Intracranial Dural Arteriovenous Fistulas.

Dural arteriovenous fistulas (DAVFs) are abnormal communications between meningeal arteries and dural venous sinuses and/or cortical veins. Although many fistulas are benign and do not require treatment, some may carry a significant risk of bleeding or cause symptoms and warrant treatment. This review provides a review of various aspects of intracranial DAVFs including epidemiology, pathophysiology, clinical presentation, imaging characteristics, classification, natural history, and management options. By exploring these topics, we aim to enhance understanding of this condition and facilitate patient care.

Evaluation of C-arm CT metal artifact reduction algorithm during intra-aneurysmal coil embolization: Assessment of brain parenchyma, stents and flow-diverters.

PURPOSE: Flat panel C-arm CT images acquired in the interventional suite provide valuable information regarding brain parenchyma, vasculature, and device status during the procedure. However, these images often suffer from severe streak artifacts due to the presence of metallic objects such as coils. These artifacts limit the capability to make diagnostic inferences and thus need to be reduced for better image interpretation. The main purpose of this paper is to systematically evaluate the accuracy of one such C-arm CT based metal artifact reduction (MAR) algorithm and to demonstrate its usage in both stent and flow diverter assisted coil embolization procedures. METHODS: C-arm CT images routinely acquired in 24 patients during coil embolization procedure (stent-assisted (12) and flow-diverter assisted (12)) were included in this study in a retrospective fashion. These images were reconstructed without and with MAR algorithm on an offline workstation and compared using quantitative image analysis metrics. This analysis was carried out to assess the improvements in both brain parenchyma and device visibility with MAR algorithm. Further, ground truth reference images from phantom experiments and clinical data were used for accurate assessment. RESULTS: Quantitative image analysis of brain parenchyma showed uniform distribution of grayscale values and reduced image noise after MAR correction. The line profile plot analysis of device profile in both phantom and clinical data demonstrated improved device visibility with MAR correction. CONCLUSIONS: MAR algorithm successfully reduced streak artifacts from coil embolization in all cases, thus allowing more accurate assessment of devices and adjacent brain parenchyma.

Metal coverage ratio of pipeline embolization device for treatment of unruptured aneurysms: Reality check.

BACKGROUND AND PURPOSE: The metal coverage ratio (MCR) of a flow diverter influences the intra-aneurysmal hemodynamics; a high MCR will occlude an aneurysm early, while a low MCR may delay aneurysm occlusion. The true MCR of a pipeline embolization device (PED) could be lower due to oversize, device deformation, or aneurysm location. In this study deviation of the true MCR from the nominal MCR is assessed and whether their difference affects aneurysm occlusion rate is determined. METHODS: A total of 40 consecutive patients, each of them treated by one PED for their aneurysms at the internal carotid artery (ICA), were retrospectively analyzed. The DynaCT images of these deployed PEDs were used to determine their true dimensions and estimate three MCRs (local, mean, and nominal). These data were compared in two groups of patients who had different aneurysm outcomes at six months. RESULTS: The difference in the local MCR between two groups is small, but statistically significant (24.5% vs 21.6%, p=05). The local MCR is consistently lower than the nominal MCRs (23.2% vs 30.2%, p<0.001); however, the difference between the mean and local MCRs is small (23.9% vs 23.2%). CONCLUSIONS: An expectation that a PED can achieve a MCR of 30% may not be reasonable. Device oversize and deformation during deployment lower the local MCR by 5-7%. A lowered MCR affects the aneurysm occlusion rate at six months.

Incidence and clinical implications of carotid branch occlusion following treatment of internal carotid artery aneurysms with the pipeline embolization device.

