TESTS IN EPILEPSY: THE MR SCAN (MRI)
This is often called MRI (magnetic resonance imaging) or nuclear magnetic resonance (NMR). The technique has nothing to do with radiation or X-rays, but records energy given out by atoms as they change their orientation after a brief magnetic pulse. The pictures or images produced have the same general appearance as CT scans, because the information processed by the computer is much the same as. Again it is necessary for the patient to lie still while the images are being taken.
The procedure is noisier than CT scanning and may, in some patients produce a claustrophobic feeling, as the patient is almost entirely enclosed in a tunnel. MRI usually takes about 25-35 minutes, but may take longer. Occasionally some contrast dye is injected into a vein, as in CT scanning, and then the scan repeated to demonstrate some additional details. Children may find the procedure more uncomfortable than having a CT scan and because of this more often need to have a brief general anaesthetic so that they lie still.
MRI gives a much clearer picture of those areas of the brain (the temporal lobes) which are most often responsible for intractable epilepsy, and so patients who are considered possibly to be suitable for surgery will certainly need an MRI. MRI is also useful for children in whom the epilepsy is thought to be due to a congenital malformation of the brain. Because of its greater costs (at present) MRI is unlikely to replace completely CT scanning, but there is no doubt that the level of detail obtained is far superior with MRI.
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