A second-generation, endoluminal, flow-disrupting device for treatment of saccular aneurysms

BACKGROUND AND PURPOSE

We report a preclinical study of a second-generation endoluminal device (Pipeline Embolization Device [PED-2] for aneurysmal occlusion and compare the PED-2 with its first-generation predecessor (PED-1).

MATERIALS AND METHODS

Our Institutional Animal Care and Use Committee approved all studies. The PED-2 is a braided endoluminal, flow-diverting device and was implanted across the necks of 18 elastase-induced aneurysms in New Zealand white rabbits and followed for 1 month (n = 6), 3 months (n = 6), and 6 months (n = 6). A second PED-2 was implanted in the abdominal aorta to cover the origins of the lumbar arteries. Angiographic occlusion rates were documented as complete, near-complete, and incomplete. Parent artery percent diameter stenosis was calculated. Results were compared with a previous publication focused on the PED-1, with use of the same model. We compared ordinal outcomes using Fisher Exact or chi(2) tests. We compared continuous data using analysis of variance.

RESULTS

Occlusion rates (complete and incomplete) for the PED-2 were noted in 17 cases (94%) and 1 (6%), respectively, compared with 9 cases of complete (53%) and 8 (47%) of incomplete occlusion with the PED-1 (P = .0072). No incidents of branch artery occlusion or distal emboli in vessels downstream of the parent artery were observed with the PED-2. Parent artery neointimal hyperplasia was minimal in most cases and was significantly less than in the PED-1.

CONCLUSIONS

The PED-2 is a biocompatible and hemocompatible device that occludes saccular aneurysms while preserving the parent artery and small-branch vessels in our animal model.

Spinal extradural arteriovenous malformations with parenchymal drainage: venous drainage variability and implications in clinical manifestations

OBJECT

Although nontraumatic spinal arteriovenous malformations and fistulas (AVMs and AVFs) restricted to the epidural space are rare, they can lead to significant neurological morbidity. Careful diagnostic imaging is essential to their detection and the delineation of the pathological anatomy. Aggressive endovascular and open operative treatment can provide arrest and reversal of neurological deficits.

METHODS

The authors report on 6 cases of extradural AVMs/AVFs causing progressive myelopathy. Clinical findings, diagnostic evaluation, treatment, and outcome are discussed. Special consideration is given to the anatomy of the lesions and the operative techniques used to treat them. A review of the literature concerning extradural vascular malformations is also presented.

RESULTS

All 6 cases of extradural AVMs had an extradural fistulous location with intradural medullary venous drainage. These cases illustrate progressive myelopathy through cord venous congestion (hypertension) that can be caused by an extradural nidus or fistula. In 4 cases, a large epidural lake was identified on angiography. At surgery, the epidural lake was obliterated and medullary drainage interrupted. All patients had stabilization of their neurological deficits and successful obliteration of the AVM/AVF was obtained.

CONCLUSIONS

Extradural AVMs and AVFs are a poorly described entity with published clinical experience limited to sporadic case reports and small series. Although these lesions have a purely extradural location of arteriovenous shunting and early venous drainage, they can be responsible for acute and progressive neurological symptoms similar to those caused by their dural-based intradural counterparts. With careful imaging recognition of the pathological anatomy, surgical and endovascular techniques can be used for the treatment of extradural AVMs affording effective and durable obliteration with stabilization or reversal of neurological symptoms. Venous drainage directly correlates the pathologic mechanisms of presentation. Specific attention must be paid intraoperatively to the epidural lake common to both variants so that recurrence is avoided.

Intra-arterial stroke therapy: an assessment of demand and available work force

Intra-arterial therapy is currently applicable to a small subset of patients with ischemic stroke, but it will likely have an expanding role as new devices are introduced. This review evaluates the demand for such therapy and the physician work force available to provide such therapy in the United States. The available literature was reviewed to assess how many patients might need intra-arterial therapy annually and how many skilled neurointerventionalists are available to provide intra-arterial therapy for acute stroke. The number of acute ischemic strokes in the United States that will be amenable to intra-arterial therapy can only be crudely estimated, but it is certainly less than 126,000 per year and will quite likely be no more than 20,000 cases per year. The future demand for intra-arterial reperfusion techniques may change, but the number of patients who require intra-arterial thrombolysis is currently quite low. The overall number of neurointerventionists is currently adequate, though there might be local shortages.

Morbidity and mortality associated with creation of elastase-induced saccular aneurysms in a rabbit model

BACKGROUND AND PURPOSE

Elastase-induced aneurysms in rabbits have been proposed as a useful preclinical tool for device development. The object of this study was to report rates of morbidity and mortality associated with the creation and embolization of elastase-induced rabbit aneurysms and to assess the impact of operator experience on these rates.

MATERIALS AND METHODS

Elastase-induced model aneurysms were created in New Zealand white rabbits (n = 700). One neuroradiologist/investigator, naive to the aneurysm-creation procedure at the outset of the experiments, performed all surgeries. All morbidity and deaths related to aneurysm creation (n = 700) and embolization procedures (n = 529) were categorized into acute and chronic deaths. Data were analyzed with single-regression analysis and analysis of variance. To assess the impact of increasing operator experience, we broke the number of animals into 50-animal increments.

RESULTS

There were 121 (17%) deaths among 700 subjects. Among 700 aneurysm-creation procedures, 59 deaths (8.4%) were noted. Among 529 aneurysm-embolization procedures, 43 deaths (8.1%) were noted. Nineteen additional deaths (2.7% of 700 subjects) were unrelated to the procedures. Simple regression-indicated mortality associated with procedures diminished with increasing operator experience (R(2) = 0.38, P = .0180), and that for each 50-rabbit increment mortality was reduced, on average, by 0.6%.

CONCLUSIONS

Mortality rates of approximately 8% are associated with both experimental aneurysm creation and with embolization in the rabbit elastase-induced aneurysm model. Increasing operator experience is inversely correlated with mortality, and the age of the rabbit is positively associated with morbidity.

Fate of manuscripts previously rejected by the American Journal of Neuroradiology: a follow-up analysis

BACKGROUND AND PURPOSE

This is a follow-up article to "Fate of Submitted Manuscripts Rejected from the American Journal of Neuroradiology: Outcomes and Commentary." The purpose of this study was to quantify differences in citation frequency between manuscripts published in the American Journal of Neuroradiology (AJNR) and those published after AJNR rejection and to understand citation frequency differences among rejected manuscripts.