BACKGROUND: The use of flow diverters such as the pipeline embolization device (PED) for treatment of intracranial aneurysms carries the risk of side branch occlusion. OBJECTIVE: To determine the incidence and clinical outcomes associated with supraclinoid internal carotid artery (ICA) branch occlusion after deployment of PEDs for ICA aneurysms. METHODS: We reviewed patients who underwent endovascular treatment with PEDs for ICA aneurysms between June 2011 and March 2013. Forty-nine patients (43 women, mean age 56.3±1.8 years, 68 aneurysms) in whom PEDs traversed the origin of supraclinoid ICA branches (ophthalmic [OA], posterior communicating [PcommA], and anterior choroidal artery [AChA]) were selected for this study. Follow-up angiograms (mean follow-up, 12.8±0.8 months) were studied to determine the location of PEDs and the patency of ICA branches. RESULTS: PEDs were placed across the ostia of 49 OAs, 14 PcommAs, and 11 AChAs. Multiple PEDs were deployed in 16 patients. Rate of branch occlusion was 4% (2/49) for the OA, 7.1% (1/14) for the PcommA, and 0% for the AChA. Patients with branch occlusion did not endure new neurological deficits. ICA branch occlusion was not associated with the number of PEDs covering the ostia (P=.76) or the origin of ICA branches from the aneurysm (P=.24). CONCLUSION: The incidence of major supraclinoid ICA branch occlusion after treatment with PEDs was low. These events were not associated with new neurological deficits nor were they related to the number of PEDs deployed or the origin of ICA branches from the aneurysm.

Emergency endovascular management of penetrating gunshot injuries to the arteries in the face and neck: a case series and review of the literature.

INTRODUCTION: Penetrating gunshot injuries (GSI) to supra-aortic arteries that cause life-threatening blood loss or major neurologic deficits are increasingly managed using modern endovascular treatment (EVT). We report our experience with EVT of acute GSIs and review the existing literature. METHODS: Emergency EVT was performed in nine of 10 patients (7 men, age 17-50 years) with acute GSIs to supra-aortic arteries requiring acute management. One patient presented with acute and delayed injuries and underwent EVT 4 weeks after initial admission. Patient selection was based on clinical presentation and radiographic findings from a cohort of 55 patients with GSIs to the face, neck or head between February 2009 and March 2012. RESULTS: EVT was successfully performed in all patients. Two transections of the vertebral arteries were embolized with coils and/or liquid embolic agent (acrylic glue). Eight penetrated external carotid artery branches were occluded with liquid embolic agents (acrylic glue or Onyx) or particles. One severe dissection of the internal carotid artery with a subsequent thromboembolic event was treated with stenting. All except one patient survived with minor or no residual deficits. CONCLUSIONS: Emergency management of GSI injuries to the head and neck may involve all aspects of current EVT. Understanding endovascular techniques and being able to make rapid and appropriate treatment decisions in the setting of acute GSI to the face and neck can be a life-saving measure and greatly benefits the patient's outcome.

Management of ruptured dissecting intracranial aneurysms in infants: report of four cases and review of the literature.

BACKGROUND: Intracranial cerebral aneurysms in the pediatric population are infrequent, and those occurring in infants less than 1 year old are extremely rare. Of intracranial aneurysms in children, dissecting aneurysms are the most common type seen. While spontaneous dissecting aneurysms usually present with ischemia, hemorrhage can also occur. METHODS: A retrospective review of our patients revealed that from July 1, 2007 to June 30, 2012, four infants were treated for ruptured distal dissecting intracranial aneurysms at Texas Children's Hospital. Mycotic aneurysms and collagen vascular disorder were excluded in all four cases. All patients presented in our series presented with subarachnoid hemorrhage, and three had intraventricular hemorrhage. All patients underwent conventional catheter angiography for diagnosis. All patients in this series were managed in the acute or subacute period with surgical or endovascular trapping without distal bypass procedures. All four patients tolerated sacrifice of the parent vessels feeding these distal aneurysms well. CASE REPORT AND REVIEW OF LITERATURE: We describe the presentation and management of these rare cases and then review the current literature on the management of these dissecting aneurysms in infants.

Hemodynamics of small aneurysm pairs at the internal carotid artery.

