Overestimation of ischemic core on baseline MRI in acute stroke.

BACKGROUND AND PURPOSE: In patients with acute ischemic stroke (AIS), overestimation of ischemic core on MRI-DWI has been described primarily in regions with milder reduced diffusion. We aimed to assess the possibility of ischemic core overestimation on pretreatment MRI despite using more restricted reduced diffusion (apparent diffusion coefficient (ADC) ≤620 × 10-6 mm2/s) in AIS patients with successful reperfusion. MATERIALS AND METHODS: In this retrospective single institutional study, AIS patients who had pretreatment MRI underwent successful reperfusion and had follow-up MRI to determine the final infarct volume were reviewed. Pretreatment ischemic core and final infarction volumes were calculated. Ghost core was defined as overestimation of final infarct volume by baseline MRI of >10 mL. Baseline clinical, demographic, and treatment-related factors in this cohort were reviewed. RESULTS: A total of 6/156 (3.8%) patients had overestimated ischemic core volume on baseline MRI, with mean overestimation of 65.6 mL. Three out of six patients had pretreatment ischemic core estimation of >70 mL, while the final infarct volume was <70 mL. All six patients had last known well-to-imaging <120 min, median (IQR): 65 (53-81) minutes. CONCLUSIONS: Overestimation of ischemic core, known as ghost core, is rare using severe ADC threshold (≤620 × 10-6 mm2/s), but it does occur in nearly 1 of every 25 patients, confined to hyperacute patients imaged within 120 min of symptom onset. Awareness of this phenomenon carries implications for treatment and trial enrollment.

Impact of collateral flow on tissue fate in acute ischaemic stroke.

BACKGROUND: Collaterals may sustain penumbra prior to recanalisation yet the influence of baseline collateral flow on infarct growth following endovascular therapy remains unknown. METHODS: Consecutive patients underwent serial diffusion and perfusion MRI before and after endovascular therapy for acute cerebral ischaemia. We assessed the relationship between MRI diffusion and perfusion lesion indices, angiographic collateral grade and infarct growth. Tmax perfusion lesion maps were generated and diffusion-perfusion mismatch regions were divided into Tmax >or=4 s (severe delay) and Tmax >or=2 but <4 s (mild delay). RESULTS: Among 44 patients, collateral grade was poor in 7 (15.9%), intermediate in 20 (45.5%) and good in 17 (38.6%) patients. Although diffusion-perfusion mismatch volume was not different depending on the collateral grade, patients with good collaterals had larger areas of milder perfusion delay than those with poor collaterals (p = 0.005). Among 32 patients who underwent day 3-5 post-treatment MRIs, the degree of pretreatment collateral circulation (r = -0.476, p = 0.006) and volume of diffusion-perfusion mismatch (r = 0.371, p = 0.037) were correlated with infarct growth. Greatest infarct growth occurred in patients with both non-recanalisation and poor collaterals. Multiple regression analysis revealed that pretreatment collateral grade was independently associated with infarct growth. CONCLUSION: Our data suggest that angiographic collateral grade and penumbral volume interactively shape tissue fate in patients undergoing endovascular recanalisation therapy. These angiographic and MRI parameters provide complementary information about residual blood flow that may help guide treatment decision making in acute cerebral ischaemia.

Intra-arterial thrombolysis for acute stroke in patients 80 and older: a comparison of results in patients younger than 80 years.

BACKGROUND AND PURPOSE: Intra-arterial fibrinolytic therapy is a promising treatment for acute ischemic stroke. Few data are available on its use in elderly patients. The purpose of this study was to compare the baseline characteristics, complications, and outcomes between intra-arterially treated ischemic stroke patients aged > or = 80 years and their younger counterparts. METHODS: Patients aged > or = 80 years (n = 33) were compared retrospectively with contemporaneous patients aged < 80 years (n = 81) from a registry of consecutive patients treated with intra-arterial thrombolysis over a 9-year period. RESULTS: The very elderly and younger cohorts were very similar in baseline characteristics, including pretreatment stroke severity (National Institutes of Health Stroke Scale [NIHSS] 17 versus 16), differing only in history of stroke/transient ischemic attack (42% versus 22%, P = .01) and weight (66.8 versus 75.8 kg; P = .02). Significant differences in recanalization (TIMI 2-3) rates could not be detected between the very elderly and younger patients (79% versus 68%, P = .10). Rates of major symptomatic hemorrhage (7% versus 8%) and any intracerebral hemorrhage (39% versus 37%) did not differ. Outcomes at 90 days showed lower rates of excellent functional outcome (mRS < or = 1, 26% versus 40%, P = .02) and survival (57% versus 80%, P = .01) among the very elderly. CONCLUSIONS: Intra-arterial fibrinolysis in the elderly can be accomplished with recanalization rates and hemorrhage rates equal to that in younger patients. Although mortality rates are higher and good functional outcomes are lower than in younger persons, nondisabling outcomes may be achieved in a quarter of patients. These findings suggest that the investigation and use of intra-arterial thrombolytic treatment in very elderly patients should not be avoided but pursued judiciously.

