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Monday, December 11, 2017

What is a "Lumbar Puncture"?

This post pertains to a particularly important procedure that doctors need to perform on children (and adults) with certain specific kinds of illnesses. 

The procedure is known as a LUMBAR PUNCTURE. In this procedure, we insert a needle under sterile, aseptic conditions into the spine of a child to extract a few millilitres of CEREBROSPINAL FLUID - the watery fluid that bathes our brain and spinal cord - to analyse it to diagnose neurological conditions and nervous system infections. 

In children, we do not remove the CSF with a syringe; rather, we collect as it drops into a bottle

The most common diagnosis we are trying to corroborate is MENINGITIS. This means infection or inflammation of the meninges - the covering of the brain and the spinal cord. Children with suspected meningitis present with a short illness of high fever, inability to stare or to look at bright light, a stiffness of the neck and, in cases where the doctor is not consulted acutely, other significant neurological symptoms like headache, pain in the limbs, inability to flex one's legs on to the abdomen, and, in severe cases, loss of consciousness, or even fits.

A non-blanching rash may also be a harbinger of a particularly sinister kind of bug - the meningococcus. See my OTHER post on this kind of rash. 

While the exact procedure for a lumbar puncture varies from country to country or system to system the general steps are the same. Consent from a parent/parents is required. This may be verbal or written, depending on where this is being done. For example, in India, we take written consent, while in the U.K., it is all right to take verbal consent. The consent must include the fact that not only is the procedure explained, but also its side-effects. 

The child is laid on a flat-topped bed or procedure bed. He is turned on one side. The doctor aims to puncture in the centre of the back where the spine is located; he must be adequately immobilised by helper members of the medical crew. Usually, parents are advised NOT to stay beside the child but to wait outside the procedure room. A support worker may be allocated to stay with the parents for support. 

After cleaning the back, a needle is passed into the space between two of the back vertebrae till it is inside the cerebrospinal fluid. As the CSF drops, it is collected into bottles for examination and for organism culture studies. The needle is then withdrawn and disposed of safely. The puncture site is sealed with "OpSite" a kind of plastic dressing spray. This is then covered over with a small, circular bandage and the child is handed over to the anxious parents. 

The common side-effect of a lumbar puncture is a minor headache. Usually, there are no other harmful effects. Theoretically, there is a risk of introducing bugs through the puncture into the nervous system. This is very rare, however. 

Results of the tests are usually available within the hour. Based on the initial results, doctors will advise parents on which way the treatment is likely to go ahead. Usually, if an infection was suspected, doctors will have ALREADY started antibiotics or antiviral drugs, or both, even before a lumbar puncture is carried out. Usually, such antibiotic or antiviral therapy is then continued till the culture results from the fluid are made available - which could be up to 3-5 days later.

To summarise:

1. A lumbar puncture is putting a needle into the centre of the back to collect cerebrospinal fluid
2. Usually, this procedure is done to prove/disprove the presence of infection of the nervous system organs or tissues, usually, the meninges.
3. The procedure needs verbal consent in most countries. 
4. It is carried out with the strictest antisepsis. 
5. The procedure is generally safe and tolerated well by almost all children,
6. Theoretically, there is a rare risk of introducing infection. 
7. Results of the test will guide further therapy. 

Thank you.

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Dr. Fuhrman

Dr. Fuhrman