Cerebral aneurysms carry significant risks because rupture-related subarachnoid hemorrhage leads to serious and often fatal consequences. The rupture risk increases considerably for multiple aneurysms. Multiple aneurysms can grow from the same location of an artery, and the interaction between these aneurysms raises the rupture risk even higher. Four aneurysm pair cases at the internal carotid artery are investigated for their hemodynamic behaviors using patient-specific modeling. For each case, aneurysms are separated from the parent artery and three models are reconstructed, one with two aneurysms and the other two models with only one of the two aneurysms. Results show that the relative anatomic location of one aneurysm to the other may determine the hemodynamic environment of an aneurysm. The presence of a proximal aneurysm reduces the intra-aneurysmal flow into the distal aneurysm; the proximal aneurysm and larger aneurysm have a greater area under low wall shear stress. The average intra-aneurysmal inflow ratio ranges from 16% to 41%, and reduction of the inflow ratio by an aneurysm pair varies from 6% to 15%. The maximum wall shear stress increases for serial aneurysms, but decreases for parallel aneurysms. Interaction between parallel aneurysms is not significant; however, the proximal aneurysm in serial aneurysms may be subject to a greater rupture risk.

An imageable retinoid acid derivative to detect human cancer xenografts and study therapeutic dosing to reduce its toxicity.

Developing agents with 'seek, treat and see' capability is critical for personalized molecular medicine. Those agents will specifically target the disease markers for diagnosis and apply the biologically effective dose for treatment. Retinoids regulate a multitude of biological processes. In addition, retinoic acid can reverse premalignancy, significantly decrease second primary tumors and provide a treatment benefit in head and neck, lung, esophagus, colon and bladder cancer. These data suggest that cancer cells can take up retinoids. Therefore, retinoids are potential tumor-imaging agents. We developed near-infrared (NIR)-labeled retinoid agents to detect human cancers, visualize drug redistribution within the body, determine the optimal biological dose and reduce systemic toxicity. Our data demonstrate that the retinoid agent, but not the free dye, binds to the human tumor cells and is internalized, where it permits the imaging of human cancer xenografts. The high dose of retinoid agent is significantly associated with systemic toxicity. In summary, synthetic NIR-labeled retinoid agents can be used to detect multiple human cancer xenografts as the agent is internalized by cancer cells. The binding of the agent to the tumor xenografts is dependent on the redistribution of the agent. Therapeutic agents labeled with reporters will interrogate tumor-drug interactions and permit analysis of biodistribution, pharmacokinetics and pharmacodynamics in real time. At the same time, we can apply the biologically effective dose for therapy, instead of the traditional maximum tolerated dose, to reduce systemic toxicity.

Target-specific agents imaging ectopic and orthotopic human pancreatic cancer xenografts.

OBJECTIVES: This study aimed to develop target-specific binding agents for in vitro and in vivo imaging of human pancreatic cancer. METHODS: A monoclonal neutrophil gelatinase-associated lipocalin (NGAL)-specific antibody and a peptide specific for matrix metalloproteinase (MMP) were labeled with a near-infrared dye for in vitro and in vivo imaging studies. Fluorescence or confocal microscopy was used to determine antibody or peptide binding and internalization of agents into human AsPC-1, Panc-1, and MiaPaCa pancreatic cancer cell lines and in mice bearing ectopic or orthotopic pancreatic tumor transplants. RESULTS: Both the NGAL-specific antibody and MMP peptide bound to pancreatic cancer cells with high specificity; most NGAL-specific antibody localized to the cytosol. In vivo imaging results demonstrated high signal intensity of both agents bound to the tumor. The average tumortr-to-background ratio of antibody and peptide was 1.29 and 2.86, respectively. Signal was also detectable in the liver, kidneys, and bladder. CONCLUSIONS: Both NGAL-specific antibody and MMP peptide bound to cancer cells, and the labeled antibody was internalized. These results demonstrate that both agents can be used to enhance detection of human pancreatic cancer xenografts. However, the biodistribution patterns of these agents might limit their use in research and clinical practice.