MATERIALS AND METHODS

In this study, a MEDLINE search identified all manuscripts published in AJNR in 2005 and those initially rejected by AJNR in 2004 but subsequently published elsewhere. Once identified, the citation frequencies of both groups were determined by using SCOPUS. Citation data were used in comparative studies between AJNR rejected and accepted articles and in studies comparing citation frequency differences among rejected manuscripts as a function of journal and/or publication classifications.

RESULTS

Among 315 subsequently published rejections from AJNR in 2004, 696 citations accumulated between 2005 and 2007 (2.4 citations/journal year), whereas 441 AJNR articles published in 2005 accumulated 2490 citations between 2005 and 2007 (6.4 citations/journal year, P < .0001). One-way analysis of variance suggested that rejected manuscripts classified as technical reports and/or published in journals classified as either neuroradiology or general radiology had significantly higher citation frequencies than other submission types and journal classifications. Nonparametric analysis of citation frequency showed significant correlations with impact factors of respective publishing journals (rho = 0.444).

CONCLUSION

Results from this study suggest that publications initially rejected from AJNR have a significantly lower citation frequency than those accepted by AJNR. Among rejected manuscripts, citations frequencies were highest in technical reports and among journals close to the neuroradiologic discipline.

Gene expression profiling of experimental saccular aneurysms using deoxyribonucleic acid microarrays

BACKGROUND AND PURPOSE

The molecular characteristics of the pathophysiology of saccular aneurysms remain poorly understood. The purpose of the current study was to investigate the expression of various groups of genes at different stages of aneurysm age in elastase-induced saccular aneurysms in rabbits through the use of deoxyribonucleic acid (DNA) microarrays.

MATERIALS AND METHODS

A microarray consisting of genes related to cell adhesion, apoptosis, cell signaling, growth, inflammation, vascular remodeling, and oxidative stress was constructed by using rabbit nucleotide sequences. Elastase-induced saccular aneurysms were created at the origin of the right common carotid artery (CCA) in 12 rabbits. Two weeks (n=6) and 12 weeks (n=6) after aneurysm creation, ribonucleic acid (RNA) was isolated from the aneurysm and the control unoperated left CCA and was used for microarray experiments. Real-time polymerase chain reaction (RT-PCR) was performed for validation of microarray results.

RESULTS

Of 209 genes, 157 (75%) at 2 weeks and 88 (42%) at 12 weeks demonstrated statistically significant differential expression between aneurysm tissue and the control left CCA tissue (P < .05). Multiple genes implicated in vessel wall remodeling were found to be elevated at 2 weeks and at 12 weeks. Expression of cell adhesion molecules and antioxidant enzymes was down-regulated at 2 weeks but was not significantly different from that of controls at 12 weeks. Most transcription factors, inflammatory genes, and structural genes showed underexpression at both time points. The expression profiles of selected genes were confirmed by RT-PCR.

CONCLUSION

Multiple genes in diverse pathways have been differentially expressed in the rabbit aneurysm model.

Rescue retrieval of AngioGuard embolic capture system after failure of capture sheath retrieval in carotid angioplasty and stenting

This report describes the cases of 2 patients with failed retrieval of an AngioGuard distal protection device after carotid stent placement with rescue retrieval by use of a vertebral catheter. An AngioGuard was deployed before carotid angioplasty and stent placement. Attempted removal of the device with the provided recapture sheath was unsuccessful. A 5F 120-cm vertebral catheter was used to recapture and remove the AngioGuard. This technique is a simple and readily available solution for the retrieval of failed removal of a protection device.

Coils in a nutshell: a review of coil physical properties

Since its inception, endovascular coil technology has grown substantially as multiple manufacturers entered the market with an ever-increasing number of new products. Practitioners are now inundated with a choice of coils that vary on the basis of factors such as size, composition, stiffness, and detachment mechanism. The seasoned interventionalist had the benefit of evolving with this technology and, therefore, is likely to understand many of the practical nuances of coil development; for more junior practitioners, who did not experience the ongoing changes in technology, this review will provide a basic framework for the fundamentals of coil design.

Endovascular embolization of paragangliomas: A safe adjuvant to treatment

BACKGROUND AND PURPOSE

Paragangliomas are tumors of neural crest origin commonly arising from the carotid body, vagal nerve, or jugular bulb. The definitive treatment for these tumors is surgical resection, often augmented with pre-operative embolization due their highly vascular nature. We present our experience examining the efficacy and safety of endovascular embolization of these rare tumors.

METHODS

A review of patient's diagnosed with paragangliomas who underwent pre-operative embolization over a 5-year period (2002-2007) was conducted. The tumor subtype, efficacy of embolization, method of embolization, and rate of complication were noted.

RESULTS

A total of 38 patients underwent selective arterial embolization of their paraganglioma using polyvinyl alcohol (PVA) particles ranging in size from 100-1000 microns. The tumor subtypes treated were carotid body (n = 20), glomus vagale (n = 10), and glomus jugulare (n = 8). The average age at presentation was 44 years (range, 15-81). Twenty-two patients were female and sixteen were male. The most common artery embolized was the ascending pharyngeal branch of the external carotid artery. Post-embolization angiography revealed an average decrease in blood flow to tumor of 75%. With the exception of transient facial pain documented in 1 patient, there were no known complications from embolization.

CONCLUSIONS

The endovascular embolization of paragangliomas using PVA prior to surgical resection is a very safe and efficacious procedure that may reduce operative blood loss and associated morbidity.

Endovascular treatment of experimental aneurysms with use of fibroblast transfected with replication-deficient adenovirus containing bone morphogenetic protein-13 gene

BACKGROUND AND PURPOSE

Modified coils have failed to improve long-term recanalization of aneurysms. This study examined whether ex vivo transduction of replication-deficient adenovirus containing the bone morphogenetic protein-13 gene (Ad-BMP-13) in fibroblast allografts would improve angiographic results via increased collagen synthesis, compared with fibroblast-coated platinum coils (FBC) and bare platinum coils (PA).

