What is a Lumbar Puncture?

A lumbar puncture, also called a spinal tap, is a diagnostic procedure used to collect cerebrospinal fluid (CSF) from around the spinal nerves in the lower back. This test is an important step in evaluating patients with normal pressure hydrocephalus (NPH) and other neurological conditions.

The procedure helps physicians assess CSF pressure, analyze fluid for abnormalities, and determine whether patients may benefit from more permanent treatments, such as a ventriculoperitoneal (VP) shunt.

Why Lumbar Puncture is Important in NPH Diagnosis

Diagnosing NPH requires more than just reviewing a patient’s symptoms and imaging studies. A high-volume lumbar puncture (removing approximately 30 ml, or about one ounce, of CSF) allows specialists to evaluate:

Changes in walking, balance, or cognition after fluid removal
CSF pressure levels
Laboratory findings, including specialized tests for Alzheimer’s disease when applicable

By assessing a patient’s clinical response after the procedure, doctors can better predict the potential benefits of long-term CSF diversion therapies.

How the Procedure is Performed

Setting: Lumbar punctures are typically performed in the clinic or as an outpatient procedure.
Technique: A thin, hollow needle is carefully inserted into the lower back to drain CSF. In some cases, fluoroscopic (X-ray) guidance is used to ensure precision.
Aftercare: About 30 ml of fluid is drained and sent for laboratory analysis. Patients are asked to remain lying down for about one hour after the procedure before going home.

Safety and Risks

Lumbar puncture is generally well-tolerated, but as with any medical procedure, there are potential risks, including:

Headache from CSF leakage
Infection at the puncture site
Bleeding or hematoma
Over-drainage of fluid
Rare injury to a nerve root

To minimize risks, patients are advised to avoid blood thinners, including aspirin-containing medications, prior to the procedure unless otherwise directed by their physician.

Preparing for Your Lumbar Puncture

Before your procedure, your care team will provide detailed instructions, including:

Which medications to stop beforehand
What to expect during and after the test
How to monitor for side effects once you are home

Most patients are able to resume normal activities the following day, although some may need additional rest if a headache develops.

Next Steps After Lumbar Puncture

The results of your lumbar puncture, along with imaging and clinical evaluation, help your physician create a personalized treatment plan. If you respond positively to fluid removal, you may be a candidate for a VP shunt procedure, which can provide long-term symptom relief from NPH.