Small unruptured aneurysms are thought to have a low risk of rupture, but the management of such lesions is still contro- versial. A 73-year-old man with a small anterior communication artery aneurysm, 4 mm in diameter, while on follow-up, developed an aneurysmal subarachnoid hemorrhage 2 weeks after the detection of a newly emerged bleb on the surface of the aneurysm. In conclusion, the formation of a bleb should be considered as a warning sign of an impending rupture, and treatment should be provided even for patients with small aneurysms. INTRODUCTION CASE REPORT Rupture of intracranial aneurysms causes aneurysmal sub- A 73-year-old man was diagnosed with a UIA of the anterior arachnoid hemorrhage (aSAH), resulting in high mortality and communicating artery (A-com), and had been followed up for 2 morbidity rates . Due to the risk of complications, however, years at the outpatient department of the Institution. Computed indications for treatment of unruptured intracranial aneurysms tomography angiography (CTA) revealed an A-com UIA with a (UIAs) need to be carefully considered . Some specialists state height of 2.7 mm and width of 2.1 mm (Fig. 1, upper-left). During that UIAs require surgical treatment, regardless of their size or the follow-up using magnetic resonance angiography (MRA), the risk factors for rupture, as long as surgery is technically pos- UIA was considered to be stable (Fig. 1, upper-middle and right). sible. Others, in contrast, assert that patients with a single UIA Two years after the initial diagnosis, MRA demonstrated an smaller than 5 mm in size, because of their very low rupture irregular shape of the aneurysm (Fig. 1, lower-left), and further rate, should undergo observation . Various risks of rupture, CTA examination revealed a newly emerged bleb on its surface such as aneurysm size, location, shape, growth and ethnic fac- (Fig. 1, lower-middle). tors, had been reported [3–6], but the indication for surgical We considered the emergence of the bleb as a risk for early treatment of UIAs is still debatable. rupture, and planned the surgery. However, 2 weeks after the Here we report a case of a ruptured anterior communicating examination, while the patient was waiting for admission, he artery aneurysm, which was initially small in size, but later developed a sudden headache and was transported to our hos- showed de novo bleb formation preceeding rupture. pital. Computed tomograms taken on admission showed Received: March 27, 2018. Accepted: May 5, 2018 Published by Oxford University Press and JSCR Publishing Ltd. All rights reserved. © The Author 2018. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/ licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact firstname.lastname@example.org Downloaded from https://academic.oup.com/jscr/article-abstract/2018/5/rjy117/5017810 by Ed 'DeepDyve' Gillespie user on 21 June 2018 2 A. Yamano et al. Figure 1: Initial computed tomography angiogram of the unruptured cerebral aneurysm. A saccular aneurysm, 2.7 × 2.1 mm in size, is arising from the anterior com- municating artery (upper-left). Follow-up magnetic resonance angiography. Images at 6 months (upper-middle) and 1 year (upper-right) after the initial diagnosis show the unchanged aneurysm. Two years after diagnosis, the shape of the aneurysm changed (lower-left). Computed tomography angiogram shows a de novo bleb (lower-middle). Computed tomography after the aneurysm rupture indicates aSAH (lower-right). subarachnoid hemorrhage (Fig. 1, lower-right), and surgery was more to aneurysm rupture. In our case, the rupture occurred 2 performed the same day. Surgical ﬁndings showed that the weeks after the detection of the de novo bleb; therefore, we bleb was the rupture point. Postsurgical recovery was unevent- suggest that bleb formation in a UIA may also signal the begin- ful, but higher brain dysfunction remained. ning of a ‘high-risk period’ for subsequent rupture. According to the American Heart Association/American Stroke Association guidelines, several factors, including patient DISCUSSION age and aneurysm location and size, should be taken into The management of incidental small UIAs is controversial and account when considering surgical clipping as the mode of treat- many factors need to be considered in the decision-making ment for UIA. Although small UIAs are reported to carry low risk process. We have already reported that even small aneurysms of rupture [3, 6], the majority of patients with aSAHs have aneur- require treatment in certain cases . Our case, in which rup- ysms with a diameter of <10 mm . This suggests the