New Brain Scan May Predict Alzheimer's

A new imaging technique that measures the random motion of
water within the brain may prove useful for detecting early signs of
Alzheimer's disease.

The technique, known as diffusion tensor imaging (DTI) or diffusion MRI, is
used to assess changes in the white matter regions of the brain.

But it is increasingly clear that DTI can also be used to identify very
small structural changes in the gray matter of the brain, which is critical for
learning and memory, researcher Giovanni A. Carlesimo, MD, PhD, of Italy's Tor
Vergata University tells WebMD.

In a study published in the Jan. 19 issue of Neurology, Carlesimo and
colleagues found that DTI scanning predicted declines in memory performance
with more accuracy than traditional MRI.

"This type of brain scan appears to be a better way to measure how healthy
the brain is in people who are experiencing memory loss," Carlesimo says in a
news release. "This might help doctors when trying to differentiate between
normal aging and diseases like Alzheimer's."

MRI, DTI, and Alzheimer's

The researchers recruited 76 healthy people between the ages of 20 and 80
for their study.

They performed DTI scanning of the hippocampus, which is the region of the
brain that controls memory. They also performed conventional MRI scanning to
assess the overall volume of the hippocampus and the study participants
completed a battery of tests designed to measure memory function.

The researchers found that DTI scanning was better able to predict memory
performance than measurement of hippocampus volume, especially in study
participants over the age of 50.

But Carlesimo says more study is needed to prove that DTI scanning actually
predicts Alzheimer's disease in people who have not yet shown clear evidence of
memory impairment.

"There is wide agreement among researchers and clinicians that in order to
be effective, [drug] treatments should start as soon as possible in patients
with Alzheimer's disease," he says. "This, in turn, makes it critical to
identify people at high risk for the disease as early and as accurately as
possible."

Alzheimer's Diagnosis Remains a Challenge

The diagnosis of Alzheimer's disease and other age-related dementias remains
a challenge, geriatric psychiatrist and Alzheimer's Foundation of America (AFA)
spokesman Richard E. Powers, MD, tells WebMD.

Powers chairs the AFA's scientific advisory board and is medical director of
the Alabama Department of Mental Health.

"A good clinical evaluation is still the best tool we have," he says. "MRI
scanning can tell us if the hippocampus is smaller than it should be, but it
can't tell us the cause of the damage."

He says DTI is one of several imaging techniques that may prove more useful
than conventional MRI for diagnosing and even predicting the onset of
Alzheimer's disease.

Positron tomography (PET) scanning combined with a novel brain-imaging agent
called Pittsburgh Compound B shows promise for detecting the abnormal brain
proteins, known as amyloid plaques, which characterize Alzheimer's disease.

And high-resolution MRI also shows evidence of being more sensitive than
traditional measurement of hippocampal volume for assessing memory
impairment.

Powers predicts that within the decade, clinicians will be much better able
to identify patients who will develop Alzheimer's disease before the onset of
symptoms.

"I believe that five to 10 years down the road we will be able to tell
someone we are 99% certain that they will develop dementia within 10 years," he
says.

By Salynn Boyles
Reviewed by Louise Chang
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