Transvenous treatment of spontaneous dural carotid-cavernous fistulas using a combination of detachable coils and Onyx.

Three patients with spontaneous dural carotid-cavernous fistulas were treated by using a combination of detachable coils and Onyx liquid embolic agent. Cavernous sinus was accessed via the superior ophthalmic vein or inferior petrous sinus approach. In all cases, a complete angiographic closure of the fistulas was achieved with full recovery from neuro-ophthalmologic symptoms. This report suggests that the controlled and excellent penetration of Onyx is superb for blocking the intricate communication of dural carotid-cavernous fistulas.

Endovascular mechanical clot retrieval in a broad ischemic stroke cohort.

BACKGROUND AND PURPOSE: Our aim was to describe an expanded experience with endovascular mechanical embolectomy in a broad group of patients, including those not meeting entry criteria for the MERCI multicenter trials. METHODS: We performed an analysis of all patients with ischemic stroke treated with the Merci Clot Retrieval Device at a single academic center outside of the Mechanical Embolus Removal in Cerebral Ischemia (MERCI) trials. RESULTS: Twenty-four patients were treated with the device. Nine were MERCI trial ineligible: 4 received intravenous (IV) tissue plasminogen activator (tPA), 1 received IV tPA and was younger than 18 years of age, and 4 had time-to-treatment of longer than 8 hours. Mean age was 64 years (range, 14-89 years; 42% women). Median National Institutes of Health Stroke Scale (NIHSS) score was 21 (range, 11-30). Median symptoms-to-procedure-start time was 303 minutes (range, 85-2385 minutes). Recanalization (Thrombolysis in Myocardial Infarction, 2-3) was achieved in 15/24 (63%). In device-only patients, recanalization occurred in 10/16. In patients who failed IV tPA undergoing rescue embolectomy, recanalization was achieved in 4/5. Three patients unresponsive to device therapy received rescue intra-arterial tPA/abciximab; recanalization was achieved in 2/3. Recanalization was achieved in 3/4 patients in whom treatment was started longer than 8 hours after symptom onset. Asymptomatic hemorrhage occurred in 38%; symptomatic hemorrhage, in 8%. Three device fractures occurred; none worsened clinical outcome. In-hospital mortality was 17%; 90-day mortality, 29%. Good 90-day functional outcome (modified Rankin Scale,

Fluid equations applied to blood flow measurement using digital videodensitometry.

RATIONALE AND OBJECTIVES: Time-dependent fluid flow is computed from projection radiographs without bolus tracking by applying the fluid equations of continuity and incompressibility. METHODS: The fluid equations are combined and integrated to yield an equation that describes instantaneous mass conservation within a vessel segment. The technique is demonstrated using phantom images and patient data obtained using a digital subtraction angiography (DSA) system. RESULTS: Instantaneous and mean flow rates are successfully computed with this algorithm, but the uncertainties are overestimated. In a 1.0-cm diameter tube, instantaneous and mean velocities corresponding to 7.3 cm per frame are computed within 13% uncertainty using a 4.0-cm segment length. Mean flow rates computed from standard diagnostic angiograms taken from three different projections agree within 16%. CONCLUSIONS: This technique can successfully compute time-dependent flow rates from DSA image sequences with large fluid displacements between frames. The accuracy is strongly dependent on the magnitude of the contrast density gradient.

Combined embolization and surgical treatment of arteriovenous malformation of the orbit.

