Lumbar puncture: Difference between revisions
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==Contraindications== |
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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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*Coagulopathy |
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**Platelets <30-40 |
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**INR ≥1.4-1.6 |
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**[[Hemophilia]] |
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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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* |
*Position appropriately: lateral decubitus or sitting and leaning over a table |
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* |
*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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*Inset spinal needle in the midline |
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*Measure opening pressure |
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== |
==Investigations== |
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* |
*Consider INR/PTT if concern about coagulopathy |
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* |
*Consider platelet count (should be >100) |
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* |
*Consider CT head if focal neurological signs, papilledema, GCS ≤12 |
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**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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*Local pain |
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*Post-LP headache, better when supine |
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**Treat with caffeine, fluids, and acetaminophen |
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*Brief radicular pain |
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*Rare: |
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**Spinal epidural hematoma |
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**Bacterial meningitis or spinal abscess |
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**Cerebral herniation |
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==Interpretation== |
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{| class="wikitable" |
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{| |
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! |
!Etiology |
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!Gram stain |
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!Cell count |
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!CSF glucose |
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!CSF protein |
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|[[Bacterial meningitis]] |
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|Positive in 60-80% |
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|Elevated >1000 neutrophils |
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|Reduced <0.4 CSF:serum |
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|Elevated >1g/L |
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|[[Viral meningitis]] |
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|Negative |
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|Moderate elevation <100 lymphocytes |
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|Normal or mildly reduced |
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|Normal or mildly elevated |
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|- |
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| Fungal or tuberculous meningitis |
|[[Fungal meningitis|Fungal]] or [[tuberculous meningitis]] |
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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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|Often very low |
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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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*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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*[[Hypoglycorrhachia]] refers to low CSF glucose |
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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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* |
*WBC normalizes last, and can still be useful even the following day |
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=== Opening Pressure === |
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* Usual range is 5 to 20 cm H<sub>2</sub>O |
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⚫ | |||
* See [[Increased intracranial pressure#Differential Diagnosis|causes of increased intracranial pressure]] |
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=== 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 |
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* Highly suggestive of CNS disease |
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=== Correction for Traumatic Tap === |
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* If increased RBCs are seen, may need to adjust |
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* Allow 1 WBC for every 700-1000 RBCs |
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* Allow 0.01 mg/mL protein for every 1000 RBCs |
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==Further Reading== |
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⚫ | |||
[[Category:Neurology]] |
[[Category:Neurology]] |
Latest revision as of 13:11, 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
- Platelets <30-40
- INR ≥1.4-1.6
- Hemophilia
- Anticoagulation
- Within 4 hours of prophylactic low molecular weight heparin (LMWH)
- Within 24 hours of therapeutic LMWH
- Within 7 days of clopidogrel (but no delay for aspirin)
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
- Usual range is 5 to 20 cm H2O
- See causes of increased intracranial 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
- Straus S, et al. How Do I Perform a Lumbar Puncture and Analyze the Results to Diagnose Bacterial Meningitis? JAMA. 2006;296(16):2012-2022.