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Mononuclear Cell Count in Cerebrospinal Fluid (CSF) – Manual Differential

Published: August 9, 2026Updated: August 16, 2026

This test measures the number of certain white blood cells (mononuclear cells) in your cerebrospinal fluid (CSF), which surrounds your brain and spinal cord. It helps assess conditions affecting the central nervous system.

Quick summary

["This test helps diagnose or monitor inflammation, infection, or other issues in your brain or spinal cord."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
75655-1
Short code
Mononuc Cells CSF Manual
Synonyms
Mononuc Cells CSF Manual
Category
chemistry
Sample
csf
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
manual-count
Specimen volume
1-2 mL
Stability
Immediate analysis required, Refrigerated: 1h
Hemolysis max
200
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may order this test if you have symptoms like headaches, neck stiffness, confusion, or neurological problems. It can also be part of a broader evaluation for conditions such as meningitis, encephalitis, or other brain/spinal cord disorders.

What Does the Test Involve?

A small amount of CSF is collected through a procedure called a lumbar puncture (spinal tap). The sample is then examined under a microscope by a trained technician to count the mononuclear cells (e.g., lymphocytes, monocytes). This is done manually for accuracy.

What to Expect Before the Test

You may receive a local anesthetic to numb the area where the needle will be inserted. You’ll lie on your side with your back bent slightly. The test usually takes a few minutes, and you may feel mild pressure or discomfort during the procedure.

What to Expect After the Test

After the procedure, you may feel a mild headache or neck stiffness. Stay hydrated and avoid strenuous activity for a short time. Your provider will give specific instructions based on your situation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CSF Mononuclear Cell Count (Manual)

Frequently asked questions

What does a high mononuclear cell count in CSF mean?
A high count may suggest chronic inflammation, autoimmune disorders, or certain infections affecting the central nervous system. Your healthcare provider will review your symptoms and other test results to determine the cause.
How is this test different from a standard white blood cell count?
This test specifically measures mononuclear cells in CSF, which is a specialized fluid surrounding the brain and spinal cord. A standard white blood cell count measures cells in blood, not CSF, so the results and clinical relevance differ.
Can I eat or drink before this test?
You may drink clear fluids but avoid eating solid foods for a few hours before the procedure. Follow your provider’s specific instructions for the best results.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy