ISUIA, Lancet - 2003
Unruptured Intracranial Aneurysms: Natural History, Clinical Outcome, and Risks of Surgical and Endovascular Treatment | The Lancet
In this paper[1], the authors enrolled patients with unruptured intracranial aneurysms from multiple centers in the USA, Canada, and Europe from 1991 to 1998 for prospective assessment. They concluded that site, size, and group specific risks
Study Specifics
- Journal: The Lancet
- Publication history: July 12, 2003
- Study type: Prospective assessment
- Enrollment
- Interval: 1991-1998
- 61 centers in the USA, Canada, and Europe
- At least one unruptured intracranial aneurysm
- mRS: 1 or 2
- Exclusion
- Fusiform, traumatic, or mycotic aneurysm
- Maximum diameter < 2 mm
- SAH from a single ruptured aneurysm
- An unruptured aneurysm that was manipulated before
- Unknown cause of previous intracranial hemorrhage
- Case of previous intracranial hemorrhage not repaired
- A malignant brain tumor
- Study objective
- To describe the natural history of unruptured aneurysms
- To determine whether specific subgroups have a greater risk of rupture
- Classification
- No surgery (natural history)
- Group 1: Patients without SAH from a separate aneurysm
- Group 2: Patients with SAH from a separate aneurysm - Open surgery
- Endovascular surgery
- No surgery (natural history)
- Total patients: 4060
- Natural history
- Total patients: 1692
- Male: 431 (25.5%)
- Female: 1261 (74.5%)
- Group 1: 1077
- Group 2: 615
- Mean age: 55.2 (SD 13.1)
- White: 1550 (91.6%)
- Total aneurysms: 2686
- Single: 1006 (59.7%)
- Multiple: 679 (40.3%)
- Follow-up: 6544 patientyears
- Mean follow-up: 4.1 years (SD 2.00)
- Rupture: 51 (3%)
- Within 5 years: 49 (96.1%)
- Death: 33 (65%)
- Total patients: 1692
- Predictors of hemorrhage
- Size (relative risk, [95% confidence interval])
- 7-12 mm: 3.3, [1.3-8.2] (p=0.01)
- 12 mm*: 17, [8.0-36.1] (p<0.0001)
- Location (ICA as reference)
- Tip of BA: 2.3 [1.1-4.8] (p=0.025)
- Cavernous artery: 0.15 [0.04-0.64] (p=0.01)
- PCOM: 2.1 [1.1-4.2] (p=0.02)
- Size (relative risk, [95% confidence interval])
- 5-year mortality
- Death: 193 (11.4%)
* The original paper reads as 12 mm. Typo? Should be >12 mm?
Reference Points
- Larger aneurysmal size was associated with a greater risk of rupture in group 1 patients who did not have surgery, but not in group 2.
- Patients in group 2 with aneurysms < 7 mm had higher rupture rates than did those in group 1 (p<0.0001).
- These results do not show that family history of rupture increases the risk in aneurysms <7 mm in group 1.
- The lowest-risk natural history group includes asymptomatic patients in group 1 with unruptured aneurysms <7 mm in diameter in the anterior circulation.
Limitation
- Follow-up <5 years in over half the patients studied
Comment
Since the publication of this paper, the management landscape for unruptured intracranial aneurysms has witnessed substantial transformation over the past two decades. Notably, there has been a discernible shift from traditional open surgery towards a predominant reliance on endovascular interventions. In light of this evolution, we reviewed solely on the natural history of these aneurysms in this paper, excluding the surgical aspects.