The speed of ferumoxytol uptake on magnetic resonance imaging (MRI) may indicate if a cerebral aneurysm is unstable and likely to rupture soon, say US researchers.
"This novel MRI technique holds promise for patients harboring unruptured cerebral aneurysms," write David Hasan (University of Iowa, Iowa City) and team in Stroke.
They say: "The current study provides preliminary evidence that aneurysms with early uptake of ferumoxytol on MRI are prone to rupture and thus may warrant early operative intervention."
Hasan et al assessed 30 aneurysms in 22 patients who underwent MRI 24 hours after infusion of ferumoxytol. Uptake of ferumoxytol offers a guide to the phagocytic activity of inflammatory cells, such as macrophages.
Seven aneurysms had marked ferumoxytol uptake, four of which were surgically clipped. The other three were managed conservatively, but all ruptured within 6 months. All but one of these aneurysms were at least 7 mm in size, and all those that ruptured were at least 15 mm.
An additional 23 aneurysms had no ferumoxytol uptake at 24 hours. Five of these were excluded from further analysis, but 18 were reimaged at 72 hours after infusion, at which point 16 showed ferumoxytol uptake. Eight of these were clipped and the other eight were managed conservatively, but none ruptured or increased in size during the following 6 months.
Fifteen (94%) of the aneurysms with late ferumoxytol uptake were smaller than 14 mm and half were smaller than 7 mm, the researchers note.
Histologic analysis of surgical samples revealed upregulation of several inflammatory markers in unruptured aneurysms with early ferumoxytol uptake (clipped) versus those with late uptake (conservatively managed).
These markers were upregulated to a similar degree in all aneurysms with early uptake, whether ruptured or unruptured.
"This finding strongly suggests that aneurysms with early signal changes are unstable lesions with high risk of rupture when we did not intervene early," conclude Hasan and team.
They also note that their study supports an important role for inflammation as a cause of aneurysm rupture, rather than just a consequence.
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