neces- ture of the aneurysm occurred after the detection of the de sity of treatment for small but high-risk UIAs, ergo it is necessary novo bleb, suggests that bleb formation should be considered to determine authentic risk factors for treatment indication. as a warning sing of an impending rupture. In a previous report we suggested the importance of appro- Various studies have reported that size and location of the priate timing for treatment of small asymptomatic UIAs from UIA are considered as risk factors of aneurysm rupture [3, 6]. the viewpoint of functional recovery . Preventive surgery Irregular aneurysm shape was also shown to be an independ- might be considered in selected young patients in cases of cer- ent risk factor [4, 6]. Even if the presence or development of a tain ‘higher-risk’ aneurysm locations, expanding aneurysms, or bleb in a UIA was suspected to carry risk of rupture [3, 4], the in patients with a family history of aneurysmal hemorrhage, as risk of a newly emerged bleb itself with subsequent aSAH, as in well as in those who cannot continue their normal lives know- our case, has not been reported. Recent studies have shown ing that they harbor a UIA. We suggest that aneurysms with a some other factors pertaining to risk of UIA rupture. Inoue and de novo bleb formation should also be included in this list. colleagues reported that the annual rupture risk of growing Indication for treatment of small aneurysms is still a difﬁcult UIAs was higher than that of nongrowing UIAs (18.5%) . issue, but bleb formation could contribute to the treatment Other previous study demonstrated that the period of UIA decision-making process. growth carried a high rupture risk during conservative follow- In conclusion, we should consider multiple factors to assess up with CTA. Additionally, Sato and Yoshimoto  brought to the risk of UIA rupture, since prophylactic treatment has non- light a discrepancy between etiologic data and clinical practice, negligible complications. The formation of a de novo bleb in a showing that while small aneurysms theoretically carry a very UIA could be a predictor of early rupture; hence, treatment low risk of rupture, small ruptured aneurysms are commonly should be considered following bleb formation in small UIAs. observed. The authors suggested the presence of a ‘high-risk period’ after the formation of an intracranial aneurysm . ACKNOWLEDGEMENTS Taking the ﬁndings of these reports together, the ‘high-risk per- iod’ seems to be the period after the formation of an aneurysm We thank Alexander Zaboronok, MD, PhD, Assistant Professor and during its growth. However, it is yet to be established of the Department of Neurosurgery, Faculty of Medicine, whether growth or de novo bleb formation of UIAs contributes University of Tsukuba, for critical revision of the article and Downloaded from https://academic.oup.com/jscr/article-abstract/2018/5/rjy117/5017810 by Ed 'DeepDyve' Gillespie user on 21 June 2018 Intracranial aneurysm rupture following bleb formation 3 helpful suggestions, and Thomas Mayers, Medical English 4. Lindgren AE, Koivisto T, Björkman J, von Und Zu Fraunberg Communications Center, Faculty of Medicine, University of M, Helin K, Jääskeläinen JE, et al. Irregular shape of intracra- Tsukuba, for native English revision. nial aneurysm indicates rupture risk irrespective of size in a population-based cohort. Stroke 2016;47:1219–26. 5. Murayama Y, Takao H, Ishibashi T, Saguchi T, Ebara M, CONFLICT OF INTEREST STATEMENT Yuki I, et al. Risk analysis of unruptured intracranial aneur- All authors have no conﬂict of interest, and have registered ysms: prospective 10-year cohort study. Stroke 2016;47: online Self-reported COI Disclosure Statement Forms through 365–71. the website for JNS members. 6. UCAS Japan Investigators. Morita A, Kirino T, Hashi K, Aoki N, Fukuhara S, Hashimoto N, et al. The natural course of unruptured cerebral aneurysms in a Japanese cohort. N Engl REFERENCES J Med 2012;366:2474–82. 1. Rinkel GJ, Algra A. Long-term outcomes of patients with 7. Yanaka K, Matsumaru Y, Mashiko R, Hyodo A, Sugimoto K, aneurysmal subarachnoid haemorrhage. Lancet Neurol 2011; Nose T. Small unruptured cerebral aneurysms presenting 10:349–56. with oculomotor nerve palsy. Neurosurgery 2003;52:553–7. 2. Wiebers DO, Whisnant JP, Huston J III, Meissner I, Brown RD 8. Inoue T, Shimizu H, Fujimura M, Saito A, Tominaga T. Jr, Piepgras DG, et al. 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Journal of Surgical Case Reports – Oxford University Press
Published: May 29, 2018
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