What is a lumbar puncture?
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Lumbar puncture is a procedure which aims to collect cerebrospinal fluid. In order to do this, a hollow needle is introduced in the spinal cord of the lower back. This is one of the most complicated procedures to have done and therefore, it is often feared by patients.
Cerebrospinal fluid is a sterile liquid which is made up of 99% water, and it helps to protect the brain by cushioning it from shocks up the spinal cord. By analysing this liquid, doctors can detect potential traces of disease or infection, especially meningitis and multiple sclerosis.
The appearance of the liquid acts as an initial indicator: if there is a problem, there will be signs of bacterial infection; if the liquid is red, this implies that blood is present in it and this is a sign of subarachnoid haemorrhage. The great advantage of lumbar puncture is that it allows a very quick and reliable diagnosis to be made.
Lumbar puncture procedure
Contrary to common preconception, lumbar puncture is absolutely painless if it is carried out properly. The procedure commonly takes place in a hospital, under strong local anaesthetic. The extremely fine needle is introduced into the lower back, between the fourth and fifth vertebrae, while the patient is sat down with a rounded back. The liquid is collected in tubes in order to be studied.
The lumbar puncture procedure generally lasts between ten and fifteen minutes. In difficult cases, it can be carried out under x-ray image guidance and therefore lasts slightly longer.
The first results (colour of the liquid) are obtained immediately but a more thorough analysis in a laboratory can take more time.
Complications from lumbar puncture
Physical consequences from lumbar punctures very rarely occur. In the worst case scenario, patients can suffer from severe headaches or nausea. Indeed, when a doctor removes the cerebrospinal fluid, the brain is less cushioned and feels heavier in the cranium. In order to limit these side-effects, drinking lots of water and staying lay down for several hours after the procedure are both recommended.
In some cases, post-lumbar puncture syndrome can occur. It can be recognised through the presence of headaches, throbbing and neck pain. These clinical signs usually disappear when you lie down. Post-lumbar puncture syndrome doesn’t usually last any longer than a few day but if it becomes extremely restrictive, it is possible to use a blood patch. This is when a small dose of clean blood is injected which clots, and helps to close the hole which results in these symptoms.
