A lumber puncture (spinal tap) is one of the main investigations carried out to test if someone has meningitis.
What happens during a lumbar puncture?
A doctor or specialist nurse will perform the lumber puncture. The patient is asked to curl up on their side or sit up with their head and shoulders bent over. This helps to open up the space between the bones of the lower spine (lumber region). A local anaesthetic is injected into the site where the lumber puncture will be performed to numb the area. A small fine needle is then inserted into one of the spaces between the bones of the lower spine and a sample of cerebrospinal fluid (CSF) taken. The sample of CSF is sent to the hospital laboratory for testing. When a patient has meningitis, it is this fluid that becomes infected.
A lumber puncture can be performed for other medical reasons such as removing fluid to reduce the pressure in the skull or injecting certain medicines.
When will I receive the results?
Some results will be available within a few hours and will help to confirm whether the patient has meningitis. Full results e.g. to identify the specific type of bacteria or virus causing infection, may take several days or longer.
What are the potential side effects of a lumbar puncture?
A lumbar puncture is a commonly performed procedure, and although can be uncomfortable, is safe. Some temporary side effects can occur and include headaches or backpain which usually improve in a few days. If side effects persist or become worse, the patient should seek medical advice.
Is a lumber puncture always necessary?
Doctors recommend this procedure when meningitis is suspected as it is the only way to confirm a diagnosis of meningitis. The results can also help the doctors give the most appropriate treatment. Ideally the lumber puncture is carried out as soon as possible, and before the patient is given antibiotics. This is because antibiotics can sometimes affect the results. In some cases, a lumber puncture may not be possible or may need to be delayed e.g. the patient may be too sick to undergo the procedure. In these cases the doctors usually start antibiotics and review treatment once more information is known about the patient’s condition.