Radiology, Vol 162, 111-114, Copyright © 1987 by Radiological Society of North America
Partially thrombosed giant intracranial aneurysms: correlation of MR and pathologic findings
SW Atlas, RI Grossman, HI Goldberg, DB Hackney, LT Bilaniuk and RA Zimmerman
Two patients with surgically and angiographically proved partially
thrombosed giant aneurysms of the middle cerebral artery were studied with
computed tomography (CT) and magnetic resonance (MR) imaging. MR and
histopathologic findings were correlated. The central location of
methemoglobin, with its high intensity (surrounding the patent lumen, seen
as signal void), in giant aneurysms is directly opposite the initial
peripheral appearance of methemoglobin in extra-aneurysmal intracerebral
hematomas. More peripherally, the thrombosed portion of the lumen is
layered with intensities that represent stages of clot (methemoglobin and
hemosiderin). Three characteristics enable differentiation of giant
aneurysms from intracerebral hematoma: signal void in residual patent
lumen; laminated, staged thrombus with intervening layers of hemosiderin
and methemoglobin that is initially centrally, rather than only
peripherally, located; and signal void in the vessel from which the
aneurysm arises. Hemorrhage from prior bleeding can be readily identified
and separated from perianeurysmal edema on MR images. MR appears to be a
specific, noninvasive method for diagnosing partially thrombosed giant
intracranial aneurysms and is superior to CT and angiography in
characterizing these lesions.
