Aneurysm Coiling

Shape memory PU has been proposed as a candidate for aneurysm coils [106]. An intracranial aneurysm can go undetected until the aneurysm ruptures, causing... 

The high morbidity and mortality in patients with ruptured aneurysms prompted interest in repair of aneurysms that are diagnosed before they have ruptured. Following publication of the initial results of the International Study of Unruptured Intracranial Aneurysms (ISUIA 1998), enthusiasm for this strategy was markedly reduced. In this study patients were classified in those with no history and those with history of SAH. The risk posed by unruptured aneurysms was reported lower than had been previously expected and also morbidity and mortality to treat aneurysms were higher than had previously been reported. The updated results of the same group analysed 6544 patients years of prospective follow up of untreated aneurysms, 1692 had no treatment, 1917 had surgical repair and 451 had their unruptured aneurysm coiled. The cut off... 

Hampikian, J. M., Heaton, B. C., Tong, F. C., Zhang, Z., Wong, C. P. (2006). Mechanical and radiographic properties of a shape memory polymer composite for intracranial aneurysm coils. Materials Science and Engineering C, 26(8), 1373-1379. 

Endovascular coiling is preferred to surgical clipping for the treatment of intracranial aneurysms, which affect between 2% and 6% of the world population (Ahuja et al., 1993 Horowitz, Samson, Purdy, 1997). Hampikian et al. (2006) evaluated the feasibility of using a novel block copolymer polyurethane, CalomerT, to replace platinum in aneurysm coils. The thermomechanical and radiographic properties were tested for both SMP polyurethane and a composite made of SMP with 3% metal filler. The intracranial aneurysm helical coils made from the SMP composite were successfully deployed inside an aneurysm model with simulated fluid forces. The scientists at Lawrence Livermore National Laboratory also developed a laser-activated SMP foam device for aneurysm occlusion (Maitland et al., 2007). Their SMP was synthesized from HDI, HPED, and TEA, similar to that used in the clot removal device (Wilson et al., 2005). In their preliminary in vitro basilar aneurysm model study, the... 

Late rebleeding occurs in 2-3% of patients in the first 10 years after clipping of an aneurysm, half of such bleeds being caused by newly developed aneurysms. After endovascular coiling, the long-term risks are unclear, being recorded at 0.7% between one month and one year in ISAT (Molyneaux et al. 2005) and at 2-3% in one month to four years in a Dutch cohort (Sluzewski et al. 2005). 

Unruptured aneurysms not associated with SAH should normally be clipped or coiled if they are symptomatic, for instance if there is a third nerve palsy caused by a posterior communicating artery aneurysm (Fig. 30.2) (Raps et al. 1993). The optimal management of incidental unruptured asymptomatic aneurysms is unclear because the risk of rupture is... 

Niemann DB, Wills AD, Maartens NF et al. (2003). Treatment of intracerebral hematomas caused by aneurysm rupture coil placement followed by clot evacuation. Journal of Neurosurgery 99 843-847 Olafsson E, Gudmundsson G, Hauser WA (2000). Risk of epilepsy in long-term survivors of surgery for aneurysmal subarachnoid hemorrhage a population-based study in Iceland. Epilepsia 41 1201-1205... 

New England Journal of Medicine 336 28-40 Schwartz TH, Solomon RA (1996). Perimesencephalic nonaneurysmal subarachnoid hemorrhage review of the literature. Neurosurgery 39 433-440 Sluzewski M, van Rooij WJ, Beute GN et al. (2005). Late rebleeding of ruptured intracranial aneurysms treated with detachable coils. American Journal of Neuroradiology 26 2542-2549 Smith ER, Carter BS, Ogilvy CS (2002). 

For subarachnoid hemorrhage surgical clipping of the causative aneurysm or resection of the arteriovenous malformation is the mainstay of treatment. Endovascular coiling of the aneurysm can also be performed. Post-operative infection (either brain or respiratory) is an uncommon complication and not believed to be any more common than after other invasive surgical procedures. Hypervolemic-hemodilution and hypertensive (HHH) therapy is used to prevent spasm. There may be a role for anti-inflammatory measures for the prevention of vasospasm and delayed cerebral ischemia, as shown in a recent pilot study of patients treated with statins (Lynch et al., 2005). 

In a study by Fanning et al. (2007) 100 intracranial aneurysms were embolized with HydroCoils in conjunction with bare platinum coils, where a basket of bare platinum coils were positioned in the aneurysm, followed by the introduction of HydroCoils. The treatment group showed a 20% increase in the mean packing density when the same number of coils was used in the control... 

Matrix detachable coils (Boston Scientific Neurovascular) are another example of modified endovascular coils, employing a stainless steel delivery wire coated with a bioabsorbable copolymer of 90% polyglycolide and 10% polylactide. In a study by Murayama et al. (2003), matrix detachable coils were shown to accelerate the rate of aneurysm healing in swine aneurysm models, specifically by promoting the formation of a thick neointimal layer at the aneurysm neck more quickly bare platinum coils (Murayama et al, 2003). Taschner et al. (2005) evaluated the use of Matrix detachable coils in 25 patients with intracranial aneurysms. Again, stable emboUzed aneurysms were achieved over a six-month period, but only when Matrix coils were used in conjunction with bare platinum coils (Taschner et al, 2005). 

The procedure for Onyx administration in an aneurysm is similar to the plug and push technique described for AVM embolization, but with the additional consideration of inflation and deflation of the balloon during the procedure such that blood flow in the parent artery is not restricted for an extended period of time. Overall, this may tend to increase procedure times when embolizing aneurysms with Onyx as opposed to coil embolization. 

These materials have an obvious application to fusiform aneurysms, which are difficult to treat using coils or liquid embolics due to migration into the parent vessel. Shape memory polymers can potentially remove this limitation since the device is pre-formed to the aneurysm topography. Metcalf et al (2003) investigated a porous polyurethane shape memory polymer as an embolic device for fusiform aneurysms in an animal model. In this study, thick neointimal formation was found over aneurysm necks after a 12-week period. The porous nature of this material may have encouraged cell infiltration and neointimal growth to seal off the aneurysm from the rest of the vasculature (Metcalfe et al,... 

Cloft, H. J. KaUmes, D. F. (2004) Aneurysm packing with HydroCoil embolic system versus platinum coils initial clinical experience. American Journal of... 

Farming, N. F., Berentei, Z., Brerman, P. R. Thornton, J. (2007) HydroCoil as an adjuvant to bare platinum coil treatment of 100 cerebral aneurysms. Neuroradiology, 49, 139-148. 

International Subarachnoid Aneurysm Trial (ISAT) Collaborative Group. (2002) International Subarachnoid Aneurysm Trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms a randomised trial. The Lancet, 360, 1267-1274. 

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