未破裂脳動脈瘤の自然経過と治療成績

Abstract

The management of patients with unruptured intracranial aneurysms (UIAs) is controversial. We aimed to assess the natural history of UIAs and evaluate the surgical results. We analyzed 154 patients (181 saccular UIAs) with no history of subarachnoid hemorrhage (SAH) from a different aneurysm. Aneurysms were detected by magnetic resonance angiography (MRA) or by 3-dimensional CT angiography. Although the most frequent reason for the diagnosis was routine brain examinations of healthy patients or a vague symptom such as headache or dizziness, 15 patients were symptomatic. The natural history in patients who did not have surgery (follow-up group: 76 cases, 95 aneurysms) was assessed, and the surgical outcome of UIAs (surgical group: 78 cases, 86 aneurysms) was evaluated. Among 76 patients in the follow-up group, 7 had SAH. The mean latency period to aneurysm rupture was 3.2 months. The aneurysms with subsequent bleeding ranged from 5 to 25 mm (19.3 mm on average), whereas those without ranged from 1 to 28 mm (4.5 mm on average). The rupture rates of UIAs in anterior and posterior circulation were 6.2% and 14.3%, respectively. All ruptured cases were females. Mortality and morbidity associated with UIAs in the follow-up group were 3.9% and 3.9%, respectively. In the surgical group, no mortality was noted. Permanent morbidity associated with prospective repair of UIAs was 5.1%, although the morbidity of the patients with preoperative Rankin scores of 0 or 1 was 1.3%. Transient morbidity was observed in 6 patients (7.7%) with the size of the aneurysm 19.8 mm on average. The natural history and surgical results in patients with UIAs are modified by several factors including aneurysm size and location, the patient's age and gender, the medical status and the patient's preoperative Rankin score. The present results indicated that these factors should be considered in deciding whether to treat UIAs, and that careful assessment of the surgical benefits might be essential especially in the cases of larger aneurysm size (more than 15 mm) because they are associated either with a greater risk of rupture or with a higher surgical risk.