Prevalence of cerebral aneurysms in patients with persistent primitive trigeminal artery

OBJECT: The aim of this study was to determine the prevalence of cerebral saccular aneurysms in patients with persistent primitive trigeminal artery (PPTA). The prevalence of cerebral saccular aneurysms in patients with PPTA previously has been reported to be 14 to 32%, but this rate range is unreliable because it is based on collections of published case reports rather than a series of patients chosen in an unbiased manner. METHODS: The authors retrospectively evaluated their own series of 34 patients with PPTA to determine the prevalence of cerebral aneurysms in this population. The prevalence of intracranial aneurysms in patients with PPTA was approximately 3% (95% confidence interval 0-9%). CONCLUSIONS: The prevalence of intracranial aneurysms in patients with PPTA is no greater than the prevalence of intracranial aneurysms in the general population.     

Nylon-fiber-induced neutrophil fragmentation

We have investigated the effects of mechanical elution of neutrophils from nylon-wool fiber (NWF) using the scanning electron microscope and biochemical analysis of elution fractions. We have determined that mechanical removal of neutrophils from nylon-wool fiber disrupts neutrophils adherent to nylon-wool fiber and augments release of granules, release of peripheral cytoplasmic fragments, and release of lactic dehydrogenase, a soluble cytoplasmic enzyme. Mechanical shearing of the adherent cell, and not adherence per se, causes the fragmentation. The extent of fragmentation is proportional to the NWF surface area available to neutrophils and is maximal at the temperature for optimal adherence and spreading. Agents that decrease cell spreading (n-ethylmaleimide and cold) diminish fragmentation. Cytochalasin B, an agent that destabilizes the neutrophil cortex, increases fragmentation. Fragmentation may be an important contributing cause of the abnormal morphology, function, and in vivo survival of nylon-wool-fiber procured human neutrophils. The prevention of fragmentation would appear to be necessary to insure the procurement of optimally functioning cells. Elution of NWF-adherent neutrophils in the cold might be a practical way to diminish neutrophil damage during clinical filtration leukapheresis.     

Patency of the Anterior Choroidal Artery after Flow-Diversion Treatment of Internal Carotid Artery Aneurysms

BACKGROUND AND PURPOSE:Treatment of cerebral aneurysms with flow diverters often mandates placement of the device across the ostia of major branches of the internal carotid artery. We determined the patency rates of the anterior choroidal artery after placement of flow-diversion devices across its ostium.MATERIALS AND METHODS:We analyzed a consecutive series of patients in whom a Pipeline Embolization Device was placed across the ostium of an angiographically visible anterior choroidal artery while treating the target aneurysm. Patency of the anterior choroidal artery after Pipeline Embolization Device placement was determined at immediate postoperative and follow-up angiography. Data on pretreatment aneurysm rupture status, concomitant coiling, number of Pipeline Embolization Devices used, neurologic status at follow-up, and follow-up MR imaging/CT findings were collected.RESULTS:Fifteen patients with 15 treated aneurysms were included in this study. In the immediate postprocedural setting, the anterior choroidal artery was patent on posttreatment angiography for all 15 patients. Of the 14 patients with follow-up angiography at least 6 months after Pipeline Embolization Device placement, 1 (7%) had occlusion of the anterior choroidal artery and 14 had a patent anterior choroidal artery (93%). No patients had new neurologic symptoms or stroke related to anterior choroidal artery occlusion at follow-up. Of the 9 patients with follow-up CT or MR imaging, none had infarction in the vascular territory of the anterior choroidal artery.CONCLUSIONS:In this small study, placement of a Pipeline Embolization Device across the anterior choroidal artery ostium resulted in occlusion of the artery in only 1 patient. It was not associated with ischemic changes in the distribution of the anterior choroidal artery in any patient.

Flow-diverter devices such as the Pipeline Embolization Device (PED; Covidien, Irvine, California) are increasingly being used in the embolization of intracranial aneurysms as both alternatives and adjuncts to endovascular coiling.^1–4 Flow diverters limit aneurysmal blood flow but maintain blood flow into large vessels and perforating vessels covered by the device.⁵ Although many in vitro and experimental models have demonstrated long-term patency rates of branch vessels covered by the PED, the long-term patency of major branch vessels is not well-established.^6–8 In this study, we assessed the immediate and long-term patency rates of the anterior choroidal artery (AchoA) in patients following the placement of a PED across the AchoA ostium.     