Surgical cannulation of a cortical draining vein for endovascular treatment of a dural arteriovenous fistula of the cavernous sinus.

Dural arteriovenous fistulas (DAVF) of the cavernous sinus most commonly present with ocular symptoms and can be observed or treated with endovascular approaches, surgery, or radiosurgery. Combined surgical-endovascular approaches have been used for fistulas that are not amenable to standard endovascular approaches. A 40-year-old man presented with ocular symptoms from a cavernous sinus DAVF. Multiple previous transarterial and transvenous embolization attempts had failed. The patient underwent craniotomy for surgical exposure and cannulation of an arterialized sylvian vein. Subsequently he underwent coiling and onyx embolization of the DAVF. The intervention resulted in effective obliteration of the fistula. If a cavernous sinus DAVF is refractory to treatment, surgical exposure and cannulation of a cortical draining vein can facilitate transvenous endovascular treatments.

Timing and size of flow impingement in a giant intracranial aneurysm at the internal carotid artery.

Flow impingement is regarded as a key factor for aneurysm formation and rupture. Wall shear stress (WSS) is often used to evaluate flow impingement even though WSS and impinging force are in two different directions; therefore, this raises an important question of whether using WSS for evaluation of flow impingement size is appropriate. Flow impinging behavior in a patient-specific model of a giant aneurysm (GA) at the internal carotid artery (ICA) was analyzed by computational fluid dynamics simulations. An Impingement Index (IMI) was used to evaluate the timing and size of flow impingement. In theory, the IMI is related to the WSS gradient, which is known to affect vascular biology of endothelial cells. Effect of non-Newtonian fluid, aneurysm size, and heart rate were also studied. Maximum WSS is found to be proportional to the IMI, but the area of high wall shear is not proportional to the size of impingement. A faster heart rate or larger aneurysm does not produce a larger impinging site, and the Newtonian assumption overestimates the size of impingement. Flow impingement at the dome occurs approximately 0.11 s after the peak of flow waveform is attained. This time delay also increases with aneurysm size and varies with heart rate and waveform.

Hemodynamic effect of Neuroform stent on intimal hyperplasia and thrombus formation in a carotid aneurysm.

Stents play an important role in management of cerebral aneurysms. A stent reconstructs the parent artery, assists coil embolization, and decreases flow activity within an aneurysm. However, an in-stent stenosis often occurs within the stented artery and compromises the circulation at the parent artery. Hemodynamic basis of re-stenoses from aneurysm stenting is not fully understood. An 8mm cavernous carotid aneurysm with a wide neck was treated by a Neuroform stent first and by coils five weeks later. A comparison of the difference in morphology during this five-week period reveals the presence of intimal hyperplasia in the internal carotid artery, 1.3mm thick at the proximal end and 1mm at the distal end of the stent, and 1mm thick thrombus at the postero-inferior side of the aneurysm. Computational fluid dynamic analyses show that the site of intimal hyperplasia is exposed to low wall shear with high oscillatory shear index (OSI), and the location of thrombus is subject to high OSI. Intimal hyperplasia and thrombus occur at comparable rates, but at different hemodynamic conditions; however, both prefer regions with high OSIs.

Cross-flow at the anterior communicating artery and its implication in cerebral aneurysm formation.

The anterior communicating artery (ACoA) is an important element of the circle of Willis. While the artery itself is short and small, a large number of intracranial aneurysms can be found at the ACoA. Four subject-specific ACoA models are constructed from 3D rotational angiographic images. The ACoA of these models ranged from 1.7 to 2.7 mm in diameter and 1.5 to 5.7 mm in length. Pulsatile flows through these four ACoA models are studied numerically. Blood is found to move in two opposite directions simultaneously within the ACoA, giving a much higher wall shear at the ACoA. These two opposite flow streams produce a cross-flow that is dependent on the flow rates at the anterior cerebral arteries and internal carotid arteries (ICAs). A larger and shorter ACoA allows flow through the ACoA easily, leading to a greater cross-flow and higher hemodynamic forces on the artery. This cross-flow may disappear when there is a sufficient net flow for a smaller and longer ACoA. Wall shear stress can be as high as 185 Pa at smaller ACoAs, but it can be lowered by asymmetric waveforms at the ICAs. A functional circle of Willis also promotes cross-flow at both the ACoA and posterior communicating arteries.

