Lumbar Puncture

Aka: Lumbar Puncture, Spinal Tap

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II. Indications

  1. Suspected CNS Infection
    1. Meningitis
    2. Encephalitis
    3. Tuberculous Meningitis
    4. Neurosyphilis
  2. Evaluate for Hemorrhagic CVA (Subarachnoid Hemorrhage)
    1. Hemorrhage suspected despite negative Head CT (at >6 hours from Headache onset)
    2. Head CT not available
  3. Diagnostic Chemistry Evaluation
    1. CSF Gamma Globulin (Multiple Sclerosis)
    2. Guillain-Barre Syndrome
    3. Transverse Myelitis
  4. CSF Dynamics
    1. Pseudotumor Cerebri (opening pressure)
    2. Spinal block diagnosis (Queckenstedt test)
    3. Normal Pressure Hydrocephalus evaluation
      1. Katzman infusion
      2. Radionucleotide cisternography
  5. CSF Cytology
    1. Carcinomatous Meningitis
    2. Lymphomatous Meningitis
  6. Imaging Adjuncts
    1. CT Myelogram
  7. Therapeutic Lumbar Puncture
    1. Methotrexate infusion (CNS Leukemia)
    2. Amphotericin B infusion (fungal Meningitis)
    3. Removal of fluid to decrease Intracranial Pressure
      1. Pseudotumor Cerebri
      2. Headache associated with Subarachnoid Hemorrhage

III. Contraindications

  1. Local infection at Lumbar Puncture site
  2. Cerebral mass lesion or significant structural abnormality (risk of Herniation)
    1. Large Brain Abscess
    2. Brain Tumor (especially posterior fossa)
    3. Subdural Hematoma
    4. Intracranial Hemorrhage
    5. Arnold-Chiari Malformation
  3. Increased Intracranial Pressure
    1. Papilledema
    2. Cushing's triad (Hypertension, Bradycardia, irregular respirations)
  4. Focal neurologic deficits (obtain head imaging first)
    1. Cranial Nerve deficit
    2. New Anisocoria
    3. Decorticate Posturing or Decerebrate Posturing
    4. Altered Level of Consciousness (esp. GCS <9-13)
  5. Unstable Patients
    1. Status Epilepticus
    2. Shock
  6. Uncorrected Bleeding Disorder
    1. Coagulopathy secondary to Cirrhosis or Alcoholism (INR >1.8)
    2. Anticoagulation (e.g. DOAC)
      1. Heparin (SQ or IV) stopped for 4-6 hours before LP (may restart 2-4 hours after)
      2. LMWH (e.g. Enoxaparin) stopped for 24 hours if therapeutic dosing (12 hours if daily prophylactic dosing)
        1. May restart 4 hours after LP
      3. Dabigatran stopped for 2-3 days if GFR>50 ml/min (3-5 days if GFR <50 ml/min)
        1. May restart 6 hours after LP
      4. Rivaroxaban or Apixaban stopped for 1-2 days if GFR>50 ml/min (3-5 days if GFR <50 ml/min)
        1. May restart 6 hours after LP
      5. Fondaparinux prophylaxis stopped 36 hours before LP (may restart 12 hours after LP)
    3. International Normalized Ratio (INR) >1.5 on Warfarin
      1. May restart Warfarin 4 hours after LP
    4. Severe Thrombocytopenia
      1. Platelet Count <50,000 (or <40,000 if experienced operator)
    5. Disseminated Intravascular Coagulation (DIC)
    6. Platelet ADP Receptor Antagonist (e.g. Clopidogrel)
      1. Aspirin alone is not a contraindication to LP
      2. Hold Platelet ADP Receptor Antagonist for 7 days before LP (may restart 6 hours after LP)

IV. Precautions

  1. Obtain CT Head before Lumbar Puncture if significant risk factors for CNS Mass
    1. Do not delay empiric Antibiotics for CT Head if Bacterial Meningitis suspected
    2. DO obtain Blood Cultures before Antibiotics
  2. Indications for CT Head before Lumbar Puncture
    1. CSF Shunt
    2. Hydrocephalus
    3. Trauma
    4. Known Intracranial Mass
    5. Recent neurosurgery
    6. Papilledema
    7. Focal neurologic deficit
    8. New onset Seizures within the last week
    9. Significantly Altered Level of Consciousness
    10. Immunocompromised (HIV, Immunosuppressant medication use, transplant patient, Chemotherapy)
  3. Contraindications fo Lumbar Puncture based on CT Head findings
    1. Midline shift
    2. Cistern Loss (Suprachiasmatic, basilar, superior cerebellar, quadrigeminal plate)
    3. Posterior fossa mass
  4. Increased Intracranial Pressure
    1. Monitor CSF Pressure with inline manometer while withdrawing CSF
    2. Do not drop CSF Pressure more than 50% of opening pressure with Lumbar Puncture

