Alzheimer's Club

"Neuroscientists say they've made substantial progress toward developing a new way to diagnose early-stage Alzheimer's disease: through brain scans.

Anne Fagan, Ph.D., associate professor of neurology at Washington University, led a study on these new detection tests. She presented the results at the Nov. 15 meeting of the Society for Neuroscience in Washington, D.C.

Fagan says that early detection of Alzheimer's could eventually prove useful in the clinical prevention and treatment of the disease.

"When clinical symptoms start," Fagan said, "the disease process has already been at work in the patient for many years and possibly even decades. Up to 30 percent of neurons in vulnerable areas are already dead, and you can't get them back. So finding markers that can help us identify patients prior to symptoms is really our big push now."

Fagan and her colleagues studied a group of 24 people, some of whom had cognitive impairments believed to be signs of mild Alzheimer's disease and some who were cognitively normal.

In those subjects with suspected Alzheimer's, the researchers found low levels of amyloid-beta 42 in their cerebrospinal fluid (CSF), which bathes the spinal cord and brain. This finding was not a surprise, as A-beta 42 is known to be the primary ingredient in the plaque buildups that are consistently found in Alzheimer's patients' brains. Decreasing levels of A-beta 42 in CSF would be expected as excess protein accumulates in the brain instead of being swept away in the fluid like it normally is.

For the second component of their research, the scientists looked at positron emission tomography (PET) scan results from these same patients' brains. The scans used a new imaging agent called PIB (Pittsburg compound B) that sticks to amyloid plaque long enough to be detected through a PET scan. The researchers found that the scans showed plaque in all those patients with low CSF levels of A-beta 42.

Interestingly, low CSF levels of A-beta 42 and corresponding brain scans positive for plaque were also found in three of the cognitively normal patients.

This raised a question: Will these three people develop the cognitive impairments characteristic of Alzheimer's disease sometime in the future?

"For now, definitive diagnosis of Alzheimer's disease still cannot be made until autopsy," Fagan said. "It's going to take a number of years for us to fully assess these results, because all we can do now is follow the participants closely, waiting to see if they eventually develop Alzheimer's dementia."

Fagan added that the study results provide new hope in the ongoing fight to find effective ways to detect and treat Alzheimer's disease.

"The hope is that 10 to 20 years from now, we'll give people a PIB scan, draw and analyze their CSF, and combine that with other factors to get a global score for their personal risk of Alzheimer's disease," she said. "We have disease-modifying treatments on the way to clinical trials right now, and tests that can help us detect Alzheimer's earlier will both help us put those treatments to better use and assess the results they produce in patients."

Alzheimer's disease affects up to 4.5 million Americans, most of them age 60 and older. The most common form of dementia among elderly people, Alzheimer's interferes with the parts of the brain controlling thought, memory and language. The cause of Alzheimer's disease is unknown, and for now there is no cure.

Neurologist Steve Poceta, a member of myDNA's Medical Advisory Board, says definitive diagnosis of Alzheimer's remains virtually impossible, especially early in the disease.

"This is frustrating for many patients and their families, which adds to the burden of this disease. Definitive diagnosis is presently desirable for prognosis and for social planning, but eventually is desirable so that treatments can be started as early in the process as possible."

He adds that the findings suggest that it might be possible to distinguish those people who have "mild cognitive impairment" suggestive of Alzheimer's from other patients.

"Unfortunately, this study suffers from the same problem that other studies have - the results are not 100 percent or even 99 percent. Some of the patients who appeared to be normal also had abnormal PET scans, so we do not yet know if this research tool will be useful in the clinic trying to diagnose patients."

"As the authors point out, early detection will be very important once we have medications that can treat the underlying disease process, as opposed to current medications that only treat the symptoms," Poceta says.

Currently, neither definitive early diagnosis nor disease-modifying therapy is possible at this time, but Poceta is excited about the study.

"Studies exactly like these are exciting and are beginning to show more promise in the battle against Alzheimer's. In the meantime, patients with Alzheimer's or related illnesses benefit the most from close contact with physicians, family members and other caregivers, as well as from available medications."

Source: Test predicts Alzheimer's? myDNA News (28 Dec 2005) [FullText]