DWI Abnormalities and Stroke in Patients Treated With Lecanemab

Key Takeaways

• Interval stroke, defined as diffusion-weighted imaging abnormalities consistent with stroke, was reported in 11 of 261 lecanemab-treated patients during follow-up.
• The lesions were small, asymptomatic, and were most often cerebellar or cortical.
• Stroke cases were older, had lower median MoCA scores, and ARIAs remained significantly associated with stroke incidence after matching.

The lesions were not reported as symptomatic clinical strokes at presentation. Investigators used the term interval stroke for these findings. The reported imaging pattern and observed relationship with ARIAs framed the main findings in this cohort.

Investigators collected data from lecanemab initiation to the last follow-up and compared patients with interval stroke against those without stroke. The stroke subgroup included 11 patients within the full 261-patient cohort, allowing comparison across demographic and clinical features. Patients with interval stroke were older than those without stroke, with ages of 80.1 versus 74.3 years. They also had lower median Montreal Cognitive Assessment scores, 19 versus 22. The comparison centered on age and cognitive status. These differences characterized the subgroup in which interval stroke was identified.

The investigators focused on diffusion weighted imaging abnormalities considered consistent with stroke in patients receiving lecanemab. Within the stroke subgroup, lesions were described as small and asymptomatic rather than clinically overt events. By location, they were mostly cerebellar in 36.4% of cases or cortical in 36.4%. This distribution defined the imaging phenotype within the reported stroke cases. The interval strokes were presented mainly as imaging findings rather than symptomatic presentations.

Amyloid-related imaging abnormalities were more prevalent among patients with stroke than among those without stroke, occurring in 54.5% and 20.8%, respectively. After propensity score matching, ARIAs remained significantly associated with stroke incidence, with P = 0.011. This matched analysis examined the relationship while accounting for measured confounding factors. The reported association does not establish that ARIAs caused these lesions or accounted for every stroke event.

The investigators also raised a tentative possibility that restricted diffusion lesions and ARIAs could share an immune-mediated mechanism. These data support an observed association between ARIAs and interval stroke in this lecanemab-treated cohort, while leaving mechanism and downstream significance unresolved.