collagen sponges and implanted subcutaneously into the SCID mice. After allowing the bone to mature for 8 weeks, tumor cell suspensions were implanted percutaneously into the bone. The bone–tumor complexes were subsequently harvested, decalcified, and prepared for histological examination.

Conclusions

The authors have developed a novel, reproducible SCID mouse model of bone/spine metastasis by using bone derived from human osteoblasts and subsequently introduced human tumor lines. They believe this model will be useful for studying the basic biology of bone metastases.

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David W. Newell, James M. Schuster and Anthony M. Avellino

✓ The use of a microanastomotic device for direct connection of intracranial vessels can be helpful to facilitate removal of distally located middle cerebral artery (MCA) aneurysms. The authors report on two patients who presented for treatment with large aneurysms distally located on the MCA. The aneurysms were completely excised and the proximal and distal portions of the parent vessel were connected in an end-to-end fashion by using a microanastomotic device. The time required to crossclamp the vessel for excision of the aneurysm and primary anastomosis was 10 minutes in one case and 15 minutes in the other. The short crossclamp time and high-quality anastomosis afforded by this device may be useful in the treatment of these difficult lesions and the prevention of cerebral ischemia.

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Gregory G. Heuer, Michael F. Stiefel, Robert L. Bailey and James M. Schuster

✓Spinal ependymomas are a common type of primary spinal cord neoplasm that frequently occurs in the lumbar spine. The authors report on two patients who presented with acute neurological decline after hemorrhage into ependymomas of the filum terminale. Both were transferred to the authors' institution because of diagnostic uncertainty and a concern about possible intradural vascular abnormalities. Both patients underwent lumbar laminectomies for tumor resection. The pathological finding in each case was myxopapillary ependymoma. Both patients made a significant recovery and were ambulatory and continent at follow-up review. These cases illustrate the rare but clinically significant incidence of acute neurological decline caused by hemorrhagic cauda equina ependymomas, including the potential for delayed diagnosis and treatment.

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Gregory G. Heuer, Brandon C. Gabel, Deb A. Bhowmick, Michael F. Stiefel, Robert W. Hurst and James M. Schuster

✓Spinal arteriovenous fistulas (AVFs) are relatively uncommon lesions that are often diagnosed in a delayed fashion. The authors present a cause of a symptomatic high-flow AVF that developed in a patient after traumatic injury to the upper cervical spine. The patient presented to the trauma bay after a motor vehicle collision, and was found to have a C-2 fracture involving the transverse foramen. Although the patient was neurologically intact on presentation, 6 hours after admission weakness developed on his left side. Imaging studies demonstrated complete transection of the distal cervical aspect of the right vertebral artery (VA) at the base of C-2, with antegrade and retrograde flow into a direct AVF, resulting in early filling of the right internal jugular vein and other external draining veins. The patient was treated endovascularly with coil occlusion of the VA both proximal and distal to the transection. The patient's weakness improved over the next 7 days. At the 12-week follow-up examination, the patient's fractures had healed and he was neurologically intact.

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Jared M. Pisapia, Nikhil R. Nayak, Ryan D. Salinas, Luke Macyszyn, John Y. K. Lee, Timothy H. Lucas, Neil R. Malhotra, H. Isaac Chen and James M. Schuster

OBJECTIVE

As odontoid process fractures become increasingly common in the aging population, a technical understanding of treatment approaches is critical. 3D image guidance can improve the safety of posterior cervical hardware placement, but few studies have explored its utility in anterior approaches. The authors present in a stepwise fashion the technique of odontoid screw placement using the Medtronic O-arm navigation system and describe their initial institutional experience with this surgical approach.

METHODS

The authors retrospectively reviewed all cases of anterior odontoid screw fixation for Type II fractures at an academic medical center between 2006 and 2015. Patients were identified from a prospectively collected institutional database of patients who had suffered spine trauma. A standardized protocol for navigated odontoid screw placement was generated from the collective experience at the authors' institution. Secondarily, the authors compared collected variables, including presenting symptoms, injury mechanism, surgical complications, blood loss, operative time, radiographically demonstrated nonunion rate, and clinical outcome at most recent follow-up, between navigated and nonnavigated cases.

RESULTS

Ten patients (three female; mean age 61) underwent odontoid screw placement. Most patients presented with neck pain without a neurological deficit after a fall. O-arm navigation was used in 8 patients. An acute neck hematoma and screw retraction, each requiring surgery, occurred in 2 patients in whom navigation was used. Partial vocal cord paralysis occurred after surgery in one patient in whom no navigation was used. There was no difference in blood loss or operative time with or without navigation. One patient from each group had radiographic nonunion. No patient reported a worsening of symptoms at follow-up (mean duration 9 months).

CONCLUSIONS

The authors provide a detailed step-by-step guide to the navigated placement of an odontoid screw. Their surgical experience suggests that O-arm–assisted odontoid screw fixation is a viable approach. Future studies will be needed to rigorously compare the accuracy and efficiency of navigated versus nonnavigated odontoid screw placement.