The lumbar puncture is a diagnostic, and very occasionally therapeutic, procedure involving the sampling of cerebrospinal fluid from the lumbar subarachnoid space.
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Indications
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- Diagnosis of infection (meningitis, encephalitis).
- Diagnosis of immune conditions such as Guillian-Barre syndrome and multiple sclerosis.
- Investigation of CNS involvement in oncology/haematology (mostly lymphoma).
- Other subspecialty nonsense.
- Administration of intrathecal medication (the most common of which would be spinal anaesthesia).
- Symptomatic relief for idiopathic intracranial hypertension.
Contraindications
- Thrombocytopenia (of 20 or less, ideally >50).
- Other coagulopathies or use of heaprins in the previous 24hours.
- Signs of increased intracranial pressure.
- Infection at puncture site.
A CT head should be completed prior to the procedure if there is any suspicion of raised ICP.
Equipment (in vague order of use)
- Disinfectant solution.
- Sterile gloves.
- Sterile drape.
- Local anaesthetic: with syringe, filter needle, and fine-bore needle.
- Spinal needle. Pencil point needles are less traumatic but require skin puncture.
- (Manometer and three way valve for opening pressure)
- CSF collection vials
The puncture
Unless the opening pressure is required, having the patient sitting and bent forward provides the best access to the anatomy.
Palpate the iliac crests to find the intercristal line. Know that this line intersects with the body or endplate of the male L4 vertebral body and the female L5 vertebral body; for completeness, know that this is not alway accurate.
The L4/5 space is the place. If it all goes to pot there, the L3/4 space is a suboptimal second choice. The author suggests this should be marked.
Anaesthetise with subdermal and subcutaneous infiltration of local anaesthetic followed by deep infiltration. Don’t accidentally inject the lidocaine intrathecally…
If using a pencil point needle break the skin with another implement; otherwise, introduce the needle and advance it about 15° cephalad through the subcutaneous tissues. Hopefully between the spinous processes and against the ligamentum flavum. Pass the needle through the ligaments in increments removing the stylet to check for CSF return.
If one is measuring opening pressures, attach the manometer and allow it to fill.
Fill the tubes with at least 1mL each.
Replace the stylet, remove the needle. Let the patient rest supine, advise them about the potential headache. They needn’t be reclined and monitored for the classical six hours.
Further reading:
- South Eastern Sydney Local Health District (SESLHD). Lumbar Puncture - Adult; SESLHDPR/613 [Internet]. Sydney: NSW Health; 2024 Dec. Link