Lumbar Puncture
Last updated 26th June 2019 - Tom Heaton
Indications
- Diagnostic
- CNS infection
- SAH
- Measure CSF pressure
- Other neurological
- GBS
- MS
- GBS
- CNS infection
- Therapeutic
- Intrathecal injection
- Anaesthesia (spinal)
- Chemotherapy
- Anaesthesia (spinal)
- Therapeutic drainage
- Intrathecal injection
Analysis
There are a number of values that can be measured from CSF.
It can also be sent for special tests if needed.
This is a good video on the subject: https://www.youtube.com/watch?v=AN_JI7HBMos
Protein
This is usually increased in infection, and also in some other CNS disorders.
Highest in TB, then bacterial infections, then viral.
Other CNS causes of elevation can generally be considered as inflammatory processes: GBS, sarcoidosis, vasculitis, CNS blood
Glucose
There are absolute values for this but it is usually a ratio of serum levels.
A ratio of 0.6 is normal.
Infections (although less common in viral) lower this level, as can inflammatory processes (vasculitis, sarcoidosis).
WBC
This refers to the cell count, which may be impacted by trauma from the sampling.
There is normally on very few monocytes present.
In the case of a ‘bloody tap’ a ratio of 1:500 WBC:RBC (or equivalent to the peripheral ratios) is taught, but may be misleading.
Bacterial infections show a polymorphonuclear leukocytosis.
Other infections (viral, TB, fungal) show more of a lymphocytosis.
Seizures and GBS can also elevate the levels
Appearance
The appearance should be clear and colourless.
It may be frankly turbid in bacterial infection.
In SAH it may be very bloody, but there can be some blood from traumatic sampling
Opening Pressure
The normal opening pressure is 8-15 cmH20 (up to 20 is quoted in some links)
Over 20 is high.
It is important that this is measured in the lateral position.
Gram Stain/Culture
This will be undertaken in cases of presumed bacterial infection to look for evidence of bacterial cells (and their characteristics).
Culture of the CSF can then be undertaken.
Special Tests
It can also be sent for special tests if needed.
This is a good video on the subject: https://www.youtube.com/watch?v=AN_JI7HBMos
- Protein - 0.18-0.45 g/L
- Glucose - 2.5-3.5 mmol/L
- Ratio to serum 0.6
- WBC - <3
- Appearance
- Opening pressure
Protein
This is usually increased in infection, and also in some other CNS disorders.
Highest in TB, then bacterial infections, then viral.
Other CNS causes of elevation can generally be considered as inflammatory processes: GBS, sarcoidosis, vasculitis, CNS blood
Glucose
There are absolute values for this but it is usually a ratio of serum levels.
A ratio of 0.6 is normal.
Infections (although less common in viral) lower this level, as can inflammatory processes (vasculitis, sarcoidosis).
WBC
This refers to the cell count, which may be impacted by trauma from the sampling.
There is normally on very few monocytes present.
In the case of a ‘bloody tap’ a ratio of 1:500 WBC:RBC (or equivalent to the peripheral ratios) is taught, but may be misleading.
Bacterial infections show a polymorphonuclear leukocytosis.
Other infections (viral, TB, fungal) show more of a lymphocytosis.
Seizures and GBS can also elevate the levels
Appearance
The appearance should be clear and colourless.
It may be frankly turbid in bacterial infection.
In SAH it may be very bloody, but there can be some blood from traumatic sampling
Opening Pressure
The normal opening pressure is 8-15 cmH20 (up to 20 is quoted in some links)
Over 20 is high.
It is important that this is measured in the lateral position.
Gram Stain/Culture
This will be undertaken in cases of presumed bacterial infection to look for evidence of bacterial cells (and their characteristics).
Culture of the CSF can then be undertaken.
Special Tests
- Xanthochromia
- Oligoclonal bands
- Extended culture - listeria and cryptococcus
- Cryptococcal antigen
- India ink stain - for cryptococcus
- Viral PCR - enterovirus, HSV and others
- Cytology
- ZN stain - for acid fast bacilli
Pathology
Some pathologies have clear ‘phenotype’ of CSF.
Bacterial Meningitis
Viral Meningitis
Fungal/TB
Bacterial Meningitis
- Protein - high - >1
- Glucose - low - < 2.2 (ratio <0.4)
- WBC - high
- >500
- Mainly PMN
- >500
- Opening pressure can be elevated
- The CSF can appear turbid
Viral Meningitis
- Protein - < 1
- Glucose - normal (ratio >0.6)
- WBC - high
- < 1000
- Monocytes
- Very high PMN count less common
- < 1000
- Opening pressure may be normal or only mildly increased
- The appearance can be normal
Fungal/TB
- Protein - 0.1-0.5
- Glucose - low - 1.6-2.5 (ratio <0.4)
- WBC - Slightly high
- 100-500
- Monocytes
- 100-500
- There may be a fibrinous appearance
Links & References
- Nickson, C. CSF Analysis. LITFL 2019. https://litfl.com/csf-analysis/
- Cadogan, M. Lumbar puncture. LITFL. 2016. https://lifeinthefastlane.com/lumbar-puncture/
- Thomas, H. Lumbar puncture (LP) _ OSCE guide. Geeky Medics. https://geekymedics.com/lumbar-puncture-osce-guide/
- Crit IQ. CSF Interpretation. Youtube. 2014. https://www.youtube.com/watch?v=AN_JI7HBMos