V. Equipment: General

  1. See spinal needle types below
  2. Sterile drape
  3. Sterile Vials
  4. Lidocaine 1% in 5-10 ml syringe with 27 gauge needle (for local skin and soft tissue Anesthesia)
  5. Povidone-Iodine (Betadine) with scrub brushes for application
    1. Preferred in Lumbar Puncture due to chemical arachnoiditis risk with Chlorhexidine (due to preservative)
    2. If Chlorhexidine is used, allow to fully dry (for 3-5 minutes) before spinal needle entry

VI. Equipment: Spinal Needle Types

  1. Needle Lengths
    1. Infant: 1.5 inch
    2. Child: 2.5 inch
    3. Adults: 3.5 inch (up to 6 inch needle may be needed in large or obese adults)
  2. Standard spinal needle (Quincke Needle, 20 to 22 g)
    1. Easier to obtain successful Spinal Tap
    2. Higher Incidence of post-dural Headache (22% in one study)
    3. Insert needle bevel parallel to long axis of spine (faces laterally)
  3. Atraumatic or blunt spinal needle (Sprotte needle, Whitaker needle) - preferred if experienced operator
    1. Smaller tapered needle with blunt tip (typically 20-22 g)
    2. Requires first puncturing the skin with a larger bore needle (18 g) deep enough to draw a small amout of blood
    3. Then pass the blunt tipped needle through the created hole
    4. Significantly lower Spinal HeadacheIncidence (9% compared with 22% with cutting needle)
      1. Castrillo (2015) Spine J 15(7): 1572-6 +PMID: 25794941 [PubMed]
    5. Flow rates via blunt tipped needles are at least as fast as cutting needles
      1. Pelzer (2014) Neurol Sci 35(12): 1997-9 +PMID: 25139108 [PubMed]
  4. References
    1. Orman and Reed in Herbert (2017) EM:Rap 17(4): 7
    2. Thomas (2000) BMJ 321:986-90 [PubMed]

VII. Technique: Adults

  1. Anxiolysis
    1. Consider Midazolam 2 mg IV before procedure
  2. Patient positioning
    1. Lateral decubitus position (required if performing opening pressure)
      1. Fetal Position
      2. Back at right angles to bed (hips and Shoulders squared, in the same plane)
        1. Position transverse processes parallel to floor
    2. Sitting position
      1. Leaning forward, holding a pillow
  3. Location (most important factor in successful LP)
    1. Mark midline spinous process between iliac crests
      1. Corresponds with L3-L4 or L4-L5 interspace
    2. Palpate spinous process with thumb (middle of thumb corresponds to middle of canal)
    3. Consider Ultrasound (high frequency linear probe)
      1. Benefits
        1. Identifies midline (spinous processes if not palpable)
        2. Identifies interspaces
        3. Estimates insertion depth
      2. Use a skin marker to place markers to either side of Ultrasound probe in transverse and longitudinal
        1. Start in transverse orientation (perpendicular to spine) to localize midline spinous process
        2. Rotate probe to longitudinal orientation to identify inter-spinous process space
  4. Anesthesia
    1. Consider 10 cc syringe Lidocaine 2% with Epinephrine (not in LP kit)
    2. Infiltrate planned LP track with 4 cc and a Field Block around the track with another 4-5 cc
  5. Spinal needle insertion
    1. Use 20 to 22 gauge spinal needle
    2. Insert needle bevel parallel to long axis of spine (faces laterally)
    3. Keep needle parallel with bed (and floor)
    4. Angle needle toward Umbilicus (parallel to the spinous process in sagittal plane)
      1. Needle Angled at 15 degrees cephalad in adults
      2. Needle Angled at 30 degrees cephalad in children (ages 1 to 12 year)
      3. Needle Angled at up to 40 degrees cephalad in infants (age <1 year)
    5. Insert needle until pop is felt or CSF fluid flows
      1. Insertion depth varies in adults, but typically 50-75% of spinal needle length
        1. Insertion length may approach 90-100% needle length in large adults (consider 6 inch needle)
        2. Insertion length 3-4 cm in young children (4-5 cm in older or obese children)
        3. Insertion length 1.5 to 2 cm in infants
      2. Walk the needle in slowly in steps (checking for CSF flow with each step)
      3. Coughing or Valsalva Maneuver increases flow
    6. Replace the stylet before removing the spinal needle
      1. Helps prevent Spinal Headache
  6. Mis-directed Needle hits bone
    1. Withdraw needle to skin level and redirect (angling slightly up or slightly down)
      1. Replace the stylet before removing the spinal needle
    2. Confirm midline and at an interspace
  7. Adjuncts to difficult Lumbar Puncture
    1. Fluoroscopy
    2. Paramedian approach
      1. Indicated in older patients with calcified spinous ligaments
      2. Insertion is shifted 1 cm, horizontally off midline
        1. Angle needle insertion toward midline

