"What is tragic is that these patients are commonly misdiagnosed and we have new evidence that suggests drugs now on the market for AD could work best in these hippocampal sparing patients possibly better than they work in the common form of the disease," Dr. Murray says.
The researchers benefit greatly from one of the largest brain banks in the country more than 6,500 brain donations as well as a collaborative environment between neuroscience research and neurology at Mayo Clinic, she says.
Both hallmark proteins of AD amyloid beta (Aβ), which forms Aβ plaques, and tau, which produces tangles are found across all subtypes of AD, including hippocampal sparing AD. The researchers developed a mathematical algorithm to classify AD subtypes using tangle counts. "What is fascinating is that all the AD patient subtypes had the same amount of amyloid, but for some reason tau tangles were found in strategic cortical regions disproportionate to the hippocampus."
In these patients, tau preferentially damages and eventually destroys neurons in parts of the brain involved in behavior, motor awareness and recognition, as well as use of speech and vision, Dr. Murray says.
She says she hopes this research, the second high-profile Mayo study to highlight hippocampal sparing AD, will "open the minds" of clinicians who are trying to diagnose dementia, helping them understand that loss of memory is not present in every AD patient.
"Our studies support the notion that dementia related to AD does not necessarily equate to a loss of memory, and points to the need for more research in amyloid and tau imaging biomarkers to help clinicians accurately diagnose AD regardless of subtype," Dr. Murray says.
|Contact: Kevin Punsky|