Objective:

To characterize the efficiency and use of urgent MRIs for detecting new or worsening amyloid-related imaging abnormalities (ARIA) in patients receiving lecanemab at a multi-campus academic medical center. 

Background:

ARIA is an adverse event of amyloid-targeting immunotherapies. Symptoms are often nonspecific and overlap with non-ARIA pathologies. Early ARIA detection is critical as it can prompt changes in monitoring and treatment.

Design/Methods:

A chart review was conducted for all patients (n=530) who received at least one lecanemab infusion from December 2023 to September 2025. An urgent brain MRI was defined as an MRI ordered outside the standard monitoring window (as outlined within lecanemab’s FDA label), or a repeat scan within the standard monitoring window due to new or worsening symptoms after a prior negative scan. Symptoms prompting an MRI were elicited by scheduled screening questionaries at each infusion or via unscheduled patient-initiated communication. 

Results:

Of 128 urgent MRIs, 13 (10.2%) revealed new or worsening ARIA. Headache was the most common symptom prompting an urgent MRI (46.8% of urgent scans), followed by confusion (25.0%) and dizziness (10.2%), with other neurologic symptoms accounting for the remaining 18.0%. Among MRIs that detected new or worsening ARIA, headache was present in 61.5% of cases, followed by dizziness (30.7%) and confusion (7.6%). Carriership of an APOE ε4 allele was more prevalent among patients with ARIA detected on urgent MRI (84.6%) than in the overall lecanemab-treated cohort (64.1%). Urgent MRIs prompted by scheduled symptom screens yielded a threefold greater ARIA detection rate (17.8%) compared to patient-initiated calls (6.8%). 

Conclusions: