Unruptured intracranial aneurysms: prospective data have arrived

• Published in: The Lancet (British edition) 2003-07, Vol.362 (9378), p.90-91
• Main Authors: White, PM, Wardlaw, Joanna
• Format: Article
• Language: English
• Subjects: Age Factors; Aneurysms; Disease management; Humans; International studies; Intracranial Aneurysm - therapy; Middle Aged; Patients; Prospective Studies; Recruitment; Risk Factors; Rupture, Spontaneous; Systematic review
• ISSN: 0140-6736; 1474-547X
• DOI: 10.1016/S0140-6736(03)13891-3

The major controversy arising from the 1998(2) paper was the 0[middot]05% yearly rupture rate identified by ISUIA for small anterior-circulation aneurysms in patients with no previous history of subarachnoid haemorrhage (group 1)(2) compared with that in earlier reports (0[middot]7%(6)). This extremely low rate of rupture meant that in most instances the risks of treatment outweighed the natural history risk. In their systematic review,(6) [Gabriel Rinkel] et al identified a total of 1145 years of follow-up in patients with asymptomatic aneurysms and no previous subarachnoid haemorrhage. There were nine ruptures: aneurysmal size could be extracted for eight of the nine and all but one were in aneurysms 10 mm or larger (Rinkel GJE, University Medical Centre, Utrecht, Netherlands, personal communication). So there was one (at most two) ruptures in small aneurysms (all sites) in group 1 patients in the systematic review, which gives an annual rupture rate for small aneurysms of 0[middot]1% (at most 0[middot]2%). This rate is similar to the retrospective ISUIA data.2 By comparison, in 1077 patients in group 1 in the prospective arm of ISUIA, annual rupture risk for anterior-circulation aneurysms under 7 mm was 0% and 0[middot]52% for aneurysms of 7-12 mm, with an overall rate for aneurysms of 12 mm or less of about 0[middot]15%. A 7 mm cutoff agrees well with a previous study.7 What ISUIA does not resolve is the discrepancy between the extremely low rupture risk in asymptomatic aneurysms under 7 mm, compared with the large proportion of ruptured aneurysms in this size category (61% were 5 mm or less in one recent series(8)). Rupture risk is substantially higher for larger aneurysms, posterior-circulation aneurysms (including aneurysms in the posterior communicating artery), and in patients with a history of subarachnoid haemorrhage.2,6 The prospective ISUIA data corroborate this finding with a relative risk for aneurysms of 7-12 mm of 3[middot]3, of 17 for those over 12 mm, of 5 for posterior-circulation aneurysms, and of 3 for group 2 (patients with previous subarachnoid haemorrhage).