Lumbar puncture

What is a lumbar puncture?

A lumbar puncture (LP), sometimes called a ‘spinal tap’ is a medical procedure carried out to obtain a sample of cerebrospinal fluid (CSF) – by inserting a needle between two bones in your lower spine (vertebrae). CSF is the fluid that bathes and protects the brain and spinal cord. It is produced constantly, so the small amount removed during an LP is rapidly replaced.

Why am I having an LP?

CSF testing can provide doctors with information about how the brain and spinal cord is working. When this is combined with a history, examination, and possible scan results, an LP can help to diagnose a wide range of neurological conditions. These include infection, bleeding, inflammation, and reduced or raised pressure within the head (driven by cerebrospinal fluid). An LP may also sometimes be used to drain pressure if this is elevated or causing neurological problems. A lumbar puncture may also be carried out to inject chemotherapy drugs, contrast material, or other medications into the CSF.

An LP is not compulsory. However, if an LP is not performed your doctors may find it more difficult to be sure of the diagnosis and this may stop them from providing the correct treatment for you. The exact reason for your lumbar puncture should have already been explained or would be explained to you shortly before the procedure by the doctor or advanced health practitioner. Please ask them about any queries you have in your mind while giving consent to perform the procedure.

How is the test performed?

The doctor will usually position you on your side at the edge of the bed, with your knees curled up to your stomach, trying to keep your back at right angles to the bed. Occasionally the procedure is performed in a sitting position. The amount of CSF taken will depend on whether you are undergoing the procedure for an investigation or treatment. It may be necessary to remove more fluid if the lumbar puncture is being done as treatment for a condition.

What will I feel?

The skin of the lower back is cleaned with an antiseptic; the antiseptic feels wet and cold. A local anesthetic is then injected under the skin with a very fine needle, this will usually sting for a few seconds and then numb the area. You should continue to be able to feel the doctor’s hands on your back, but you should not feel pain.

You may then feel a sensation of pushing or pressure as the lumbar puncture needle is inserted and sometimes a brief, sharp pain when the needle is moved forward. It is normal to experience such pain, often down one leg and this does not indicate anything wrong (if anything, it means the doctor is in the right place as the needle will have touched a nerve – it is almost impossible to cause damage to a nerve during this procedure).

The pain should stop within a few seconds but if it persists you should let the doctor know. Even if there is discomfort it is important to try not to move. Once the needle is correctly positioned, the doctor will measure the pressure of the fluid coming out and collect samples for sending to the lab for testing. The needle will be removed, and a small plaster will be put on the skin. This can be removed the next day.

The entire procedure usually takes about 30-45 minutes. After the lumbar puncture, you may be asked to lie flat for approximately an hour. You will usually be advised to drink plenty of fluids after this. If you feel OK, you can get up and about gently. You can sometimes go home the same day if you are well, and the results of the CSF are normal. It is advisable to take things easy for a couple of days and drink plenty of fluids.

What are the alternatives?

There is no alternative test to replace a lumbar puncture as there is no other way of sampling spinal fluid, although imaging such as CT or MRI can be used to help in some cases but may not be conclusive.

What are the potential side-effects and risks of the procedure?

Lumbar punctures are safe procedures that are commonly performed in the hospital.

Common complications include:

• Headache: Post–LP headaches occur in 10-30% of patients. It is caused by the slow leak of CSF through the puncture site into the tissue and typically starts within several hours to two days of the LP. It is not dangerous, and the leak closes by itself over a few days. In most cases, it resolves in a few days with simple painkillers and good hydration. See below for further advice on post-LP headaches.
• Backache: Localised back pain or bruising at the site of the procedure, which usually resolves in a few days.
• Bleeding: This may occur near the puncture site or, rarely into the epidural space. Your doctor would clarify with you before the procedure if you are at high risk of bleeding or taking any blood thinning tablets and would advise appropriately about the steps to be taken accordingly in these circumstances. If you are on blood thinning tablets, you may be asked to stop taking the tablets a few days beforehand by your doctor.
• Failure of the procedure: Sometimes it might be difficult to gain CSF as the space between the bones of the spine is very small or due to previous spinal operations. In this case, a second attempt might be carried out at one level below or it will be stopped, and further procedure will be booked for you to be done under the guidance of an X-ray.

