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Why a lumbar puncture is part of blood cancer care | CION Cancer Clinics
A lumbar puncture is done in leukaemia to check whether cancer cells have reached the fluid around the brain and spinal cord, and often to give chemotherapy straight into that fluid. Many medicines given through a vein cannot reach it. Being asked for one does not mean the brain is affected. This page explains who needs it, what happens, and what the CSF report means. At CION Cancer Clinics, our haematologist reviews abnormal blood reports with you, orders only the tests that answer your question and explains each result plainly.
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Medically reviewed by Dr. Basudev PokhrelConsultant Haematologist · last reviewed September 2026, next review due September 2027
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On this page
- Why is a lumbar puncture done in leukaemia?
- Who usually needs a lumbar puncture, and who usually does not?
- What happens during a lumbar puncture?
- What do the words on a CSF report mean?
- What do families fear about a lumbar puncture?
- What can a lumbar puncture not tell you?
- Common questions about lumbar puncture in blood cancer
The short answer
Why is a lumbar puncture done in leukaemia?
A lumbar puncture checks whether leukaemia or lymphoma cells have reached the fluid around the brain and spinal cord. The same needle is often used to put chemotherapy straight into that fluid, because many medicines given through a vein do not reach it well.
Why the brain and spine need their own check
The brain and spinal cord sit inside a protective barrier that keeps many substances in the blood out. That barrier also keeps most chemotherapy out. Leukaemia cells that slip into this space can survive treatment that clears the blood and marrow, and come back later. A doctor finds out whether they are there by testing a small sample of cerebrospinal fluid, or CSF, the clear fluid that bathes the brain and spinal cord.
Two jobs, one needle
At diagnosis, the main job is to look. During treatment, the main job is often to give medicine directly into the fluid. This is called intrathecal chemotherapy. It may be repeated several times across the treatment plan, even when the first sample was clear, to stop cells settling there.
What it does not mean
Being asked for a lumbar puncture does not mean the doctors think the brain is affected. For some blood cancers it is a routine part of every plan.
Tell the team about any blood thinner or any bleeding problem before the procedure. Do not stop a medicine on your own; the team will tell you what to do.Which blood cancers
Who usually needs a lumbar puncture, and who usually does not?
It depends on how likely a particular blood cancer is to reach the fluid. Your haematologist decides for your own case.
Acute lymphoblastic leukaemia
In children and adults, lumbar punctures are a standard part of treatment. The first one checks the fluid, and later ones usually carry medicine to protect the brain and spine.
Some aggressive lymphomas
Fast-growing lymphomas, or those near the spine, kidneys, testes or sinuses, may need the fluid checked and sometimes treated.
Your team weighs
- The lymphoma type
- Where it has spread
- Blood test markers of activity
Acute myeloid leukaemia
Not routine for everyone. It is considered when there are symptoms such as headache or facial weakness, a very high white count, or certain subtypes.
Usually not needed
Chronic leukaemias, myeloma and slow lymphomas rarely need it at diagnosis unless there are symptoms pointing to the brain or nerves.
Not sure whether this applies to you?
Ask an oncologistOn the day
What happens during a lumbar puncture?
Checks first
Your blood counts, especially platelets, and clotting are checked. If platelets are low, a transfusion may be given first. The team decides this, so ask rather than assume.
Getting into position
You lie on your side with your knees pulled to your chest, or sit leaning forward over a pillow. Curving the back opens the gaps between the bones. Children are usually given sedation.
Numbing and the needle
The skin on the lower back is cleaned and numbed. A thin needle goes in below the point where the spinal cord ends, so the cord itself is not in the path. You may feel pressure.
Sample and medicine
A few drops of fluid are collected. If chemotherapy is planned, it is given through the same needle. The needle comes out, a dressing goes on, and you rest lying down for a while.
!
After a lumbar puncture, when to go to hospital now
Go to the nearest emergency department or call 108 the same day if there is fever with a stiff neck, a severe headache that does not ease on lying flat, new weakness or numbness in the legs, loss of bladder or bowel control, or fluid or blood leaking from the site. Say the person has leukaemia and had a lumbar puncture. A mild headache that eases when lying down is common and is not this.
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On your report
What do the words on a CSF report mean?
- CSF cytology or cytospin
- The fluid is spun so cells collect on a slide, then examined for leukaemia or lymphoma cells.
- Blasts seen or not seen
- Blasts are immature cancer cells. "Not seen" is reassuring for that sample, but a small number can be missed.
- CNS status
- A grading of whether the brain and spinal cord area is involved. It helps set how much treatment goes into the fluid.
- Traumatic tap
- Some blood from the needle mixed into the sample. It is common and can make the result harder to read.
