Lumbar puncture (LP)
What is a lumbar puncture (LP)? Who will perform this test? An LP is a common and routine procedure, also A doctor trained in performing this procedure known as a spinal tap, where a very small will do the LP. A trained children’s nurse will hold needle is inserted through the base of the spine your infant in the appropriate position (which to collect a sample of the fluid surrounding the is lying on their side curled up in a tight ball). brain and spinal cord. This fluid is called Another team member may also be present to cerebrospinal fluid (CSF). help.
Why do we need to do this? Can you be present during the LP? LP is the only way to confirm a case of Yes, you can tell the team that you would like to meningitis (swelling of the lining of the brain be present. However, many parents find it caused by an infection in the CSF). distressing to see any procedures being done on their baby and would rather not be present. This National guidelines strongly recommended that is perfectly understandable. Please let the team an LP is done alongside other routine know and they will usually agree to whatever investigations, such as blood and urine tests, works best for you but be aware that it is best to look for signs of infection if meningitis is to be quiet so the doctor can concentrate on the suspected. This is a routine and very important procedure. investigation. Is it a painful procedure? Getting a sample of CSF will help Drs to find out An LP is an uncomfortable procedure similar to if your child has meningitis and if what is a blood test or drip being inserted. Some causing it so that they can treat your child in the children simply do not like being held in best way. position to have the LP even though this part is not painful. Sucrose might be offered to your If your child needs to access support in the infant undergoing LP if you agree. Giving future because of problems which arise as a sucrose has been shown to have a calming result of meningitis, a confirmed diagnosis often effect and is safe, effective and easy to improves access to support and after care. administer.
How much fluid needs to be taken? Four to five drops of the CSF is collected into three to four different sterile tubes. What happens to the samples taken? Can there be complications or side effects The samples are sent to the laboratory urgently following LP? for immediate tests to find out whether cells Complications following LP are extremely rare which fight infection or bacteria can be seen in infants and children. The brain constantly under the microscope. Glucose and protein produces CSF and the small amount removed levels in the sample are also measured because during a lumbar puncture is quickly replaced. they can provide clues as to what type of There may be pain at the site of the needle infection is present. insertion in the lower back. Usually this settles with simple pain killers and time. Older children The laboratory will try and grow any bacteria and adults can experience a post LP headache which might be contained in the sample. This and for this, the treatment is bed rest and can take 24-48 hours. analgesia.
Often it is not possible to grow bacteria from a There is no evidence that doing a LP can cause sample. Additional tests such as a ‘PCR test’ infection, although your Doctor would not may be done to try and identify what bug might perform a LP if there was infection in the be present. A PCR test works by detecting small overlying skin. Other reasons for not doing a LP amounts of genetic material form a virus or would include an obvious bleeding tendency in bacteria within the sample. your child and if there was evidence of excessive pressure in the brain; in this situation When will you get the result? your Doctor would delay performing the LP until The cell count and protein and glucose test the pressure had settled. results should be available within a couple of hours and in general will indicate whether an Can you as a parent or carer refuse this infection is present. Further tests such as procedure? culture (where laboratory staff try to grow As a parent you have a right to refuse this test, bacteria from a sample) or PCR testing will take but this will not be in your child’s best interests from 2 days to 2 weeks depending on the as it can affect your child’s care both now and in infection. the future. Please note:
What happens next? An LP is the only way to confirm a case of If your child is not already on antibiotics, an meningitis
antibiotic will likely be given to them If meningitis is present, but no LP has been immediately following an LP. This antibiotic is to done, your Doctor will not have the complete cover the usual causes of bacterial meningitis. information needed to guide both the Sometimes, when a severe viral infection called antibiotics to be used and the duration of herpes simplex is suspected, an antiviral antibiotics needed to successfully treat the medicine called acyclovir is also given until all meningitis.
the test results are back. If meningitis is never confirmed by LP it can sometimes be more difficult to access the appropriate follow up care for your child.
Please consider this information carefully and discuss it with your medical team.
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