Embolic materials for endovascular treatment of cerebral lesions

Large, Wide-Neck, Side-Wall Aneurysm Treatment in Canines Using NeuroCURE: A Novel Liquid Embolic

BACKGROUND

Untreated intracranial aneurysms can rupture and result in high rates of morbidity and mortality. Although there are numerous approved endovascular aneurysm treatment devices, most require dual anti-platelet therapy, are minimally biocompatible, or are prone to recanalization. Neurovascular Controlled Uniform Rapid Embolic (NeuroCURE) is an innovative polymer gel material with long-term stability, biocompatibility, and hemocompatibility developed for the treatment of large, wide-neck aneurysms.

METHODS

Sidewall aneurysms were surgically created in 10 canines and NeuroCURE was injected through a 0.025 microcatheter under a single balloon inflation period. Aneurysm treatment was angiographically assessed post-embolization and pre-term with Raymond-Roy occlusion classification and a qualitative flow grade scale. Aneurysm neck stability and biocompatibility was histologically assessed to grade platelet/fibrin thrombus, percent endothelialization, and neointimal formation. Aneurysm sac stability was assessed by NeuroCURE sac content, inflammation, and neo-angiogenesis scales.

RESULTS

Explanted aneurysms exhibited a smooth surface at the aneurysm neck with nearly complete neointimal coverage at 3-months. By 6-months, neck endothelialization was 100% in all animals (average Raymond-Roy occlusion classification of 1.2), with no instances of aneurysm recanalization or parent vessel flow compromise. Biocompatibility assessments verified a lack of inflammatory response, neo-angiogenesis, and platelet/fibrin thrombus formation.

CONCLUSION

The NeuroCURE material promotes progressive occlusion of wide-necked side wall aneurysms over time without the need for dual antiplatelet agents. NeuroCURE also promotes neointimal tissue infill without dependence on thrombus formation and thus resists aneurysm recanalization. NeuroCURE remains a compelling investigational device for the treatment of intracranial aneurysms.

Endovascular embolization of brain arteriovenous malformations with Eudragit-E

Eudragit-E was originally developed as a non-adhesive liquid embolic material in the late 1990s and is a copolymer of methyl and butyl methacrylate and dimethylaminoethyl methacrylate that is dissolved in ethanol and iopamidol. This material has been used for endovascular embolization of brain arteriovenous malformations (AVMs) for some time but is currently not widely used. Because safety and feasibility of Eudragit-E has not been well documented, we here report our experience using this material for treating 22 human brain AVMs. From June 1998 to February 2014, 30 endovascular procedures using Eudragit-E were performed to treat 22 patients, including 14 men and 8 women with a mean age of 41.1 years (15-70 years). The mean follow-up period was 56 months (12-129 months), and the Spetzler-Martin grades were I (4 patients), II (9 patients), III (5 patients), and IV (4 patients). Residual AVMs were treated with stereotactic radiosurgery or surgery. The rate of complete obliteration with embolization alone was 27.3%. The overall obliteration rate after endovascular embolization with/without subsequent stereotactic radiosurgery or surgery was 72.7%. Eudragit-E caused two cases of cerebral infarction. One case of intracerebral hemorrhage due to postoperative hemodynamic changes also occurred. The rate of complications directly related to embolization was 10.0%. The safety and effectiveness of Eudragit-E embolization were satisfactory.

In vitro and in vivo demonstration of physically and chemically in situ gelling NIPAAm-based copolymer system

Poly(NIPAAm-co-hydroxyethylmethacarylate (HEMA)) acrylate and poly(NIPAAm-co-cysteine ethyl ester (CysOEt)) were synthesized and characterized by GPC(gel permeation chromatography), rheology, NMR (nuclear magnetic resonance), and Ellman's method. Upon mixing of these materials in aqueous solution, they formed gels immediately at body temperature owing to temperature-driven physical gelling, and gradually cured by chemical cross-linking through Michael-type addition reactions between thiols and acrylates. The rate of nucleophilic attack in the Michael-type addition reaction was shown to be highly dependent on the mole ratio of thiol to acrylate at neutral pH. Physical and chemical gelation improved the mechanical properties of the materials compared to purely physical gels. In vitro and in vivo results revealed that chemical and physical gels formed stiffer less viscoelastic materials compared to purely physical gels. Physical and chemical gel systems using thermosensitive polymer with acrylates and thermosensitive polymer with thiols showed minimum toxicity.