- Protein and glucose
- Chemical readings of the fluid. Unusual values can point to infection or disease, and are read with the cell findings.
Commonly believed
What do families fear about a lumbar puncture?
"The needle can paralyse him."
The needle goes in below the level where the spinal cord ends, into a space holding only fluid and loose nerve roots. Serious nerve damage is very rare. Tell the team at once about any new leg weakness afterwards.
"Taking out spinal fluid will weaken the brain."
Only a few drops are taken, and the body replaces this fluid constantly. Headache after the procedure comes from a small leak at the puncture, and usually settles with rest and fluids.
"If cells are found in the fluid, nothing can be done."
Cells in the fluid change the plan, not the intention to treat. More medicine into the fluid, different drugs through the vein, and sometimes radiotherapy are used. Your haematologist will explain what it means for your case.
"She will have back pain for life."
Soreness at the site for a day or two is common. Long term back pain from a lumbar puncture is uncommon. If pain is getting worse rather than better, tell the team.
Being straight with you
What can a lumbar puncture not tell you?
A clear sample is good news for that sample. It does not prove that no cells will ever reach the fluid, which is why protective doses continue even after a clear result. A single lumbar puncture also cannot tell you how well the whole treatment will work.
Why it may be repeated so many times
Families often worry that repeated procedures mean something is going wrong. In most plans for acute lymphoblastic leukaemia, repeat lumbar punctures are scheduled from the start, as a way to deliver medicine. Ask for the planned schedule, so each one does not feel like a new alarm.
Who it may not suit on a given day
It may be postponed if platelets are too low, clotting is abnormal, there is infection in the skin of the lower back, or a scan suggests raised pressure inside the head. Postponing in these situations is a safety decision, not a delay in care.
How CION can help
CION's haematology team can explain why a lumbar puncture has been advised in your plan, go through the CSF report with you, and coordinate care with qualified centres where needed.
Questions we are asked
Common questions about lumbar puncture in blood cancer
Does a lumbar puncture hurt?
The numbing injection stings briefly. After that most people feel pressure rather than sharp pain, and sometimes a short tingle down one leg if a nerve root is touched. Children are usually sedated. Tell the doctor if it hurts, because more numbing medicine can be given.
How long does it take?
The needle part is usually short, though getting into a good position can take longer. You will then be asked to rest lying down for a while before going home or back to the ward. Plan for a few hours at the hospital in total, and bring someone with you.
Why do I get a headache afterwards?
A little fluid can leak from the small puncture, lowering the pressure around the brain. The headache is typically worse when sitting or standing and better when lying flat. Rest and fluids help. If it is severe, lasts, or comes with fever or a stiff neck, seek care the same day.
Is it the same as a bone marrow test?
No. A bone marrow test takes a sample from inside the hip bone to look at where blood is made. A lumbar puncture takes fluid from the space around the spinal nerves in the lower back. They answer different questions, and many patients with leukaemia need both.
Can the chemotherapy in the spine cause side effects?
Yes, though they are usually mild. Headache, feeling sick and back soreness are the most common. Rarely, there can be confusion, seizures or weakness, which need urgent attention. Your team will tell you what to watch for after each procedure.
What if my platelets are low on the day?
Low platelets raise the chance of bleeding near the spine. The team may give a platelet transfusion first, or move the procedure to another day. Reference ranges differ between laboratories, and the decision uses your full picture, so let the team decide rather than reading a single number yourself.
Can my child go back to school after it?
Usually after resting for the rest of that day, if the headache is mild and your child feels well. Avoid rough play and heavy lifting until the next day. School attendance during leukaemia treatment also depends on blood counts, so ask the team about the wider plan.
Can we refuse the lumbar puncture?
You can ask questions and take time to decide. But in blood cancers where it is standard, skipping it can let cells survive in the fluid and come back later. Talk through your fears with the haematologist, including sedation and pain relief, before deciding against it.
Your Haematologist
Meet CION's haematologist. One specialist for your blood report and your plan.
Dr. Basudev Pokhrel reviews blood counts, transfusion needs and blood disorders, and works with the CION tumour board on blood cancers.
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Sources
- National Cancer Institute — Lumbar puncture (definition)
- Cancer Research UK — Tests and scans
- Leukemia & Lymphoma Society — Leukemia
- Cancer.Net — Navigating Cancer Care
- National Health Mission — National Health Mission
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
Flow Cytometry in Blood Cancer: What It DecidesThe marker test also used on spinal fluidRisk Stratification: Favourable, Intermediate, AdverseHow findings shape the intensity of treatmentLeukaemia guideThe wider picture of leukaemia treatmentGetting a Haematology Diagnosis: Marrow, Flow and MolecularEvery test in the diagnostic pathway
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