Lumbar puncture

Lumbar puncture (LP) is a diagnostic and/or therapeutic procedure in which a spinal needle is passed into the subarachnoid space and cerebrospinal fluid (CSF) is removed, CSF opening pressure is measured, and/or medications are injected. CSF analysis may aid in the diagnosis of meningitis, intracranial hemorrhage, multiple sclerosis, and meningeal carcinomatosis. Drainage of CSF is used in the treatment of idiopathic intracranial hypertension and normal pressure hydrocephalus. Untreated elevated intracranial pressure, bleeding disorders, and spinal abscesses are contraindications to lumbar puncture. CNS imaging and/or correction of coagulopathies should be considered prior to performing a lumbar puncture if the risk caused by procedural delay is acceptable. Post-lumbar puncture headache is a common complication, especially in young women, and is often accompanied by nausea and visual changes. The severity of post-lumbar puncture headache ranges from mild to incapacitating. Pharmacologic or interventional management may be necessary.

CSF testing for CNS diseases ^[1]

• CNS infections (bacterial, viral, mycobacterial)
• Subarachnoid hemorrhage (SAH)
• CNS malignancies and paraneoplastic syndromes
• Guillain-Barré syndrome
• Multiple sclerosis
• Neuroborreliosis

Urgent indications for lumbar puncture include suspected meningitis and SAH with negative CT scan.

CSF pressure measurement and/or drainage

• Idiopathic intracranial hypertension (pseudotumor cerebri)
• Normal pressure hydrocephalus

Intrathecal administration of pharmaceuticals

• Antibiotics
• Chemotherapy
• Anesthesia
• Contrast

Prior to LP, an effort should be made to identify potential contraindications and reduce patient risk. ^[1][2]

• Increased risk of cerebral herniation
  • E.g., due to space-occupying lesion with mass effect or posterior fossa mass
  • Obtain head CT if criteria for imaging prior to LP are present.
  • ↑ ICP: Consider specialist consultation for the management of elevated ICP prior to LP.
• Coagulopathy or thrombocytopenia
  • Increased risk of epidural hematoma and spinal cord compression
  • Consider correction if platelet count < 40 x 10⁹ /L or INR > 1.5. ^[2][3]
• Current anticoagulant use
  • Delay procedure, if feasible. ^[2][4]
    • NSAIDs (including aspirin): no delay required
    • Unfractionated IV heparin: 4–6 hours after last dose
    • Low-molecular-weight heparin: 12–24 hours after last dose
    • Coumadin: until INR ≤ 1.4
    • Direct oral anticoagulants (DOACs)
      • Length of delay depends on the agent and patient renal function.
      • See “Periprocedural management of DOAC therapy” for details.
  • Consider anticoagulant reversal if LP is needed urgently.
• Infection at the procedure site: e.g., cellulitis, abscess

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

Spinal needles ^[2]

• Design
  • Atraumatic (e.g., Whitacre, Sprotte needles): lower rates of post-lumbar puncture headache, fewer traumatic taps
  • Cutting bevel (e.g., Quincke): fewer failed procedures, faster fluid collection
• Size
  • Small (≥ 24 gauge): fewer complications, more procedure failures
  • Large (≤ 22 gauge): faster procedure time, faster fluid collection

A 20-gauge or 22-gauge atraumatic needle is recommended for most diagnostic lumbar punctures. ^[5][6]

Anatomical structures

• The needle passes through skin, fascia, fat, supraspinous ligament, interspinous ligament, ligamentum flavum, epidural space, dura mater, arachnoid mater, and subarachnoid space.
• Loss of resistance occurs when piercing the supraspinous ligament and the ligamenta flava and dura.

Landmarks

In adults, lumbar puncture is most commonly performed in the midline of the L3-L4 or L4-L5 interspace.

• Midline: identified by palpation of the spinous processes
• L4 spinous process
  • Typically at the intersection of a line connecting the posterior iliac crests and a line connecting the spinous processes
  • Easiest to identify when the patient is upright

To keep the spinal cord alive, insert the needle between L3 and L5.

Positioning

• Upright
  • Advantage: easier to identify midline and maintain the correct needle trajectory
  • Appropriate for infants, children, and adults
  • Patient sits with lumbar spine and hips in flexion.
• Lateral recumbent
  • Advantage: comfortable for the patient, required for accurate CSF pressure measurement ^[1]
  • Appropriate for older children and adults ^[7]
  • Patient lies in the lateral recumbent fetal position with lumbar spine in flexion and head on a pillow.

