Lumbar puncture for MS

A lumbar puncture is one of the tests that can be used to help diagnose MS. It involves removing and analysing a sample of cerebrospinal fluid (CSF), the fluid that surrounds the brain and spinal cord within the skull and backbone. A lumbar puncture is sometimes referred to as a spinal tap. 

On this page we look at what is involved in having a lumbar puncture and how it can help with the diagnosis of MS.

The first steps in the diagnosis of MS are to have your medical history taken and some initial tests such as a neurological examination. This is usually followed by an MRI scan of the brain. If the results of these tests do not give enough evidence to make a diagnosis of MS, your neurologist may refer you for a lumbar puncture to help confirm MS or rule out other conditions.

The immune system produces antibodies to fight infection. In MS, antibodies cross the blood-brain barrier and attack the myelin surrounding nerves. As a result, the level of antibodies in the cerebrospinal fluid (CSF) of someone with MS is higher than it should be. Your CSF can be analysed to see if there are markers of inflammation present which are typical for MS. The following tests may be carried out on the CSF sample obtained from your lumbar puncture to look for evidence to support a diagnosis of MS.

If you have multiple sclerosis, the number of white blood cells in your cerebrospinal fluid (CSF) is usually up to seven times higher than normal. If the count is even higher than this, it is probably due to an infection of some sort, rather than MS.

Oligoclonal bands (OCBs) are distinct bands of antibodies that may be seen in your cerebrospinal fluid (CSF) and serum when tested. Over nine in 10 people with MS have OCBs in their CSF.

If your CSF sample is analysed for OCBs, a sample of blood will usually be taken at the same time as your lumbar puncture, so a serum sample can be checked for comparison. If OCBs are found in your CSF but not in your serum, or if there are more OCBs in your CSF than your serum, this can indicate MS. This test alone cannot confirm or rule out MS, as up to one in 10 people diagnosed with MS will have a normal result with no OCBs present.

Oligoclonal bands are not unique to MS and can be seen in other conditions including viral encephalitis (NHS.UK), bacterial meningitis (NHS.UK) and lupus (NHS.UK).

A newer spinal fluid test has emerged for diagnosing MS. It looks for kappa free light chains (kFLCs), which are small protein fragments made by the antibody-producing cells. Normally they are assembled into antibodies, but if there is inflammation in the central nervous system (CNS), an excess of light chains is produced which are released into the cerebrospinal fluid (CSF). Elevated levels of kFLCs could indicate MS. 

This test is quicker and easier to perform than the one for oligoclonal bands (OCBs). It does not require a blood sample for comparison, so it’s likely that this test will be used more routinely in the future.

Watch Professor Alasdair Coles explain why a lumbar puncture may be used to help diagnose MS.

Having a lumbar puncture can be uncomfortable or unsettling, but it is a common procedure. It is usually carried out in a hospital by a doctor or specialist nurse. Waiting times for an appointment vary around the UK, but typically it should be within a few weeks of your referral. Your neurologist should tell you if there is anything you will need to do before your appointment. For example, you may need to stop taking some medicines, such as blood thinners, for a short time before the procedure.

You should ask your neurologist if you have any questions or concerns about having a lumbar puncture. 

A lumbar puncture appointment will usually be about an hour, but the procedure itself typically takes about 20 minutes to half an hour. Tell the doctor or nurse if you are especially worried about needles.

The doctor or nurse will ask you to lie on a hospital bed or couch on your left-hand side and then to bring your knees up to your chest into a foetal position. Once you’re in the correct position they will feel around your lower back to find the right place to insert the lumbar puncture needle. This will be in the area of your spine that’s below your spinal cord but above your pelvis.

If they are struggling to locate the right area, you may need to have the procedure sitting upright instead. It is easier to find the right spot to insert the needle in this position, but the side position is preferred as it allows for a reading to be taken to assess the pressure of the cerebrospinal fluid (CSF) before samples are taken.

Once identified, the area will be marked and cleaned to reduce the risk of infection. You may have drapes put over the area. A local anaesthetic will be injected to numb the skin, so you don’t feel the lumbar puncture needle as it is inserted. The local anaesthetic usually only takes a few minutes to take effect.

The lumbar puncture needle is longer and thinner than a needle that would be used to take a blood sample. This is so it only leaves a small hole when removed. The needle will be partially inserted and if you are lying on your side, a medical instrument called a manometer will be attached to measure the pressure of your CSF. If the pressure is lower or higher than expected, this may indicate another condition.

The next step is to collect some cerebrospinal fluid. The CSF comes out of the thin needle in small drops. Usually around 20 drops will be collected in each of three tubes. The needle is then removed.

Watch consultant neurologist Nick Cunniffe explain how to prepare for a lumbar puncture and demonstrate the procedure on a manikin. 

There is always a very small risk of infection when a needle is introduced into your body. The doctor will wash their hands, wear sterile gloves, and clean the area thoroughly to reduce this risk. 

When a needle is removed from your body there is always a small risk of bleeding. This is why you will usually be asked to stop taking any blood thinners beforehand as they can prevent a clot from forming if you bleed.

The most common side effect is a headache, with around three in 10 people experiencing a headache following a lumbar puncture. It is known as a low-pressure headache, which gets worse when standing and improves when lying down. It is caused by cerebrospinal fluid (CSF) leaking from the site where the needle was inserted.

Usually, a lumbar puncture headache goes away on its own within a day or two, but they can persist for longer. To reduce the risk of headache, you should try to lie flat for one to two hours after the procedure if you can and drink plenty of water. Caffeinated drinks such as coca cola, coffee or tea may also help. 

If your symptoms last more than a couple of days, or aren’t helped by fluids, rest or painkillers such as paracetamol or ibuprofen, you should contact the team that carried out your lumbar puncture. They may decide that you need to return to the hospital to have a blood patch carried out. This is where a small amount of your own blood is injected to seal the leak. Less than one in 100 people require a blood patch following a lumbar puncture.

Lumbar punctures are usually very safe and more serious complications are extremely rare. The NHS website has more information on the possible complications of a lumbar puncture (NHS.UK).

You should get your results within a few weeks. If you’ve not heard anything after a month, contact your neurologist. You may have a follow-up appointment to discuss the results and what happens next. If this doesn’t happen, ask to talk to your neurologist about your lumbar puncture results if you have any questions.

• Your Lumbar Puncture (ClinicSpeak) – a visual guide to the process from Barts Health NHS Trust
• Lumbar puncture (NHS.UK) – information from the NHS website