Newsletter No. 411

4 No. 411, 19.1.2013 腦 動脈瘤對人的健康有嚴重的潛在危機，香港人口中 約百分之二至百分之六的人有此隱患，其成因估計 是與高血壓、血管硬化或遺傳致令血管壁變弱有關。動脈 瘤破裂是腦出血的原因之一，可引致嚴重殘障、昏迷或死 亡（死亡率高達百分之四十五）。每個腦動脈瘤破裂的機 率，是每年百分之一點三，儘管看似不大，但對患者來說， 已足以令他們提心吊膽。在整體人口中，每十萬人就有十 點五人會出現腦動脈瘤破裂。 傳統治療腦動脈瘤的方法，是以手術夾從外夾閉動脈瘤頸 部，但這種開腦手術有很大風險；另一種治療方法是以彈 簧圈經血管栓塞動脈瘤，雖然創傷性低，但應用在「梭型」 的動脈瘤並不太可行。如果動脈瘤的體積大以致覆蓋血管 主幹，或瘤頸寬闊，更需要配合輔助性支架，以固定彈簧 圈位置。即使治療成功，復發的機會亦高達百分之十五（有 輔助支架）至百分之十七（無輔助支架）。 中大透視微創治療基本臨床科學中心與本港七所醫院，在 中心總監兼中大影像及介入放射學系教授 余俊豪 帶領下， 完成亞洲首個以「植入式擾流器」治療腦動脈瘤的臨床研 究，發現這是對付此隱患的一種安全有效療法。 以植入式擾流器治療腦動脈瘤是醫學界一大突破。擾流器 是一個由細密金屬絲編織而成的管狀裝置，以導線和導管 引導，從皮膚經血管植入有動脈瘤病變的血管主幹內腔部 份，屬於透視微創治療。擾流器放置後，會改變血流方向， 從而阻斷血液流入動脈瘤，使之最終萎縮。這療法可應用 於各種形狀的動脈瘤，並且不會影響其周邊血管。 余教授說：「植入式擾流器證明能有效治療亞洲人的腦動 脈瘤，對身為醫生的我來說是天大喜訊，因為我們現在有 了可靠的工具治療此症。出現動脈瘤的那段血管，基本上 會重新建構成新的血管，因為擾流器表面會被新的一層血 管內皮細胞完全覆蓋，成為這條新血管的一部分。在我看 來，植入式擾流器是對付腦動脈瘤幾近完美的療法。」 有關研究在2008年9月至2011年9月進行，涉及一百四十三 名病人和一百七十八個動脈瘤。研究發現擾流器能有效治 療體積較大、瘤頸較寬、梭型、涉及血管分支和經彈簧圈 栓塞後復發的動脈瘤。雖然以此療法，需要一定時間才能 完全閉塞動脈瘤，但以這種療法閉塞的動脈瘤至今沒有復 發，治療導致病人血管分支閉塞或狹窄的情況極少。 中大建議醫學界採用植入式擾流器為腦動脈瘤的首選治 療方法。研究結果已於2012年12月刊載於放射科權威期 刊《放射學》。如能在腦動脈瘤破裂前及早發現，並以植 入式擾流器治療，每年香港有數百人可以因而保住性命。 余教授說：「這種科技還能改進，如果擾流器的物料能加 強內皮化，就能縮短完全閉塞動脈瘤的時間，在完全內皮 化後，還可在人體內分解和吸收。」 C erebral aneurysm is a serious potential health hazard that occurs in about 2–6% of the population in Hong Kong. It is thought to be associated with hypertension, atherosclerosis, and congenital factors leading to vessel wall weakening. Aneurysm rupture (when a blood vessel in the brain breaks) is a cause of intracranial bleeding that may lead to severe disability, comatose or even death (the death rate is as high as 45%). The risk of rupture of an aneurysm is about 1.3% per year, remote but sufficiently alarming to one who lives with it. In the overall population, the incidence of aneurysm rupture is 10.5 per 100,000 people. Conventionally, cerebral aneurysms are treated by clipping their necks but the open brain surgery involved presents great risk. 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 keep the coils in place. Even so, the recurrence rates of aneurysms could be as high as 17% for coil embolization and 15% for stent-assisted coiling. The Vascular and Interventional Radiology Foundation Clinical Science Centre at CUHK has successfully conducted Asia’s first clinical research with seven medical centres in Hong Kong on the use of ‘flow diverters’ (pipeline) in treating cerebral aneurysms. Under the leadership of Prof. Yu Chun-ho Simon , the Centre’s director and professor at the Department of Imaging and Interventional Radiology at CUHK, the study discovered that flow diverter (pipeline) is a safe and effective approach to treating cerebral aneurysms. Pipeline embolization device placement is a technological breakthrough in the treatment of cerebral aneurysms. A flow diverter is a tube-like device composed of tightly knitted fine metal strips, to be implanted in the vascular segment affected by the aneurysm using percutaneous endovascular methods. After placement of the flow diverter, blood flow is diverted away from the aneurysm so that, with blood traffic stopped, the aneurysm eventually regresses. The device works equally well with different sizes or morphologies of the aneurysm, and it does not affect adjacent blood vessels. Professor Yu said, ‘The fact that the concept of flow diverter (pipeline) is proved effective for cerebral aneurysms among Asians is wonderful news to me as a doctor, because we now have a reliable device that can be used safely for treating our patients with aneurysms. 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 the technology of flow diverter (pipeline) is almost a perfect solution for aneurysms.’ The clinical study was conducted from September 2008 to September 2011, involving 143 patients and 178 aneurysms. In this study, the flow diverter 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 treated with flow diverters to become completely occluded, recurrence of these occluded aneurysms is virtually unheard of. Occlusion or stenosis of the parent artery after placement of flow diverters is extremely rare. CUHK recommends the flow diverter (pipeline) as a preferred treatment for unruptured aneurysms and recurrent aneurysms. The results of the study were published in the journal Radiology in December 2012. If cerebral aneurysms could be found out before they rupture and treated with flow diverter (pipeline), hundreds of lives could be saved in Hong Kong a year. Professor Yu said, ‘The technology can be further improved if the device is made of material that could enhance endothelialization and therefore shorten the time required for complete aneurysm occlusion, and that could also be decomposed and absorbed after the device is completely endothelialized.’ 拆除腦中的定時炸彈 Dismantling Time-bombs in the Brain 箭咀所指為植入式擾流器 Flow diverter (pipeline) (see arrow)