Surveillance Frequency for Known Cerebral Aneurysms

Key Evidence Supporting Surveillance

Between 4% and 18% of unruptured aneurysms demonstrate growth on imaging follow-up, with growing aneurysms carrying a 12-fold higher risk of rupture compared to stable aneurysms, and aneurysm growth is most commonly associated with size >7 mm, but smaller aneurysms can also grow and rupture 1, 2, 3
Aneurysm remnants occur in up to 11% of surgically clipped aneurysms, recurrence is more frequent after endovascular repair, and recurrence is most common within 6 months of treatment but can occur later 1, 2
De novo aneurysm formation occurs in 1% to 8% of patients with treated aneurysms 1, 2

The American College of Radiology recommends MRA head as the ideal surveillance modality due to its noninvasive nature and ability to obtain diagnostic information without IV contrast, with pooled sensitivity of 95% and specificity of 89% for aneurysm detection 1, 2, 3
CTA head is an acceptable alternative with >90% sensitivity and specificity, but requires IV contrast and involves radiation exposure, and sensitivity decreases for aneurysms <3 mm and those adjacent to bone 1, 2, 3

For untreated aneurysms, more frequent surveillance is recommended for aneurysms >7 mm or those showing any growth 1, 2, 3
For treated aneurysms, first surveillance at 6 months, annual follow-up until complete occlusion is confirmed, and continued surveillance for de novo aneurysm formation 1, 2

Cervicocerebral arteriography is not ideal for routine surveillance due to its invasive nature and potential complications 1, 2, 3
CT head and CT head perfusion have no role in aneurysm surveillance 1, 2, 3
Vessel loops and infundibular vessel origins can cause false-positives on MRA 1, 2, 3