Lumbar Puncture (Spinal Tap)

A lumbar puncture (spinal tap) is a procedure to collect cerebrospinal fluid (CSF) from the space around the spinal cord in the lower back. It is essential for diagnosing meningitis, encephalitis, subarachnoid hemorrhage, and neurological conditions like multiple sclerosis and Guillain-Barre syndrome.

Lumbar puncture diagnoses central nervous system infections (bacterial, viral, fungal meningitis), subarachnoid hemorrhage, multiple sclerosis, certain cancers (leptomeningeal disease), normal pressure hydrocephalus, and measures spinal fluid pressure (idiopathic intracranial hypertension).

Blood tests (coagulation studies, platelet count) are checked. Inform your doctor about blood-thinning medications. A CT scan of the head may be done first to rule out elevated intracranial pressure. No fasting is typically required.

You sit up or lie on your side in a curled position. After local anesthesia, a thin needle is inserted between lumbar vertebrae (L3-L4 or L4-L5) into the subarachnoid space. CSF is collected in tubes for analysis. Opening pressure is measured. The procedure takes 15-30 minutes.

Lie flat for 1-2 hours afterward. Drink plenty of fluids with caffeine to help prevent headache. Some patients experience a post-lumbar puncture headache (10-30%) that typically resolves in a few days. Rest and avoid strenuous activity for 24 hours.

Risks include post-LP headache (most common), back pain at the puncture site, bleeding, infection, nerve root irritation, and very rarely, cerebral herniation (if done with elevated intracranial pressure — hence the CT scan beforehand).

For some indications, blood tests or imaging (MRI of the brain and spine) may provide alternative diagnostic information. However, CSF analysis is irreplaceable for diagnosing meningitis, measuring opening pressure, and certain neurological conditions.

Covered by insurance when medically indicated. Emergency lumbar punctures for suspected meningitis are always covered. Pre-authorization is not typically required for this procedure.