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Stroke. 1999;30:2759-2768

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(Stroke. 1999;30:2759-a.)
© 1999 American Heart Association, Inc.

Letters to the Editor

Treatment for Ruptured Aneurysms and Screening for Unruptured Aneurysms

Yuhei Yoshimoto, MD

Department of Neurosurgery, Koshigaya Hospital, Dokkyo University School of Medicine, Saitama, Japan


*    Introduction
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To the Editor:

I read with interest the letter to the editor from Yamashita et al, "Trend in Outcome of Cerebral Aneurysmal Rupture Since 1985: A Proposal for Future Treatment,"1 and would like to comment on a couple of points.

I think that the population-based study of cerebral aneurysms conducted by Yamashita et al2 has greatly contributed to our understanding of the epidemiology of subarachnoid hemorrhage (SAH) and the recent results of treatment. In the letter, 3119 patients with SAH between 1985 and 1997 in Yamaguchi prefecture were enrolled, corresponding to 240 patients annually. All of these patients were admitted to 1 of 28 neurosurgical centers. Thus, the average number of patients treated per institute was only 8.6 per year. I basically agree with the opinion of the authors that, judging from the trend of treatment results over the last 13 years, the outcome of SAH patients will not improve dramatically in the near future. However, I think that it may be possible to improve the outcome by concentrating these 240 patients in 3 or 4 institutes. It has been shown that in many kinds of diseases, treatment results in hospitals managing a larger number of patients are superior to those in hospitals treating a smaller number of patients. Therefore, after initial resuscitation, patients with SAH should be transferred to such institutes, where intensive care, including surgery for aneurysms and management of cerebral vasospasm, should be managed. Because the present situation in Yamaguchi prefecture could also apply to most of the other parts of Japan, it would be desirable to reform our medical system with such a perspective in mind.

Second, as the authors discussed, considering the high mortality due to SAH, it is reasonable to shift our attention to the screening of asymptomatic populations for unruptured aneurysms in order to prevent SAH in future. In the same issue of the journal, we reported the results of cost-effectiveness analysis of such screening.3 We demonstrated that the cost-effectiveness of screening depends largely on assumptions about the annual rate of SAH (rupture rate) from unruptured aneurysms. A program of screening is cost-effective for a rupture rate of 1% to 2% per year, as reported previously.4 5 In contrast, such screening is neither cost-effective nor beneficial if the rupture rate is 0.5% per year. A rupture rate of at least 0.75% per year of the rupture rate would be necessary to justify screening. Thus, the rationale for such screening would seem to be lost, based on data from the recent large-scale international study.6

So far, several comments about the international study—both favorable and unfavorable—have been reported.7 8 9 10 11 12 Although this was the largest study of its type, it appeared to include some inconsistent data. In particular, the risk of subsequent rupture of aneurysms smaller than 10 mm was extremely low (0.05% per year) if patients had no history of SAH. In fact, it may be as low as the incidence of SAH in the general middle-aged or elderly population.2 13 By contrast, most ruptured aneurysms in patients with SAH are of this size.7 I have some concern about the 424 patients in this subgroup of the retrospective cohort, details of which did not appear in the paper. These patients would not have been representative of the overall population of patients with unruptured aneurysms. Why were they not treated surgically, but merely followed up? These patients may constitute a group who were judged by their physicians to have a low risk of aneurysm rupture (eg, intracavernous aneurysms or those with calcified walls, or thrombosed). It seems we should at least be prudent in applying these data to any decision making. I would like to reemphasize that an understanding of the natural history of unruptured aneurysms, ie, the "overall rupture rate," is essential for discussion of the screening and/or treatment of unruptured aneurysms.


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  1. Yamashita K, Kashiwagi S, Kato S. Trend in outcome of cerebral aneurysmal rupture since 1985: a proposal for future treatment. Stroke.. 1999;30:1730–1731.[Free Full Text]
  2. Yamashita K, Kashiwagi S, Kato S, Takasago T, Ito H. Cerebral aneurysms in the elderly in Yamaguchi, Japan: analysis of the Yamaguchi data bank of cerebral aneurysms from 1985 to 1995. Stroke.. 1997;28:1926–1931.[Abstract/Free Full Text]
  3. Yoshimoto Y, Wakai S. Cost-effectiveness analysis of screening for asymptomatic, unruptured intracranial aneurysms: a mathematical model. Stroke.. 1999;30:1621–1627.[Abstract/Free Full Text]
  4. Juvela S, Porras M, Heiskanen O. Natural history of unruptured intracranial aneurysms: a long-term follow-up study. J Neurosurg.. 1993;79:174–182.[Medline] [Order article via Infotrieve]
  5. Yasui N, Suzuki A, Nishimura H, Suzuki K, Abe T. Long-term follow-up study of unruptured intracranial aneurysms. Neurosurgery.. 1997;40:1155–1160.[Medline] [Order article via Infotrieve]
  6. The International Study of Unruptured Intracranial Aneurysms Investigators. Unruptured intracranial aneurysms: risk of rupture and risks of surgical intervention. N Engl J Med.. 1998;339:1725–1733.[Abstract/Free Full Text]
  7. Caplan LR. Should intracranial aneurysms be treated before they rupture? N Engl J Med.. 1998;339:1774–1775.[Free Full Text]
  8. Barenstein A, Flamm ES, Kupersmith MJ. Unruptured intracranial aneurysms. N Engl J Med.. 1998;340:1439–1440. Letter.
  9. Connolly ES, Mohr JP, Solomon RA. Unruptured intracranial aneurysms. N Engl J Med.. 1998;340:1440–1441. Letter.
  10. Stieg PE, Friedlander R. Unruptured intracranial aneurysms. N Engl J Med.. 1998;340:1441. Letter.
  11. Kirkpatrick PJ. Time to reconsider treatment options for intracranial aneurysms. Lancet.. 1999;353:942–943.[Medline] [Order article via Infotrieve]
  12. Ausman JI. The New England Journal of Medicine report on unruptured intracranial aneurysms: a critique. Surg Neurol.. 1999;51:227–229.[Medline] [Order article via Infotrieve]
  13. Kiyohara Y, Ueda K, Hasuo Y, Wada J, Kawano H, Kato I, Shinkawa A, Ohmura T, Iwamoto H, Omae T, Fujishima M. Incidence and prognosis of subarachnoid hemorrhage in a Japanese rural community. Stroke.. 1989;20:1150–1155.[Abstract/Free Full Text]

