Aneurysm Treatment Practice
The earliest techniques of endovascular embolization were developed by neurosurgeons and neuroradiologists in the 1960s and 1970s to treat "inoperable" cerebrovascular lesions. Since this early age of neurointerventional science, the vast majority of aneurysm embolization procedures have been performed by interventional neuroradiologists and endovascular neurosurgeons. The former draw on their mastery of angiography and image-guided surgical techniques as qualifications, and the latter draw on their anatomical expertise and in-depth understanding of aneurysms. For decades, these specialties have worked together to advance the technical feasibility of complex intracranial vessel navigation and aneurysm embolization.
Early history of neurointerventional
Intravascular cannulation has been widely used in diagnostic and therapeutic strategies in clinical medicine. The pioneer of intravascular cannulation was the clergyman Stephen Hales in the early 18th century, who conducted experiments on horse models. The widespread impact of intravascular cannulation was recognized when Andre Frederic Cournand, Werner Forssmann and Dickinson Richards received the Nobel Prize in Physiology or Medicine in 1956 for their discoveries regarding cardiac cannulation. Diagnostic cerebral angiography was first described in 1927 by Antonio Caetano de Abreu Freire for the intracranial circulation, with the aim of imaging abnormal vascular patterns surrounding brain tumors. He later won the 1949 Nobel Prize in Physiology or Medicine for his work on lobotomy for the treatment of mental illness. Following these landmark advances regarding intravascular cannulation and angiography, the first therapeutic intravascular cannulation of human cervical vessels was reported by Alfred Lussenhop and Alfredo Velasquez in 1964, when they described a case of intracervical A case of ruptured arterial saccular aneurysm was successfully embolized using a 2.5 mm spherical silicone embolization device. Despite the reported poor final clinical outcomes for the patients, this early experience was critical to the development of neurointerventional therapies and was followed by multiple attempts to improve endovascular navigation and reduce vascular trauma. The 1960s also saw the use of the first microcatheters, magnetic guidance strategies, and the emergence of a method of aneurysm embolization using a detachable magnetic tip and attached metallic embolic particles. Balloon occlusion technology came to prominence in the 1970s when Serbinenko reported treating more than 300 brain aneurysms using this technique. Although some centers and operators advocate the use of balloon embolization to treat intracranial aneurysms, this strategy was ultimately considered unsafe, with the disadvantages of high aneurysm rupture rates and poor treatment durability. It was not until the advent of coil technology that routine endovascular treatment of intracranial aneurysms became a feasible technique. Before the advent of endovascular coiling technology, endovascular treatment of intracranial aneurysms primarily involved occlusion of the parent vessel after a trial of balloon occlusion of the aneurysm that failed surgical clipping.
Intravascular coil embolization
The evolution of endovascular treatment devices has gone through many iterations of treatment strategies. each treatment has various hypothesized mechanisms of action. The advent of endovascular coiling technology marked a major turning point in neurointerventional therapy as it enabled durable aneurysm occlusion without significant risk to the patient. Although coils are already available to treat a variety of intracranial pathologies and parent vessel occlusions, Guglielmi, Vinuela, Sepetka, and Macellari utilize a delivery system that is smaller than the traditional 5F and 4F sizes to aid intracranial vessel navigation. These access tools were paired with soft platinum releasable coils, which evolved into stretch-resistant coils by placing sutures or guidewires within a first-order helix. Intra-aneurysmal coils were developed in the 1990s. embolization techniques. Their strategy was based on positioning the microcatheter tip to the neck of the saccular aneurysm before coil microcatheter delivery by Sadek Hilal and advancing platinum coils using a stainless steel delivery guidewire. A forward direct current is then applied to the proximal portion of the delivery guidewire to initiate electrocoagulation and release of the platinum coil within the aneurysm. The electrocoagulation aspect of their strategy is based on early work by Sean Mullan of the University of Chicago, who used an open surgical approach to treat cavernous sinus aneurysms and used copper wires to puncture the aneurysms. In their first clinical experience using this strategy, Guglielmi et al achieved partial or complete aneurysm occlusion in all patients, with only one case of transient neurological deficit. At the time, the prevailing hypothesis was that intraaneurysmal occlusion was achieved by electrocoagulation acting on negatively charged white blood cells, red blood cells, and blood components by promoting clot formation through the application of a positively charged coil. Later studies confirmed that the therapeutic benefit of coils was achieved by filling the space with platinum coils, and that platinum coils with non-electrodecompression had similar efficacy and recurrence rates. Potential mechanisms to prevent aneurysm rupture include slowing blood flow in and out of the aneurysm to promote thrombus formation and subsequent intimal growth, as well as other mechanical effects such as flow steering or biological interaction of coils with the aneurysm wall.
The International Subarachnoid Aneurysm Trial (ISAT), a trial of the treatment of ruptured intracranial aneurysms, was published in 2002 and showed that treating aneurysms with endovascular coiling resulted in better disability survival than surgical clipping. . This result drove a shift in the treatment of most intracranial aneurysms from “clipping first” to endovascular treatment and triggered a surge in the number of brain aneurysms treated with endovascular coiling. In fact, from 2004 to 2014, a total of 79,627 intracranial aneurysms in the United States were treated with endovascular coiling, while 42,256 were treated with surgical clipping, a dramatic shift in the distribution of treatment types before the release of ISAT.
After widespread adoption of endovascular coils to treat brain aneurysms in clinical neurointerventional practice, device developers began designing bioactive coils. Later, to better embolize the space within the aneurysm sac, bioinert hydrogel-coated coils were developed. Coated and modified coils continue to be of great practical value among neurointerventionalists. Although initial results from randomized trials comparing recurrence rates with hydrogel coils versus bare platinum coils in the treatment of aneurysms have been mixed, more recent level 1 evidence suggests that the use of hydrogel coils in ruptured aneurysms may be better than using Bare platinum coils are more beneficial. Unfortunately, similar benefits were not observed with bioactive coils. Later manufacturers revisited bare platinum coils with different relief techniques or space-filling properties.
Intravascular coil embolization has several limitations. These include aneurysm recurrence, coil herniation and migration, limited use in wide-neck saccular aneurysms, challenges with aneurysms containing arterial branches, and difficulty in catheter positioning for distal aneurysms. These limitations will be addressed through follow-up devices and innovative delivery system designs. Despite these limitations, endovascular coils are still frequently used in patients with acute ruptured aneurysms and in patients who cannot tolerate antiplatelet therapy.