We examined three patients with arteriovenous malformation of the orbit. At initial examination, all patients had a slowly progressive mass effect combined with congestive symptoms and clinical signs typical of an orbital vascular lesion. Arteriovenous malformation of the orbit was diagnosed on the basis of clinical and radiographic assessment, including the use of digital subtraction angiography and in one patient, magnetic resonance imaging. Treatment of each patient involved neuroradiologic embolization of the vascular lesion followed by surgical excision. Transient complications of endovascular management occurred. In one patient particulate emboli migrated into the central retinal artery after postembolization orbital surgical excision; consequent focal ischemic retinopathy contributed to short-term visual field deficits, which eventually resolved spontaneously. In another patient, spasm of the ophthalmic artery occurred during embolization, resulting in a transient afferent pupillary defect and loss in visual acuity to 20/60, which resolved over the subsequent week. High-flow orbital vascular lesions represent a considerable treatment challenge because of the complex anatomic and hemorrhagic characteristics of the malformation. Neuroradiologic characterization and embolization as a preoperative adjuvant is not without risk but offers an important advantage in the treatment of these formidable lesions. A combination of endovascular and surgical management may allow otherwise inoperable lesions to be treated successfully.

Endovascular occlusion of intracranial aneurysms with electrically detachable coils: correlation of aneurysm neck size and treatment results.

PURPOSE: To devise a method to measure aneurysm neck size on angiographic films, and to correlate the sizes obtained with the extent of endovascular aneurysm occlusion, performed with electrically detachable coils. METHODS: The angiograms of 79 intracranial aneurysms treated by endovascular occlusion using electrically detachable coils were retrospectively analyzed. A method using the average reported caliber of the major intracranial vessels was applied to determine the aneurysm neck sizes on the diagnostic angiograms. The cases were divided into two groups according to neck size, 4 mm being the discriminative value for small and wide necks. The posttreatment angiogram of each case was analyzed to evaluate the degree of occlusion achieved by the technique. RESULTS: Necks were successfully measured in 95% of the aneurysms. Complete aneurysm thrombosis was observed in 85% of the small-necked aneurysms and in 15% of the wide-necked aneurysms. CONCLUSIONS: Accurate angiographic measurements of neck diameter can be obtained in most aneurysms. The size of an aneurysm neck correlates well with the results of the endovascular treatment. Small-necked aneurysms can be satisfactorily occluded with this technique. In wide-necked aneurysms this technique should be reserved for lesions having a high surgical risk.

An in vivo arteriovenous malformation model in swine: preliminary feasibility and natural history study.

PURPOSE: To assess the feasibility, natural history, and preliminary physiologic validation of creating an in vivo arteriovenous malformation model in swine. METHODS: A transorbital puncture technique into the cavernous sinus was used to create an arteriovenous communication between the rostral rete and the cavernous sinus in eight swine. Short-term patency and hemodynamic behavior were assessed clinically and by serial angiography. Acute phase physiologic characterization of four models was also performed, using intravascular pressure and Doppler blood flow velocity measurements. RESULTS: Large arteriovenous shunts between the rostral rete and cavernous sinus were consistently produced, which mimicked the angiographic features of cerebral arteriovenous malformations in humans. Classic changes in intraarterial and intravenous pressures and blood flow velocities were also observed. Early pathophysiologic evolution occurred in two animals, consisting of recruitment of previously unseen collateral vessels. Spontaneous occlusion of the arteriovenous shunt occurred in most animals within 7 days because of a rigorous fibroblastic response. CONCLUSIONS: A simple technique for creating an arteriovenous malformation model in swine is now possible and is promising for future studies.

Delayed venous occlusion following embolotherapy of vascular malformations in the brain.

PURPOSE: To describe the nature and features of delayed venous thrombosis following embolization of arteriovenous fistulae. METHODS: Retrospective review of the available clinical history, details of embolization procedures, and results of follow-up angiography were carried out on all embolization procedures performed on high-flow vascular malformations of the brain done at our institution since 1987. RESULTS: Four patients were identified who had delayed (greater than 1 week) venous thrombosis/occlusion after embolization of the malformation associated with neurologic complications. Two patients had arteriovenous fistula and two had vein-of-Galen malformations. These patients had no untoward embolization of the venous outlet as a cause of the venous occlusion. CONCLUSIONS: It is postulated that thrombosis in the arteriovenous fistula group was induced by conversion (due to embolization) of a patulous high flow venous outlet into a slow flow system; in the vein-of-Galen group, the occlusion was thought to be due to high-flow venopathy.

Acute subdural hemorrhage complicating embolization of a cerebral arteriovenous malformation.

We present a case of a young adult in whom acute subdural hemorrhage developed immediately after embolization of a cerebral arteriovenous malformation with glue. Inadvertent venous outlet obstruction with glue was implicated in the production of the hemorrhage. Possible mechanisms of spread of blood to the subdural space are discussed. Awareness of the possibility of iatrogenic subdural hemorrhage is necessary before undertaking embolization procedures.

