Diagnosing MS
By now you are probably aware that MS is not easily diagnosed, as there is no single laboratory test, symptoms or physical findings that can, by themselves, determine whether a person has MS. A clinical diagnosis is made on the basis of a person’s medical history, an assessment of symptoms reported by the person and the presence of abnormalities detected by the neurologist (but not always noticeable to the person) during a comprehensive neurological examination.
At this time, a neurologist can only make a clinically definite MS diagnosis if the following criteria are met:
- There must be objective evidence of two attacks, that is, two episodes of demyelination in the central nervous system;
- The two attacks must be separated in time (at least one month apart) and space (indicated by evidence of inflammation and/or plaques in different areas of the central nervous system); and
- There must be no other reasonable explanation for the attacks or the symptoms the person is experiencing.
The type and number of symptoms vary with each individual depending on
where demyelination occurs in the CNS. It is not known why this process occurs or why some people experience more or different symptoms from others. As far as we know the person who develops MS has done nothing to cause the disease or its symptoms and could not have prevented it from occurring.
There has also been much discussion about a possible relationship between stress in people’s lives and the onset or worsening of MS. Although a variety of research studies have been conducted in an effort to identify a possible link between stress and MS, no conclusive evidence of such a link has been demonstrated. Trying to remove stress from your life could prove to be impossible, but might also remove much of what is most interesting and fulfilling. Learning to manage life’s stresses comfortably and effectively may be a more realistic goal.
A definite diagnosis of MS will be made only when all other explanations of the signs and symptoms can be excluded. This helps to explain why it may take a long time for some people to get a definitive explanation for their puzzling and uncomfortable symptoms. While for many people their medical history and neurological examination will provide sufficient
information to support a clinically definite diagnosis of MS, for others, further tests may be needed to confirm it.
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The most common test used today is Magnetic Resonance Imagining (MRI) scan, which produces pictures of the brain and spinal cord without the use of x-rays. Such pictures identify lesions in the CNS; however an MRI may not always be conclusive of a diagnosis of MS. Other tests used to confirm a diagnosis of MS may include evoked potentials which measure the speed and efficiency of nerve conduction along different pathways in the CNS. These are non-invasive and well tolerated by most people.
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In order to rule out other medical conditions and support the diagnosis of MS, it may be necessary for a person to have a lumbar puncture (spinal tap). In this test, cerebrospinal fluid (fluid that surrounds the brain and spinal cord) is collected via a needle inserted into a space in the spinal column and then chemically analysed. The neurologist is looking for certain indications of abnormality in the immune system. While the results of this test are not specific to MS, they can help distinguish MS from other neurological conditions that resemble MS. As this test is somewhat uncomfortable, it is not done as frequently as MRI or evoked potentials.
It is important to remember that there is no one test that will tell a doctor whether a person has MS or not. Your medical history and the symptoms and signs of CNS demyelination that you and your doctor will piece together provide the clearest evidence for the MS diagnosis.
1. McDonald, W. et al. Annals of Neurology 2001; 50:121-127.