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spinal tap

A spinal tap, also known as a lumbar puncture, is a diagnostic procedure for multiple sclerosis and other neurological conditions. It involves collecting samples of cerebrospinal fluid (CSF), the fluid in central nervous system, blood serum and ordinary blood, analysing and comparing them. Examination of the CSF cannot be used to definitively diagnose nor exclude multiple sclerosis, but the results can be indicative of MS and are used to support a clinical diagnosis. The spinal tap is the only common diagnostic procedure commonly used for multiple sclerosis that causes significant discomfort and that has potentially severe side-effects.

I shall discuss the possible results of the spinal tap with respect to multiple sclerosis, after describing the procedure to obtain the CSF sample.

The Test Itself

The test involves lying on your side in the foetal position. The skin on your lower back is scrubbed clean to remove the possibility of infection and a local anaesthetic is injected. A spinal needle is then inserted into subarachnoid space between the 3rd and 4th lumbar vertebrae and the CSF pressure is recorded. A sample of the CSF is then taken. The entire procedure usually takes about 30 minutes but may take longer.

The anaesthetic injection stings when it is injected and the spinal needle causes a sensation of hard pressure and can hurt a little. The overall discomfort experienced during the spinal tap itself is not great.

It is important that you lie horizontally with your head slightly below the rest of your body for at least 6 hours after the test. Because the test will remove a small amount of your cerebrospinal fluid, the resulting drop in pressure can produce a splitting headache often with accompanying nausea. This usually lasts for no more than 24 hours but it some cases can last for up to a week.

Rarely complications such as bleeding into the spinal canal or continued leaking of CSF after removal can occur. If the tap is performed on someone with raised CSF pressure, the side-effects can be very severe occasionally resulting in brain damage or even death.

Results

A process called Electrophoresis is usually used to analyse the CSF and a phenomenon called IgG oligoclonal banding is often a corollary of MS.

In around 5% of clinically definite MS case, the CSF is normal.

In around 90% of cases, the Immunoglobin-G (IgG) index (a formulaic calculation comparing IgG levels in the blood with those in the blood serum) is raised to around 0.7. This gives rise to the IgG oligoclonal bands seen in the electrophoresis. Other conditions, especially viral infections and tumours are also associated with similar results.

In around 35% of cases, CSF helper T-cells counts are raised.

In around 80% of cases in acute relapse, myelin basic protein (MBP) levels are significantly raised.
 
Immunologic abnormalities in CSF, whole blood and serum in MS patients
Cerebrospinal Fluid Serum Blood
Increased gamma interferon (IFN-G) Increased IFN-G Increased IFN-G
Increased Immunoglobin-G (IgG) and oligoclonal bands Increased Tumor necrosis factor (TNF) Increased interleukin-2 (IL-2)
Increased Tumor necrosis factor (TNF) Increased interleukin-2 (IL-2) Increased IL-4
Increased activated Helper T-cells (CD4+) cells Increased IL-2 receptors Increased IL-1
Increased myelin basic protein (MBP) Decreased prostaglandin E release by macrophages   
   Decreased Killer T-cells (CD8+)   

Spinal Tap links:
Spinal Headache Prevention
CSF collection
Oligoclonal IgG bands in cerebrospinal fluid in various neurological diseases
CerebroSpinal Fluid In Multiple Sclerosis
Oligoclonal Banding and Multiple Sclerosis
Spinal Tap


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