Computational modelling for the embolization of brain arteriovenous malformations

Treatment of arteriovenous malformations (AVMs) of the brain often requires the injection of a liquid embolic material to reduce blood flow through the malformation. The type of the liquid and the location of injection have to be carefully planned in a pre-operative manner. We introduce a new model of the interaction of liquid embolic materials with blood for the simulation of their propagation and solidification in the AVM. Solidification is mimicked by an increase of the material's viscosity. Propagation is modelled by using the concept of two-fluids modelling and that of scalar transport. The method is tested on digital phantoms and on one anatomically derived patient AVM case. Simulations showed that intuitive behaviour of the two-fluid system can be confirmed and that two types of glue propagation through the malformation can be reproduced. Distinction between the two types of propagation could be used to identify fistulous and plexiform compartments composing the AVM and to characterize the solidification of the embolic material in them.

Selective arterial embolization with n-butyl cyanoacrylate in the treatment of aneursymal bone cyst of the thoracic vertebra: a case report

STUDY DESIGN

A case report of aneurysmal bone cyst of the mobile spine.

OBJECTIVE

To present a pediatric case of aneurysmal bone cyst (ABC) of the mobile spine treated successfully by selective arterial embolization (SAE) with n-butyl cyanoacrylate (NBCA).

SUMMARY OF BACKGROUND DATA

The endovascular treatment is an important treatment option for the ABC of the mobile spine. However, there are few reported case treated by SAE with NBCA.

METHODS

A 12-year-old healthy boy was introduced with a complaint of back pain. Computed tomography showed an osteolytic expanding mass in the pedicle, lamina, and spinous process on the level of T10. Magnetic resonance imaging revealed a multicystic mass with fluid-fluid levels that extended into the spinal canal and compressed the spinal cord from the dorsal side. Digital subtraction angiography showed an abnormal blood supply from the posterior spinal branch of the left T9 artery. An abnormal mass was diagnosed as an ABC based on these neuroradiologic examinations.

RESULT

The patient underwent SAE with NBCA (Histoacryl, B. Braun, Melsungen, Germany) diluted with Lipiodol (Laboratorie Guerbet, France) in a rate of 1:4. Computed tomography performed 1 month after treatment revealed partial ossification of the bone cortex. MR imaging showed shrinkage of the cyst and decompression of the spinal cord. Back pain of the patient disappeared and the shrunken cyst was stable without recurrence during the 3-year follow-up period.

CONCLUSION

SAE in a pediatric case with ABC of the mobile spine was effective in improving of clinical symptom and shrinking of the cyst.

Biomaterials Used in Injectable Implants (Liquid Embolics) for Percutaneous Filling of Vascular Spaces

The biomaterials currently used in injectable implants (liquid embolics) for minimally invasive image-guided treatment of vascular lesions undergo, once injected in situ, a phase transition based on a variety of physicochemical principles. The mechanisms leading to the formation of a solid implant include polymerization, precipitation and cross-linking through ionic or thermal process. The biomaterial characteristics have to meet the requirements of a variety of treatment conditions. The viscosity of the liquid is adapted to the access instrument, which can range from 0.2 mm to 3 mm in diameter and from a few centimeters up to 200 cm in length. Once such liquid embolics reach the vascular space, they are designed to become occlusive by inducing thrombosis or directly blocking the lesion when hardening of the embolics occurs. The safe delivery of such implants critically depends on their visibility and their hardening mechanism. Once delivered, the safety and effectiveness issues are related to implant functions such as biocompatibility, biodegradability or biomechanical properties. We review here the available and the experimental products with respect to the nature of the polymer, the mechanism of gel cast formation and the key characteristics that govern the choice of effective injectable implants.

Reduced medication dependency and improved symptoms and quality of life 12 months after enteryx implantation for gastroesophageal reflux

BACKGROUND

The need is well recognized for additional data on endoluminal therapies for gastroesophageal reflux disease (GERD). This prospective multicenter clinical trial was designed to assess safety and effectiveness of Enteryx, a nonresorbable copolymer implanted into the lower esophagus, in reducing usage of proton pump inhibitors (PPIs) and improving reflux symptoms and quality of life.

METHODS

Enteryx implantation was performed under fluoroscopic visualization without general anesthesia in 93 patients with symptomatic GERD responsive to and relapsing upon cessation of PPI therapy. Subjective and objective data were collected up to 12 months postprocedure. The criterion for treatment success was reduction in PPI dosage of > or =50%.

RESULTS

At 12 months, treatment success was attained in 86% (confidence interval, 77%-93%) of 74 evaluable patients and elimination of PPI therapy in 65% (confidence interval, 53%-76%). The treatment success rate by intent-to-treat analysis was 69% (confidence interval, 58%-78%). Reflux-related heartburn (P < 0.0001), regurgitation symptoms (P = 0.0005), and physical (P < 0.0001) and mental quality of life (P = 0.0012) scores improved. The most frequent complications were chest pain (77%), dysphagia/odynophagia (27%), and sensation of fever (26%).

CONCLUSIONS

Enteryx implantation provides an effective and safe alternative for management of gastroesophageal reflux, reducing medication dependency and symptoms and enhancing quality of life.