MATERIALS AND METHODS

Aneurysms were embolized with Ad-BMP-13-coated coils (n = 20). Rabbits were sacrificed at 14 days and at 1, 3, and 6 months after implantation. Digital subtraction angiography (DSA) evaluated stability after embolization. Histologic specimens were examined with a qualitative grading system. Masson trichrome evaluated collagen deposition. Findings were compared with previously reported controls for PA and FBC in the same model and time points.

RESULTS

The grading system showed a greater total score (P = .0002) in Ad-BMP-13 (6.8 +/- 1.6) and FBC (6.3 +/- 2.4) compared with PA (4.7 +/- 2.4). A group main effects test showed that aneurysm neck tissue coverage in Ad-BMP-13 (2.5 +/- 1.1) was higher (P = .0007) than both FBC (1.6 +/- 1.4) and PA (0.9 +/- 1.1). Ad-BMP-13 had more (P < .0001) collagen deposition than the FBC and PA. One- and 3-month Ad-BMP-13 collagen depositions increased (P < .05) over the FBC and PA. Finally, Ad-BMP-13 showed radiographic stability in 15 (75%) cases, coil compaction in 4 (20%) cases, and progressive occlusion in 1 (5%) case. There were no differences in angiographic results (P = .6522).

CONCLUSION

The Ad-BMP-13-coated coils can improve neck coverage and dome fibrosis in the rabbit model, even in the absence of observed differences in angiographic outcome.

Subarachnoid hemorrhage as a presentation of basilar artery dissection

INTRODUCTION

Subarachnoid hemorrhages caused by intracranial dissections are rare. The management of dissections in these cases not clear.

METHODS

Case report.

RESULTS

An 82-year-old woman presented with acute drowsiness and vomiting. CT scan demonstrated extensive subarachnoid hemorrhage and hydrocephalus that subsequently required placement of ventriculoperitoneal shunt. Angiography revealed extensive basilar artery dissection and no aneurysms. The dissection did not produce a critical stenosis and, taking into consideration that the patient had a previous occlusion of her distal left vertebral artery, it was decided to manage the patient conservatively. On a 3-month follow-up, the patient was free of recurrent events.

CONCLUSION

Basilar artery dissection can present with subarachnoid hemorrhage. No guidelines are available for management of basilar artery dissections and treatment should be tailored to the individual patient.

But did you use HydroCoil? Perianeurysmal edema and hydrocephalus with bare platinum coils

SUMMARY

Bioactive coils were developed to improve aneurysm packing and accelerate neointimal healing. Recent reports, however, have implicated these coils in the development of aseptic meningitis, perianeurysmal edema, and hydrocephalus. This report demonstrates that the same clinical phenomena can occur with the use of bare platinum coils.

Vascular Compression as a Potential Cause of Occipital Neuralgia: A Case Report

Vascular compression is a well-established cause of cranial nerve neuralgic syndromes. A unique case is presented that demonstrates that vascular compression may be a possible cause of occipital neuralgia. A 48-year-old woman with refractory left occipital neuralgia revealed on magnetic resonance imaging and computed tomographic imaging of the upper cervical spine an atypically low loop of the left posterior inferior cerebellar artery (PICA), clearly indenting the dorsal upper cervical roots. During surgery, the PICA loop was interdigitated with the C1 and C2 dorsal roots. Microvascular decompression alone has never been described for occipital neuralgia, despite the strong clinical correlation in this case. Therefore, both sectioning the dorsal roots of C2 and microvascular decompression of the PICA loop were performed. Postoperatively, the patient experienced complete cure of her neuralgia. Vascular compression as a cause of refractory occipital neuralgia should be considered when assessing surgical options.

Transorbital puncture for the treatment of cavernous sinus dural arteriovenous fistulas

This report describes a series of patients for whom dural arteriovenous fistulae (DAVFs) of the cavernous sinus were successfully embolized using a percutaneous, transorbital technique to directly cannulate the cavernous sinus. A vascular access needle and catheter are percutaneously advanced along the inferolateral aspect of the orbit to access the cavernous sinus via the superior orbital fissure. Safe and effective embolization is achieved without the need for a surgical cut-down.

Fate of submitted manuscripts rejected from the American Journal of Neuroradiology: outcomes and commentary

BACKGROUND AND PURPOSE

The purpose of this study was to determine the publication fate of submissions previously rejected from the American Journal of Neuroradiology (AJNR) to provide guidance to authors who receive rejection notices.

MATERIALS AND METHODS

A retrospective search by using MEDLINE of all submissions rejected from AJNR in 2004 was performed to identify subsequently published manuscripts. The fate of subsequently published manuscripts was analyzed as a function of submission type (major study, technical note, or case report), publication delay, publishing journal type (neuroradiology, general radiology, or clinical neuroscience journal), impact factor, publication volume, and circulation volume.

RESULTS

Of the 554 rejected submissions to AJNR, 315 (56%) were subsequently published in 115 different journals, with the journal Neuroradiology publishing the greatest number of articles (37 [12%] of 315). The mean publication delay was 15.8 +/- 7.5 months. Major studies were more likely than case reports to be subsequently published (P = .034), but all 3 subtypes were published at rates greater than 50%. Radiologic journals collectively published approximately 60% of subsequent publications, whereas neurosurgery and neurology journals published 27% of rejected manuscripts. The mean impact factor of journals subsequently publishing rejected manuscripts was 1.8 +/- 1.3 (AJNR = 2.5), and 24 (7.5%) manuscripts were subsequently published in journals with higher impact factors than AJNR.

CONCLUSIONS

These findings should give hope to authors receiving a rejection from AJNR, because greater than 50% of articles rejected from AJNR are subsequently published within 2-3 years, irrespective of publication type, into high-quality journals.

Relationship between aneurysm volume and histologic healing after coil embolization in elastase-induced aneurysms: a retrospective study

BACKGROUND AND PURPOSE

There are, to our knowledge, no histologic data correlating aneurysm volume with histologic healing following coil embolization of aneurysms. We report a retrospective study comparing histologic outcome with aneurysm volume in elastase-induced aneurysms in rabbits.