To accurately measure opening pressure, the patient must be in the lateral recumbent position. ^[1]

Prepackaged kits usually contain most of the materials needed for lumbar puncture. Familiarize yourself with the kit used at your institution. ^[7]

• Sterile gloves
• Sterile drape
• Antiseptic
• Spinal needle
• 3-way stopcock
• Manometer
• 4 collection tubes with caps open for ease of access
• Local anesthetic (e.g., 1% lidocaine)
• Syringe
• 25-gauge and 22-gauge needles (for local anesthetic)
• Gauze

• Perform a thorough neurological examination. ^[8]
• Obtain informed consent.
• Identify landmarks for lumbar puncture and mark the desired spinal needle entry site.
• Place the patient in the optimal position for lumbar puncture.
• Don PPE and maintain a sterile technique.
• Perform wide skin preparation.
• Apply a fenestrated sterile drape.
• Assemble the manometer with a three-way stopcock (if measuring opening pressure).

Accessing the subarachnoid space ^[1]

1. Infiltrate local anesthesia into the skin over the needle entry site with a 25-gauge needle.
2. Infiltrate local anesthesia into the deep tissue along the needle tract with a 22-gauge needle.
3. Place the spinal needle at the entry site and orient it towards the umbilicus.
4. Advance the needle slowly until a loss of resistance is felt.
5. Remove the stylet and look for CSF flow from the needle hub.
   • CSF flow: Proceed with pressure measurement and/or CSF collection.
   • No CSF flow: Replace the stylet and advance slowly until loss of resistance occurs again.

Obtaining opening CSF pressure

1. Attach the manometer with a three-way stopcock to the needle hub.
2. Turn the stopcock so the manometer opening is contiguous with the needle hub.
3. Allow the manometer to fill until the level has equilibrated.

CSF collection ^[6]

1. If a manometer is attached to the needle, turn the three-way stopcock to allow CSF to drain from the manometer.
2. Fill pre-numbered sample tubes in sequential order.
   • A minimum of 1–2 mL is required in each tube. ^[3]
   • Use only passive flow: Do not aspirate CSF.
   • A total collection volume up to 30 mL is considered safe. ^[2]
3. Reinsert the stylet, withdraw the needle from the patient, and apply a dressing to the puncture site.

Unable to access subarachnoid space

• Prevention
  • Position the patient with as much lumbar and hip flexion as possible. ^[9]
  • Use enough local anesthetic to minimize patient discomfort and movement.
  • Check for successful dural puncture with frequent stylet withdrawal. ^[10]
• Management
  • Change needle trajectory. ^[1]
  • Reposition the patient if lumbar flexion is suboptimal.
  • Consider using a higher or lower interspace.
  • Consider using a long spinal needle. ^[11]
  • Consider radiology consult for lumbar puncture under fluoroscopy. ^[12]

Consult a more experienced provider if lumbar puncture is unsuccessful after four attempts. ^[2]

• CSF collection tubes labeled and transported to lab ^[6]
• Procedure documented
• Relevant CSF studies ordered

• Gram stain and culture to differentiate pathogens (see “Diagnosis” in 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!

Post-lumbar puncture headache ^[1][2][17]

Etiology

Post-lumbar puncture headache is caused by CSF leakage after intentional or accidental lumbar puncture.

Risk factors

• Female sex
• < 40 years of age
• Low BMI ^[18]

Clinical features

• Frontal or occipital headache
  • Typically worsens when patient is upright and improves when patient is supine
  • Presents up to 48 hours after the procedure
  • Generally lasts 1–2 days but may persist for months
• Nausea, vomiting, dizziness, tinnitus, and visual disturbances
• Symptoms may be mild to incapacitating.

Diagnosis

• Clinical diagnosis in the absence of headache red flags
• If intracranial hemorrhage or brain tumor are suspected, obtain imaging for headache.
• If meningitis is suspected, collect blood and CSF cultures (see “Diagnostics for meningitis”).

Treatment

• Supportive care
  • Oral analgesics
  • Generous fluid intake
  • Bed rest
  • Caffeine (off-label, PO preferred) ^[17]
• Epidural blood patch
  • Indicated in severe refractory post-lumbar puncture headache
  • Technique: epidural injection of autologous blood at the site of lumbar puncture
  • Typically performed by an anesthesiologist or interventional radiologist

Prevention

Use a small-gauge (e.g., ≥ 24 gauge), atraumatic needle for lumbar puncture.

Other

• Infection
  • Spinal epidural abscess
  • Meningitis
• Hemorrhage
  • CSF may appear bloody if there is cutaneous vessel injury during lumbar puncture.
  • May result from a lesion of the venous plexus in the central subarachnoid space
  • Rarely results in epidural hematoma
• 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 ICP and brain herniation.”
• Epidermoid tumor

Severe back pain and/or neurological deficits that begin after a lumbar puncture should raise concern for epidural hematoma.

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