Bulletin No. 1, 2013

Dismantling Time Bombs in the Brain 37  Conventionally cerebral aneurysms are treated by clipping the necks of the aneurysms, the blood-filled bulges in the wall of a blood vessel. However the open brain surgery this method involves presents great risks. Endovascular coil embolization is a less invasive approach but its feasibility is limited by the fusiform morphology of the aneurysm. For large-sized aneurysms that have incorporated the parent vessel, or aneurysms with wide necks, stent-assisted coiling is necessary to help the coils stay in place. Even so, the recurrence rate of aneurysms could be as high as 17% for coil embolization and 15% for stent-assisted coiling. The Vascular and Inter ventional Radiology Foundation Clinical Science Centre at CUHK, jointly with seven medical centres in Hong Kong, has successfully conducted Asia’s first clinical research on the use of ‘flow diverters’, a pipeline embolization device (PED), in treating cerebral aneurysm. Flow diverters are tube- like devices comprising tightly-knit fine metal strips, that are implanted using percutaneous endovascular methods, in the vascular segment affected by the aneurysm. Under the leadership of Prof. Simon Chun Ho Yu , the centre’s director and professor at the Department of Imaging and Interventional Radiology, the study found this to be a safe and effective approach to treating cerebral aneurysm. PED placement is a technological breakthrough in the treatment of cerebral aneurysm. After placement of the flow diverter, blood flow is diverted away from the aneurysm so that the latter eventually regresses. The device works equally well with different sizes or morphologies of aneurysm, and does not affect adjacent blood vessels. Professor Yu said, ‘We now have a safe and reliable device that can be used to treat aneurysm. The vascular segment harbouring the aneurysm is basically reconstructed into a new vessel as the surface of the device is completely covered with a new layer of endothelium and becomes incorporated into the vessel. To me this technology is almost a perfect solution for aneurysm.’ The clinical study involving 143 patients and 178 aneurysms was conducted from September 2008 to September 2011. The flow diver ter was found to be a safe and effective treatment for aneurysms with unfavourable morphological features such as wide neck, large size, fusiform morphology, incorporation of side branches, and post-treatment recanalization. Although it takes time for the aneurysms to become completely occluded, recurrence of occluded aneurysms is virtually unheard of. Occlusion or stenosis of the parent artery after placement of flow diverters is extremely rare. The results of the study were published in Radi o l ogy in De cember 2012. I f cerebral aneurysms are treated with the flow diverter before they rupture, hundreds of lives in Hong Kong can be saved a year. Professor Yu said, ’The technology can be further improved if the device is made of material that can enhance endothelialization and therefore shorten the time required for complete aneurysm occlusion. It would also help if the material can decompose and be absorbed after the device is completely endothelialized.’ Flow diverter (pipeline) ( see arrow )