What are the indications and contraindications for a lumbar puncture (LP)?

Lumbar Puncture: Indications and Contraindications

Lumbar puncture (LP) is indicated for diagnostic purposes in suspected central nervous system infections, subarachnoid hemorrhage with negative CT, inflammatory neurological disorders, and neoplastic diseases affecting the CNS, but is absolutely contraindicated in patients with increased intracranial pressure with evidence of mass lesion, infection at the puncture site, severe cardiorespiratory compromise, and uncorrected coagulopathy. 1

Indications for Lumbar Puncture

Diagnostic Indications:

• Suspected CNS infections:
  • Meningitis (bacterial, viral, fungal)
  • Encephalitis
  • Neurosyphilis
  • Cryptococcal meningitis in immunocompromised patients 1
• Subarachnoid hemorrhage with negative CT scan 2, 3
• Inflammatory neurological disorders:
  • Multiple sclerosis
  • Guillain-Barré syndrome
  • Acute disseminated encephalomyelitis 1
• Suspected idiopathic intracranial hypertension 1
• Neoplastic diseases affecting the CNS 1
• Unexplained altered consciousness or focal neurologic signs in febrile patients 4

Therapeutic Indications:

• CSF removal to reduce intracranial pressure in idiopathic intracranial hypertension
• Administration of intrathecal medications (e.g., antibiotics, chemotherapy)
• Management of cryptococcal meningitis with daily LPs 1

Absolute Contraindications

• Increased intracranial pressure with evidence of mass lesion 1, 2
• Infection at the puncture site 1
• Severe cardiorespiratory compromise 1
• Uncorrected coagulopathy:
  • Coagulation parameters should be normal
  • Platelet count should be ≥100 × 10⁹/L
  • Patients on anticoagulants require special consideration 1

Relative Contraindications

These conditions may require neuroimaging before LP:

• Moderate to severe impairment of consciousness (GCS <13) 4
• Focal neurological signs (including unequal, dilated or poorly responsive pupils) 4, 1
• Papilledema 4, 1
• After seizures until stabilized 4
• Immunocompromised state with focal neurological findings 1
• History of CNS disease 1
• Abnormal posture or posturing 4
• Relative bradycardia with hypertension 4
• Abnormal 'doll's eye' movements 4
• Systemic shock 4
• Respiratory insufficiency 4
• Suspected meningococcal septicemia (extensive or spreading purpura) 4

Pre-Procedural Evaluation

Clinical Assessment

• Clinical assessment, not cranial CT, should be the primary determinant of LP safety 4
• GCS assessment: Score <13 or fluctuation >2 requires CT before LP 4, 1

When to Perform CT Before LP

• If clinical contraindications suggest possible raised intracranial pressure 4
• For patients with new focal neurologic findings suggesting disease above the foramen magnum 4
• If mass lesion is suspected 4

Laboratory Assessment

• Coagulation studies: Parameters should be normal before LP
• Platelet count: Should be ≥100 × 10⁹/L
• Anticoagulation management:
  • Patients on warfarin: Adequate reversal with vitamin K, prothrombin complex concentrate, or fresh frozen plasma
  • Patients on heparin: Reversal with protamine 4, 1

CSF Analysis

Standard CSF Tests:

• Cell counts and differential
• Glucose and protein concentrations
• Gram stain and bacterial cultures 4

Additional Tests Based on Clinical Suspicion:

• Cryptococcal antigen testing
• Fungal staining and cultures
• Acid-fast bacillus smears and cultures
• Cytologic examination for neoplasia
• PCR tests (for HSV, CMV, JC virus, West Nile virus, etc.)
• Serologic test for syphilis 4

Pitfalls and Caveats

1. Failure to perform LP when indicated: Studies show that many children who should receive LPs are not getting them, despite their value in management 5

2. Performing LP without addressing contraindications: Always assess for contraindications before proceeding 4

3. Delaying antibiotics when meningitis is suspected: If bacterial meningitis is suspected and LP is delayed, empirical antibiotics should be started after blood cultures are obtained 4

4. Relying solely on CT to rule out raised ICP: CT is not a reliable tool for diagnosing raised intracranial pressure and should not be used alone for this purpose 4

5. Not reviewing LP results in clinical context: CSF findings must be interpreted in the context of the patient's clinical presentation and other laboratory results 1

6. Neglecting to reassess: In situations where LP is initially contraindicated, the situation should be reviewed every 24 hours, and LP performed when safe 4

7. Using traumatic needles: Atraumatic (pencil-point) needles significantly reduce the risk of post-dural puncture headache 1

By following these guidelines and understanding both the indications and contraindications for lumbar puncture, clinicians can maximize diagnostic yield while minimizing risks to patients.