A new type of brain scan is more sensitive than basic MRI in detecting early signs of age-related cognitive decline, according to a recent study.

As published online in the journal Neurology last week, a type of MR scan known as diffusion tensor imaging, which measures the random movement of water through tissue, can help predict how well healthy adults perform on cognitive tasks.

Doctors in Rome, Italy tested 76 healthy adults, from between 20 to 80 years of age, on a battery of psychological exams, such as seeing how well they could recall lists of words or reproduce complex figures. The participants then underwent normal MRI and DTI-type scans on a Siemens-made 3T Allegra machine.
What the doctors found was that people who performed relatively worse on the cognitive tasks showed higher mean diffusivity values in part of their brain called the hippocampus, long known to be involved in coding memories. High mean diffusivity values, a quantitative measure performed on DTI scan results, imply large gaps between cells, allowing more water to pass through. This could indicate brain cell loss.

"An increased diffusivity is generally interpreted as resulting from an increase in the extracellular space as a consequence of a loss of neurons, axons and dendrites," Giovanni Carlesimo, M.D., Ph.D., lead author and a neuroscientist with the Santa Lucia Foundation in Rome, Italy, explains to DOTmed News by email.

While it's known that shrinkage of the hippocampus is involved in clinical conditions such as Alzheimer's disease and mild cognitive impairment, Dr. Carlesimo believes this is one of the first studies to use DTI scans to show changes to the hippocampus associated with normal, run-of-the-mill aging. Basic MRI scans from the study measuring volume of the hippocampus did not correlate with results on the cognitive task tests. And autopsy studies and previous experiments using MRI imaging on older otherwise healthy adults have generally failed to pick up significant changes in volume or structure of hippocampi.

OLD AGE OR EARLY DISEASE?

What the doctors are not sure about is if the faint cognitive decline in some of the subjects in the study is the first wobble of Alzheimer's, and if the DTI scans will help doctor's catch the disease earlier than with other modalities.

Dr. Carlesimo notes that their findings line up with other available evidence. In earlier studies, in patients with certain forms of mild cognitive impairment or Alzheimer's, mean diffusivity values in the hippocampus are higher than in normal adults of the same age, and those values correlate significantly with performance on cognitive tasks similar to ones used in this study.

More Industry Headlines