MATERIALS AND METHODS

Aneurysm volume and histologic healing after coil embolization were retrospectively analyzed in 37 elastase-induced aneurysms in rabbits. Aneurysm dimensions (including neck, width, height, and volume) were measured and calculated. Packing density (PD) was calculated. Angiographic results were evaluated as recurrence, stable, and progressive occlusion. An ordinal grading system was used to evaluate the histologic healing after embolization. Correlations among aneurysm volume, PD, and histologic healing were analyzed by conducting linear regression analysis.

RESULTS

For all the aneurysms in this study, mean aneurysm volume was 80.8 +/- 48.6 mm(3) (from 22 to 192 mm(3)), mean PD was 30.4 +/- 8.3% (from 17% to 49%), and mean histologic score was 6.1 +/- 2.0 (from 0.5 to 9.5), respectively. Correlations between aneurysm volume and PD, aneurysm volume and histologic healing, and aneurysm packing and histologic healing were all significant (P < .01).

CONCLUSION

In this study, aneurysms with smaller volumes and higher PD were associated with the most complete histologic healing. The incomplete healing seen in the larger aneurysms is consistent with the higher incidence of recurrences after endovascular treatment that is seen in large human aneurysms.

Molecular Indices of Apoptosis Activation in Elastase-Induced Aneurysms After Embolization With Platinum Coils

BACKGROUND AND PURPOSE

Even though endovascular coils have been widely used for the treatment of intracranial aneurysms, the cellular and molecular responses of aneurysms to the coils after embolization remain poorly understood. The aim of the present study was to understand the mechanism of apoptosis in aneurysms embolized with platinum coils in the rabbit model of elastase-induced aneurysms.

METHODS

Elastase-induced saccular aneurysms were created at the origin of the right common carotid artery in 30 rabbits. Aneurysms were allowed to mature for 8 weeks, after which 20 aneurysms were embolized with platinum coils by endovascular means. After 2 (n=10) and 4 (n=10) weeks of implantation, aneurysm samples harboring coils were harvested for apoptotic studies. The remaining 10 uncoiled aneurysms were used as controls; additional controls included the left common carotid artery, which had not undergone any surgical procedure. Control samples were harvested at 12 weeks after aneurysm creation.

RESULTS

Expression of procaspases-3, -8, and -9 was elevated in coiled aneurysms embolized with platinum coils at both time points when compared with uncoiled aneurysms and the left common carotid artery. Cleaved caspases-3, -8, and -9 were found to be expressed only at 4 weeks after embolization. Cells within the aneurysm cavity were terminal dUTP nick end-labeling-positive at 4 weeks only. These apoptotic cells were identified as smooth muscle actin-positive cells. Expression of tumor necrosis-alpha was high in coiled aneurysms when compared with controls. There was no significant difference in the expression of Fas ligand among groups. Decreased expression of antiapoptotic proteins Bcl-2 and phospho-Bad, as well as increased expression of proapoptotic proteins Bax and Bid, was observed in coiled aneurysms at both time points.

CONCLUSIONS

Activation of apoptosis in aneurysms after embolization with platinum coils is induced by both tumor necrosis factor-alpha-mediated extrinsic and Bcl-2-mediated intrinsic pathways.

The influence of hemodynamic forces on biomarkers in the walls of elastase-induced aneurysms in rabbits

INTRODUCTION

Biological and biophysical factors have been shown to play an important role in the initiation, progression, and rupture of intracranial aneurysms. The purpose of this study was to evaluate the association between hemodynamic forces and markers of vascular remodeling in elastase-induced saccular aneurysms in rabbits.

METHODS

Elastase-induced aneurysms were created at the origin of the right common carotid artery in rabbits. Hemodynamic parameters were estimated using computational fluid dynamic simulations based on 3-D-reconstructed models of the vasculature. Expression of matrix metalloproteinases (MMPs), their inhibitors (TIMPs) and markers of vascular remodeling were measured in different spatial regions within the aneurysms.

RESULTS

Altered expression of biological markers relative to controls was correlated with the locations of subnormal time-averaged wall shear stress (WSS) but not with the magnitude of pressure. In the aneurysms, WSS was low and expression of biological markers was significantly altered in a time-dependent fashion. At 2 weeks, an upregulation of active-MMP-2, downregulation of TIMP-1 and TIMP-2, and intact endothelium were found in aneurysm cavities. However, by 12 weeks, endothelial cells were absent or scattered, and levels of pro- and active-MMP-2 were not different from those in control arteries, but pro-MMP-9 and both TIMPs were upregulated.

CONCLUSION

These results reveal a strong, spatially localized correlation between diminished WSS and differential expression of biological markers of vascular remodeling in elastase-induced saccular aneurysms. The ability of the wall to function and maintain a healthy endothelium in a low shear environment appears to be significantly impaired by chronic exposure to low WSS.

Bone formation in elastase-induced rabbit aneurysms embolized with platinum coils: report of 2 cases

Histologic findings in 71 elastase-induced rabbit aneurysms embolized with platinum coils were retrospectively reviewed. Mature bone formation was found in 2 aneurysms, one with coils implanted for 3 months and the other with coils implanted for 1 year. We present the histologic findings and offer potential explanations for these observations. These findings may be relevant in understanding mechanisms of aneurysm healing after coil embolization.

Balloon-assisted coiling of intracranial aneurysms: evaluation of local thrombus formation and symptomatic thromboembolic complications

BACKGROUND AND PURPOSE

Remodeling balloons are used to assist in endovascular coiling of aneurysms. We evaluated our experience with balloon-assisted coiling (BAC) in an attempt to determine whether this technique increased the rate of thrombus formation or symptomatic thromboembolic complications.

MATERIALS AND METHODS

In 3 years, we treated 221 patients with intracranial aneurysms. Statistical analysis was performed to assess whether BAC increased the rate of thrombus formation or symptomatic thromboembolic complications. Patient demographics, aneurysm size, location, neck width, antiplatelet therapy, and rupture status were evaluated.

RESULTS

We detected no statistically significant difference in rates of thrombus formation (14% versus 9% with and without BAC, respectively, P=0.35) or symptomatic thromboembolic events (7% versus 5% with and without BAC, respectively, P=0.76), though our power to detect small differences was limited. There was also no correlation with age, sex, rupture status, aneurysm size, or location. There was a significant increase in the rates of thrombus formation (6% versus 16%, P=0.02) and symptomatic thromboembolic complications (3% versus 10%, P=0.04) in aneurysms that were classified as narrow- or wide-necked, respectively. The use of clopidogrel was associated with a decrease in the rate of complications (P=0.01).

