(National-NBC) November 28, 2006 - Tens of thousands of Americans are diagnosed with Alzheimer's each year, but some scientists now question if doctors are overlooking other possible causes for dementia.
A brain scan offers clues about what's causing memory loss, explains UCSD neurologist Adam Fleisher.
"The spaces inside the brain and outside the brain as the brain is shrinking," said neurologist Adam Fleisher.
But forgetfulness and mental decline don't always mean Alzheimer's.
Creutzfeldt-Jakob disease or CJD, a rare brain infection associated with mad cow disease, also causes dementia. And some scientists suggest some cases of Alzheimer's are actually CJD.
"And 'CJD, Creutzfeldt-Jakob disease' can mimic the early stages of Alzheimer's disease," adds Fleisher.
That's where the similarities stop. Alzheimer's usually begins around age 72, while CJD can strike at any age.
Short-term memory loss is associated with Alzheimer's, while long-term memory loss is common early on among CJD patients.
Mental decline also happens in a matter of months with CJD, instead of years for Alzheimer's patients. And, physical symptoms don't appear until the late stage of Alzheimer's, but they're almost immediate with CJD.
"So if someone is having a rapidly progressing dementia then you have to think of things other than Alzheimer's," said Fleisher.
There's no test to tell for sure whether memory loss is Alzheimer's or CJD, but the right diagnosis will make a difference in getting treatment.
"There is not a definitive treatment for CJD. And although there's not a definitive treatment for Alzheimer's disease, the disease has a much longer process and we do have ways to slow down the disease now," added Fleisher.
The Centers for Disease Control is now collecting autopsy data to determine if Alzheimer's disease is indeed being mis-diagnosed.
So far, they say more than 92% of Alzheimer's cases are correctly diagnosed.
updated 2:28pm by Bryce Mursch