Rare complications include:

• Infection: Extremely rarely, patients may develop an infection following a lumbar puncture that can be serious. This risk is minimized by cleaning the area before the procedure with an antiseptic solution. Watch out for signs of brain infection, such as fever, body rash, persisting headache, sickness, or photophobia (worsening headache with light), and seek help immediately by calling 111 or attending A&E.
• Injuries to the nerves: This is a rare complication, where you might feel a temporary loss of sensation or pins and needles in your legs.
• Permanent nerve injury: Extremely rare, this can occur causing disability, muscle weakness, and bladder, or bowel problems. This risk is almost negligible as the procedure is done at a level much below where the spinal cord ends, and at this space, there are only fine nerve endings, which are amenable to a minor injury, as the procedure is done blindly.
• Brainstem herniation: This again is an extremely rare complication and will happen when there is a mass in either your spine or head area. A CT brain scan or MRI will usually be done before you have an LP to make sure it is as safe as possible to proceed.

Getting your results

Your results for the CSF testing will be made available between a few hours to a few weeks depending on what tests are being carried out. Some tests for infection and bleeding can be done quickly and other tests like checking for bacteria, viruses, inflammation markers or cells are complex and may take 48-72 hours to complete, or sometimes up to a couple of weeks.

Important information

Post-LP headache

If you experience a post-LP headache you should lie down as much as possible and rest. You need to keep drinking plenty of fluid. Painkillers are probably best avoided and should not be needed if you stay flat most of the time. You would not normally need to seek medical advice as this most commonly settles within a couple of days. If, however, the headache is persisting despite drinking plenty of fluids, we would normally recommend against taking painkillers beyond two or three days — if persisting and is severe it is worth seeking advice from the doctors or staff on the ward where the lumbar puncture was performed as persistent low-pressure headache may be very debilitating but if treated early it may settle very quickly.

Sometimes patients will be admitted for intravenous fluids for a day or two and if these are not helpful, we will often consider an intravenous infusion of caffeine. If caffeine does not help turn off the headache, sometimes we repeat this up to once or twice and occasionally if there are still problems with headaches which are only occurring withstanding, we would consider proceeding to a blood patch where a repeat lumbar puncture procedure is performed, but this time an injection of 10 mL of your blood is injected into the space to seal up any hole that might be present and causing the continued leakage of cerebrospinal fluid.

Additional symptoms to be aware of

If you develop any of the following symptoms, please seek immediate help by contacting your GP or the ward/department for advice: (out of hours please attend your nearest A&E)

• New weakness or numbness of buttocks, legs, or feet
• New urine or stool incontinence (loss of control), retention, or constipation
• Fever (temperature >38oC or above), associated with new skin rash, vomiting, persistent headache, photophobia (bright light hurting your eyes)
• Clear fluid or blood leaking from your back
• Neck stiffness
• Confusion

Return to normal activities or work

You can usually return to normal activities immediately, including work, if you feel fine and have not developed any side-effects from the procedure. However, it is usually best to avoid sports and strenuous activities for 24 to 48 hours.

Taking part in research -The Liverpool Neuroscience Biobank at The Walton Centre (LNBW)

Established in 2011, the aim of the Liverpool Neuroscience Biobank at The Walton Centre (LNBW) is to enable and support neuro-oncological and neurology research. It includes samples gifted from patients who attend The Walton Centre. Doctors, scientists and researchers in Liverpool and within the Brain Tumour North West collaboration are actively engaged in research.

This research will aid in the diagnosis and treatment of various neuro-oncology and neurological conditions. We collaborate with researchers at The University of Liverpool, BRAIN UK, Alder Hey Children’s Hospital and the UKCRC Tissue Directory. So far more than 5000 patients have gifted samples to the LNBW biobank supporting more than 35 projects, enabling us to carry out important research.

We are grateful to all those who have gifted to the LNBW biobank - thank you! All patients undergoing a clinical procedure at The Walton Centre are invited to gift samples to the LNBW biobank for research.

To gift to the LNBW biobank, you will be provided with the information required to help you decide if gifting is something you want to do. For further information please contact us at: wcft.LNBW@nhs.net

For more information about lumbar puncture or the contents of this leaflet, please ask the doctor or the nurse practitioner performing your procedure.

Useful contact numbers

• Chavasse Ward: 0151 556 3897
• Sherrington Ward: 0151 556 3455
• Main Switchboard: 0151 525 3611

Your comments and feedback

We would appreciate your views on our leaflet and lumbar puncture procedure. Please contact the patient experience team for any feedback or comments at

Email: wcft.patientexperience@nhs.net 
Phone: 0151 556 3091