Dural arteriovenous fistula in children: endovascular treatment and outcomes in seven cases.

BACKGROUND AND PURPOSE: Dural AVF is a vascular anomaly that rarely occurs in children and is best treated by endovascular embolization. We report our experience using various endovascular embolization techniques in the treatment of dural AVF in a pediatric population. METHODS: Seven children with angiographically proven dural AVF were treated with endovascular embolization using microcoils, N-butylcyanoacrylate, detachable balloons, and/or silk suture. All imaging studies, embolization procedures, and patient charts were retrospectively reviewed. RESULTS: Seven children had been treated for dural AVF at our institution since 1987. Three newborns presented with congestive heart failure. Four older children (10 months-10 years) presented with signs referable to venous hypertension, including seizures, hydrocephalus, and proptosis. Embolization approaches included transarterial, transvenous, and direct puncture after neurosurgical exposure of a dural sinus. The number of embolizations ranged from 1 to 13 sessions per patient. All patients experienced symptomatic improvement after each embolization session. The three newborns showed marked improvement in cardiac function that allowed discharge to home. Clinical follow-up ranged from 3 weeks to 9 years (mean, 4.1 years). Two children with partially embolized dural AVF died, and one was lost to follow-up. Four children are alive after complete embolization of their dural AVF; two are developmentally normal, and two have mild developmental delay. CONCLUSION: Endovascular embolotherapy is the current treatment of choice for dural AVF. Embolization therapy may be life saving in the setting of cardiac failure and curative in cases of small or simple fistulae. Multiple, complex dural AVF are usually not curable, and treatment is aimed at symptomatic relief. Treatment strategies focus on the location and/or complexity of the fistula, the patient's clinical status, and the neurologic prognosis.

Potential toxic effects of superselective injection of amobarbital sodium on microvasculature: a study in an animal model.

PURPOSE: To determine whether microvascular damage occurs from superselective intraarterial injection of amobarbital sodium using the swine endovascular embolization model. METHODS: Thirty-four swine underwent percutaneous femoral puncture for superselective catheterization of the proximal artery of the rete. Varying concentrations of amobarbital sodium were prepared (12.5 to 100 mg/mL solution) in either normal saline or sterile water (105 mOsm/L to 1138 mOsm/L) of which one concentration was infused slowly into one ipsilateral rete. Control infusions were also performed. Histopathologic changes were evaluated at 30 minutes and 10 days after infusion, using standard light and electron microscopy techniques. RESULTS: Moderate vasospasm occurred only in three swine at 100 mg/mL amobarbital sodium in normal saline. Light microscopy showed no significant histologic changes in the retia at any of the tested concentrations of amobarbital sodium. Electron microscopy showed ultrastructural alterations in the intima only at the higher amobarbital sodium concentrations. CONCLUSIONS: Concerns for inducing significant damage to cerebral microvasculature by superselective injection of amobarbital sodium at the usually recommended concentrations and doses are probably not justified.

Use of a Doppler guide wire for intravascular blood flow measurements: a validation study for potential neurologic endovascular applications.

PURPOSE: To conduct a validation study of a Doppler guide wire for potential neuroendovascular applications. METHODS: A 12-MHz, 0.018-inch Doppler guide wire was evaluated in eight swine under various blood flow conditions using two types of in vivo cerebrovascular models (physiologic and arteriovenous shunting). Flow conditions were mechanically and pharmacologically altered. Doppler average peak velocity was compared with volumetric blood flow, and flow profile corrections were calculated and analyzed. Qualitative aspects of the Doppler guide wire spectra were also assessed. RESULTS: Plots of average peak velocity versus volumetric blood flow showed excellent linear relationships (r2 > 0.94), which were maintained at high flow conditions (average peak velocity, 99 to 236 cm/sec; volumetric blood flow, 392 to 889 mL/min). Values of flow profile correction varied from 0.43 to 0.94 and showed no consistent relationship to changes in volumetric blood flow. CONCLUSIONS: The excellent correlation between average peak velocity and volumetric blood flow over a wide range of blood flow conditions and the additional qualitative information of the Doppler guide wire spectra establish a foundation for clinical implementation. The unpredictable variations of flow profile corrections remain obstacles for calculating volumetric blood flow based on Doppler guide wire average peak velocity.

An experimental arteriovenous malformation model in swine: anatomic basis and construction technique.

