This is a procedure to help doctors diagnose neurological conditions. (Neurological conditions are those that affect the nervous system.) Lumbar puncture has been an important diagnostic tool since it was introduced in 1891, but it’s now done only rarely in patients with stroke symptoms. It's also called spinal puncture or spinal tap.

The process involves taking samples of the cerebrospinal fluid (or CSF) from around the spinal cord. The tests are done on the fluid samples. This helps doctors gain important information:

• The presence of blood or blood products in the CSF suggests bleeding. This test may be done to determine if a patient has had a subarachnoid hemorrhage. The CSF would have red blood cells in the fluid in this case. Hemorrhagic strokes occur when an artery ruptures and bleeds into or onto the brain.
• CSF analysis can also indicate changes due to tumor, infection and inflammation. Infection and inflammation may lead to symptoms that mimic a stroke.
• Spinal puncture allows the doctor to determine how high the pressure is within the central nervous system.

What other tests can be used to diagnose stroke?

Imaging techniques such as computed tomography (CT) and magnetic resonance imaging (MRI) can be done during acute stroke. In most cases they permit effective, safe diagnosis of ischemic stroke (caused by blood clots) and of bleeding into the brain. These tests largely eliminate the need for lumbar puncture in stroke. These imaging systems also help identify tumors and other conditions that mimic stroke. New monitoring devices can measure CSF pressure and detect changes in intracranial pressure. Pressure-induced shifts in regions of the brain can be imaged by CT and MRI.

For stroke information, call the American Stroke Association at 1-888-4-STROKE.

Related AHA and ASA publications:

• Know the Facts, Get the Stats... heart disease, stroke and risks
• How Stroke Affects Behavior  
• Understanding Stroke (also in Spanish)
• "What Are Stroke and TIA?" and "What Are the Warning Signs of Stroke and TIA?" in Let's Talk About Stroke kit (also in Answers By Heart Spanish kit)