Å®ÉúСÊÓƵ

Doctors in Japan and the US are using an imaging system which can ‘see’
biochemical changes in the brain of people suffering from Alzheimer’s disease.
The imaging system, known as magnetic resonance spectroscopy (MRS), detects
biochemical imbalances in the brain’s cortex.

Mariko Ide of Kyoto Prefectural University of Medicine in Japan believes
that MRS could become ‘a routine procedure for the early diagnosis of Alzheimer’s
»å¾±²õ±ð²¹²õ±ð’. There is currently no cure for the condition, which leads to dementia
and is a major cause of disability in the elderly.

MRS is related to magnetic resonance imaging (MRI), a technique which
uses a strong magnetic field to create a computer-generated picture of the
brain’s interior based on the distribution of water and fat.

Whereas MRI provides information on the structure of the brain, MRS
shows how certain biochemicals used in metabolism are distributed within
the brain. Many standard MRI machines can be adapted to perform MRS by upgrading
the hardware and software. Å®ÉúСÊÓƵs at the MRC Cyclotron Unit in London
already use another scanning technique, positron emission tomography, to
assess the blood flow and the relative activity of different regions in
the brain.

Ide and her colleagues in Japan detected biochemical changes in an area
of the brain called the temporal cortex, which lies towards the sides of
the brain. Using a 3D variation of MRS she found that a compound called
N-acetylaspartate (NAA) was significantly reduced in people with Alzheimer’s
disease. This, she says, ‘may be a good indication of Alzheimer’s disease
at an early stage’.

NAA is important because unlike other compounds it occurs only in the
neurons – nerve cells that perform the functions of the brain such as thinking
and seeing. NAA is not found in the glial cells, the other type of cell
in the brain.

The Japanese findings are supported by a related study carried out by
Dieter Meyerhoff, assistant professor of radiology at the University of
California in San Francisco. The study used MRS on Alzheimer’s patients
and found a decrease in NAA at the back of the cortex. Meyerhoff also observed
an increase in another biochemical, choline, which is present in cell membranes.
He regards this as highly significant because the decrease in NAA suggests
a corresponding reduction in nerve cells, and an increase in choline may
be indicative of Alzheimer’s disease.

Meyerhoff has compared MRS brain images of healthy elderly people with
those of young individuals to rule out the possibility that the biochemical
changes could be related to age, but has found no differences between young
and old subjects. However, he did find measurable differences between healthy
old subjects and those with Alzheimer’s disease.

Nevertheless, Meyerhoff thinks it is too early to predict the diagnostic
value of MRS. ‘We are seeing things that are consistent with postmortem
findings of Alzheimer’s disease,’ he says. He adds ‘postmortem studies indicate
that the increased choline (to NAA) ratio seems to be specific to Alzheimer’s
»å¾±²õ±ð²¹²õ±ð’.