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Introduction and historical background 21 Galvanopuncture) of aneurysms. In 1866 a 50% success rate in a series of 50 cases involving electropuncture was reported, including four carotid, one ‘temporal’ and one ophthalmic aneurysm.288 In 1879, Corradi suggested that an electrical current applied to a permanently inserted metallic coil would combine the dual benefits of wire insertion and electrothrombosis. The merger of Moore’s original wire work with the application of electrical current became widely referred to as the Moore- Corradi method.286 The method we use nowadays, inserting coils in a cerebral aneurysm and detaching them with an electrical current, resembles this 150-year-old technique and was developed more than a century later.196 The first successful report of (silver) wiring and electrothermic thrombosis of an intracranial aneurysm through direct access via the orbit was made by Werner in 1941.289 Few more attempts were made using this technique,290 but complication rates were high. It was not until the early 1970s, when the Russian neurosurgeon Serbinenko developed a detachable balloon that an exclusively endovascular approach to the treatment of intracranial aneurysms became possible.291 Balloon placement within aneurysms proved not to be the best endovascular solution however, and after the introduction of endovascular embolization coils in 1975,292 focus shifted towards coil occlusion of cerebral aneurysms.293 Because coils behave unpredictably and are not retrievable once advanced into the aneurysm, the technique did not gain widespread acceptance. This changed when Guido Guglielmi observed accidental electrolytic detachment of the electrode tip while applying current to a stainless steel electrode introduced into an experimental aneurysm, and so developed the detachable coil which later became known as the Guglielmi Detachable Coil (GDC; Boston Scientific/Target Therapeutics, Fremont CA).195,196 Aneurysm treatment with these GDC’s was rapidly accepted by interventional radiologists and neurosurgeons , and by 2004, more than 125,000 patients with ruptured and unruptured aneurysms had been treated with the GDC system.294 Initially, endovascular treatment was used solely in patients considered poor candidates for surgical treatment295 such as patients with severe neurological deficits; an aneurysm in the posterior circulation or in the cavernous segment of internal carotid artery; patients aged 75 years or over; or patients presenting to the hospital during the high-risk period for cerebral vasospasm i.e. 3-10 days after aneurysm rupture. Furthermore, coiling was limited to aneurysms with narrow necks. Wide-necked aneurysms, defined from an endovascular standpoint as those with a dome-to-neck ratio of less than 2 or a neck diameter greater than 4 mm, were not considered suitable for coil embolization until technological advances were made in the late 1990s and early 2000s.294 Three major advances have expanded the indications for coil embolization of these wide-necked aneurysms. First, the introduction of three-dimensional coils has allowed complex framing configurations to be achieved with less coil protrusion into the parent artery.296 Second, the development of balloon assisted coil embolization by Moret et al has allowed for improved packing density of coils and also reduces the risk of coil protrusion into the parent vessel.297 In this technique, a compliant balloon is navigated and inflated across the neck of an aneurysm as coils are introduced into the aneurysm through the microcatheter. A welcome advantage is that the balloon can also arrest flow in the parent artery in the event of an intraprocedural aneurysm rupture. This ‘remodeling technique’, as Moret called the balloon assisted coiling, became widely accepted even though higher complication


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