Sean Moen

The Emergence of Endovascular Treatment–Only Centers for Treatment of Intracranial Aneurysms in the United States

BACKGROUND Because of the availability of new technology, the spectrum of endovascular treatment for intracranial aneurysms has expanded widely. Some centers have started offering only endovascular treatment to patients with intracranial aneurysms (endovascular treatment-only centers [ETOCs]). Our objective was to identify the proportion and outcome of patients treated at ETOCs in the United States. METHODS We determined the proportion of ETOCs in the United States using Nationwide Inpatient Survey data files from 2010. We compared short-term outcomes between ETOCs and endovascular and surgical treatment centers (ESTCs). The outcomes studied were none to minimal disability, moderate to severe disability, in-hospital mortality, postprocedure complications, length of stay, and hospital charges. RESULTS Out of 85 hospitals performing endovascular treatment of unruptured aneurysms, 13 (15%) were categorized as ETOCs. Out of the 10,447 patients with unruptured aneurysms, 1245 (12%) were treated at ETOCs. ETOCs were more likely to be nonteaching hospitals (55% versus 45%, P=.02). The rates of in-hospital mortality (1.2% versus 1.8%) and none to minimal disability (88% versus 84%) were similar in patients treated at ETOCs and ESTC hospitals. The mean hospitalization charges were similar, but length of stay (4±7 days versus 6±10 days, P<.0001) was significantly shorter among patients treated at ETOCs. Only 2.7% patients required secondary neurosurgical procedures at the ETOCs compared with 5.8% in ESTCs (P=.09). CONCLUSION The recent emergence of ETOCs and provision of treatment with comparable outcomes and shorter length of stay at these hospitals may change the pattern of intracranial aneurysm treatment in the United States.

Stent placement for palliation of cor triatriatum dexter in a dog with suspected patent foramen ovale

An 11 month old spayed, female dog presented with exercise intolerance and cyanosis upon exertion. Echocardiography revealed an imperforate cor triatriatum dexter with mild tricuspid valve dysplasia, an underfilled right ventricle and significant right to left shunting across a presumptive patent foramen ovale. Balloon dilation of the abnormal atrial membrane was initially successful in creating a communication between the right atrial chambers, but stenosis of the original perforation and persistent clinical signs prompted a second intervention. A balloon expandable biliary stent was placed across the abnormal partition, improving caudal venous return to the right ventricle and reducing the right to left shunt. Three months after stent placement, resting oxygen saturation had normalized. Six months after stent placement, exercise tolerance had improved and exertional cyanosis had resolved. Long term follow up will be necessary to assess for remodeling of the right ventricle with improved venous return. Stent placement can be considered as a palliative treatment option for cor triatriatum dexter, especially for stenosis post-balloon dilation.

Hemodynamics in a giant intracranial aneurysm characterized by in vitro 4D flow MRI

Experimental and computational data suggest that hemodynamics play a critical role in the development, growth, and rupture of cerebral aneurysms. The flow structure, especially in aneurysms with a large sac, is highly complex and three-dimensional. Therefore, volumetric and time-resolved measurements of the flow properties are crucial to fully characterize the hemodynamics. In this study, phase-contrast Magnetic Resonance Imaging is used to assess the fluid dynamics inside a 3D-printed replica of a giant intracranial aneurysm, whose hemodynamics was previously simulated by multiple research groups. The physiological inflow waveform is imposed in a flow circuit with realistic cardiovascular impedance. Measurements are acquired with sub-millimeter spatial resolution for 16 time steps over a cardiac cycle, allowing for the detailed reconstruction of the flow evolution. Moreover, the three-dimensional and time-resolved pressure distribution is calculated from the velocity field by integrating the fluid dynamics equations, and is validated against differential pressure measurements using precision transducers. The flow structure is characterized by vortical motions that persist within the aneurysm sac for most of the cardiac cycle. All the main flow statistics including velocity, vorticity, pressure, and wall shear stress suggest that the flow pattern is dictated by the aneurysm morphology and is largely independent of the pulsatility of the inflow, at least for the flow regimes investigated here. Comparisons are carried out with previous computational simulations that used the same geometry and inflow conditions, both in terms of cycle-averaged and systolic quantities.

