Cogswell, Petrice M

Abstract Background Amyloid‐Related Imaging Abnormalities (ARIA), an adverse event associated with Alzheimer's disease anti‐amyloid immunotherapies, occur in the form of edema or sulcal effusion (ARIA‐E) and microhemorrhages and superficial siderosis (ARIA‐H). Conventional teaching is that ARIA‐H is permanent hemosiderin staining of the brain. In clinical trials we have noticed that some ARIA‐H microhemorrhages that occur with regional ARIA‐E appear to later resolve. The goal of this study is to illustrate that, opposed to current understanding, some ARIA‐H microhemorrhages may resolve. Methods We identified participants from the Dominantly Inherited Alzheimer's Network Trial Unit (DIAN‐TU) and open label extension (OLE) gantenerumab studies that had ARIA‐E and at least one ARIA‐H microhemorrhage. The T2* GRE sequence from all available MRI exams in a patient were co‐registered and reviewed by a board‐certified neuroradiologist. Individual microhemorrhages were tracked over the serial exams. We defined disappearing/resolving microhemorrhages as those appeared with or following ARIA‐E, were visualized on at least 2 MRI exams, and were subsequently not visualized on at least 2 MRI exams. Results A total of 12 patients met inclusion criteria of which 5 (41%) had microhemorrhages that resolved over 10‐40 months follow‐up after the incident ARIA. These microhemorrhages occurred in clusters in the region of ARIA‐E, and only some of the regional microhemorrhages resolved over follow‐up. Examples are shown in Figures 1‐3. Conclusions The disappearance (resolution) of ARIA‐H microhemorrhages is relevant to the management and continued dosing of patients receiving anti‐amyloid immunotherapies as this is guided by the presence of ARIA (including cumulative treatment emergent microhemorrhages) as well as clinical symptoms. A microhemorrhage number alone may not be indicative of the potentially dynamic nature of ARIA‐H.

Abstract Background White matter hyperintensity topography, particularly posterior confluent and subcortical multispot (WMH‐MS), has been implicated as surrogate imaging biomarker of cerebral amyloid angiopathy (CAA). Usefulness of WMH‐MS for prediction of future cerebral microbleeds (CMB's) has significant clinical implications for anti‐amyloid therapy risk assessment. Our primary goal was to identify the prevalence of positive WMH‐MS status and their utility for predicting the incident CMBs in a population‐based sample. Our secondary goal was to evaluate its usefulness after accounting for amyloid (surrogate for CAA) and WMH burden (surrogate of small vessel disease) which are both risk factors for CMBs. Method We identified 651 participants (mean age (SD) 69.8 (10.0) years, 55% male) from the Mayo Clinic Study of Aging, who had 3T baseline whole brain fluid‐attenuated inversion recovery (FLAIR) MRI and at least two T2*‐weighted gradient recalled echo (GRE) sequences (concomitant with or after FLAIR) which were used to ascertain CMBs. Amyloid positron emission tomography (PiB‐PET) scans were available in 87% of the sample. Visual reads on FLAIR scans were performed using a 4‐point Fazekas rating scale of periventricular and deep WMH (positivity: Fazekas ≥ 2) and a 3‐point MS severity visual scale (positivity: nWMH‐MS > 10 circular or ovoid WMH spots, Figure 1) according to established criteria. Using univariate and multivariable logistic regression, we assessed the independent association of WMH‐MS > 10 and Fazekas ≥ 2 for prediction of incident CMB's. Result The frequency of WMH‐MS pattern was greater in those who developed an incident CMB compared to those who did not develop a CMB (20.8% vs. 2.8%, p < 0.001). Older age and male sex were predictive of incident CMBs (Figure 2A). In univariate models, presence of WMH‐MS pattern but not Fazekas was associated with incident CMBs after adjusting for age and sex. The associations remained significant after additional adjustment for APOE4 , hypertension, number of baseline CMBs (Prior CMB), and amyloid effects (Figure 2B). Conclusion Visually identified WMH‐MS patterns on FLAIR‐MRI were predictive of incident CMBs in this population and may be useful markers of CAA. Future studies evaluating its utility as an additional biomarker of amyloid related imaging abnormalities in clinical trials are necessary.