MS The Disease
How is Multiple Sclerosis Diagnosed?
A diagnosis of MS usually begins with a discussion of your symptoms and medical history with your doctor. This is often followed by neurological examinations, including an MRI scan. Published criteria cite the incidence of two separate attacks of the illness, and two or more lesions in the white matter of the central nervous system, confirmed by an MRI, as requirements of an MS diagnosis. Other commonly performed tests include: (ref nd10)
- Evoked potential studies - used to measure the speed of nervous system transmissions, which may
indicate damage due to MS.
- Lumbar puncture - used to detect abnormal proteins or other substances within the cerebral
spinal fluid.
- CT brain scan - used to exclude alternative diagnoses.
MRI Scan
MRI, short for Magnetic Resonance Imaging, uses a strong magnetic field to create images ('scans') of the brain (figure) and spinal cord. The MRI scan shows any defects in the white matter. This type of examination has also shown that people with MS can have patches of inflamed myelin without symptoms.
There is some link between the amount of disease activity shown on the MRI scan and the progress of the disease, but the link is not very clear and is difficult to interpret. This means, unfortunately, that it is not at present possible to use the results of MRI to predict how the disease will develop.
Figure: MRI scan of the brain with typical MS lesions. Round-to-oval-shaped MS lesions can be seen (in white) around the butterfly shape (dark).
Evoked Potentials
There are several types of evoked potential test. Each tests the passage of nerve impulses from the brain to a specific part of the body. These impulses control a particular body function, such as hearing, sight or movement. A neurologist may wish to perform just one or all of these tests.By measuring what are known as evoked potentials or evoked responses, certain nerve fibres (axons) can be checked. This means that when MS is present it is possible to see whether certain nervous impulses are slowed down in the axons (because of demyelination). The more demyelination, the slower the transmission of impulses measured
Lumbar Puncture
After administering a local anaesthetic, the doctor puts a needle into the lower back ('lumbar') to take a sample of the fluid surrounding the brain and spinal cord (the 'cerebrospinal fluid'). In people with MS this fluid shows specific changes that match the presence of inflammation.