PMC10175602_01
MRI and PET images for case 1. The case was diagnosed as probable CAA after a symptomatic left temporal ICH with disseminated cortical superficial siderosis (cSS) on MRI (A-D). Two months prior to his clinical symptoms, mild left temporal T2 FLAIR hyperintensity was already seen (B), which may suggest insidious onset of ARIA-E. The patient then developed progressive lethargy and spontaneous ARIA-E, showing white matter hyperintense lesions with leptomeningeal enhancement and mass effects in the right cerebellum [(E), arrow], left temporal (F), bilateral medial frontal, and parietal lobes (G) on T2 FLAIR images before steroid treatment. A newly developed cSS in the posterior medial frontal region [(H), white box] was observed on SWI, which was not seen 2 months earlier (D). The cerebral edema significantly improved after steroid treatment (I-K). Progressively disseminated cSS was also observed (L). High amyloid deposition in the posterior medial frontal region was detected on amyloid PET 2 years before CAA-ri [(M), red box]. Amyloid deposition decreased in the medial frontal region 6 months after CAA-ri [(N), red box]. The patient showed positive tau pathology on tau PET scans (O, P).
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F1
The patient received a routine MRI follow-up which showed mild left temporal T2 FLAIR hyperintensity lesions (Figures 1A-D) and the patient was nearly as his usual condition at that time. Brain MRI revealed a leptomeningeal enhancement (Figures 1E-G) with edema of the bilateral high posterior frontal lobes, right medial parietal lobe, left temporo-parieto-occipital lobes and right cerebellum (Figure 1E), as well as new focal cSS in the posterior medial frontal region (Figure 1H, white box) that were absent in the MRI performed 2 months earlier (Figure 1D). Follow-up brain MRI 1 month later showed resolution of the edematous changes (Figures 1I-K). However, higher amyloid deposition was noted in the posterior medial frontal regions (Figure 1F, red box), which overlapped with the location of the newly developed cSS (Figure 1H, white box). Amyloid PET was repeated 6 months after CAA-ri and revealed focally decreased amyloid uptake in the posterior medial frontal lobe (Figures 1M, O, red boxes) and the left temporal lobe. The patient also underwent cerebral tau PET using 18F-T807 2 years earlier and 2 months after CAA-ri, which confirmed a cerebral phosphorylated-tau pathology (Figures 1N, P).
PMC10175602_02
MRI and PET images for case 2. In the second case, multiple hyperintense foci in the bilateral temporal lobes (A) and cortical and subcortical edema in the right frontal and bilateral parietal regions (B, C) were observed on T2 FLAIR imaging before steroid treatment. Previous ischemic insult was also demonstrated [(B), arrow]. Multiple strictly lobar microbleeds were detected in the bilateral cerebral hemispheres on SWI. (D) Follow-up T2 FLAIR imaging after steroid treatment showed resolution of the aforementioned edematous changes and hyperintense foci (E-G). The microbleed became more prominent after the CAA-ri (H). Amyloid PET confirmed amyloid deposition at 10 months after CAA-ri, but the uptake pattern did not correlate with the regions of FLAIR hyperintensities (I). Tracer binding was not observed in the regions affected by previous ischemic insults [(I), arrow]. No significant tau deposition was observed on a tau PET scan (J).
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F2
MRI showed bilateral cerebral hemispheres FLAIR hyperintensities (Figures 2A-C) and multiple cortical-subcortical microbleeds (Figure 2D). Moreover, superficial siderosis were seen in the surface of brain stem and cerebellum (not shown in figure), which was probably owing to previous surgery of cerebellar hematoma evacuation. Brain MRI (Figures 2E-G) 4 months after discharge showed resolution of the edematous changes, but the number of cerebral microbleed increased (Figure 2H). No significant tau deposition was noted (Figure 2J).