The Diagnosis Is Alzheimer’s. But That’s Probably Not the Only Problem.

The Diagnosis Is Alzheimer’s. But That’s Probably Not the Only Problem.

Gina Kolata

But it wasn’t just Alzheimer’s disease, the researchers found. Although Mr. Gallup’s brain had all the hallmarks — plaques made of one abnormal protein and tangled strings of another — the tissue also contained clumps of proteins called Lewy bodies, as well as signs of silent strokes. Each of these, too, is a cause of dementia.

Mr. Gallup’s brain was typical for an elderly patient with dementia. Although almost all of these patients are given a diagnosis of Alzheimer’s disease, nearly every one of them has a mixture of brain abnormalities.

For researchers trying to find treatments, these so-called mixed pathologies have become a huge scientific problem. Researchers can’t tell which of these conditions is the culprit in memory loss in a particular patient, or whether all of them together are to blame.

Another real possibility, noted Roderick A. Corriveau, who directs dementia research programs at the National Institute of Neurological Disorders and Stroke, is that these abnormalities are themselves the effects of a yet-to-be-discovered cause of dementia.