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Detection of magnetic fields in brain used to diagnose epilepsy

21 October, 2003

A study has investigated
whether the weak magnetic fields caused by electrical signals in the
brain can be used to diagnose and treat epilepsy.

The magnetic fields
can be measured by means of magnetoencephalography (MEG) and this study
has investigated the extent to which direct measurement of electrical
activity in the brain can be coupled with MEG to diagnose the condition.

Professor Christoph
Baumgartner of the Neurological
University Clinic at Vienna General Hospital
has looked into the effect of combining both electroencephalography
(EEG), one of the usual methods of measuring unusual activity in the
brain, with MEG. The results of the research indicate that a new approach
of using both methods is better than either EEG or MEG alone at localising
the hyperactive regions of the brain.

Dr Baumgartner explained:

"Although highly
effective drugs are now available, about 20 per cent of all patients
do not respond to them. Surgery is an effective alternative for most
sufferers. This involves removing the irregular parts of the brain.
But to ensure that seizure freedom achieved in this way does not come
at the cost of neurological deficits, the affected area must be precisely
localised before the operation."

Dr Baumgartner explained
that with EEG, the accuracy of the measurements is limited by the fact
that the scalp and the skull act as insulators. A non-involved reference
is also needed to interpret the electrical signals. However, this is
often subject to other distorting factors, making it difficult to pinpoint
the hyperactive regions of the brain. Due to this, it is currently
necessary to implant electrodes in the brain to obtain the necessary
spatial resolution, and hence reliable results.

Dr Baumgartner added:

"Instead of
this procedure, which is extremely unpleasant for the patient and involves
a risky operation, MEG can be used in tandem with EEG. Both methods
are based on the same physiological process - changes in the potentials
of nerve fibre ends - but they measure different effects and can thus
complement each other."