How is the diagnosis made?

The clinical history is a key component of the diagnostic process. The rate at which the symptoms came on and the length of time they are present are useful indicators as to whether or not your symptoms relate to an episode of inflammation as happens in multiple sclerosis. Also, a detailed history will help establish if you may have had similar although maybe less severe symptoms in the past that may have been a milder episode. The history will help your neurologist also as they consider alternative causes for your symptoms (discussed below).

The next part of establishing the diagnosis lies in the neurological examination. During this your neurologist will ensure the nerves in your arms, legs and face are working properly. If there are abnormalities on the neurological examination it will help your neurologist localise where the problem is within the central nervous system.

With the detailed history and examination complete your doctor will then have formulated a “differential diagnosis”. This is medical terminology for the list of possible diagnoses based on your history and examination. This will help in the decisions regarding further investigations.

The most likely and helpful first test will be an MRI scan of your brain and part or all of your spinal cord. In multiple sclerosis the areas where the myelin has been lost will show up as white spots on your brain. The MRI will establish if you have these white spots, where they are, how big they are and how many you have. This will help your neurologist in further establishing the diagnosis and also assessing the level of severity. The greater the number of lesions the more severe the myelin loss. You may receive intravenous contrast or dye during the scan. This is given to see if any of the white spots “light up” or enhance with contrast. When the white spots are active (as in there is an active process causing myelin loss) they will enhance with the contrast. This again gives useful information in terms of level of disease activity. This information will be used in the decision regarding the most suitable treatment.

Following this your neurologist might decide to proceed with a lumbar puncture or spinal tap. During this procedure a sample of the fluid surrounding your brain and spinal cord (referred to as cerebrospinal fluid) is taken and analysed. In multiple sclerosis there may be a marker of inflammation found in this fluid. This is called an “oligoclonal band”. At the same time as the cerebrospinal fluid is sampled a blood sample is taken. This is tested for the same marker of inflammation. The value of this test is really to add weight to the likely diagnosis of multiple sclerosis.

Another test that may be helpful in making the diagnosis of multiple sclerosis is called a visual evoked potential. An evoked potential is a test that measures the electrical activity of the brain in response to stimulation of certain pathways. In multiple sclerosis the visual pathways are often affected even when there are no visual symptoms. The visual pathways are stimulated by putting a checkerboard in front of your eyes. Then electrodes are placed on the scalp over the area that receives visual information. The length of time it takes for the response to get from the eye to the brain is measured. In people with multiple sclerosis with involvement of the optic nerves this length of time is often prolonged. This is a harmless and generally painless test.

There are several other conditions that can present in a similar fashion to multiple sclerosis. For this reason you may have more tests (often blood tests) to look for alternative diagnoses. Multiple sclerosis is, as detailed above, an inflammatory demyelinating condition. However, there are other inflammatory demyelinating conditions that are not multiple sclerosis. One of these is a condition called neuromyelitis optica. It is also an autoimmune condition that has similar features to multiple sclerosis even though it is caused by a different type of inflammation. A blood test to look for a specific antibody will help rule this out. There are also inflammatory conditions that primarily affect parts of the body outside of the nervous system (for example the joints or lungs) that can uncommonly cause inflammation of the nervous system. Again these are mostly diagnosed through blood tests and include conditions such as sjogrens syndrome (primarily manifesting as inflammation of the salivary and tear duct glands causing dry eyes and dry mouth), systemic lupus erythematosus (primarily causing inflammation of the joints, kidneys, lungs and other organs), sarcoidosis (primarily affecting the lungs and skin) and vasculitis (an inflammation of blood vessels so it can really affect any part of the body although uncommonly affects the central nervous system). There can be unusual genetic conditions also or infections that can cause inflammation of the nervous system. Deficiency of vitamin B12 can lead to neurological symptoms so it is not at all uncommon to have this level checked when you present with any neurological symptoms. These are just examples of what are often referred to as “multiple sclerosis mimics”. In general, a thorough history and examination should lead your neurologist to narrow down the list of possible diagnoses and decide on which extra blood tests you need based on that.