Hemodynamic relationship between intracranial aneurysm and carotid stenosis: review of clinical cases and numerical analyses.

OBJECTIVE: Coexistence of both an intracranial aneurysm and a stenosis at the same internal carotid artery is infrequent, but it may complicate therapeutic management of either disease. It is unclear if a stenosis plays any role in development of intracranial aneurysms. We study patients with intracranial aneurysms at our hospital and investigate if there is a relationship between a carotid stenosis and an intracranial aneurysm. METHODS: Two hundred and nine patients who were treated for their intracranial aneurysms in a 2-year period were reviewed. Fifty-four patients were found to have at least one intracranial aneurysm and one intracranial or extracranial carotid stenosis. Ten of them had bilateral stenoses; 17 aneurysms were on the ipsilateral side of the stenosis, and eight on the contralateral side. Nineteen aneurysms were elsewhere. Two cases were selected for detailed computational fluid dynamics (CFD) analyses: one with an intracranial and the other with an extracranial stenosis. RESULTS: Aneurysms on the contralateral side of a carotid stenosis are significantly larger than those aneurysms on the ipsilateral side or with bilateral stenoses (13.6 versus 6.6 mm; P < 0.01). CFD studies show that wall shear stress at the aneurysm is more likely affected by an adjacent intracranial stenosis than by an extracranial stenosis. CONCLUSIONS: Intracranial carotid aneurysms contralateral to a carotid stenosis are significantly larger than aneurysms with a carotid stenosis elsewhere. Rupture can occur on aneurysms with an extracranial carotid stenosis on the contralateral side or with an intracranial carotid stenosis on the ipsilateral side.

Indirect measurement of aneurysm wall thickness using digital stethoscope.

OBJECTIVE: No existing in vivo technique can measure aneurysm wall thickness for evaluation of rupture risk. Intracranial aneurysms produce bruits at a special range of frequency that are highly influenced by the wall thickness. Understanding of the mechanism that generates bruits may allow us to learn aneurysm behavior non-invasively. METHODS: A new theory was proposed to account for an interaction between an aneurysm and its parent vessel. Four patients with ophthalmic aneurysms were studied with a digital electronic stethoscope before and after endovascular treatment. Energy spectra of bruits were obtained from digital recording at both eyes. Change of energy spectra was used as an objective indication for aneurysm bruits. Additional four cases were obtained from a previous report. RESULTS: Aneurysm bruits are affected by both aneurysm size and wall thickness. These sounds disappear after coil embolization and parent artery occlusion, but not by stenting. Both large and small aneurysms generate sounds at high frequency. Aneurysms at 6 mm produced very low frequency sound. Wall thickness decreases with aneurysm size, and the decrease is more pronounced at 8 mm. CONCLUSIONS: Interaction between an intracranial aneurysm and its parent vessel is important in interpretation of aneurysm bruits. An analysis of in vivo measurements shows a rapid decline in wall thickness for 8 mm aneurysms.

Endovascular stenting of traumatic extracranial carotid artery dissections in the pediatric population: a case report.

BACKGROUND: Traumatic extracranial carotid artery injuries are rare in children. Treatment options include surgery, anticoagulation therapy and endovascular treatment. There have been only limited reports in the literature documenting endovascular carotid stent placement in the pediatric population. In these reports, stent deployment was utilized in the setting of pseudoaneurysm formation. CASE REPORT: Here we report a case of endovascular carotid stenting for traumatic carotid dissection in a 15 year-old boy. An uncovered bare self-expanding stent was used to treat progressive high-grade stenosis in the early post-injury period. CONCLUSION: At 6 months post-procedure, complete healing of the carotid artery was demonstrated on follow-up angiogram.

