Alzheimer’s disease is notoriously hard to diagnose early as there is no definitive test for it. And as the likelihood of developing it increases with age, the majority of symptoms, such as memory loss, can be mistaken for part of the normal aging process. Even taking medication for aches and pains can make us forgetful, so it is not necessarily an indication of cognitive impairment.
Now, a new study from Northwestern Medicine warns that relying on clinical symptoms of memory loss could mean missing the diagnosis of other forms of dementia caused by Alzheimer's that don’t initially affect memory.
Currently, however, memory loss is the main contender for the diagnosis of Alzheimer's, though there are many different types of Alzheimer’s that can also affect a person's language, behavior, personality, or spatial judgment, depending on which part of the brain it attacks.
“These individuals are often overlooked in clinical trial designs and are missing out on opportunities to participate in clinical trials to treat Alzheimer’s,” explained the study's lead author Emily Rogalski, associate professor at Northwestern’s Cognitive Neurology and Alzheimer’s Disease Center.
In the study, published in the journal Neurology last month, the team identify patients with the clinical features of primary progressive aphasia (PPA). This is a rare form of Alzheimer's that causes a progressive decline in a person's ability to use language. Memory and other thinking capacities are relatively unaffected early in PPA.
Because PPA can be caused by either Alzheimer's or frontotemporal lobar degeneration (FTLD), another neurodegenerative disease, the researchers used amyloid PET scans to identify and confirm amyloid deposits, a protein that accumulates on the brain and is a definite indicator of Alzheimer's.
They strongly demonstrated that just relying on a person’s clinical symptoms isn’t enough to confirm whether PPA stems from Alzheimer's or FTLD. Thus, memory loss is not enough to diagnose Alzheimer's, and biomarkers, such as amyloid PET imaging, are necessary for confirming the neuropathological cause.
“We wanted... to raise awareness about the early clinical and brain features of PPA to develop metrics which would advocate for their inclusion in clinical trials targeting Alzheimer’s disease,” Rogalski said. “These individuals are often excluded because they don’t have memory deficits, but they share the same disease [Alzheimer’s] that’s causing their symptoms.”