CONCLUSION

In this series, we detected no significant increase in the rates of either intraprocedural thrombus formation or symptomatic thromboembolic events in patients treated with BAC. Larger studies are required to confirm our observations. Wide-necked aneurysms were independently associated with increased rates of thrombus formation and symptomatic thromboembolic complications, whereas the use of clopidogrel was protective (P=0.01).

Cerebral Aneurysm Formation in Nitric Oxide Synthase-3 Knockout Mice

We sought to evaluate the influence of specific vasoactive gene knockouts on the process of intracranial aneurysm formation in mice. Thirty wild type, 7 nitric oxide synthase (NOS)-2 knockout, 6 NOS-3 knockout, and 8 plasminogen activator inhibitor (PAI)-1 knockout female mice underwent left common carotid artery ligation at 2 to 6 months of age. After a survival period (average 20.4 months +/- 1.5 months), the brains were perfusion fixed with 10% buffered formalin for 10 minutes and then perfused with India ink. Brain and intact cerebral circulation were surgically removed and further fixed in 10% buffered formalin for 4 additional days. The basal cerebral circulation of each brain was examined for the presence of intracranial aneurysms under a surgical microscope (3x-21x). Suspected aneurysms were further dissected for histological analysis. Specimens were embedded in epoxy resin, cut into 0.5 and 1.0 micron sections, and stained with Toluidine blue. A neuropathologist blinded to genotype and surgical microscopy results examined the slides for evidence of aneurysmal pathology. Two intracranial aneurysms in 2 NOS-3 knockout mice were confirmed by histology. No intracranial aneurysms were confirmed in any wild type, NOS-2 knockout, or PAI-1 knockout mice. Histological analysis of aneurysms revealed loss of elastica, subendothelial collagen deposition, and perivascular lymphocytic infiltration. Our results suggest that NOS-3 knockout, but not PAI-1 or NOS-2 knockout, predisposes to the formation of intracranial aneurysms in mice subjected to unilateral carotid artery ligation. Due to small sample sizes however, selection bias cannot be excluded and further investigation is necessary to confirm our results.

A new endoluminal, flow-disrupting device for treatment of saccular aneurysms

BACKGROUND AND PURPOSE

We report a preclinical study of a new endoluminal device for aneurysm occlusion to test the hypothesis that the device, even without use of intrasaccular coil placement, could occlude saccular aneurysms without causing substantial parent artery compromise or compromise of adjacent, small branch arteries.

METHODS

The Pipeline Neuroendovascular Device (Pipeline NED; Chestnut Medical Technologies, Inc) is a braided, tubular, bimetallic endoluminal implant aimed at occlusion of saccular aneurysms through flow disruption along the aneurysm neck. The device was implanted across the necks of 17 elastase-induced aneurysms in the New Zealand white rabbit model and followed for 1 month (n=6), 3 months (n=5), and 6 months (n=6). In each subject, a second device was implanted in the abdominal aorta to cover the origins of lumbar arteries. Aneurysm occlusion rates by angiography (grade 1, complete occlusion; grade 2, near-complete occlusion; and grade 3, incomplete occlusion) were documented. Percent area stenosis of the parent arteries was calculated. Presence of distal emboli in the downstream vessels in the parent artery and branch artery stenosis or occlusion was noted.

RESULTS

Grades 1, 2, and 3 occlusion rates were noted in 9 (53%), 6 (35%), and 2 (12%) of 17 aneurysms, respectively, indicating an 88% rate of complete or near complete occlusion. No cases of branch artery occlusion or distal emboli in the downstream vessels of the parent artery, specifically the subclavian artery, were seen. Parent artery compromise from neointimal hyperplasia was minimal in most cases.

CONCLUSIONS

The Pipeline NED is a trackable, bio- and hemocompatible device able to occlude saccular aneurysms with preservation of the parent artery and small, adjacent branch vessels.

Endovascular treatment of aneurysms: healing mechanisms in a Swine model are associated with increased expression of matrix metalloproteinases, vascular cell adhesion molecule-1, and vascular endothelial growth factor, and decreased expression of tissue inhibitors of matrix metalloproteinases

BACKGROUND AND PURPOSE

The mechanism of aneurysm healing after coiling remains poorly understood. The purpose of the study was to obtain a better understanding of the cellular and molecular events that are associated with aneurysm healing after endovascular coiling in a swine aneurysm model.

MATERIALS AND METHODS

Twenty sidewall aneurysms were created surgically in common carotid arteries in 10 swine. These aneurysms were embolized immediately after creation by using platinum coils by endovascular means. Two and 12 weeks after implantation, aneurysm samples were collected for histologic and biochemical analysis.

RESULTS

All aneurysms were completely or nearly completely occluded angiographically at the time of embolization and at follow-up. At 2 weeks, aneurysm cavities were filled with inflammatory cells and myofibroblasts. At 12 weeks, aneurysm cavities were filled with richly vascularized fibrous tissue and disorganized collagen bundles. The expression of matrix metalloproteinase (MMP)-2 and -9 was found to be elevated at 2 weeks. Expression remained greater than that in control tissue at 12 weeks but was significantly decreased compared with the earlier time point. Expression of tissue inhibitors of MMPs (TIMPs) was diminished at both time points. Expression of vascular cell adhesion molecule-1 (VCAM-1) and vascular endothelial growth factor (VEGF) was elevated at both 2 weeks and 12 weeks. Endothelial nitric oxide synthase expression was not different from that in controls. Transforming growth factor-beta expression was elevated at 2 weeks only.

CONCLUSION

The coil occlusion in this model that is prone to heal is associated with increased expression of MMP-2, MMP-9, VCAM-1, and VEGF, and decreased expression of TIMPs.

Endovascular treatment of epistaxis in patients with hereditary hemorrhagic telangiectasia

BACKGROUND AND PURPOSE

The treatment of epistaxis in patients with hereditary hemorrhagic telangiectasia can be very challenging. The purpose of our study was to evaluate our experience with endovascular epistaxis embolization in patients with hemorrhagic hereditary telangiectasia and to compare this with our experience in patients treated for idiopathic epistaxis.

