Procedural Steps
Patient Positioning
Site Preparation
Local Anesthesia
Needle Insertion
Collection of CSF
Removal of Needle
Post-procedural Care
Interpretation of Results
CSF Pressure

LP Pressure Quick Guide

The lumbar puncture, or "LP", is a frequently performed procedure in emergency departments, neurology and radiology clinics and hospital wards. In the emergency department, LP can yield information that can rapidly differentiate benign from emergent conditions.

In general, an LP may be done to:

  1. analyse the cerebrospinal fluid (CSF)
  2. measure the CSF pressure
  3. access the intrathecal space for either drainage of CSF or injection of fluid or to administer medications into the intrathecal space
  4. to perform myelography

The most common emergency department indications for a LP include clinical suspicion of meningitis (bacterial, viral or fungal) or to rule out subarachnoid hemorrhage.

Do not let LP (or CT scan) delay antibiotics and fluid resuscitation in patients with probable meningitis.

In neurology clinics and other settings, LP is used to detect disorders with local immunoglobulin production in the CNS such as multiple sclerosis and SSPE, malignant infiltrates such as acute leukemia and lymphoma, and blockage of the spinal canal.

Major contra-indications to lumbar puncture are:

  • symptoms or signs of raised intracranial pressure. These include a decreased level of consciousness, localizing (focal) neurologic signs and papilledema. LP in patients with raised ICP may lead to uncal herniation and death,
  • a severe bleeding diathesis or coagulation disorder or the patient is on anticoagulation therapy,
  • infection at the planned site of the puncture

When performed correctly, the LP procedure can be rapidly completed with little discomfort or risk to the patient. Using the sterile conditions recommended in this learning module, the introduction of infection by the LP procedure itself to the spinal cord would be extremely rare. A small chance of bleeding at the site exists. However "post-LP headache" is a relatively common occurrence (in up to even greater than 30% of patients depending on the LP needle type and caliber selected - see Preparation). This headache begins usually within hours to a few days after the LP procedure and is usually made worse with a positional change to the upright posture. The headache can be very severe and although the headache usually improves over time, the headache can last up to 3 weeks. A "blood patch" may be required to seal the hole in the lumbar meninges.

Bed rest (although frequently recommended), whether prone or supine, immediately after LP does not prevent the headache.

Headache Cybertext / Postural Headaches from Lumbar Punctures, Dural Rents & Shunts


A non-postural headache after an LP is uncommon. If the onset is early, consider a puncture-induced meningitis and for those headaches of later onset consider a possible subdural effusion.

A signed informed consent should be obtained from the patient or a substitute decision maker after explaining the risks and benefits of the procedure. The consent form should ideally be signed by the patient in the presence of a witness. This should include a discussion of the likelihood of "post-LP headache" and the small risk of bleeding or introducing infection.

A patient information sheet for LP.


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