VIII. Technique: Infants

  1. Spinal needle: 22 gauge 1.5 inch
  2. Location
    1. Stay below L3 level (spinal cord ends at L2-3 in infants (in contrast with L1-2 in adults)
  3. Positioning
    1. Infant sitting, with helper holding arms and legs
      1. Consider having a second assistant or parent stabilize head or neck
    2. Alternatively, lateral decubitus position may offer better immobilization of infant
      1. Hips should be flexed
    3. Avoid excessive neck flexion (head in relatively neutral position)
      1. Neck flexion risks airway closure and apnea
  4. Additional pearls
    1. Depth is superficial in an infant
      1. Insertion length is 1.5 to 2 cm in infants (1.5 cm in newborns)
    2. Consider topical or Local Anesthetic
      1. LMX4 applied 30 minutes before procedure OR
      2. EMLA applied 60 minutes before procedure OR
      3. Lidocaine 1% with Epinephrine, raising a small subcutaneous wheal over the landmark
    3. Consider sedation
      1. Oral 30% Glucose solution (newborns up to age 6 weeks) OR
      2. Intranasal Fentanyl
    4. May remove stylet after entering skin
      1. Before entering skin, Epidermis may plug needle
      2. However, after skin entry, stylet removal makes it less likely to miss the space
      3. Replace the stylet before removing the spinal needle
    5. May allow for 1 additional CSF WBC for every 1000 CSF RBCs
      1. Lyons (2017) Ann Emerg Med 69(5): 622-31 [PubMed]
    6. Risk factors for failed Lumbar Puncture in infants
      1. Age <3 months
      2. Spinous processes not visible or palpable
      3. Patient movement
      4. Inexperienced provider
      5. Nigrovic (2007) Ann Emerg Med 49(6): 762-71 +PMID: 17321005 [PubMed]

IX. Labs: Standard CSF Orders

  1. See Cerebrospinal Fluid Examination
  2. Opening Pressure (normal 6-20 cmH2O)
    1. Obtain in left lateral decubitus position with legs extended and patient relaxed
  3. CSF tube collection
    1. Adult: Collect 2 ml in each of 4 tubes
    2. Child: Collect 1 ml in each of 4 tubes
    3. Infant: Collect 0.5 ml in each of 4 tubes
  4. Tube 1
    1. Gram Stain
    2. Culture and sensitivity
  5. Tube 2
    1. CSF Glucose (normal >=60% of Serum Glucose)
    2. CSF Protein (normal 15 to 45 mg/dl)
    3. Consider CSF Lactate in suspected Meningitis (esp. children)
      1. CSF Lactate >3.5 mmol/L is suggestive of Bacterial Meningitis
      2. Send CSF lactate on ice and run in lab within 20 minutes
  6. Tube 3
    1. CSF Cell Count with Differential (or from tube 4)
      1. Normal WBC <=5/mm3
      2. Consider cell count also from tube 1 (for comparison if RBCs present)
  7. Tube 4: Other labs determined by indication
    1. CSF PCR (Meningitis or Encephalitis panels including Bacterial Antigens, HSV, VZV)
    2. Tuberculosis Testing (AFB RNA PCR, Adenosine deaminase)
    3. Lyme PCR
    4. Parasite stains (e.g. india ink, cryptococcal Antigen)
    5. Multiple Sclerosis Testing (e.g. oligoclonal bands, IgG index, myelin basic Protein)
    6. Cancer cytology
    7. Neurosarcoidosis (ACE Level)
    8. Neurosyphilis (VDRL)

X. Complications

  1. Spinal Headache
  2. Unexpected rise in Intracranial Pressure
  3. Worsening of spinal block
  4. Seizure
  5. Brain Herniation (associated with Increased Intracranial Pressure, CNS Mass)
  6. Spinal Epidural Hematoma (1 in 150,000)
  7. Spinal Infection (Epidural Abscess, Diskitis)
  8. Iatrogenic Meningitis (rare)
    1. Pandian (2004) J Hosp Infect 56(2):119-24 +PMID: 15019223 [PubMed]

XI. References

  1. Claudius and Behar in Herbert (2017) EM:Rap 17(11): 5
  2. Esherick (2025) Lumbar Puncture, Hospital Procedures Course
  3. Weingart and Swaminathan (2024) EM:Rap Critical Care Malebag: I Love Doing LPs, accessed 3/3/2024
  4. Mount (2017) Am Fam Physician 96(5): 314-22 [PubMed]

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