Arterial embolization using poly-N-acetyl glucosamine gel in a rat kidney model

Aqueous solutions of poly-N-acetyl glucosamine (p-GlcNAc) exhibit a liquid-gel transition at physiological pH and temperature. This feature inspired the authors to conduct a study to evaluate the macro- and histological changes of rat kidneys after embolization using either p-GlcNAc gel injection into the renal artery or ligation of the renal artery. The procedures were performed in 46 rats through open abdominal surgeries. Animals were sacrificed at 3 days and at 1, 3, 5, and 8 weeks postoperatively. The results of both macro-observation and histological study showed that p-GlcNAc gels were effective in causing necrosis and subsequent fibrosis in all embolized kidneys. The data indicate that p-GlcNAc gel may have promise as an effective agent for therapeutic embolization.

Medical Devices of the Head, Neck, and Spine

There are many medical devices used for head, neck, and spinal diseases and injuries, and new devices are constantly being introduced. Many of the newest devices are variations on a previous theme. Knowing the specific name of a device is not important. It is important to recognize the presence of a device and to have an understanding of its function as well as to be able to recognize the complications associated with its use. The article discusses the most common and important devices of the head, neck, and spine, including cerebrospinal fluid shunts and the Codman Hakim programmable valve; subdural drainage catheters, subdural electrodes, intracranial electrodes, deep brain stimulators, and cerebellar electrodes; coils, balloons, adhesives, particles, and aneurysm clips; radiation therapy catheters, intracranial balloons for drug installation, and carmustine wafers; hearing aids, cochlear implants, and ossicular reconstruction prostheses; orbital prostheses, intraocular silicone oil, and lacrimal duct stents; anterior and posterior cervical plates, posterior cervical spine wiring, odontoid fracture fixation devices, cervical collars and halo vests; thoracic and lumbar spine implants, anterior and posterior instrumentation for the thoracic and lumbar spine, vertebroplasty, and artificial disks; spinal column stimulators, bone stimulators, intrathecal drug delivery pumps, and sacral stimulators; dental and facial implant devices; gastric and tracheal tubes; vagus nerve stimulators; lumboperitoneal shunts; and temperature- and oxygen-sensing probes.

Endoscopic implantation of enteryx for treatment of GERD: 12-month results of a prospective, multicenter trial

OBJECTIVES

This study aimed to assess the efficacy and safety of endoscopically implanting a nonresorbable biocompatible polymer (Enteryx) in the distal esophagus and proximal gastric cardia for the treatment of gastroesophageal reflux disease (GERD).

METHODS

In a prospective, multicenter, international trial, 85 well-controlled GERD patients who were receiving chronic proton pump inhibitor (PPI) therapy underwent Enteryx implantation under fluoroscopic visualization, without general anesthesia. After the procedure, patients were discharged within approximately 2-4 h. Patients were judged to be treatment responders if after implantation they reduced PPI dosage by >/=50%. Follow-up evaluations were conducted at 1, 3, 6, and 12 months and included medication usage, symptoms, quality of life, endoscopy, pH monitoring, manometry, and documentation of adverse events.

RESULTS

At 12 months, 80.3% (95% CI = 69.9%-88.3%) of 81 evaluable patients were treatment responders. Of the responders, 87.7% completely discontinued PPIs, and 12.3% reduced PPI dosage by >/=50%. Treatment response was more likely in patients with residual implant volume of >/=5 mL (p = 0.027). Other patient and treatment variables were not predictive. Both GERD heartburn and regurgitation symptom scores significantly improved at 12 months compared with baseline (p < 0.001). There were significant reductions in median supine, upright, and total percent time of esophageal exposure to pH <4. Endoscopically assessed esophagitis grades were unchanged. No serious adverse events were encountered. Transient retrosternal chest pain was experienced by 91.8% of patients. This pain was seldom severe and was typically successfully managed with prescription pain medication.

CONCLUSIONS

Enteryx implantation allows most patients to discontinue PPI therapy, improves their symptoms, and reduces esophageal acid exposure. The effects of implantation are long-lasting, and morbidity is transient and minimal. The procedure requires basic endoscopic skills and seems to provide a useful option in the effective clinical management of GERD.

Treatment of pelvic arteriovenous malformations with ethylene vinyl alcohol copolymer (Onyx)

In this article, two successful embolizations of large pelvic arteriovenous malformations (AVMs) with use of ethylene vinyl alcohol, a radiopaque, nonadhesive liquid casting agent, are reported. Both patients presented with large symptomatic pelvic AVMs requiring therapy. Coaxial microcatheter techniques were used to achieve complete success in one case and partial success in the other. Clinical success has been maintained in both patients at 2-year follow-up.