We assessed the feasibility of creating an experimental arteriovenous malformation model in swine by diverting and increasing blood flow through bilateral retia mirabilia. This was achieved by surgical formation of a large right-sided carotid-jugular fistula, in combination with endovascular occlusion of several neck arteries ipsilateral to the fistula. Using this technique, 11 of 13 swine demonstrated an acute-phase angiographic simulation of an arteriovenous malformation. There was rapid circulatory diversion from the left ascending pharyngeal artery ("feeder"), across both retia ("nidus"), and fast retrograde flow into the right ascending pharyngeal and common carotid arteries ("draining vein") toward the fistula. The relevant vascular anatomy of the swine head and neck is outlined, and steps in the construction of this arteriovenous malformation model are detailed.

Angiographic diagnosis and management of head and neck schwannomas.

Schwannomas are tumors derived from nerve sheath cells, which are often located in the head and neck, including the CNS. Although a definitive vascular pattern has been previously characterized for these lesions, preoperative embolization of the more vascular schwannomas has not been described. In a review of eight patients with schwannomas who underwent angiography at our institution since 1987, a characteristic vascular pattern became apparent that helped distinguish these lesions from other lesions of the head and neck. The lesions were moderately vascular with tortuous tumor vessels. Scattered, small puddles of contrast medium seen in the mid-arterial, capillary, and venous phases were believed to be characteristic of these lesions. Multiple feeding vessels were noted in all but one case, but these were only minimally enlarged. No arteriovenous shunting or vascular encasement was identified. Six of eight lesions were embolized with significant devascularization and no morbidity or mortality. In patients with head and neck tumors whose angiographic findings include a pattern of moderate hypervascularity, tortuous tumor vessels, and, in particular, scattered contrast puddles without arteriovenous shunting or vascular encasement, schwannoma should be suspected. Embolization is a useful and safe presurgical adjunct in the treatment of vascular schwannomas.

Endovascular treatment of fusiform aneurysms with stents and coils: technical feasibility in a swine model.

PURPOSE: To assess the biomechanical feasibility of treating experimental fusiform aneurysms endovascularly with a combination of stents and coils. METHODS: An experimental model was surgically constructed in the necks of nine swine to simulate intracranial fusiform aneurysms possessing important "perforators" or side branches. Balloon-expandable metal stents were positioned across the aneurysms in eight swine. In five of these, additional treatment was intraaneurysmal placement of detachable microcoils. Attempts were made to deposit these coils strategically away from the origin of the side branch. RESULTS: Stent placement was successful in seven swine but failed in one swine because of stent-aneurysm size mismatch. Two swine treated with only stents showed no significant alterations in blood filling of the aneurysm or side branch. Satisfactory coil placement (outside the stent, within the aneurysm sac, and away from the orifice of the side branch) was achieved in four of the five swine treated with stents and coils. Careful fluoroscopic monitoring and controlled coil delivery were necessary to avoid covering the sidebranch origin. These aneurysms could not be packed densely after detachment of the first coil because of the resultant radiographic overlap of multiple coil loops on the stent and its lumen in all projections. In one swine there was inadvertent untoward reentry of the coil tip into the expanded stent lumen during its delivery. CONCLUSION: Endovascular treatment of experimental fusiforms aneurysms using stents and coils is technically feasible. The stent maintains patency of the parent artery while allowing strategic coil placement in the aneurysm sac away from the origin of side branches. This technique may prove useful in the future treatment of intracranial fusiform aneurysms. However, potential sources of technical difficulties have been identified, and further longterm studies using an appropriate intracranial stent will be necessary before human application.

Laboratory simulations and training in endovascular embolotherapy with a swine arteriovenous malformation model.

We assessed the suitability of a swine experimental arteriovenous malformation model for laboratory simulations and training in endovascular embolotherapy. Embolizations with liquid glue or particles were performed in 10 animals. The parameters of injection (microcatheter position, concentration and volume of embolic agent, injection rate) were deliberately varied to simulate results that may be observed in clinical practice. A range of successful and less desirable therapeutic outcomes or complications was simulated. In one model, intravascular mean blood pressure in the "terminal feeder" rose after "nidus" embolization, consistent with observations in feeders of cerebral arteriovenous malformations. Experience in the technical aspects of embolotherapy was gained by repeated performances using this model. Simplicity of creation, clear angiographic visibility of feeders, a nidus and a draining vein, and hemodynamic similarities with cerebral arteriovenous malformations make this an attractive in vivo experimental model for learning the principles of embolotherapy, testing new embolic agents, and training/gaining experience in embolization techniques.

Intraarterial thrombolysis for treatment of acute stroke: experience in 26 patients with long-term follow-up.

