Lumbar puncture: Difference between revisions

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== Contraindications ==
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==Contraindications==
   
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* Increased intracranial pressure, with focal neurological deficits, new seizures, or papilledema
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*Increased intracranial pressure, with focal neurological deficits, new seizures, or papilledema (CT head first; see Investigations, below)
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* Infection at the procedure site
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*Infection at the procedure site
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* Coagulopathy
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*Coagulopathy
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** Platelets <30
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**Platelets <30-40
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** INR >1.6
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**INR ≥1.4-1.6
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** Hemophilia
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**[[Hemophilia]]
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** Anticoagulation
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**Anticoagulation
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***Within 4 hours of prophylactic [[low molecular weight heparin]] (LMWH)
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***Within 24 hours of therapeutic [[LMWH]]
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***Within 7 days of [[clopidogrel]] (but no delay for [[aspirin]])
   
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== Procedure ==
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==Procedure==
   
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* Position appropriately: lateral decubitus or sitting and leaning over a table
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*Position appropriately: lateral decubitus or sitting and leaning over a table
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* Landmark using posterior superior iliac crests (PSIS) (marks L4)
+
*Landmark using posterior superior iliac crests (PSIS) (marks L4)
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** Can go above (L4/L5 space) or below (L3/L4 space)
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**Can go above (L4/L5 space) or below (L3/L4 space)
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* Inset spinal needle in the midline
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*Inset spinal needle in the midline
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* Measure opening pressure
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*Measure opening pressure
   
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== Investigations ==
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==Investigations==
   
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* Consider INR/PTT if concern about coagulopathy
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*Consider INR/PTT if concern about coagulopathy
−
* Consider platelet count (should be >100)
+
*Consider platelet count (should be >100)
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* Consider CT head
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*Consider CT head if focal neurological signs, papilledema, GCS ≤12
  +
**IDSA: immunocompromised, history of CNS disease (including stroke and mass lesion), or new, uncontrolled, or continuous seizures
   
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== Complications ==
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==Complications==
   
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* Local pain
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*Local pain
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* Post-LP headache, better when supine
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*Post-LP headache, better when supine
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** Treat with caffeine, fluids, and acetaminophen
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**Treat with caffeine, fluids, and acetaminophen
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* Brief radicular pain
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*Brief radicular pain
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* Rare:
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*Rare:
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** Spinal epidural hematoma
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**Spinal epidural hematoma
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** Bacterial meningitis or spinal abscess
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**Bacterial meningitis or spinal abscess
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** Cerebral herniation
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**Cerebral herniation
   
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== Interpretation ==
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==Interpretation==
   
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{| class="wikitable"
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{|
 
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! Etiology
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!Etiology
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! Gram stain
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!Gram stain
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! Cell count
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!Cell count
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! CSF glucose
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!CSF glucose
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! CSF protein
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!CSF protein
 
|-
 
|-
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| Bacterial meningitis
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|[[Bacterial meningitis]]
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| Positive in 60-80%
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|Positive in 60-80%
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| Elevated >1000 neutrophils
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|Elevated >1000 neutrophils
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| Reduced <0.4 CSF:serum
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|Reduced <0.4 CSF:serum
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| Elevated >1g/L
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|Elevated >1g/L
 
|-
 
|-
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| Viral meningitis
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|[[Viral meningitis]]
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| Negative
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|Negative
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| Moderate elevation <100 lymphocytes
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|Moderate elevation <100 lymphocytes
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| Normal or mildly reduced
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|Normal or mildly reduced
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| Normal or mildly elevated
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|Normal or mildly elevated
 
|-
 
|-
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| Fungal or tuberculous meningitis
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|[[Fungal meningitis|Fungal]] or [[tuberculous meningitis]]
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| Negative, except for cryptococcus on India ink or TB on acid-fast
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|Negative, except for [[Cryptococcus]] on [[India ink]] or TB on acid-fast stain
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| Moderate elevation, usually lymphocytes
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|Moderate elevation, usually lymphocytes
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| Often very low
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|Often very low
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| Elevated
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|Elevated
 
|}
 
|}
   
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* Correction for a bloody tap is 1 excess WBC for every 700 RBCs
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*Correction for a bloody tap is 1 excess WBC for every 700 RBCs
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* Lymphocytosis may be seen in bacterial meningitis if Listeria infection or prior antibiotics
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*Lymphocytosis may be seen in bacterial meningitis if [[Listeria]] infection or prior antibiotics
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* Xanthochromia suggests subarachnoid hemorrhage
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*[[Xanthochromia]] suggests subarachnoid hemorrhage
  +
*[[Hypoglycorrhachia]] refers to low CSF glucose
   
