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Diagnosis and tests

Lumbar puncture and cerebrospinal fluid

The related article (“ALL: symptoms and diagnosis”) explains the blood smear. This topic looks closely at the procedure that checks whether leukaemia has spread to the brain and spinal cord: the lumbar puncture.

Last updated: ~1 min read
A side view of the lower back and a thin needle.
Figure 1.The space between vertebrae.

01Short answer

The brain and spinal cord are surrounded by a clear fluid, the cerebrospinal fluid (CSF). In some leukaemias, especially ALL, leukaemia cells can get into it. In a lumbar puncture, a small amount of fluid is taken with a thin needle from the lower back, between two vertebrae. The skin is numbed first; the person lies on their side with knees pulled up to the chest, or sits leaning forward. In the lab, the fluid is checked for cell count, under the microscope (cytospin) and sometimes by flow cytometry. In ALL the procedure serves both diagnosis and treatment: medicine can be given straight into the fluid through the same needle (intrathecal treatment). When platelets are very low, the procedure is planned with care.

02Simple explanation

CSF surrounds the brain.

Lumbar puncture: fluid from the lower back.

Diagnosis and treatment together.

03Scientific explanation

CNS status: in ALL, the result is usually grouped as CNS1 (no blasts), CNS2 (a few blasts) or CNS3 (many blasts or symptoms), which affects how intensive treatment is.

Traumatic tap: if blood mixes into the sample, interpretation becomes harder, so the procedure is done carefully.

04What happens in the body?

The space between vertebrae

The needle enters below the spinal cord, into the space with fluid.

Clear fluid

Normal CSF is clear; a small amount is collected into a few tubes.

Tubes in a rack — Lumbar puncture and cerebrospinal fluid
Figure 2.Tubes of clear CSF — Lumbar puncture and cerebrospinal fluid

A comfortable position

Curling up on your side opens the gaps between the vertebrae.

A person lying on their side with a pillow.
Figure 3.A comfortable position on your side.

05A lumbar puncture

Four steps.

Position — Curl up on your side.1PositionCurl up on your side.
Numbing — The skin is numbed.2NumbingThe skin is numbed.
Fluid — A little is taken.3FluidA little is taken.
Rest — Lie down afterwards.4RestLie down afterwards.

06What is checked in CSF

TestWhat it shows
Cell countWhether cells are increased
CytospinWhether blasts are present
Flow cytometryA few leukaemia cells
Protein and glucoseInflammation or infection
CultureIf infection is suspected

07Key terms

CSF
Cerebrospinal fluid.
Lumbar puncture
Taking CSF from the lower back.
Intrathecal
Given directly into the CSF.
CNS
Central nervous system.
Cytospin
A way of collecting CSF cells onto a slide.

08Key points

  • CSF surrounds the brain.
  • In ALL, leukaemia can enter it.
  • The procedure is done under local numbing.
  • Diagnosis and treatment can be combined.
  • CNS status affects treatment.
  • Report any headache afterwards.

09Frequently asked questions

Does it hurt?

With numbing, you usually feel pressure; children are often given anaesthesia.

What should I do afterwards?

Lie down for a while and drink fluids; your team will give you the rules.

Why is it done many times?

In ALL, intrathecal treatment is part of the plan.

10Questions for your doctor

Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.

  1. Does it hurt?

  2. What should I do afterwards?

  3. Why is it done many times?

My questions

12Sources

  1. MedlinePlus. Cerebrospinal fluid (CSF) collection
  2. MedlinePlus. Cerebrospinal fluid (CSF) analysis
  3. National Cancer Institute (NCI). Adult ALL treatment (PDQ), patient version
  4. National Cancer Institute (NCI). Find NCI-Supported Clinical Trials
  5. Cancer Research UK. Acute promyelocytic leukaemia (APL)
  6. MedlinePlus. Flow cytometry
  7. Cancer Research UK. Types of acute myeloid leukaemia (AML)
  8. Leukemia & Lymphoma Society. Genetic testing and AML
  9. ESMO. ESMO Clinical Practice Guidelines: Haematological Malignancies
  10. American Cancer Society. Informed Consent
Medical disclaimerThis information is for educational purposes only and does not replace medical advice.
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