Preoperative silk suture embolization of cerebral and dural arteriovenous malformations

OBJECT

The aim of this study was to evaluate the use of silk sutures as a medical implant when applied for the embolization of cerebral and dural arteriovenous malformations (AVMs). The facility of surgery and the clinical significance of complications related to preoperative silk suture embolization were evaluated immediately after surgery and at long-term follow up.

METHODS

Thirty-four patients harboring 29 cerebral and five dural AVMs underwent embolization in which silk alone or in association with other agents was used. Medical and radiological records obtained in these 34 patients were reviewed retrospectively. The cerebral AVMs were classified according to the Spetzler-Martin grading system and the dural AVMs to the Djindjian grading system. The facility of the resection and the adverse outcomes, including new neurological deficits, hemorrhage, and fever, as well as histopathological evidence of vessel inflammatory changes, were determined in each case. In all 23 surgical cases, the AVM could be easily manipulated and excised. New temporary neurological deficits occurred in three patients. A high Spetzler-Martin grade was not associated with a higher incidence of new neurological deficits. One delayed-onset hemorrhage was detected after embolization. Fever was present in 24% of the patients. No sign of significant vasculitis or perivascular inflammation was found on radiological or histopathological examination.

CONCLUSIONS

Silk sutures are safe embolic agents especially for proximal occlusion of AVM feeding vessels. New permanent neurological deficits were not encountered in this series. Fever was considered to be a minor, temporary side effect of silk suture embolization.

Calcium alginate gel: a biocompatible and mechanically stable polymer for endovascular embolization

The development and optimization of calcium alginate for potential use in endovascular occlusion was investigated by testing its in vitro and in vivo mechanical stability and biocompatibility. The compressive resistance, rheology, and polymer yield of reacted alginate, and the polymer viscosity of unreacted alginate, were assessed. Biocompatibility was tested by injecting calcium alginate into the kidney capsule of rats. The reactivity of alginates with various structures and levels of purity were compared visually and histologically. Results suggest that calcium alginate is a biocompatible and mechanically stable gel for endovascular applications. Purified alginates exhibited compressive strength of 22 kPa and above at 40% compression, with no significant loss in elasticity. Purified alginate strength was significantly higher than that of crude alginates (p < 0.08). Purified alginates also exhibited significantly lower tissue reaction than crude alginates (p < 0.05). Of the alginates tested, purified high guluronic acid alginates (PHG) exhibited optimal strength and polymer yield, increased biocompatibility, and decreased viscosity. Clinical embolization treatments may be improved with the development of stable and biocompatible polymers such as calcium alginate. Possible uses of improved endovascular polymers include treating arteriovenous malformations (AVMs), aneurysms, blood flow to tumors, and vascular hemorrhaging.

Experimental evaluation of cellulose acetate NF and ethylene-vinyl alcohol copolymer for selective arterial embolization

PURPOSE

Studies were conducted in rabbits to evaluate two new liquid polymeric compounds developed for selective arterial embolization.

MATERIALS AND METHODS

The compounds consisted of cellulose acetate NF (Embolyx C) or ethylene-vinyl alcohol copolymer (Embolyx E) dissolved in anhydrous dimethyl sulfoxide (DMSO) containing 30% tantalum powder. Acute renal embolization was performed to determine an optimal method of administration and level of embolization. Kidneys were embolized with and without flow around the catheter. DMSO was also injected in the same manner. Tissue sections were examined radiographically and microscopically. Tumor embolization was performed to evaluate the efficacy of the polymers and compare their embolic effects with polyvinyl alcohol (PVA) particles and gelatin sponge (Gelfoam) powder. An embolic agent, saline, or DMSO was injected into the deep femoral artery feeding an intramuscular VX2 carcinoma. Animals were followed up for 3 weeks.

RESULTS

Viscosity and administration technique affected polymer distribution and depth of penetration. Embolization with the test polymers was quicker and more easily achieved than with PVA or Gelfoam, and no recanalization occurred. Both polymers were as effective as PVA particles for tumor ablation, but DMSO caused some vascular damage.

CONCLUSION

Although use of DMSO has some drawbacks, the results of this study warrant further investigation of the Embolyx polymers for tumor embolization.

Innovative therapies for pediatric brain tumors

Success in the treatment of pediatric brain tumors has lagged behind that of other pediatric cancers. This paper highlights many of the advances that have taken place over the past few years in the surgical, radiotherapeutic, and chemotherapeutic approaches to central nervous system lesions that we hope will lead to a dramatic improvement in outcome. Innovations in neurosurgical and radiotherapeutic techniques have resulted in decreasing toxicity although substantial improvement in cure rates has not been observed. Many new techniques such as gene therapy, angiogenesis inhibitors, immunotherapy, and others that have not been part of the classic approach to these lesions are now in clinical trials in the hope that they will impact on the survival of these patients. The scientific basis for these new treatment modalities and preliminary clinical results are discussed.