MATERIALS AND METHODS

Over a 6-year period, we treated 22 patients with epistaxis by using endovascular embolization. Twelve of 22 patients had hereditary hemorrhagic telangiectasia; 10 patients had idiopathic epistaxis. The angiographic findings, efficacy of treatment, and complications for both groups were compared.

RESULTS

Patients with hereditary hemorrhagic telangiectasia had angiographic abnormalities in 92% of cases compared with only 30% in the idiopathic epistaxis group. Compared with a group of 10 patients treated for other causes of epistaxis, those with hereditary hemorrhagic telangiectasia required significantly more re-embolization treatments or additional surgical procedures because of continued or recurrent bleeding episodes after embolization (P=.03). Complications were rare; a single patient in the idiopathic epistaxis group had a self-limited groin hematoma and postembolization facial pain.

CONCLUSION

Endovascular embolization of epistaxis is a safe procedure that can be useful for patients with severe acute epistaxis or chronic persistent bleeding. Patients who undergo endovascular embolization for epistaxis related to hereditary hemorrhagic telangiectasia require repeat embolization and subsequent surgical procedures more often than those with idiopathic epistaxis.

Basilar artery stent angioplasty for symptomatic intracranial athero-occlusive disease: complications and late midterm clinical outcomes

BACKGROUND AND PURPOSE

After an initial series of basilar artery stent angioplasty indicated a high technical success rate and minimal morbidity, subsequent reports suggested significant procedural risks. We retrospectively reviewed our experience with basilar artery stent placement to assess complications and clinical outcomes.

MATERIALS AND METHODS

Ten consecutive patients with symptomatic intracranial athero-occlusive disease underwent stent placement of the basilar artery at our institution (1999-2003). We collected clinical data by chart review and determined outcomes (modified Rankin Scale [mRS]) by telephone interview. Angiographic data were analyzed by 2 blinded investigators. Clinical and angiographic variables were tested for correlation with outcome and complications using the Pearson correlation test.

RESULTS

Of 10 patients (mean follow-up time, 31 months), 4 patients suffered 6 ischemic complications that were immediate in 1, early delayed (<2 weeks) in 4, and late delayed (>2 weeks) in 1. Complications included basilar artery rupture in 1 patient, access site complications in 1 patient, and other non-neurologic complications in 5. Symptomatic restenosis occurred in 1 patient. Outcomes (mRS) were excellent (0-2) in 5 patients, good (3) in 4, and poor (4-6) in 1 patient, who died. Ischemic complications were associated with lesion lumen <or=0.5 mm and lesion angulation >45 degrees (P<.05). Less favorable clinical outcomes were associated with few ischemic complications and the presence of fewer than 2 patent vertebral arteries (P<.05).

CONCLUSIONS

Despite a significant incidence of ischemic and nonischemic complications after basilar artery stent placement, most patients in this small series achieved freedom from vertebrobasilar ischemia and good to excellent clinical outcomes at late midterm follow-up (12-46 months). Ischemic complications usually had an early delayed presentation and procedural risks correlated with lesion characteristics.

Control of aneurysm volume by adjusting the position of ligation during creation of elastase-induced aneurysms: a prospective study

BACKGROUND AND PURPOSE

Animal models with appropriate volume are crucial for preclinical assessment of aneurysm therapies. Our purpose was to control the aneurysm volume by adjusting the position of ligation during creation of elastase-induced aneurysms in rabbits.

MATERIALS AND METHODS

Sixty elastase-induced aneurysms in rabbits were created. Two different methods were used for creation, including group 1 (n=30) by using a lower ligation (from the origin of the right common carotid artery [RCCA] to the ligation point, 10 mm) and group 2 (n=30) by using a higher ligation (from the origin of the RCCA to the ligation point, 15 mm). Aneurysm sizes (neck diameter, width, and height) and volumes in the 2 groups were measured and calculated, and they were compared by using the Student t test.

RESULTS

The mean aneurysm neck diameter, width, and height for group 2 were significantly larger than those of group 1 (3.3 +/- 0.8 versus 2.7 +/- 0.6 mm, P<.001; 3.7 +/- 0.7 versus 2.5 +/- 0.7 mm, P<.001; 9.0 +/- 1.7 versus 7.3 +/- 1.9 mm, P<.001, respectively). The aneurysm volume in group 2 was significantly larger than that in group 1 (102.4 +/- 54.8 mm(3) versus 36.6 +/- 26.8 mm(3), P<.001).

CONCLUSION

The aneurysm volume of elastase-induced models in rabbits can be controlled by adjusting the position of the ligation. Using a higher ligation can create relatively more voluminous aneurysms, compared with using a lower ligation.

Ready or not, here they come: randomized trials evaluating new endovascular aneurysm therapies

Randomized trials evaluating endovascular therapy are currently underway. The results of these trials will present us with both new answers and new questions.

The Stroke Outcomes and Neuroimaging of Intracranial Atherosclerosis (SONIA) Trial

BACKGROUND

Transcranial Doppler ultrasound (TCD) and magnetic resonance angiography (MRA) can identify intracranial atherosclerosis but have not been rigorously validated against the gold standard, catheter angiography. The WASID trial (Warfarin Aspirin Symptomatic Intracranial Disease) required performance of angiography to verify the presence of intracranial stenosis, allowing for prospective evaluation of TCD and MRA. The aims of Stroke Outcomes and Neuroimaging of Intracranial Atherosclerosis (SONIA) trial were to define abnormalities on TCD/MRA to see how well they identify 50 to 99% intracranial stenosis of large proximal arteries on catheter angiography.

STUDY DESIGN

SONIA standardized the performance and interpretation of TCD, MRA, and angiography. Study-wide cutpoints defining positive TCD/MRA were used. Hard copy TCD/MRA were centrally read, blind to the results of angiography.

RESULTS

SONIA enrolled 407 patients at 46 sites in the United States. For prospectively tested noninvasive test cutpoints, positive predictive values (PPVs) and negative predictive values (NPVs) were TCD, PPV 36% (95% CI: 27 to 46); NPV, 86% (95% CI: 81 to 89); MRA, PPV 59% (95% CI: 54 to 65); NPV, 91% (95% CI: 89 to 93). For cutpoints modified to maximize PPV, they were TCD, PPV 50% (95% CI: 36 to 64), NPV 85% (95% CI: 81 to 88); MRA PPV 66% (95% CI: 58 to 73), NPV 87% (95% CI: 85 to 89). For each test, a characteristic performance curve showing how the predictive values vary with a changing test cutpoint was obtained.

CONCLUSIONS

Both transcranial Doppler ultrasound and magnetic resonance angiography noninvasively identify 50 to 99% intracranial large vessel stenoses with substantial negative predictive value. The Stroke Outcomes and Neuroimaging of Intracranial Atherosclerosis trial methods allow transcranial Doppler ultrasound and magnetic resonance angiography to reliably exclude the presence of intracranial stenosis. Abnormal findings on transcranial Doppler ultrasound or magnetic resonance angiography require a confirmatory test such as angiography to reliably identify stenosis.

Specificity of MR Angiography as a Confirmatory Test for Carotid Artery Stenosis: Is It Valid?

OBJECTIVE

We believe that many studies in the literature show a falsely elevated specificity for carotid MR angiography (MRA) in the detection of high-grade stenosis. The purpose of this study was to test the hypothesis that inclusion of a substantial proportion of normal carotid arteries in a study population will falsely elevate the specificity of MRA for confirming a high-grade carotid artery stenosis.

MATERIALS AND METHODS

Seventy-seven carotid arteries were evaluated in 63 patients suspected of having a high-grade carotid stenosis, and all vessels were evaluated with contrast-enhanced MRA. Two subgroups were created, and the specificity of MRA was calculated for each group using digital subtraction angiography (DSA) as the gold standard. Group 1 included 44 vessels classified as high-grade stenosis on sonography and all were evaluated with DSA. To test our hypothesis, group 2 included the 44 carotid arteries from group 1 plus 33 carotid arteries classified as normal or minimally narrowed on sonography and MRA.

RESULTS

In group 1, the specificity of MRA for accurately confirming a high-grade stenosis was 29% for contrast-enhanced maximum-intensity-projection (MIP) images alone and 75% for contrast-enhanced axially reformatted source images as compared with DSA. When the 33 normal arteries from group 2 were added to the data set, the specificities increased to 70% and 89%, respectively.

CONCLUSION

The calculated specificity of MRA as a confirmatory test for high-grade carotid stenosis is highly dependent on the proportion of normal carotid arteries included in the calculation. Based on our results, the specificity of MRA reported in the literature has likely been overstated because of spectrum bias.

Observer agreement in the assessment of endovascular aneurysm therapy and aneurysm recurrence

BACKGROUND AND PURPOSE

Assessments of completeness of endovascular cerebral aneurysm therapy are commonly reported in the literature. We studied several aneurysm assessment scales with regard to observer variability, which directly affects validity of these scales.

MATERIALS AND METHODS

Initial aneurysm occlusion and occlusion at a follow-up angiogram at 3-6 months were assessed independently by 2 experienced observers. Assessments of each aneurysm were made using 3 different scales: 4-response (complete, dog ear, neck remnant, incomplete), 3-response (complete, near-complete, incomplete), and 2-response (complete or near-complete, incomplete). Assessments were also made of comparisons of initial treatment angiogram with follow-up angiogram using 2 different scales: 3-response (better, same, worse) and 2-point response (not worse, worse).

RESULTS

With assessments of both initial and follow-up angiograms, interobserver and intraobserver agreement was progressively worse with increasing response choices in the scales. Observer agreement on assessments of initial angiograms (kappa values 0.48-0.67) was worse than that for follow-up angiograms (kappa values 0.66-0.97). For the comparisons of the initial angiogram with the follow-up angiogram, there was worse observer agreement with the 3-response scale (kappa values 0.64-0.71) than with the 2-response scale (kappa values 0.78-0.89).

CONCLUSION

Interobserver and intraobserver variability are inherent to assessment scales of completeness of cerebral aneurysm therapy. Observer variability is substantially better in scales that offer fewer observer responses. However, scales with fewer observer responses may not identify aneurysm subgroups that have differing risks of recurrence and/or rehemorrhage.

Kyphoplasty: an assessment of a new technology

Kyphoplasty is a new procedure for the treatment of vertebral compression fractures that is being performed with increasing frequency. Representing the Technology Assessment Committee of the American Society of Interventional and Therapeutic Neuroradiology, we present a review of the available information regarding this new technology.

HydroCoil for Endovascular Aneurysm Occlusion (HEAL) study: 3-6 month angiographic follow-up results

BACKGROUND AND PURPOSE

The HydroCoil Embolic System (HES) was developed reduce recurrences of aneurysms relative to platinum coils. This study was conducted to evaluate the recurrence rate of cerebral aneurysms 3-6 months after treatment with HES.

METHODS

We report the results in 135 cerebral aneurysms treated with HES in a prospective multicenter registry. Angiographic results 3-6 months after treatment were evaluated at a core laboratory. Wide variation in HES utilization within the HydroCoil for Endovascular Aneurysm Occlusion (HEAL) registry (HES representing 5% to 100% of the coil length used) allowed for subgroup analysis with regard to percentage length, last coil used, and packing attenuation in small (<10 mm) aneurysms.

RESULTS

The overall recurrence rate was 38 (28.1%) of 135, which included a number of large, giant, and previously recurrent aneurysms. When HES represented > or = 75% of coil length, the recurrence rate was 0 (0%) of 18, whereas with <75% length of HES, the recurrence rate was 16 (23%) of 71 (P = .035). When the final coil deposited was a HES coil, the recurrence rate was 6 (11%) of 53, whereas when the final coil was platinum, the recurrence rate was 10 (29%) of 34 (P = .047). When the packing attenuation was > or = 50%, the recurrence rate was 11 (19%) of 59, whereas for packing attenuation <50%, the recurrence rate was 5 (18%) of 28. The packing attenuation calculations were very error-prone.

CONCLUSION

Although the overall recurrence rates for small and large aneurysms in HEAL were no lower than published rates for aneurysms treated with platinum coils, patients treated in HEAL had a reduced recurrence rate when greater than 75% of the coil length used to treat an aneurysm was HES and when the final coil was HES.

