A to Z of MS
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A to Z of MS Lumbar puncture
A lumbar puncture is a diagnostic test for multiple sclerosis that involves removing and analysing a sample of cerebrospinal fluid (CSF), the fluid that surrounds the brain and spinal cord within the skull and backbone.
A lumbar puncture takes about half an hour under a local anaesthetic. A hollow needle is inserted into the base of the spine (the lumbar region refers to the section of the backbone below the ribs and above the pelvis) and a quantity of cerebrospinal fluid is drawn off.
The overall discomfort experienced during a lumbar puncture itself is not great. However, the drop in pressure in the cerebrospinal fluid caused by the removal of a sample can produce a splitting headache for some people. This usually lasts for no more than 24 hours but for some can persist for longer. To reduce the risk of headaches it is suggested that the individual lie flat for at least six hours after the procedure and drink plenty of water.
How a lumbar puncture can help diagnose MS
Analysis of cerebrospinal fluid in the diagnosis of MS is looking for:
White blood cells - the number of white cells in cerebrospinal fluid of people with multiple sclerosis is usually up to seven times higher than normal. If the count is even higher than this, it is probably due to an infection of some sort, such as Lyme's Disease, and not MS.
Oligoclonal bands - the immune system produces antibodies to fight infection. In MS, antibodies cross the blood-brain barrier and attack the myelin surrounding nerves. As a result, the level of antibodies in the cerebrospinal fluid of someone with MS is higher than it should be and is higher than the level in the blood, a sample of which is also analysed.
The test that shows the presence of antibodies is called electrophoresis. A sample of fluid is placed on a gel and voltage is applied. This causes antibodies of the same size to bunch together, forming visible 'bands'.
One band (monoclonal) in the cerebrospinal fluid is normal. The term oligoclonal bands refers to the presence of two or more bands and shows the presence of disease activity. Whilst this doesn't necessarily mean that someone has MS, about 95% of people with MS do have oligoclonal banding in their cerebrospinal fluid.
Link H, Huang YM.
Oligoclonal bands in multiple sclerosis cerebrospinal fluid: an update on methodology and clinical usefulness.
Journal of Neuroimmunology 2006;180(1-2):17-28.