Leqembi MRI Risk: What You Need to Know About Brain Imaging and Alzheimer's Treatment

When you start Leqembi, a monoclonal antibody approved for early Alzheimer’s disease that targets amyloid plaques in the brain. Also known as lecanemab, it’s one of the first drugs shown to slow cognitive decline in people with mild Alzheimer’s — but it comes with a serious monitoring requirement: regular MRI scans, brain imaging tests used to detect swelling or bleeding caused by the drug.

Leqembi works by clearing amyloid protein clumps from the brain, but in doing so, it can weaken blood vessel walls. This leads to a condition called ARIA, amyloid-related imaging abnormalities, which includes brain swelling (ARIA-E) and small brain bleeds (ARIA-H). About 1 in 5 people on Leqembi develop ARIA, and while most cases are mild or symptom-free, some can be serious. That’s why doctors require an MRI before starting treatment, then again at 5 and 14 weeks, and then every few months after that. If you’re on Leqembi and suddenly feel dizzy, confused, have a headache, or lose balance, you need an MRI right away — even if you think it’s just stress or aging.

Not everyone is at the same risk. People who carry the APOE ε4 gene — a known genetic risk factor for Alzheimer’s — are more likely to develop ARIA. Those taking blood thinners like warfarin or aspirin are also at higher risk. That’s why your doctor will check your full medication list and possibly run genetic tests before prescribing Leqembi. It’s not a drug you take lightly. The benefits are real: studies show it slows memory loss by about 27% over 18 months. But that benefit only matters if you’re monitored closely. Skipping an MRI isn’t an option — it’s like driving a car without checking the brakes.

What you’ll find in the posts below isn’t just about Leqembi. It’s about how modern Alzheimer’s treatment ties into broader drug safety, brain imaging, and the real-world trade-offs of new therapies. You’ll see how MRI risk connects to other drug monitoring practices, why some medications need constant oversight, and how patient safety is built into treatment plans that look simple on paper but are complex in practice. These aren’t abstract ideas — they’re daily decisions doctors make, and you need to understand them if you’re considering Leqembi or helping someone who is.