Artery Length Sensitivity in Patient-Specific Cerebral Aneurysm Simulations

BACKGROUND AND PURPOSE:The reconstruction of aneurysm geometry is a main factor affecting the accuracy of hemodynamics simulations in patient-specific aneurysms. We analyzed the effects of the inlet artery length on intra-aneurysmal flow estimations by using 10 ophthalmic aneurysm models.MATERIALS AND METHODS:We successively truncated the inlet artery of each model, first at the cavernous segment and second at the clinoid segment. For each aneurysm, we obtained 3 models with different artery lengths: the originally segmented geometry with the longest available inlet from scans and 2 others with successively shorter artery lengths. We analyzed the velocity, wall shear stress, and the oscillatory shear index inside the aneurysm and compared the 2 truncations with the original model.RESULTS:We found that eliminating 1 arterial turn resulted in root mean square errors of <18% with no visual differences for the contours of the flow parameters in 8 of the 10 models. In contrast, truncating at the second turn led to root mean square errors between 18% and 32%, with consistently large errors for wall shear stress and the oscillatory shear index in 5 of the 10 models and visual differences for the contours of the flow parameters. For 3 other models, the largest errors were between 43% and 55%, with large visual differences in the contour plots.CONCLUSIONS:Excluding 2 arterial turns from the inlet artery length of the ophthalmic aneurysm resulted in large quantitative differences in the calculated velocity, wall shear stress, and oscillatory shear index distributions, which could lead to erroneous conclusions if used clinically.

Computational fluid dynamics (CFD) simulations of patient-specific cerebral aneurysms provides a valuable tool for understanding the hemodynamic environment. The geometry of the aneurysm needs to be accurately represented, and the computational model needs to account for the main properties of blood flow physics to obtain realistic and accurate flow solutions. When one reconstructs the computational geometry from imaging data, such as CT angiography or MR angiography, the extent of the surrounding vasculature that must be included to obtain rigorous flow solutions is not a priori known. Inclusion of small-diameter surrounding vessels usually does not affect the flow solution results but could add significant computational effort.¹ On the other hand, exclusion or severe truncation of larger vessels might change the flow estimations, usually resulting in nonrealistic flow patterns. The operator-dependent segmentation of radiologic images of aneurysms leads to model geometries that showed errors as large as 60% in the estimated hemodynamic parameters.^2–5 However, there is no published sensitivity study designed to analyze the effect of the arterial inlet length on the intra-aneurysmal flow estimates, to our knowledge. Due to the lack of accurate, clinically measured velocity profiles and cross-sectional geometries, many current studies use generic, mathematically generated blood flow boundary conditions and short arterial lengths.As a rule of thumb, an inlet length of at least 10 artery diameters upstream of the aneurysm must be used in hemodynamic CFD simulations. In addition, the inlet boundary conditions used in the literature, usually velocity profiles, are taken as fully developed and axisymmetric.^1,4,6–8 These assumptions are valid only for flow in straight tubes, which is very different from flow in patient arteries, where the flow is not fully developed even in the common carotid artery, the location where measurements are more readily available. Therefore, using the fully developed axisymmetric velocity profile on a short artery inlet may result in unrealistic flow estimates in the aneurysm. In the absence of physiologic measurements of arterial cross-sectional velocity distributions, it is generally safer to include a longer anatomic inlet artery to let the flow solution develop realistically on the basis of the tortuosity of the arterial geometry.⁹ Thus, we hypothesized that including a longer inlet artery will minimize the effect of the inlet boundary conditions.The aim of this study was to assess the effect of truncating the arterial inlet length proximal to the aneurysm on the local intra-aneurysmal hemodynamics of ophthalmic aneurysms. The goal was to find a sufficient artery length such that the values of velocity, wall shear stress (WSS), and oscillatory shear index (OSI) in the aneurysm are less affected by the arterial length when using the same boundary conditions and fluid properties.     

Alloimmunization to platelets in heavily transfused patients with sickle cell disease

Bone marrow transplantation (BMT) is now an option for some patients with sickle cell disease (SCD). Many SCD patients are multiply transfused with red blood cells (RBCs), and may be immunized to alloantigens other than erythrocyte antigens. Because platelet refractoriness is a significant complication during BMT, we wished to determine the prevalence of alloimmunization to platelets in transfused SCD patients. Sera collected from 47 transfused and 14 untransfused SCD patients were screened for HLA and platelet-specific antibodies. Transfusion and RBC antibody histories were reviewed. A subset of the patients were rescreened 1 year later. Eighty-five percent of patients with at least 50 RBC transfusions (22 of 26), 48% of patients with less than 50 transfusions (10 of 21), and none of 14 untransfused patients demonstrated platelet alloimmunization (P < .05). Platelet alloimmunization was more prevalent than RBC alloimmunization (20% to 30%). Half of the platelet reactivity was chloroquine-elutable. Eighteen of 22 patients (82%) on chronic RBC transfusion remained platelet-alloimmunized 11 to 22 months after initial testing. In summary, 85% of heavily transfused SCD patients are alloimmunized to HLA and/or platelet-specific antigens. These patients may be refractory to platelet transfusion, a condition that would increase their risk during BMT. Leukodepletion in the transfusion support of SCD patients should be considered to prevent platelet alloimmunization.