E-068 Dual Lumen Balloon Assisted Pre-operative Embolization With Onyx for Hypervascular Head and Neck Tumors

Introduction Pre-operative embolization of hypervascular head and neck tumors can be achieved using particulate agents or liquid embolic agents. Particulate agents are preferable due to the lower cost. However, the presence of intra-tumoral arteriovenous shunts in these tumors may occasionally result in shunting of particles to the pulmonary circulation with the risk of pulmonary or paradoxical embolism. Liquid embolic agents too may be shunted to the venous side. Additionally, there may be reflux of liquid embolics into the proximal external carotid artery or the common carotid. Therefore, reducing the flow rate into the tumor during trans arterial injection of a liquid embolic agent as well as preventing unwanted reflux of the liquid embolic agent may be advantageous. Herein, we report our experience in the embolization of hypervascular head and neck tumors with high flow intra-tumoral arteriovenous shunts using a dual lumen balloon microcatheter and Ethylene Vinyl alcohol Co-polymer (Onyx). Material and Methods A series of four patients, 4 patients with glomus jugulare and one with Juvenile Nasopharyngeal Angiofibroma (mean age 34 years, 2 males and 2 females) underwent pre-operative tumor embolization. In all patients, transarterial embolization was initially attempted using particle agents. However, the presence of high flow intra-tumoral arteriovenous shunts prevented achievement of tumor ischemia even when large particles (300–500 microns) were used. Thereafter, embolization was performed by navigating a dual lumen Sceptre C balloon microcatheter into one or more of the arterial feeders to the tumor, inflating the balloon and then injecting Onyx 18 into the tumors through the balloon-microcatheter. Results We were successfully able to navigate a 4 × 10 mm Sceptre C balloon microcatheter into one or more arterial feeders arising from the external carotid artery branches (ascending pharyngeal or occipital or internal maxillary arteries) such that the tip of the microcatheter was close to the tumor in each instance. We were then able to achieve excellent penetration of Onyx into the tumor beds in every instance following injection of Onyx 18 after balloon inflation. There was no instance of embolization of Onyx into the draining venous system or the lungs. There was also no instance of reflux of Onyx into the parent artery. There were no immediate clinical complications. Mean fluoroscopy time was 51.2 min (AP and lateral), and all patients subsequently underwent successful tumor resection. Conclusion Balloon assisted Onyx embolization performed by transarterial injection of Onyx through a dual lumen balloon microcatheter may be a safe and efficient alternative to other methods for pre-operative embolization in the case of highly vascular skull base tumors with high flow intra-tumoral arteriovenous shunts. Disclosures S. Mortazavi: None. R. Tummala: None. A. Grande: 2; C; Covidien. S. Moen: None. B. Jagadeesan: 2; C; Microvention, Covidien, Lake Regional.

A simple geometric analysis method for measuring and mitigating RF induced currents on Deep Brain Stimulation leads by multichannel transmission/reception

&NA; The purpose of this work is to present a new method that can be used to estimate and mitigate RF induced currents on Deep Brain Stimulation (DBS) leads. Here, we demonstrate the effect of RF induced current mitigation on both RF heating and image quality for a variety of brain MRI sequences at 3 T. We acquired pre‐scan images around a DBS lead (in‐situ and ex‐vivo) using conventional Gradient Echo Sequence (GRE) accelerated by parallel imaging (i.e GRAPPA) and quantified the magnitude and phase of RF induced current using the relative location of the B1+ null with respect to the lead position. We estimated the RF induced current on a DBS lead implanted in a gel phantom as well as in a cadaver head study for a variety of RF excitation patterns. We also measured the increase in tip temperature using fiber‐optic probes for both phantom and cadaver studies. Using the magnitude and phase information of the current induced separately by two transmit channels of the body coil, we calculated an implant friendly (IF) excitation. Using the IF excitation, we acquired T1, T2 weighted Turbo Spin Echo (TSE), T2 weighted SPACE‐Dark Fluid, and Ultra Short Echo Time (UTE) sequences around the lead. Our induced current estimation demonstrated linear relationship between the magnitude of the induced current and the square root SAR at the tip of the lead as measured in phantom studies. The “IF excitation pattern” calculated after the pre‐scan mitigated RF artifacts and increased the image quality around the lead. In addition, it reduced the tip temperature significantly in both phantom and cadaver studies compared to a conventional quadrature excitation while keeping equivalent overall image quality. We present a relatively fast method that can be used to calculate implant friendly excitation, reducing image artifacts as well as the temperature around the DBS electrodes. When combined with a variety of MR sequences, the proposed method can improve the image quality and patient safety in clinical imaging scenarios. HighlightsImplant‐friendly patient‐specific MR scans.Mitigating induced currents on DBS leads.Validation with phantom and cadaver studies.Improvement in image artifacts around the DBS leads.Reduction of temperature increase at the contacts.

