What are the potential side effects of a lumbar puncture (LP)?

Lumbar Puncture Side Effects

Post-dural puncture headache is the most common complication of lumbar puncture, affecting up to 35% of patients when conventional needles are used, though this can be reduced to approximately 4% with atraumatic needles. 1

Most Common Side Effects

Post-Dural Puncture Headache (PDPH)

• Incidence ranges from 0.9% to 35% depending on needle type and technique, with conventional needles causing rates of 11% compared to 4.2% with atraumatic needles 1, 2
• Typically develops within 3 days of the procedure and manifests as an orthostatic headache (worse when upright, better when lying flat) 2
• Results from sustained leakage of cerebrospinal fluid from the dural tear, which can be debilitating and require return to hospital for narcotics or invasive therapy 1
• More than 85% of post-LP headaches resolve without treatment 2
• Severe cases may require an epidural blood patch (needed in only 0.3% of cases), which is effective and well-tolerated 2

Other Common Complications

• Back pain occurs frequently, though typically mild 1, 2
• Short-term numbness of the legs is among possible adverse events, generally mild and manageable 2, 3
• Nausea, vomiting, and dizziness can occur 2
• Vasovagal symptoms such as hypotension or syncope are rare 2

Serious but Rare Complications

Life-Threatening Complications

• Brain herniation is the most serious potential complication, occurring in patients with elevated intracranial pressure 1
• Incidence ranges from 1.2% in patients with papilledema to 6-12% in certain high-risk populations, though actual risk is likely "much less than 1.2%" 1
• Occurs within 8 hours after lumbar puncture in all reported cases 1

Neurological Complications

• Nerve injury typically presents as radicular symptoms including pain, numbness, or weakness in the distribution of the affected nerve root 3
• Cauda equina syndrome is very rare but serious, presenting with saddle anesthesia, bowel/bladder dysfunction, and lower extremity weakness 3
• Nerve palsies including diplopia can occur 4, 5
• Most radicular symptoms resolve in the early post-procedure period 3

Infectious and Hemorrhagic Complications

• Spinal hematoma is a less common complication 5
• Meningitis has been found to follow lumbar puncture in children with bacteremia 5
• Infectious processes at the puncture site can occur 4

Overall Safety Profile

Large-scale evidence demonstrates that lumbar puncture is generally safe when performed according to guidelines, with less than 1% of patients experiencing serious complaints requiring specialist treatment. 2

• Studies involving >7,000 patients in clinical trials and >30,000 patients in routine clinical practice confirm safety 2
• While 31% of patients report post-LP complaints, only 0.3% require epidural blood patch and 0.7% need hospitalization 2
• All patients who experienced complications had complete recovery after treatment 2
• A recent Australian study found complications in 10.3% of procedures, with the majority (8.6%) being minor and most frequently consisting of PDPH 6

Risk Factors for Complications

Patient-Related Risk Factors

• Younger age (older adults have lower risk of post-LP headache) 2
• Female sex, especially women ≤40 years of age 2
• History of headache increases risk of post-LP headache 2
• Body mass index ≤25 kg/m² 2
• Fear of the procedure (patients who are "very worried" have higher risk) 2

Procedure-Related Risk Factors

• Use of cutting-bevel needle rather than atraumatic needle 2
• Use of large-bore (≤22 gauge) needle 2
• Multiple LP attempts (risk approximately doubles with 2-4 attempts and increases five-fold with ≥5 attempts) 2
• Active rather than passive withdrawal of CSF 2
• Withdrawal of >30 mL of CSF 2
• Sitting posture during procedure 2

Key Prevention Strategies

The BMJ strongly recommends use of atraumatic (pencil-point) needles in all patients (adults and children) undergoing lumbar puncture because they decrease complications and are no less likely to work than conventional needles. 1

• Use narrow-bore needles (≥24 gauge) to significantly reduce post-LP headache risk 2
• Position patient in lateral recumbent position rather than sitting 2
• Allow passive (gravity) flow removal of CSF rather than active withdrawal with syringe 2
• Avoid multiple attempts at dural puncture 2
• Maintain adequate hydration with oral fluids post-procedure 2