Growth rate and rupture rate of unruptured intracranial aneurysms: a population approach.

BACKGROUND: Understanding aneurysm growth rate allows us to predict not only the current rupture risk, but also accumulated rupture risk in the future. However, determining growth rate of unruptured intracranial aneurysms often requires follow-up of patients for a long period of time so that significant growth can be observed and measured. We investigate a relationship between growth rate and rupture rate and develop a theoretical model that can predict average behavior of unruptured intracranial aneurysms based on existing clinical data. METHODS: A mathematical model is developed that links growth rate and rupture rate. This model assumes a stable aneurysm size distribution so the number of aneurysm ruptures is balanced by the growth of aneurysms. Annual growth rates and growth profiles are calculated from a hypothetical size distribution and data from a previous clinical study. RESULTS: Our model predicts a growth rate of 0.34-1.63 mm/yr for three different growth models when the rupture rate at 10 mm is 1%. The growth rate is 0.56-0.65 mm/yr if annual rupture rate averaged over all aneurysm sizes is assumed to be 2%. The peak of aneurysm size distribution coincides with a period of slow growth between 5 mm and 8 mm. CONCLUSION: This mathematical model can be used to predict aneurysm growth rate, and the results are consistent with previous clinical studies. Predictions from both hypothetical and clinical cases agree very well. This model explains why some aneurysms may grow into a stable size and remain so without rupture.

Paraspinal arteriovenous malformations in children.

Arteriovenous malformations (AVMs) within the spinal canal and in the paraspinal region are unusual. Spinal cord and dural AVMs or arteriovenous fistulas have been the subject of numerous reports, but paraspinal malformations causing venous congestion or hemorrhage in the spinal canal are rare and present special diagnosis and management challenges. The authors review previously published reports on 16 children with paraspinal AVMs. They also describe the 17th case of a child with a paraspinal AVM who presented with a spontaneous spinal epidural hematoma. To the best of the authors' knowledge, there has been no other case of a spinal epidural hematoma associated with a paraspinal AVM. In each of the 17 cases, the vascular lesion was successfully obliterated using endovascular therapy. Embolization with permanent occlusive agents is an effective treatment for these rare but potentially debilitating lesions.

Extracranial traumatic carotid artery dissections in children: a review of current diagnosis and treatment options.

OBJECT: Currently, no diagnostic or treatment standards exist for extracranial carotid artery dissection (CAD) in children after trauma. The purpose of this study was to review and describe the characteristics, diagnosis, and treatment of this rather uncommon sequelae of pediatric trauma. METHODS: A systematic review of the literature was performed to examine the pertinent studies of traumatic extracranial carotid artery (CA) injuries in children. RESULTS: No randomized trials were identified; however, 19 case reports or small case series consisting of 34 pediatric patients were found in the literature. The diagnosis of CAD was made in 33 of 34 patients only after the onset of ischemic symptomatology. Twenty-four of 34 patients underwent cerebral angiography to confirm diagnosis; MR angiography affirmed the diagnosis in 6 of 34 patients. There was little published experience with CA ultrasonography or CT angiography for diagnosis. Thirty of 34 patients were treated with medical therapy or observation; 2 of 4 patients treated with observation alone died. There was little experience with open surgical treatment of CAD in the pediatric population, and there were no studies on the endovascular treatment of traumatic CAD in children. The literature does not support anticoagulation therapy over antiplatelet therapy. CONCLUSIONS: As a result of this review of the literature, the authors propose the algorithms for the evaluation and treatment of traumatic extracranial CADs in children. These recommendations include utilizing MR angiography as a screening tool in cases in which the clinical suspicion of CAD is high, using conventional cerebral angiography to confirm the diagnosis, implementing antiplatelet therapy as initial medical management, and reserving endovascular stenting in cases of failed medical treatment.