Fiber Connections of the Supplementary Motor Area Revisited: Methodology of Fiber Dissection, DTI, and Three Dimensional Documentation

The purpose of this study is to show the methodology for the examination of the white matter connections of the supplementary motor area (SMA) complex (pre-SMA and SMA proper) using a combination of fiber dissection techniques on cadaveric specimens and magnetic resonance (MR) tractography. The protocol will also describe the procedure for a white matter dissection of a human brain, diffusion tensor tractography imaging, and three-dimensional documentation. The fiber dissections on human brains and the 3D documentation were performed at the University of Minnesota, Microsurgery and Neuroanatomy Laboratory, Department of Neurosurgery. Five postmortem human brain specimens and two whole heads were prepared in accordance with Klinglers method. Brain hemispheres were dissected step by step from lateral to medial and medial to lateral under an operating microscope, and 3D images were captured at every stage. All dissection results were supported by diffusion tensor imaging. Investigations on the connections in line with Meynerts fiber tract classification, including association fibers (short, superior longitudinal fasciculus I and frontal aslant tracts), projection fibers (corticospinal, claustrocortical, cingulum, and frontostriatal tracts), and commissural fibers (callosal fibers) were also conducted.

E-067 Balloon assisted Pre-operative Embolization of Hypervascular Metastatic Lesions to the Spine

Introduction It is common to perform pre-operative embolization of metastatic lesions to the spine from hyper-vascular tumors. Typically, a microcatheter is navigated into a prominent arterial feeder to the tumor arising from a segmental artery or bronchial artery. Thereafter, particles or liquid embolic agents are injected into the tumor through the microcatheter, while taking care to avoid reflux into the proximal segmental artery or the aorta. However, occasionally, there may be a diffuse network of small arterial feeders arising from the segmental artery, which supply the tumor. None of these small arteries maybe amenable to selective catheterization, and embolization may be challenging due to the risk of reflux of embolic agent into the parent artery or aorta. Herein, we report our experience with embolising such metastatic lesions by injecting particles through a dual lumen balloon microcatheter positioned within the main segmental artery and using the inflated balloon to prevent reflux into the aorta. Materials and methods We performed pre-operative embolization for hyper vascular vertebral metastases (two thoracic spine and 2 lumbar vertebrae) in a series of 3 patients (2 male and 1 female, mean age 53) with metastatic renal cell carcinoma at our institution using the 4 × 10 mm Sceptre C balloon microcatheter. In all patients, after ensuring that there was no radiculomedullary artery arising from the segmental artery supplying the tumor feeders, a 4 × 10 mm Sceptre C balloon microcatheter was navigated into the proximal aspect of the artery. The balloon was then inflated such that there was a tight seal across the origin of the artery from the aorta and embolization of the tumor was carried out with 150–300 microns PVA particles. Intermittently, the balloon was slowly deflated and DSA was carried out to assess changes in the tumor “blush”. Embolization was carried out until there was elimination of the tumor blush. Results The Sceptre C balloon microcatheter could be successfully navigated into the parent segmental vessel and inflated proximally across the origin of the vessel in all patients. Subsequent particle embolization resulted in complete elimination of the tumor “blush” in the vertebral body in every instance. There were no adverse events such as segmental arterial dissection, balloon rupture or reflux of particles into the aorta in any patient. Conclusion Pre-operative embolization of hypervascular spinal mestastatic lesions can be safely carried out using a balloon-assisted technique with a dual lumen balloon microcatheter when traditional selective catheterization of feeder vessels is not feasible. Disclosures B. Jagadeesan: None. S. Mortazavi: None. S. Moen: None. A. Grande: 2; C; Covidien, Integra. R. Tummala: 2; C; Lake Regional.