A detective is looking for a criminal in a file of mugshots, but the portraits are mixed up. Usually, they expect a man with a gray beard, but the culprit is young and clean-shaven. Similarly, doctors often fail to recognize Alzheimer's disease in those who show unusual symptoms — not memory loss, but problems with vision or speech.
Alzheimer's is typically linked to the buildup of two proteins in the brain — amyloid and tau. But spotting these proteins requires expensive and unpleasant procedures: a spinal tap or a special brain scan. So in regular clinics, the diagnosis is made differently: patients take memory and attention tests, and doctors look at the size of the hippocampus — the brain region responsible for memory. In most patients, the hippocampus shrinks, which helps the doctor. But in people with the atypical form of the disease (atAD), the hippocampus may remain normal, while other brain areas suffer. Such patients are often mistaken for having another dementia and treated incorrectly.
Researchers from several scientific centers decided to teach a computer to tell these "nonstandard" patients apart from people with other cognitive impairments. They used data from 1410 people: some had typical Alzheimer's, some atypical, some other dementia, and some were healthy. The data came from one private database and two public ones: NACC and ADNI. Doctors usually look only at the hippocampus, but the scientists added many other brain regions visible on MRI to the analysis. It turned out that these extra scans were enough to make the computer noticeably more accurate than a doctor relying only on the hippocampus.
The program learned to correctly identify atypical Alzheimer's in 69% of cases instead of the previous 52% in the NACC database, and in 77% instead of 34% in the ADNI database. At the same time, it rarely erred in the other direction: it almost never called healthy people sick. The authors also found which brain regions matter most for the distinction: areas responsible for vision, speech, and complex movements. This matches the fact that in these patients, it's not memory that fails first.
This approach could change many lives. Instead of months of wandering from doctor to doctor with a wrong diagnosis, a person gets the right treatment sooner. And doctors get a tool that hints: "Look more closely at these brain areas — maybe it's not the dementia you thought."
The hippocampus is named after the seahorse: its shape on scans resembles that animal.