A revolution in endovascular techniques as they pertain to the management of central nervous system diseases has occurred over the last 30 years. Refinements in the engineering of microcatheters and guide wires have made once inaccessible sites within the cerebrovasculature accessible. In addition, the development of detachable coil technology has fundamentally changed the way cerebral aneurysms are treated. Similarly, the production of adhesive embolisates and the manufacture of flexible stents specifically designed for the brachiocephalic and cerebral circulations have dramatically advanced the management of central nervous system arteriovenous malformations, cerebral aneurysms and atherosclerosis of the head and neck vessels.
Managing Cerebral Aneurysms
Of all the diseases within the realm of endovascular treatment, cerebral aneurysms continue to pose the greatest management challenge. The recent development of flexible stents specifically designed for navigation within the cerebral vasculature has expanded the application of coil embolization to aneurysms with wider necks. Furthermore, the production of biologically active coils, namely those that promote a neo-endothelial response at the neck of the aneurysm as well as those that expand within the aneurysm after deployment, has improved the endovascular management of more anatomically challenging aneurysms. Nonetheless, advances in the endovascular management of cerebral aneurysms likely will emerge on a number of different fronts.
Covered Stents Already employed in coronary interventions for the management of acute vessel injuries, covered stents offer a promising treatment solution for aneurysms of the cerebral vasculature that do not involve segments in which critical branches or perforating arteries arise. The cavernous portion of the carotid artery is perhaps the most amenable segment of the cerebral vasculature where covered stents could be used not only to treat enlarging, symptomatic aneurysms, but also carotid-cavernous fistulas. Such stents would need to be flexible within the cerebral vasculature and consistently remain open over long periods of time.
Embolic Agents Endovascular management of cerebral aneurysms and arteriovenous malformations also will benefit from the development of embolic agents. These agents, which likely will include liquid polymers that solidify within aneurysms, potentially could diminish recanalization rates as well as obliterate the aneurysm more uniformly. For arteriovenous malformations, embolic agents could simplify and reduce risk associated with treatment. Currently, adhesive embolization requires the catheterization and injection of multiple arterial pedicles. A potential complication of this treatment is adhesion of the catheter to the vessel wall. An agent that would not bind the catheter to the vessel wall and that could be flushed completely from within the catheter would allow multiple arterial pedicles to be embolized with just one catheter.
Single Coils Another technical advancement would be a single coil that could be detached within an aneurysm at any length. Current coil technology requires deployment of multiple coils of varying lengths within the aneurysm. A deployment system that would allow a single strand of coil to be detached at the length where the aneurysm is completely obliterated would reduce the complications associated with the current labor-intensive, multiple-coil techniques.
Improving Safety, Revolutionizing Future Treatment
The treatment and prevention of cerebrovascular accidents are other realms in which the advancement of endovascular techniques will play a decisive role. With the recent federal approval of a stent device for the treatment of carotid stenosis, the management of occlusive brachiocephalic disease will become the focus of heated debate. Endovascular techniques carry the obvious allure of minimal invasiveness and shorter recovery times though their efficacy will only be borne out through currently ongoing prospective trials. Nonetheless, the development of drug-eluting stents and a new generation of antiplatelet agents and thrombolytics foreshadow a promising future for endovascular techniques in the treatment of this common pathologic entity.
While this technology is anticipated in the near future, on the more distant horizon is the manufacture of catheters with microscopic machines on their ends that could occlude aneurysms and arteriovenous malformations, and open stenotic vessels from within. This brave new world of endovascular management would likely include robotically driven catheters or perhaps, in the near future, magnetically driven catheters. Such technology would not only simplify catheterization but also would increase security of catheter placement within the target lesion itself.
The salient feature of endovascular neurosurgery is that it is continually developing at a rapid pace. This vigorous advancement will continue to revolutionize the treatment of cerebrovascular disorders.
Felipe C. Albuquerque, MD, is assistant director of endovascular neurosurgery at the Barrow Neurological Institute in Phoenix, Ariz.
| Send your ideas for NS Innovations to William T. Couldwell, MD, NS Innovations editor, at [email protected]. |