Cerebrospinal fluid analysis

by Arwa Alburaiki and Rouda Salem Alnuaimi

Introduction

CSF is a colorless fluid that is present within the subarachnoid space, central canal of the spinal cord and the brain ventricles. It is produced at a rate of 500 ml per day, by the choroid plexus epithelial cells that are found in the brain ventricles [lateral, third and fourth ventricles], and reabsorbed back into circulation, by arachnoid granulation into dural venous sinuses. CSF is recycled about 2-3 times per 24 hr.

CSF circulates from the choroid plexus in the lateral ventricle into the third ventricle through the foramen of Monro, from the third ventricle into the fourth ventricle through the cerebral aqueduct of Sylvius. Then, it travels from the fourth ventricle into subarachnoid space through the foramen of Luschka and foramen Magendie, where it will be reabsorbed again by the Arachnoid villi back to the venous drainage system of the brain.

131 - LP - lumbar puncture

Normal CSF Composition

  • Color: Clear
  • WBC
    • < 5 cells/mm3 with less than 3PMN/mm3 in adults
    • <20 cells/mm3 with < 1 PMN cells/mm3 in neonate
  • RBCs: < 10 cells/mm3
  • Glucose: 45-80 mg/dl [CSF: serum ratio is 0.6] .
  • Protein
    • <45 mg/dl in adults
    • <20 mg/dl in children
  • Normal LP opening pressure
    • In adults: 60-200 mmH2O [6-20 cm H2O].
    • In children who are < 8 years 10-100 mmH2O.
    • In neonate: 30-60 mmH2O

CSF Analysis and Interpretation

Opening pressure

  • Low Opening pressure: CSF leakage, or dehydration.
  • High Opening pressure: overproduction, infection, bleeding, tumor, false measurement [sitting position, Valsalva or crying].

Color

  • Purulent :bacterial /TB manengitis.
  • Xanthochromia [yellow color] in case of SAH, Hyperbilirubinemia.
http://www.medfriendly.com/xanthochromia.html

Cytology

  • High WBC count
    • Viral meningitis [ predominant lymphocytes].
    • Bacterial meningitis [ predominant PMNs ].
    • Fungal infection
    • Vasculitis
    • Traumatic tap
  • High RBC count
    • Taumatic Tap
    • SAH

Biochemistry

  • Glucose level
    • Decreases in case of bacterial/TB meningitis or CNS tumor.
  • Protein
    • Increases in:
      • Bacteria/TB meningitis.
      • Blood [traumatic Taps /SAH).
      • Multiple sclerosis.
      • Guillain-Barre syndrome.

Miscellaneous test

  • India ink for Cryptococcus
  • VDRL/RPR for neurosyphilis
  • PCR for HSV or CMV

 

CSF Analysis

 NormalBacterialViralSAH
ColorClearPurulentClear/purulentBloody or xanthochromic
Opening Pressure (cm H2O)7-18>20 cm H2ONormal/highHigh
WBC/mm30-525-10000+10-500Slightly high
DifferentialsLymphocytesPMNsLymphocytesWBC/RBC ratio same to serum
RBC/mm30-5NormalNormal>500
Glucose mg/100ml45-80<20Normal/lowNormal
Protein mg/100ml15-5050-10000 50-20060-150
The source is not provided by author

 

References and Further Reading

  • Gil Z Shlamovitz. Lumbar Puncture (LP) Interpretation of Cerebrospinal Fluid – https://emedicine.medscape.com/article/2172226-overview
  • Barbara K. Blok, Dickson S. Cheung, Timothy F. Platts-Mills. First Aid for the Emergency Medicine Boards Third Edition.
  • Mike Cadogan. Lumbar Puncture – https://lifeinthefastlane.com/procedures/lumbar-puncture/