BACKGROUND AND PURPOSE: Since the approval of intravenous tissue plasminogen activator for acute ischemic stroke, great interest has been generated in cerebral fibrinolysis. Our purpose was to assess long-term outcome and hemorrhagic risk in patients with anterior circulation ischemic stroke treated with intraarterial urokinase. METHODS: Twenty-six patients were treated within 6 hours of ictus; of these, 21 were followed up for an average of 23 months. Angiographic reperfusion was classified according to thrombolysis in myocardial infarction (TIMI) grades. The Rankin Scale (RS) and the modified Barthel Index (mod BI) were used as outcome measures (good outcome: RS = 0-2, mod BI = 16-20; poor outcome: RS = 3-5, mod BI < or = 15). RESULTS: Ten of the 21 patients (average age, 48 years) had a good outcome; three (average age, 71 years) had a poor outcome; eight patients (average age, 78 years) died. Partial/complete (successful) recanalization was observed in 11 of 26 patients and minimal or no (unsuccessful) recanalization in 15. Recanalization favored a better outcome: nine of 21 had successful recanalization, with a good outcome in seven; 12 of 21 had unsuccessful reperfusion, with poor outcome/death in nine. Poor outcome was noted in five patients with internal carotid artery (ICA) bifurcation occlusions, four of whom had unsuccessful recanalization and poor outcome or death. Hemorrhage occurred in 10 of the 26 patients, with clinical deterioration in three. The average dose of urokinase was higher in the hemorrhage group, and mortality was higher in patients who hemorrhaged. CONCLUSION: Intraarterial thrombolysis is feasible in the setting of acute stroke. Successful reperfusion is associated with a better outcome, and the prevalence of hemorrhage does not exceed that which occurs in the natural history of embolic stroke. Poor outcome or death is associated with nonrecanalization, older age, hemorrhage, and ICA bifurcation occlusions.

Development of the biologically active Guglielmi detachable coil for the treatment of cerebral aneurysms. Part II: an experimental study in a swine aneurysm model.

BACKGROUND AND PURPOSE: Ion implantation is a surface-modification technology that creates a borderless surface on protein-coated platinum; this change in physical and chemical properties on the surface of Guglielmi detachable coils (GDCs) appears to enhance cell proliferation and adhesion. Our purpose was to evaluate the effect of ion implantation on GDCs in an experimental aneurysm model. METHODS: GDCs were coated with either type I collagen, fibronectin, vitronectin, laminin, or fibrinogen. Using He+ or Ne+ 1 x 10(14-15) ions/cm2, ion implantation was performed on these protein-coated GDCs (GDC-Is). A total of 56 experimental aneurysms were constructed microsurgically in the common carotid arteries of 28 swine. These experimental aneurysms were embolized with standard GDCs (n = 23), collagen GDC-Is (n = 11), vitronectin GDC-Is (n = 6), laminin GDC-Is (n = 4), fibrinogen GDC-Is (n = 6), and fibronectin GDC-Is (n = 6). The animals were sacrificed at day 14 after coil embolization. The physical properties of the new coils (friction on delivery, deployment into aneurysms, trackability, etc) and the development of tissue scarring and neoendothelium across the aneurysm's orifice were evaluated macroscopically and microscopically. RESULTS: No evidence of increased coil friction/stiffness was observed during delivery of GDC-Is through microcatheters in this aneurysm model. A more intense scar formation and neoendothelium at the neck of aneurysms were observed macroscopically when treated with GDC-Is. Significant differences in the proportion of neck coverage between standard GDCs (48.3% +/- 20.5%) and all GDC-I groups were observed (collagen GDC-I-89.4% +/- 14.9%, P < .01; vitronectin GDC-I-71.5% +/- 7.0%, P < .05; laminin GDC-I-76.5% +/- 11.0%, P < .05; fibrinogen GDC-I-74.8% +/- 13.9%, P < .05; fibronectin GDC-I-87.5% +/- 15.0%, P < .01). Light microscopy showed a well-organized fibrous tissue bridging the aneurysm's neck when using GDC-Is, whereas only a fibrin-like thin layer covered the standard GDC surfaces. CONCLUSION: GDC-Is indicated a more intense inflammatory response in the aneurysm body and dome and faster re-endothelial coverage of the neck of the aneurysm. This accelerated histologic response may decrease the chances of coil compaction and aneurysm recanalization. This technology may improve anatomic and clinical outcomes in patients harboring intracranial aneurysms.