Histopathologic analysis of foci of signal loss on gradient-echo T2*-weighted MR images in patients with spontaneous intracerebral hemorrhage: evidence of microangiopathy-related microbleeds

Abstract

Background and purpose: Patients with spontaneous intracerebral hemorrhage (ICH) frequently have small areas of signal loss on gradient-echo T2*-weighted MR images, which have been suggested to represent remnants of previous microbleeds. Our aim was to provide histopathologic support for this assumption and to clarify whether the presence and location of microbleeds were associated with microangiopathy.

Methods: We performed MR imaging and correlative histopathologic examination in 11 formalin-fixed brains of patients who had died of an ICH (age range, 45-90 years).

Results: Focal areas of signal loss on MR images were noted in seven brains. They were seen in a corticosubcortical location in six brains, in the basal ganglia/thalami in five, and infratentorially in three specimens. Histopathologic examination showed focal hemosiderin deposition in 21 of 34 areas of MR signal loss. No other corresponding abnormalities were found; however, hemosiderin deposits were noted without MR signal changes in two brains. All specimens with MR foci of signal loss showed moderate to severe fibrohyalinosis, and there was additional evidence of amyloid angiopathy in two of those brains.

Conclusion: Small areas of signal loss on gradient echo T2*-weighted images indicate previous extravasation of blood and are related to bleeding-prone microangiopathy of different origins.

fig 1.

Patient 6. A and B, Postmortem gradient-echo T2*-weighted MR images (600/15/2; flip angle, 25°) show foci of signal hypointensity in the basal ganglia bilaterally and in the left thalamus (arrows, A). Note signal loss at the surface of the specimen due to field inhomogeneity and subarachnoid blood. Foci of signal loss are also noted in the cerebellum and pons (arrow, B). C, Histopathologic section shows an old microbleed (arrow), corresponding to the largest hypointensity (corresponding arrows in B and C).

fig 2.

Cerebral amyloid angiopathy in area showing hypointense MR lesion. Yellow-green birefringency of amyloid deposits in the vessel walls under polarized light corresponds to bright spots and perivascular leakage of erythrocytes (arrow). Temporal cortex, polarization optics; alkaline Congo stain, original magnification ×32. fig 3. A, MR-positive old microbleed with a diameter of 2 to 3 mm in the subcortical white matter. Numerous darkly stained hemosiderophages are seen in the center, close to a ruptured vessel (arrows). There is extensive perivascular edema. Masson trichrome stain, original magnification ×201. B, Hypertensive angiopathy with dilatation of perivascular spaces and deposition of a few hemosiderin-laden macrophages (arrow) not seen on MR study. Reactive astrocytes are present in the surrounding neuropil. Masson trichrome stain, original magnification ×162.