title: The natural history of "contrast stasis" within aneurysm after embolization.
abstract: OBJECTIVE
  Contrast stasis within residual aneurysm sac is sometimes seen after embolization of intracranial aneurysms and is thought to represent sluggish flow prone to thrombosis. We report the short- and intermediate-term angiographic outcomes of intra-aneurysmal contrast stasis following predominantly bioactive coil embolization procedures.
  
  
  METHODS
  Contrast stasis was identified by retrospective review of 153 consecutive patients treated at two centers with endovascular embolizations for intracranial aneurysms. Contrast stasis was defined by persistent opacification despite clearance of contrast from parent artery assessed during angiography at 3-5 frames/second. The contrast stasis were classified based on relative area and location visualized on dynamic angiographic images as small (5-15% of the total aneurysm), large (> 15%), or occurring only in the aneurysm neck by an independent reviewer.
  
  
  RESULTS
  There were 44 patients (23 women: mean age 54.3±12.5 years) who had contrast stasis; 36 patients had small and 8 had contrast stasis in the neck of the aneurysm. There were no patients with large contrast stasis. Of these 44 patients, 33 patients had a mean follow up angiogram in 269.5 days; 10 patients had no follow up. In 21 patients, (18 were small and 3 were in the neck) the area of contrast stasis had spontaneously thrombosed while in 7 patients there was no change in the contrast stasis. The remaining 5 patients had increase in area of contrast stasis and required re-embolization. Size of the contrast stasis (p= 0.02) was the only statistically significant factor although there was a trend dome to neck ratio > 2 (p= 0.16) and washout on the initial angiogram (p= 0.16) affecting the thrombosis of contrast stasis.
  
  
  CONCLUSIONS
  Most small contrast stasis following coil embolization procedures spontaneously thrombose and do not require further treatment. A small proportion of patients had increase in the area of intra-aneurysmal contrast stasis and required further treatment.
  
  
  BACKGROUND
  MRAmagnetic resonance angiographyDSAdigital subtraction angiography.
authors: Zeenat Qureshi Stroke Research Center and Department of Radiology, University of Minnesota.
authors: Mohamed M
authors: MM
authors: Abdihalim
authors: Saqib A
authors: SA
authors: Chaudry
authors: Nauman
authors: N
authors: Tariq
authors: M Fareed K
authors: MF
authors: Suri
authors: Adnan I
authors: AI
authors: Qureshi