Two-Year Follow-Up of Contrast Stasis within the Sac in Unruptured Aneurysm Coil Embolization: Progressive Thrombosis or Enlargement?

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The fate of contrast stasis within an aneurysmal sac after coiling has not been established. We followed and evaluated the potential risks of recanalization of unruptured aneurysms embolized with BPCs for 2 years. A total of 301 unruptured aneurysms in 252 patients were treated with BPCs. Contrast stasis was observed on initial postembolization angiograms in 104 (34.6%) of these aneurysms. For follow-up, skull images by an angiographic unit (at 3, 9, 15, and 21 months), CE-MRA including TOF source images (at 6, 12, and 18 months), and DSA (at 24 months) were used. In 89 (85.6%) of the 104 aneurysms with contrast stasis, the stasis disappeared on 6-month MRAs and occlusions remained unchanged without recanalization for 2 years. In the remaining 15 (14.4%), recanalization occurred during follow-up. The presence of contrast stasis was not found to be associated with the obliteration rate (P = .641) or packing attenuation (aneurysms without contrast stasis 30.7% ± 11.18 versus aneurysms with contrast stasis 33.0% ± 12.11, P = .113). Contrast stasis was not found to be a risk factor for recanalization (15/104 [14.4%] versus 29/197 [14.7%], P = 1.000). Contrast stasis is a benign angiographic finding that can disappear within 6 months on follow-up MRA. In addition, contrast stasis was not found to be associated with a low obliteration rate or packing attenuation or to be a risk factor for recanalization. The present study shows that aneurysms with contrast stasis on initial postembolization angiograms are no more likely to recanalize than aneurysms without contrast stasis.