Angioplasty of an idiopathic intracranial arterial stenosis

Treatment of symptomatic intracranial atherosclerotic stenosis usually involves maximizing medical therapy. In patients with medically refractory symptoms despite maximum pharmacologic therapy, intracranial angioplasty and/or stenting has become an accepted treatment option. The use of percutaneous transluminal angioplasty (PTA) for idiopathic intracranial stenoses has not been reported to date.We describe a case of idiopathic intracranial stenosis which was refractory to medical therapy and was successfully treated with percutaneous transluminal angioplasty. The presenting symptoms included multiple episodes of aphasia and right-sided weakness as well as a left basal ganglia infarct. The patient underwent treatment with two intracranial angioplasty procedures. There was a recurrence of the stenosis and symptoms following the first procedure. However, after a second treatment with a slightly larger balloon, flow in the MCA normalized. Furthermore, the symptoms attributed to her MCA stenosis had essentially resolved. This case suggests that patients with medically refractory idiopathic intracranial stenosis can be successfully treated with percutaneous transluminal angioplasty.

Balloon-assisted coiling through a 5-French system

INTRODUCTION

We present a catheter technique that utilizes a 5F system for the purpose of balloon-assisted coiling in the setting of intracranial aneurysms.

METHODS

A standard 5F short sheath is placed in the common femoral artery, and a 5F diagnostic catheter is placed through the sheath and used for selective vessel angiography. When endovascular intervention is pursued, the diagnostic catheter is placed in the appropriate vessel and systemic heparinization is ensured. Over an exchange length wire, the 5F vertebral catheter and 5F short sheath are exchanged for a 5F Shuttle (Cook) sheath. We then routinely place a 10, 14 or 18 microcatheter over an appropriately gauged microguidewire into the aneurysm. As needed, balloon catheters are then placed across the neck of the aneurysm for remodeling purposes. During the course of the procedure, control angiography is performed through the Shuttle sheath. Following the placement of coils, the microcatheter and balloon catheter are removed and a final biplane image is obtained via the 5F Shuttle sheath.

RESULTS

This technique has been employed in 15 patients who required balloon-assisted coiling of an intracranial aneurysm. There were no technical difficulties or arterial access site complications from the procedures. Catheter mobility and torque were not affected, nor was the quality of our imaging.

CONCLUSION

We conclude that this small-diameter system provides ample "room" for catheter placement and interventional treatment while reducing the known risks of postprocedural complications. Angiographic images remain excellent and are comparable to those obtained by larger catheters.

Endovascular treatment of experimental aneurysms by use of fibroblast-coated platinum coils: an angiographic and histopathologic study

BACKGROUND AND PURPOSE

The purpose of this study was to determine whether implanting exogenous fibroblasts on platinum coils could enhance intra-aneurysmal fibrosis. Hypotheses included: (1) fibroblast-coated (FBC) platinum coils can improve angiographic results after embolization; and (2) FBC platinum coils can accelerate histological healing of embolized aneurysms.

METHODS

Experimental aneurysms in rabbits were embolized with control platinum coils (n=18) or FBC coils (n=18). Subjects were euthanized at 14 days, 1 month, 3 months and 6 months after implantation. Digital subtraction angiography was used to evaluate stability after embolization. Histological samples were examined with a grading system (range, 0 to 12) based on neck and dome healing.

RESULTS

Histology total scores and fibrosis ratio at 14 days were significantly greater in the FBC coil group compared with controls (6.6+/-1.9 versus 2.5+/-1.1, 1.2+/-0.6% versus 0.2+/-0.3%, respectively; P=0.0090). Cavities embolized with FBC coils showed cellular proliferation and thrombus organization, with an endothelialized membrane bridging the neck. There were no differences between groups in the later timepoints. The FBC coil group showed radiographic stability in 11 (61%) cases, coil compaction in 2 (11%) cases, and progressive occlusion in 5 (28%) cases. No progressive occlusion was seen in controls; 3 (17%) of 18 control cases exhibited coil compaction (P=0.0546).

CONCLUSIONS

FBC coils can accelerate early histological healing compared with control coils in the rabbit aneurysm model.

Acute vertebral compression fractures in patients with multiple myeloma: evaluation of vertebral body edema patterns on MR imaging and the implications for vertebroplasty

The presence of edema on MR imaging is a common finding in acute or subacute vertebral body compression fractures. Compression fractures can present in patients with benign osteoporosis, metastases, multiple myeloma, or hemangiomas. We present 2 patients with multiple myeloma who had symptomatic acute and subacute compression fractures documented on imaging studies without associated edema on MR imaging evaluation.

Can neck size in elastase-induced aneurysms be controlled? A retrospective study

BACKGROUND AND PURPOSE

Reproducible animal models with appropriate neck size are crucial for preclinical assessment of aneurysm therapies. Our purpose was to determine whether the neck size of elastase-induced aneurysms could be controlled by adjusting the position of the temporary occlusion balloon.

METHODS

Seventy-two elastase-induced aneurysms in rabbits were retrospectively analyzed. Three groups (group 1, n = 35; group 2, n = 32; group 3, n = 5) were defined according to different balloon position (lowest, intermediate, and highest, respectively) related to the origin of right common carotid artery (CCA). Aneurysm sizes in different groups were measured and compared; parent artery dilation was assessed as present or absent. The Wilcoxon rank sum test, the Fisher exact test, and the chi(2) test were used for statistics process.

RESULTS

The mean aneurysm neck diameter in group 1 was significantly wider than that in group 2 (P = .0001). The proportion of wide-necked (diameter of neck >4 mm) aneurysms in group 1 was significantly higher than that in group 2 (P = .0011). The mean dome/neck ratio in group 1 was smaller than that of group 2 (P = .0031). Aneurysm width and height and the frequency of parent artery dilation were not different in groups 1 and 2 (P = .43, P = .10, and P = .25). No aneurysms formed in group 3.

CONCLUSION

The neck size of elastase-induced aneurysms can be controlled by adjusting the position of the inflated balloon, with balloon positioning that bridges from the CCA to the subclavian/brachiocephalic arteries yielding narrow-necked aneurysms.