We report the current strategy for unruptured intracranial aneurysms, the rupture rate and characteristics of previously unruptured aneurysms in Japan.
The information on the unruptured aneurysms was obtained from 14 institutes with the approval of investigators, and 1,602 cases were enrolled in this study. The condition leading to the diagnosis was a history of SAH (10%), other intracranial lesions (29%), symptomatic aneurysms (6%) and brain examinations (46%).
The surgical intervention for unruptured intracranial aneurysms in each institute was indicated for patients who were healthy and under 70-75 years old with aneurysms 3-5 mm or more in size, and 1,012 cases (63.2%) were operated. As for surgical options, 89.2% had open surgery and 11.7% endovascular treatment. Endovascular treatment was intentionally selected for those with juxta-dural ring IC or posterior circulation aneurysms. The morbidity and mortality in open surgery were 6.9% and 0.2%, respectively, and those in endovascular treatment were 2.5% and 0%, respectively.
Because of rejection of operation, elderly age, poor general condition, small aneurysm or operative risk 590 patients were observed. The mean observation period was 32.6 months, and during a 1,601 person-year follow-up study there were 45 episodes of hemorrhage from a previously unruptured aneurysm, giving an average annual rupture rate of 2.8%. They were 16 males and 27 females, and their mean age was 67.6. The size of aneurysm was 10.9±6.9 mm, but there were seven aneurysms less than 5 mm. There were 12 C1-2, 11 MCA, 10 Acom, 7 Basilar tip and 5 other aneurysms. Concerning outcome, 11 (24%) had a good recovery, 1 (2%) was moderately disabled, 1 (2%) severely disabled and 32 (72%) died. In contrast to this poor outcome, a good outcome was observed in 4 out of 5 cases under 70 years old whose aneurysms were found by means of brain examination and were smaller than 10 mm in size.
In conclusion, two-thirds of unruptured intracranial aneurysms were treated by open or endovascular surgery, and the results were satisfactory. One-third of those were observed at their own request or because of their condition, and the incidence of rupture was 2.8%/year. Among the elderly patients, the outcome was poor, but relatively good in younger patients and those with small aneurysms.
2001 一般社団法人 日本脳卒中の外科学会