Response

Katsuhiro Yamashita, MD

Department of Neurosurgery, Onoda City Hospital, Onoda, Yamaguchi, Japan

Shiro Kashiwagi, MD Shoichi Kato, MD

Department of Neurosurgery, Yamaguchi University School of Medicine, Ube, Yamaguchi, Japan


*    Introduction 
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I basically agree with the opinion of Dr Yoshimoto, who proposed that all ruptured cerebral aneurysms should be treated in a small number of medical centers, each managing a larger number of patients with subarachnoid hemorrhage to subsequently improve the overall management outcome. It has already been proved in other subtypes of stroke that the management outcome of patients treated in intensive care units is better than that in general hospitals.1 However, to realize the concept of the intensive care unit for subarachnoid hemorrhage, the medical system in Japan requires drastic reform through massive political and economic effort, and a number of neurosurgeons in satellite hospitals might lose their jobs. Another problem is the factors that determine the outcome of ruptured cerebral aneurysms. According to the multivariate analysis conducted in our study, the severity of subarachnoid hemorrhage and patient age were the most important factors determining the outcome of ruptured cerebral aneurysms; the third factor was cerebral vasospasm, which can be modulated by medical intervention.2 Future research may make it possible to overcome cerebral vasospasm after subarachnoid hemorrhage. However, this will take a long time, and we are therefore forced to shift our attention to the treatment of unruptured cerebral aneurysms, which can be detected easily by MR angiography.

As we reported previously, the number of patients with unruptured cerebral aneurysms is increasing in Japan due to the development of magnetic resonance imaging, and most of these patients, excluding the elderly, actually undergo surgery.3 On the other hand, it has been reported recently that the risk of subsequent rupture of aneurysms smaller than 10 mm is extremely low (0.05% per year).4 If this is true, the screening and treatment of unruptured cerebral aneurysms cannot be justified.5 However, there was some bias in the patient selection and incorrect interpretation of the data in this international study of unruptured cerebral aneurysms, because it included cerebral aneurysms in the cavernous portion or those smaller than 5 mm, which rupture only rarely.4 6 Therefore, we consider that there is a need in Japan for a prospective study to investigate the risk of rupture of unruptured cerebral aneurysms that are detected incidentally in programs such as "Brain Check-Up." We need to clarify the natural history of unruptured cerebral aneurysms and the types that require aggressive treatment to prevent rupture with high mortality.


*    References 
up arrowTop
 up arrowIntroduction
 up arrowReferences
 up arrowIntroduction 
 *References 
 

  1. Indredavik B, Bakke F, Slordahl SA, Rokseth R, Haheim LL. Stroke unit treatment: 10-year follow-up. Stroke.. 1999;30:1524–1527.[Abstract/Free Full Text]
  2. Yamashita K, Kashiwagi S, Kato S. Trend in outcome of cerebral aneurysmal rupture since 1985: a proposal for future treatment. Stroke.. 1999;30:1730–1731.
  3. Yamashita K, Kashiwagi S, Kato S, Takasago T, Ito H. Cerebral aneurysms in the elderly in Yamaguchi, Japan: analysis of the Yamaguchi Data Bank of Cerebral Aneurysm from 1985 to 1995. Stroke.. 1997;28:1926–1931.
  4. The International Study of Unruptured Intracranial Aneurysms Investigators. Unruptured intracranial aneurysms: risk of rupture and risks of surgical intervention. N Engl J Med.. 1998;339:1725–1733.
  5. Yoshimoto Y, Wakai S. Cost-effectiveness analysis of screening for asymptomatic, unruptured intracranial aneurysms: a mathematical model. Stroke.. 1999;30:1621–1627.
  6. Kupersmith MJ, Hurst R, Berenstein A, Choi IS, Jafar J, Ransohoff J. The benign course of cavernous carotid artery aneurysms. J Neurosurg.. 1992;77:690–693.[Medline] [Order article via Infotrieve]




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