• Clinical science

Lumbar puncture

Abstract

A lumbar puncture is a diagnostic and therapeutic procedure in which a spinal needle is passed into the subarachnoid space. It enables drainage or collection of cerebrospinal fluid (CSF) as well as administration of intrathecal medications. CSF analysis may aid in the diagnosis of meningitis, multiple sclerosis, intracranial hemorrhage, or meningeal carcinomatosis. In addition, drainage of CSF can lead to symptomatic improvement in patients with idiopathic intracranial hypertension and normal pressure hydrocephalus. There are no absolute contraindications to a lumbar puncture, although increased intracranial pressure, bleeding disorders, and spinal abscesses all increase the risk of complications. A common and unpleasant, albeit harmless, complication of lumbar puncture is a post-lumbar puncture headache.

Indications

Suspected meningitis or SAH in a patient with a negative CT scan is an urgent indication for a lumbar puncture!

References:[1]

Contraindications

There are no absolute contraindications; to performing a lumbar puncture. However, there are several relative contraindications:

References:[1]

We list the most important contraindications. The selection is not exhaustive.

Procedure/application

  1. Explain the procedure to the patient (i.e., the application, purpose, possible complications).
  2. Choose a needle type
    • Pencil point or “atraumatic needles; are associated with lower rates of post-lumbar puncture headache, although conventional “cutting” needles may also be used.
    • 20- or 22-gauge spinal needles are typically used.
  3. Determine the level of entry while patient is upright.
    • Identify L4; , which is typically located at the level of the iliac crest
    • The spinal needle may be inserted either above (L3-L4 interspace; ) or below (L4-L5 interspace).
  4. Position the patient in the lateral recumbent fetal position.
    • The lower lumbar spine should be in flexion.
    • Alternatively, the patient may be positioned sitting upright or lying prone.
  5. Disinfect the skin; over the desired entry point with alcohol and chlorhexidine or povidone-iodine.
  6. Wear sterile gloves and place a sterile drape over the patient with an opening over the desired entry point.
  7. Apply local anesthesia to the desired entry point.
  8. Angle spinal needle slightly towards the umbilicus and advance slowly (the bevel should point towards the patient's side).
  9. Initial resistance followed by a noticeable loss of resistance indicates piercing of the ligamenta flava/dura and entry into the dural sac.
  10. Remove stylet after puncture and observe for flow of CSF, which indicates successful entry into the subarachnoid space.
    • If CSF pressure measurement is requested: Place a manometer over the needle hub to measure an opening pressure.
    • If administering pharmaceuticals: Inject the drug (e.g., local anesthetic such as bupivacainespinal anesthesia).
    • In diagnostic or therapeutic lumbar puncture: Serially collect CSF without active aspiration; (up to 40 mL may be collected).
  11. After completion of puncture: Insert the stylet back into the puncture needle. , withdraw the needle, apply a sterile swab, and compress the puncture site.
  12. Recommend bedrest for 1–2 hours and sufficient fluid intake.
  13. Document the lumbar puncture in the patient's file. and check labeling on the tubes.
  14. Transport/storage: If possible, immediate transport of the samples to the laboratory should be arranged. Otherwise, they should be placed in refrigerated storage (4°C).

References:[1][2]

Interpretation/findings

Cerebrospinal fluid analysis

Opening pressures (see also elevated intracranial pressure and brain herniation)

Appearance Cell type (number/μL) Lactate Protein Glucose
Normal ≤15 mm Hg Colorless and transparent Acellular (< 5 WBCs and < 5 RBCs) 1.2–2.1 mmol/L 15–45 mg/100 mL 40–75 mg/100 mL (60% of serum levels)
Multiple sclerosis Normal Colorless and transparent WBCs (< 50) Normal Normal to ↑ Normal
Guillain-Barré syndrome Normal Colorless and transparent ↑ WBCS (< 10) Normal ↑↑ Normal
Subarachnoid hemorrhage, stroke Normal or ↑ Bloody or xanthochromic (i.e., pink or yellow if hemorrhage > 6 h prior to sampling) RBCs, ↑ WBCs Normal ↑ (gamma globulin) Normal
Brain tumors Normal or ↑ Colorless and transparent Drop metastases Normal
Pseudotumor cerebri (idiopathic intracranial hypertension) ↑↑ Colorless and transparent Acellular Normal Normal Normal
Meningitis See cerebrospinal fluid analysis in meningitis.
  • Gram stain and culture to differentiate pathogens (see diagnosis of meningitis)
  • Detection of special markers, e.g., tumor markers, tau protein, PCR, or serology

Disruption of the blood-brain barrier (i.e., infections, autoimmune diseases, CNS malignancies) or intrathecal production of IgG (i.e, multiple sclerosis, CNS infections such as Lyme disease) → increased immunoglobulins (oligoclonal bands) → increased CSF protein!

References:[3][4][5]

Complications

  • Post-lumbar puncture headache
    • Etiology: : CSF leakage after lumbar puncture (rarely trauma-related CSF leak)
    • Risk factors:
      • Female
      • Young (20-40 years old)
      • Low BMI
    • Clinical features
      • Frontal or occipital headache; that presents up to 48 hours after the procedure (worsens when patient is upright, improves when patient is supine)
      • Pain can last up to 15 days
      • Nausea, vomiting, dizziness, tinnitus, and visual disturbances
    • Treatment
      • Oral analgesics
      • Sufficient fluid intake
      • Bed rest
      • Epidural blood patch
        • Indicated in severe refractory post-lumbar puncture headache
        • Involves epidural injection of autologous blood at the site of lumbar puncture
    • Prevention: : use of thin, atraumatic cannulasCSF leak syndrome is rarer
  • Infection: epidural abscess, meningitis
  • Hemorrhage
    • CSF may appear bloody if there is cutaneous vessel injury during lumbar puncture.
    • Rarely, lesion of the venous plexus in the central subarachnoid space
  • Neuropathy
    • Shooting pain radiating to a leg (due to contact with a nerve root)
    • Resolves when needle is withdrawn and redirected medially
  • Transient abducens nerve palsy
  • Brain herniation (see elevated intracranial pressure and brain herniation)

References:[6][1]

We list the most important complications. The selection is not exhaustive.