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=== CSF After Antibiotics ===
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===Interpretation After Antibiotics===
   
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* Glucose increases first, then protein, and both are often normalized within 12 hours
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*Glucose increases first, then protein, and both are often normalized within 12 hours
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* WBC normalizes last, and can still be useful even the following day
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*WBC normalizes last, and can still be useful even the following day
   
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== Further Reading ==
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=== Opening Pressure ===
   
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* Usual range is 5 to 20 cm H<sub>2</sub>O
* Straus S, ''et al.'' [https://doi.org/10.1001/jama.296.16.2012 How Do I Perform a Lumbar Puncture and Analyze the Results to Diagnose Bacterial Meningitis?] ''JAMA''. 2006;296(16):2012-2022.
 
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* See [[Increased intracranial pressure#Differential Diagnosis|causes of increased intracranial pressure]]
  +
  +
=== Protein ===
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  +
* May be increased by disruption of the blood-brain barrier (most commonly), intracranial synthesis of IgG, or impaired CSF resorption of proteins by the arachnoid villi
  +
* Highly suggestive of CNS disease
  +
  +
=== Correction for Traumatic Tap ===
  +
  +
* If increased RBCs are seen, may need to adjust
  +
* Allow 1 WBC for every 700-1000 RBCs
  +
* Allow 0.01 mg/mL protein for every 1000 RBCs
  +
  +
==Further Reading==
  +
 
*Straus S, ''et al.'' [https://doi.org/10.1001/jama.296.16.2012 How Do I Perform a Lumbar Puncture and Analyze the Results to Diagnose Bacterial Meningitis?] ''JAMA''. 2006;296(16):2012-2022.
   
 
[[Category:Neurology]]
 
[[Category:Neurology]]

Latest revision as of 08:11, 3 November 2021

Contraindications

  • Increased intracranial pressure, with focal neurological deficits, new seizures, or papilledema (CT head first; see Investigations, below)
  • Infection at the procedure site
  • Coagulopathy

Procedure

  • Position appropriately: lateral decubitus or sitting and leaning over a table
  • Landmark using posterior superior iliac crests (PSIS) (marks L4)
    • Can go above (L4/L5 space) or below (L3/L4 space)
  • Inset spinal needle in the midline
  • Measure opening pressure

Investigations

  • Consider INR/PTT if concern about coagulopathy
  • Consider platelet count (should be >100)
  • Consider CT head if focal neurological signs, papilledema, GCS ≤12
    • IDSA: immunocompromised, history of CNS disease (including stroke and mass lesion), or new, uncontrolled, or continuous seizures

Complications

  • Local pain
  • Post-LP headache, better when supine
    • Treat with caffeine, fluids, and acetaminophen
  • Brief radicular pain
  • Rare:
    • Spinal epidural hematoma
    • Bacterial meningitis or spinal abscess
    • Cerebral herniation

Interpretation

Etiology Gram stain Cell count CSF glucose CSF protein
Bacterial meningitis Positive in 60-80% Elevated >1000 neutrophils Reduced <0.4 CSF:serum Elevated >1g/L
Viral meningitis Negative Moderate elevation <100 lymphocytes Normal or mildly reduced Normal or mildly elevated
Fungal or tuberculous meningitis Negative, except for Cryptococcus on India ink or TB on acid-fast stain Moderate elevation, usually lymphocytes Often very low Elevated
  • Correction for a bloody tap is 1 excess WBC for every 700 RBCs
  • Lymphocytosis may be seen in bacterial meningitis if Listeria infection or prior antibiotics
  • Xanthochromia suggests subarachnoid hemorrhage
  • Hypoglycorrhachia refers to low CSF glucose

Interpretation After Antibiotics

  • Glucose increases first, then protein, and both are often normalized within 12 hours
  • WBC normalizes last, and can still be useful even the following day

Opening Pressure

Protein

  • May be increased by disruption of the blood-brain barrier (most commonly), intracranial synthesis of IgG, or impaired CSF resorption of proteins by the arachnoid villi
  • Highly suggestive of CNS disease

Correction for Traumatic Tap

  • If increased RBCs are seen, may need to adjust
  • Allow 1 WBC for every 700-1000 RBCs
  • Allow 0.01 mg/mL protein for every 1000 RBCs

Further Reading