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Advanced Neurology Insights on ARIA

Alzheimer’s Association Research Roundtable Workgroup A B
suggested that researchers should use FLAIR sequences
to recognize ARIA-E, and GRE or susceptibility-weighted
imaging (SWI) sequences to recognize ARIA-H . When
[22]
an in-depth understanding of the lesions is required,
radiologists must decide whether additional imaging
sequences, such as with gadolinium enhancement, are
needed .
[23]
In an ongoing, recent, real-world study of aducanumab
(NCT05097131), researchers used 3D T2 FLAIR to identify C D
ARIA-E events with a resolution ratio of 1.2 mm × 1.0 mm
× 1.0 mm, 2D T2* GRE to identify ARIA-H events with
axial positions and a resolution ratio of 1.0 mm × 1.0 mm
× 5.0 mm, and additional DWI with a resolution ratio of
2.0 mm × 2.0 mm × 5.0 mm. The field strength was 1.5 or 3.0
T. Considering the severe imbalance in the distribution of
medical resources in China, we believe that MRI sequences
should not be strictly defined, but that both ARIA-E and
ARIA-H need to be considered. The specific details should
be jointly decided by both radiologists and clinicians after
consideration of the situation. We make the following E F
suggestions: (1) use FLAIR to identify ARIA-E, (2) use T2*
GRE or SWI to identify ARIA-H, (3) use DWI to evaluate
the degree and types of edemas, and (4) use conventional
T1 sequences to display anatomical structures and make
any comparisons that may be required with the enhanced
sequences. We suggest a field strength of 3.0 T with slice
thickness ≤5.0 mm and echo time ≥20 ms.
2.3. Imaging features
The vasogenic edema of ARIA-E usually manifests
as increased MRI signal in multiple regions of the Figure 1. Typical images of amyloid-related imaging abnormalities
hemisphere in FLAIR images, affecting both gray and (ARIA). (A, B) ARIA-edema (ARIA-E) (vasogenic edema) as seen on
white matter (Figure 1A and 1B), and the sulcal effusion fluid-attenuated inversion recovery (FLAIR) images, demonstrating
increased signal in multiple regions of the right hemisphere, affecting
usually demonstrates increased MRI signal in sulci both gray and white matter. (C, D) ARIA-E (sulcal effusion) detected
(Figure 1C and 1D), which represents proteinaceous fluid on FLAIR images, demonstrating increased signal in sulci, which is
tracking in the leptomeninges and sulcal spaces [22,23,26] . thought to represent proteinaceous fluid tracking in the leptomeninges
Both subtypes are transient in nature, are not associated and sulcal spaces. (E) The white arrows indicate multiple dark foci
in the right inferior temporal and occipital lobes, suggesting ARIA-
with reduced diffusion abnormalities, and can be hemorrhage (ARIA-H) (microhemorrhage); the red arrow indicates the
distinguished by differences in anatomical sites . ARIA-H inferior sagittal sinus, and the yellow arrow indicates a susceptibility
[23]
(microhemorrhage) typically manifests as a focal, round, artifact because vascular structures and artifacts can sometimes mimic
very low-intensity (relative to the adjacent brain) lesion in the appearance of microhemorrhage and siderosis. (F) The white arrows
the brain parenchyma. It can be detected on appropriate indicate curvilinear dark sulci in the right frontal lobe, which is typical of
the appearance of ARIA-H (superficial siderosis). Both (E) and (F) were
MRI sequences, and the lesion diameter is usually <10 mm acquired as gradient refocused echo sequences. All images are copied
(Figure 1E) [22,23,26] . In contrast, superficial siderosis refers and modified from “Sperling, R.A., et al., Alzheimer’s Dement, 2011,
to curvilinear low intensities adjacent to the surface of the 7(4): p. 367-85.”; the copyright belongs to the original authors and/or the
brain (Figure 1F); it is caused by iron depositions in the publisher.
form of hemosiderin, and indicates that blood is leaking
[23]
from vessels to the adjacent subarachnoid or perivascular is almost invisible on T1, T2, and FLAIR sequences . For
space [22,23,26] . Notably, the conspicuity of microhemorrhage patients who have received treatment, all newly discovered
and superficial siderosis can be enhanced or diminished by lesions must be fully analyzed to exclude other possible
specific image acquisition attributes; for example, ARIA-H pathological changes, especially lesions on FLAIR images.

Volume 1 Issue 1 (2022) 3 https://doi.org/10.36922/an.v1i1.2